2006

 

Hallmann, A. 2006.

 

The pherophorins: common, versatile building blocks in the evolution of extracellular matrix architecture in Volvocales.

 

The Plant Journal 45:292-307

 

2005

 

Yoshida H, Yokomori T, Suyama A. A simple classification of the volvocine algae by formal languages.

 

BULLETIN OF MATHEMATICAL BIOLOGY 67 (6): 1339-1354 NOV 2005

 

Abstract: There are several explanations of why certain primitive multicellular organisms aggregate in particular forms and why their constituent cells cooperate with one another to a particular degree. Utilizing the framework of formal language theory, we have derived one possible simple classification of the volvocine algae-one of the primitive multicells-for some forms of aggregation and some degrees of cooperation among cells. The volvocine algae range from the unicellular Chlamydonionas to the multicellular Volvox globator, which has thousands of cells. The classification we use in this paper is based on the complexity of Parikh sets of families on Chomsky hierarchy in formal language theory. We show that an alga with almost no space closed to the environment, e.g., Gonium pectorale, can be characterized by PsFIN, one with a closed space and no cooperation, e.g., Eudorina elegans, by PsCF, and one with a closed space and cooperation, e.g., Volvox globator, by Ps lambda SC. This classification should provide new insights into the necessity for specific forms and degrees of cooperation in the volvocine algae. (c) 2005 Society for Mathematical Biology.

 

Cheng Q, Pappas V, Hallmann A, et al. Hsp70A and GlsA interact as partner chaperones to regulate asymmetric division in Volvox. DEVELOPMENTAL BIOLOGY 286 (2): 537-548 OCT 15 2005

 

Abstract: GlsA, a J-protein chaperone, is required for the asymmetric divisions that set aside germ and somatic cell precursors during embryogenesis in Volox carteri, and previous evidence indicated that this function requires an intact Hsp70-binding site. To determine if Hsp70A, the only known cytoplasmic Hsp70 in V. carteri, is the chaperone partner of GlsA, we investigated the localization of the two proteins during critical stages of embryogenesis and tested their capacity to interact. We found that a substantial fraction of Hsp70A co-localizes with GlsA, both in interphase and mitotic blastomeres. In addition, Hsp70A coimmunoprecipitated with GlsA, and co-expression of GlsA and Hsp70A variants partially rescued the Gls phenotype of a glsA mutant, whereas neither variant by itself rescued the mutant phenotype. Immunofluorescence analysis demonstrated that GlsA is about equally abundant in all blastomeres at all cleavage stages examined but that Hsp70A is more abundant in anterior (asymmetrically dividing) blastomeres than in posterior (symmetrically dividing) blastomeres during the period of asymmetric division. We conclude that Hsp70A and GlsA function as chaperone partners that regulate asymmetric division and that the relative abundance of Hsp70A in asymmetrically dividing embryos may determine which blastomeres divide asymmetrically and which do not.

 

 

Aono N, Inoue T, Shiraishi H. Genes specifically expressed in sexually differentiated female spheroids of Volvox carteri.

 

JOURNAL OF BIOCHEMISTRY 138 (4): 375-382 OCT 2005

 

Abstract: Volvox carteri is a multicellular green alga with only two cell types, somatic cells and reproductive cells. Phylogenetic analysis suggests that this organism has evolved from a Chlamydomonas-like unicellular ancestor along with multicellularity, cellular differentiation, and a change in the mode of sexual reproduction from isogamy to oogamy. To examine the mechanism of sexual differentiation and the evolution of oogamy, we isolated 6 different cDNA sequences specifically expressed in sexually differentiated female spheroids. The genes for the cDNAs were designated SEF1 to SEF6. The time course of accumulation of each mRNA was shown to be distinct. The expression of some of these genes was not significantly affected when the sexual inducer was removed after the induction of sexual development. Sequence analysis indicates that SEF5 and SEF6 encode pherophorin-related proteins. Of these, SEF5 has the unique structural feature of a polyproline stretch in the C-terminal domain in addition to the one found in the central region.

 

 

Wadhwa V, Kumar S, Rai S, et al. A 'pseudo outbreak' of the contamination of blood cultures with Volvox globator.

 

ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 99 (7): 719-720 OCT 2005

2004

 

Kirk MM, Kirk DL

Exploring germ-soma differentiation in Volvox

JOURNAL OF BIOSCIENCES 29 (2): 143-152 JUN 2004

 

Just A, Gruber I, Wober M, et al.

Novel method for the cryopreservation of testicular sperm and ejaculated spermatozoa from patients with severe oligospermia: a pilot study

FERTILITY AND STERILITY 82 (2): 445-447 AUG 2004

 

 

Abstract:

 

Objective: To investigate Volvox globator as an easy-to-handle vehicle and as a safe alternative for cryopreservation of functional motile sperm cells.

 

Design: Prospective, controlled, clinical pilot study.

 

Setting: Two in vitro fertilization (IVF) outpatient clinics for reproductive medicine.

 

Patient(s): Fifteen patients with severe male infertility (density <100 motile sperm per milliliter) who were recruited from two IVF programs. The sperm cells were not intended for clinical use after thawing.

 

Intervention(s): In each case, a predetermined number (n = 8) of motile and morphologically intact sperm cells were injected into each Volvox sphere and then cryopreserved. The quality of the sperm cells and the handling of the Volvox spheres were verified.

 

Main Outcome Measure(s): Postthaw recovery rate in cases of severe male infertility and the amount of motile sperm after thawing.

 

Result(s): The postthaw recovery rate was 100%. At least 60% of the sperm cells were motile after thawing.

 

Conclusion(s): The use of the spherical algae Volvox globator offers a promising, inexpensive, and easy approach to the cryopreservation of functional motile sperm cells. Volvox globator is an alternative in countries that prohibit the destructive use of oocytes, even after fertilization has failed.

 

 

Jakobiak T, Mages W, Scharf B, et al.

The bacterial paromomycin resistance gene, aphH, as a dominant selectable marker in Volvox carteri

PROTIST 155 (4): 381-393 DEC 2004

 

 

Abstract:

 

The aminoglycoside antibiotic paromomycin that is highly toxic to the green alga Volvox carteri is efficiently inactivated by aminoglycoside 3'-phosphotransferase from Streptomyces rimosus. Therefore, we made constructs in which the bacterial aphH gene encoding this enzyme was combined with Volvox cis-regulatory elements in an attempt to develop a new dominant selectable marker - paromomycin resistance (Pm-R) - for use in Volvox nuclear transformation. The construct that provided the most efficient transformation was one in which aphH was placed between a chimeric promoter that was generated by fusing the Volvox hsp70 and rbcS3 promoters and the 3' UTR of the Volvox rbcS3 gene. When this plasmid was used in combination with a high-impact biolistic device, the frequency of stable Pm-R transformants ranged about 15 per 106 target cells. Due to rapid and sharp selection, Pm-R transformants were readily isolated after six days, which is half the time required for previously used markers. Co-transformation of an unselected marker ranged about 30%. The chimeric aphH gene was stably integrated into the Volvox genome, frequently as tandem multiple copies, and was expressed at a level that made selection of Pm-R transformants simple and unambiguous. This makes the engineered bacterial aphH gene an efficient dominant selection marker for the transformation and co-transformation of a broad range of V carteri strains without the recurring need for using auxotrophic recipient strains.

 

 

Pappas V, Blakely S, Wetzel M, et al.

Functional analysis of the Volvox asymmetric division protein GlsA

MOLECULAR BIOLOGY OF THE CELL 15: 218A-218A 1207 Suppl. S NOV 2004

 

 

Cheng Q, Miller SM

Cytoplasmic Hsp70 distribution correlates with asymmetric division in the green alga Volvox carteri

MOLECULAR BIOLOGY OF THE CELL 15: 218A-218A 1206 Suppl. S NOV 2004

 

 

Kirk DL

 

Volvox

 

CURRENT BIOLOGY, 14, R599-R600; for pdf click here

 

 

Nedelcu AM, Marcu O, and Michod RE.

 

Sex as a response to oxidative stress: A two-fold increase in cellular reactive oxygen species activates sex genes.

 

P ROY SOC LOND B BIO, 271, 1591-1596; for pdf click here

 

 

Abstract:

 

Organisms are constantly subjected to factors that can alter the cellular redox balance and result in the formation of a series of highly reactive molecules known as reactive oxygen species (ROS). As ROS can be damaging to biological structures, cells evolved a series of mechanisms (e.g., cell-cycle arrest, programmed cell death) to respond to high levels of ROS (i.e., oxidative stress). Recently, we presented evidence that in a facultatively sexual lineage – the multicellular green alga Volvox carteri – sex is an additional response to increased levels of stress, and likely ROS and DNA damage. Here, we show that in V. carteri (i) sex is triggered by a ca. two-fold increase in the level of cellular ROS (induced either by the natural sex-inducing stress, namely heat, or by blocking the mitochondrial electron transport chain with antimycin A), and (ii) ROS are responsible for the activation of sex genes. As most types of stress result in the overproduction of ROS, we believe that our findings will prove to extend to other facultatively sexual lineages, which could be indicative of the ancestral role of sex as an adaptive response to stress and ROS-induced DNA damage.

 

 

Nedelcu AM and Michod RE.

 

Evolvability, modularity, and individuality during the transition to multicellularity in volvocalean green algae.

 

In Schlosser G and Wagner G (eds) “Modularity in development and evolution”. Pp. 466-489. University of Chicago Press. (for pdf click here)

 

 

2003

 

 

Desnitskiy AG.

 

Peculiarities of the geographical distribution of coenobial volvocine algae (Volvocaceae, Chlorophyta).

 

Botanical Journal (St Petersburg). 2003. Vol. 88. N 11. pp. 52-61.(in Russian, with English Summary)

 

 

Abstract:

 

Data on the geographical distribution of 36 species from 7 genera of the family Volvocaceae sensu Nozaki (Pandorina, Volvulina, Yamagishiella, Eudorina, Platydorina, Pleodorina and Volvox) have been summarized. Both cosmopolitan species and species with local distribution have been detected. An attempt was made to trace a correlation of latitudinal distribution of the coenobial volvocine algae with obligatory differentiated somatic cells (22 species of the genera Volvox and Pleodorina) with peculiarities of proceeding of the cell divisions during asexual developmental cycle. In high latitudes of the Northern Hemisphere (northward of 50-57° north) only 3 species of Volvox occur, in which the formation of new coenobia (a series of consecutive gonidial divisions) starts with the light period (in the morning), the rate of division is slow and the gonidial divisions are temporarily blocked in darkness.

 

 

Schmitt R

 

Differention of germinal and somatic cells in Volvox carteri

CURRENT OPINION IN MICROBIOLOGY 6 (6): 608-613 DEC 2003

 

 

Abstract:

Volvox carteri is a spherical alga with a complete division of labor between around 2000 biflagellate somatic cells and 16 asexual reproductive cells (gonidia). It provides an attractive system for studying how a molecular genetic program for cell-autonomous differentiation is encoded within the genome. Three types of genes have been identified as key players in germ-soma differentiation: a set of gls genes that act in the embryo to shift cell-division planes, resulting in asymmetric divisions that set apart the large-small sister-cell pairs; a set of lag genes that act in the large gonidial initials to prevent somatic differentiation; and the regA gene, which acts in the small somatic initials to prevent reproductive development. Somatic-cell-specific expression of regA is controlled by intronic enhancer and silencer elements.

 

 

Nozaki H

 

Origin and evolution of the genera Pleodorina and Volvox (Volvocales)

BIOLOGIA 58 (4): 425-431 JUL 2003

 

 

Abstract:

The previous molecular phylogenetic study using 6021 base pairs from five chloroplast genes suggested that two species of Pleodorina (P. californica, P. japonica) might have evolved from a Volvox-like alga by the decrease in colony cell number and size. However, number of species of the genus Volvox was very limited especially in the section Merrillosphaera. In the present study, 6021 base pairs of the concatenated five chloroplast genes from 10 strains representing seven taxa of the genus Volvox were added to the previous data matrix. The sequence data resolved two anisogamous/oogamous clades within a large monophyletic group comprising five advanced genera of the Volvocaceae (Yamagishiella, Platydorina, Eudorina, Pleodorina and Volvox), one containing Volvox sect. Volvox and the anisogamous genus Platydorina (32-celled flattened colony), and the other (Eudorina group) composed of three other sections of Volvox, Pleodorina and Eudorina. The isogamous genus Yamagishiella (32-celled colony) was positioned basally to the Eudorina group. Therefore, evolution of anisogamy with sperm packets from isogamy might have occurred twice within the Volvocaceae. Based on the present molecular phylogenetic analysis, species of Volvox and Pleodorina within the Eudorina group represented three and two, respectively, separate lineages. One the three Volvox lineages [composed of V (sect. Merrillosphaera) carteri, V (sect. Merrillosphaera) obversus, V. (sect. Merrillosphaera) tertius, V. (sect. Merrillosphaera) africanus and V (sect. Copelandosphaera) dissipatrix] was sister to the monophyletic group consisting of one of the two Pleodorina lineages (P. californica and P. japonica) and V (sect. Janetosphaera) aureus. In addition, species of Eudorina were basal to the two lineages of Pleodorina and three Volvox lineages within the Eudorina group, representing the ancestral situation of Pleodorina/Volvox (excluding sect. Volvox). Thus, reverse evolution from a Volvox-like alga to Pleodorina suggested previously appears unlikely.

 

 

Cheng Q, Fowler R, Tam LW, et al.

 

The role of GlsA in the evolution of asymmetric cell division in the green alga Volvox caiteri

DEV GENES EVOL 213 (7): 328-335 JUL 2003

 

 

Abstract:

Volvox carteri, a green alga in the order Volvocales, contains two completely differentiated cell types, small motile somatic cells and large reproductive cells called gonidia, that are set apart from each other during embryogenesis by a series of visibly asymmetric cell divisions. Mutational analysis has revealed a class of genes (gonidialess, gls) that are required specifically for asymmetric divisions in V. carteri, but that are dispensable for symmetric divisions. Previously we cloned one of these genes, glsA, and showed that it encodes a chaperone-like protein (G1sA) that has close orthologs in a diverse set of eukaryotes, ranging from fungi to vertebrates and higher plants. In the present study we set out to explore the role of glsA in the evolution of asymmetric division in the volvocine algae by cloning and characterizing a glsA ortholog from one of the simplest members of the group, Chlamydomonas reinhardtii, which does not undergo asymmetric divisions. This ortholog (which we have named gar1, for glsA related) is predicted to encode a protein that is 70% identical to G1sA overall, and that is most closely related to G1sA in the same domains that are most highly conserved between G1sA and its other known orthologs. We report that a gar1 transgene fully complements the glsA mutation in V. carteri, a result that suggests that asymmetric division probably arose through the modification of a gene whose product interacts with G1sA, but not through a modification of glsA itself.

 

 

Grewing A, Krings M, Galtier J, et al.

 

The oldest fossil endophytic alga and its unusual habitat

SYMBIOSIS 34 (3): 215-230 2003

 

Abstract:

Lycophyte megaspores from the Lower Carboniferous of France sometimes contain a colonial (volvocacean) alga as an endophyte. This peculiar plant-plant association was briefly described more than 100 years ago and the name Lageniastrum macrosporae introduced for the alga, but the biological significance of the discovery was never fully appreciated. Here we present a reappraisal of the original material, which to date provides the oldest unequivocal fossil evidence for endophytic algae and the only example of an alga residing in the interior of spores of vascular cryptogams.

 

 

Nedelcu AM, Michod RE

 

Sex as a response to oxidative stress: the effect of antioxidants on sexual induction in a facultatively sexual lineage

P ROY SOC LOND B BIO 270: S136-S139 Suppl. 2 NOV 7 2003 (for pdf click here)

 

 

Abstract:

The evolution of sex is one of the long-standing unsolved problems in biology. Although in many lineages sex is an obligatory part of the life cycle and is associated with reproduction, in prokaryotes and many lower eukaryotes, sex is facultative, occurs in response to stress and often involves the formation of a stress-resistant dormant form. The proximate and ultimate causes of the connection between stress and sex in facultatively sexual lineages are unclear. Because most forms of stress result in the overproduction of cellular reactive oxygen species (ROS), we address the hypothesis that this connection involves ROS and possibly reflects the ancestral role of sex as an adaptive response to the damaging effects of stress-induced ROS (i.e. oxidative stress) . Here, we report that two antioxidants inhibit sexual induction in a facultatively sexual species-the multicellular green alga, Volvox carteri. Furthermore, the nature of the sex response and the effect of an iron chelator on sexual induction are consistent with sex being a response to the DNA-damaging effects of ROS. In addition, we present preliminary data to suggest that sex, cell-cycle arrest and apoptosis are alternative responses to increased levels of oxidative stress.

 

 

Rudel D, Sommer RJ

 

The evolution of developmental mechanisms

DEV BIOL 264 (1): 15-37 DEC 1 2003

 

Abstract:

Over the past two to three decades, developmental biology has demonstrated that all multicellular organisms in the animal kingdom share many of the same molecular building blocks and many of the same regulatory genetic pathways. Yet we still do not understand how the various organisms use these molecules and pathways to assume all the forms we know today. Evolutionary developmental biology tackles this problem by comparing the development of one organism to another and comparing the genes involved and gene functions to understand what makes one organism different from another. In this review, we revisit a set of seven concepts defined by Lewis Wolpert (fate maps, asymmetric division. induction, competence, positional information, determination, and lateral inhibition) that describe the characters of many developmental systems and supplement them with three additional concepts (developmental genomics, genetic redundancy, and genetic networks). We will discuss examples of comparative developmental studies where these concepts have guided observations on the advent of a developmental novelty. Finally, we identify a set of evolutionary frameworks, such as developmental constraints, cooption, duplication, parallel and convergent evolution, and homoplasy, to adequately describe the evolutionary properties of developmental systems. (C) 2003 Elsevier Inc. All rights reserved.

 

 

Kato-Minoura T, Okumura M, Hirono M, et al.

 

A novel family of unconventional actins in volvocalean algae

J MOL EVOL 57 (5): 555-561 NOV 2003

 

Abstract:

The unicellular green alga Chlamydomonas reinhardtii has two actin genes, one encoding a conventional actin (90% amino acid identity with mammalian actin), the other a highly divergent actin (64% identity) named novel actin-like protein (NAP). To see whether the presence of conventional and unconventional actins in a single organism is unique to C. reinhardtii, we searched for genomic sequences related to the NAP sequence in several other species of volvocalean algae. Here we show that Chlamydomonas moewusii and Volvox carteri also have, in addition to a conventional actin, an unconventional actin similar to the C. reinhardtii NAP. Analyses of the deduced protein sequences indicated that the NAP homologues form a distinct group derived from conventional actin.

 

Golstein P, Aubry L, Levraud JP

 

Cell-death alternative model organisms: Why and which?

NAT REV MOL CELL BIO 4 (10): 798-807 OCT 2003

 

Abstract:

Classical model organisms have helped greatly in our understanding of cell death but, at the same time, night have constrained it. The use of other, nor-classical model organisms from all biological kingdoms could reveal undetected molecular pathways and better-defined morphological types of cell death. Here we discuss what is known and what might be learned from these alternative model systems.

 

Ohta H, Suzuki T, Ueno M, et al.

 

Extrinsic proteins of photosystem II - An intermediate member of the PsbQ protein family in red algal PSII

EUR J BIOCHEM 270 (20): 4156-4163 OCT 2003

 

Abstract:

The oxygen-evolving photosystem II (PS II) complex of red algae contains four extrinsic proteins of 12 kDa, 20 kDa, 33 kDa and cyt c-550, among which the 20 kDa protein is unique in that it is not found in other organisms. We cloned the gene for the 20-kDa protein from a red alga Cyanidium caldarium. The gene consists of a leader sequence which can be divided into two parts: one for transfer across the plastid envelope and the other for transfer into thylakoid lumen, indicating that the gene is encoded by the nuclear genome. The sequence of the mature 20-kDa protein has low but significant homology with the extrinsic 17-kDa (PsbQ) protein of PS II from green algae Volvox Carteri and Chlamydomonas reinhardtii, as well as the PsbQ protein of higher plants and PsbQ-like protein from cyanobacteria. Cross-reconstitution experiments with combinations of the extrinsic proteins and PS Its from the red alga Cy. caldarium and green alga Ch. reinhardtii showed that the extrinsic 20-kDa protein was functional in place of the green algal 17-kDa protein on binding to the green algal PS II and restoration of oxygen evolution. From these results, we conclude that the 20-kDa protein is the ancestral form of the extrinsic 17-kDa protein in green algal and higher plant PS IIs. This provides an important clue to the evolution of the oxygen-evolving complex from prokaryotic cyanobacteria to eukaryotic higher plants. The gene coding for the extrinsic 20-kDa protein was named psbQ' (prime).

 

Cole DG, Reedy MV

 

Algal morphogenesis: How Volvox turns itself inside-out

CURR BIOL 13 (19): R770-R772 SEP 30 2003

 

Abstract:

During its development, the multicellular green alga Volvox undergoes inversion, in which spherical embryos turn their multicellular sheet completely inside out. A mutant analysis has revealed that a novel kinesin motor protein is essential for completing this process.

 

Voigt J, Frank R

 

14-3-3 proteins are constituents of the insoluble glycoprotein framework of the Chlamydomonas cell wall

PLANT CELL 15 (6): 1399-1413 JUN 2003

 

 

Abstract:

The cell wall of the unicellular green alga Chlamydomonas reinhardtii consists predominantly of Hyp-rich glycoproteins, which also occur in the extracellular matrix of multicellular green algae and higher plants. In addition to the Hyp-rich polypeptides, the insoluble glycoprotein framework of the Chlamydomonas cell wall contains minor amounts of 14-3-3 proteins, as revealed by immunochemical studies and mass spectroscopic analysis of tryptic peptides. Polypeptides immunologically related to the 14-3-3 proteins also were found in the culture medium of Chlamydomonas. The levels of two of these 14-3-3-related polypeptides were decreased in the culture medium of the wall-deficient mutant cw-15. These findings indicate that 14-3-3 proteins are involved in the cross-linking of Hyp-rich glycoproteins in the Chlamydomonas cell wall.

 

 

Michod RE, Nedelcu AM

 

On the reorganization of fitness during evolutionary transitions in individuality

INTEGR COMP BIOL 43 (1): 64-73 FEB 2003 (for pdf click here)

 

Abstract:

The basic problem in an evolutionary transition is to understand how a group of individuals becomes a new kind of individual, possessing the property of heritable variation in fitness at the new level of organization. During an evolutionary transition, for example, from single cells to multicellular organisms, the new higher-level evolutionary unit (multicellular organism) gains its emergent properties by virtue of the interactions among lower-level units (cells). We see the formation of cooperative interactions among lower-level units as a necessary step in evolutionary transitions; only cooperation transfers fitness from lower levels (costs to group members) to higher levels (benefits to the group). As cooperation creates new levels of fitness, it creates the opportunity for conflict between levels as deleterious mutants arise and spread within the group. Fundamental to the emergence of a new higher-level unit is the mediation of conflict among lower-level units in favor of the higher-level unit. The acquisition of heritable variation in fitness at the new level, via conflict mediation, requires the reorganization of the basic components of fitness (survival and reproduction) and life-properties (such as immortality and totipotency) as well as the co-option of lower-level processes for new functions at the higher level. The way in which the conflicts associated with the transition in individuality have been mediated, and fitness and general life-traits have been re-organized, can influence the potential for further evolution (i.e., evolvability) of the newly emerged evolutionary individual. We use the volvocalean green algal group as a model-system to understand evolutionary transitions in individuality and to apply and test the theoretical principles presented above. Lastly, we discuss how the different notions of individuality stem from the basic properties of fitness in a multilevel selection context.

 

 

Kirk DL

 

Seeking the ultimate and proximate causes of Volvox multicellularity and cellular differentiation

INTEGR COMP BIOL 43 (2): 247-253 APR 2003

 

Abstract:

Volvox and its relatives provide an exceptional model for integrative studies of the evolution of multicellularity and cellular differentiation. The volvocine algae range in complexity from unicellular Chlamydomonas through several colonial genera with a single cell type, to multicellular Volvox with its germsoma division of labor. Within the monophyletic family Volvocaceae, several species of Volvox have evolved independently in different lineages, the ultimate cause presumably being the advantage that large size and cellular differentiation provide in competing for limiting resources such as phosphorous. The proximate causes of this type of evolutionary transition are being studied in V carteri. All volvocine algae except Volvox exhibit biphasic development: cells grow during a motile, biflagellate phase, then they lose motility and divide repeatedly during the reproductive phase. In V carteri three kinds of genes transform this ancestral biphasic program into a dichotomous one that generates non-motile reproductive cells and biflagellate somatic cells with no reproductive potential: first the gls genes act in early embryos to cause asymmetric division and production of large-small sister-cell pairs; then lag genes act in the large cells to repress the biflagellate half of the ancestral program, while regA acts in the small cells to repress the reproductive half of the program. Molecular-genetic analysis of these genes is progressing, as will be illustrated with regA, which encodes a transcription factor that acts in somatic cells to repress nuclear genes encoding chloroplast proteins. Repression of chloroplast biogenesis prevents these obligately photoautotrophic cells from growing, and since they cannot grow, they cannot reproduce.

 

Mori T, Kuroiwa H, Higashiyama T, et al.

 

Identification of higher plant GlsA, a putative morphogenesis factor of gametic cells

BIOCHEM BIOPH RES CO 306 (2): 564-569 JUN 27 2003

 

Abstract:

GlsA has been identified in an asexual-reproductive-cell (gonidia)-deficient mutant of Volvox as a chaperone-like protein essential for gonidia production. In this study, we isolated an angiosperm glsA (LlglsA) gene expressed during Lilium longiflorum pollen development. Immunoblot analyses showed that the strong LlGlsA expression occurred in the generative cell and its pattern during pollen development corresponded to that of alpha-tubulin. Morphological analyses succeeded in visualizing the dispersion of the strong LlGlsA signal in developing generative cells. In addition, multiple-immunofluorescence staining of LIGNA and alpha-tubulin revealed that some of the dot-like LlGlsA signals were co-localized with microtubule filaments. From those results, we suggest that angiosperm GlsA functions as a chaperone modifying various structures during male gametic cell formation. (C) 2003 Elsevier Science (USA). All rights reserved.

 

 

Nishii I, Ogihara S, Kirk DL

 

A kinesin, InvA, plays an essential role in Volvox morphogenesis

CELL 113 (6): 743-753 JUN 13 2003

 

Abstract:

In Volvox carted adults, reproductive cells called gonidia are enclosed within a spherical monolayer of biflagellate somatic cells. Embryos must "invert" (turn inside out) to achieve this configuration, however, because at the end of cleavage the gonidia are on the outside and the flagellar ends of all somatic cells point inward. Generation of a bend region adequate to turn the embryo inside out involves a dramatic change in cell shape, plus cell movements. Here, we cloned a gene called invA that is essential for inversion and found that it codes for a kinesin localized in the cytoplasmic bridges that link all cells to their neighbors. In invA null mutants, cells change shape normally, but are unable to move relative to the cytoplasmic bridges. A normal bend region cannot be formed and inversion stops. We conclude that the InvA kinesin provides the motile force that normally drives inversion to completion.

 

 

Bonner JT

 

On the origin of differentiation

J BIOSCIENCES 28 (4): 523-528 JUN 2003

 

 

Abstract:

Following the origin of multicellularity in many groups of primitive organisms there evolved more than one cell type. It has been assumed that this early differentiation is related to size - the larger the organism the more cell types. Here two very different kinds of organisms are considered: the volvocine algae that become multicellular by growth, and the cellular slime moulds that become multicellular by aggregation. In both cases there are species that have only one cell type and others that have two. It has been possible to show that there is a perfect correlation with size: the forms with two cell types are significantly larger-than those with one. Also in both groups there are forms of intermediate size that will vary from one to two cell types depending on the size of the individuals, suggesting a form of quorum sensing. These observations reinforce the view that size plays a critical role in influencing the degree of differentiation.

 

 

Michod RE, Nedelcu AM, Roze D

 

Cooperation and conflict in the evolution of individuality IV. Conflict mediation and evolvability in Volvox carteri

BIOSYSTEMS 69 (2-3): 95-114 MAY 2003 (for pdf click here)

 

Abstract:

The continued well being of evolutionary individuals (units of selection and evolution) depends upon their evolvability, that is their capacity to generate and evolve adaptations at their level of organization, as well as their longer term capacity for diversifying into more complex evolutionary forms. During a transition from a lower- to higher-level individual, such as the transition between unicellular and multicellular organisms, the evolvability of the lower-level (cells) must be restricted, while the evolvability of the new higher-level unit (multicellular organism) must be enhanced. For these reasons, understanding the factors leading to an evolutionary transition should help us to understand the factors underlying the emergence of evolvability of a new evolutionary unit. Cooperation among lower-level units is fundamental to the origin of new functions in the higher-level unit. Cooperation can produce a new more complex evolutionary unit, with the requisite properties of heritable fitness variations, because cooperation trades fitness from a lower-level (the costs of cooperation) to the higher-level (the benefits for the group). For this reason, the evolution of cooperative interactions helps us to understand the origin of new and higher-levels of fitness and organization. As cooperation creates a new level of fitness, it also creates the opportunity for conflict between levels of selection, as deleterious mutants with differing effects at the two levels arise and spread. This conflict can interfere with the evolvability of the higher-level unit, since the lower and higher-levels of selection will often "disagree" on what adaptations are most beneficial to their respective interests. Mediation of this conflict is essential to the emergence of the new evolutionary unit and to its continued evolvability. As an example, we consider the transition from unicellular to multicellular organisms and study the evolution of an early-sequestered germ-line in terms of its role in mediating conflict between the two levels of selection, the cell and the cell group. We apply our theoretical framework to the evolution of germ/soma differentiation in the green algal group Volvocales. In the most complex member of the group, Volvox carteri, the potential conflicts among lower-level cells as to the "right" to reproduce the higher-level individual (i.e. the colony) have been mediated by restricting immortality and totipotency to the germ-line. However, this mediation, and the evolution of an early segregated germ-line, was achieved by suppressing mitotic and differentiation capabilities in all post-embryonic cells. By handicapping the soma in this way, individuality is ensured, but the solution has affected the long-term evolvability of this lineage. We think that although conflict mediation is pivotal to the emergence of individuality at the higher-level, the way in which the mediation is achieved can greatly affect the longer-term evolvability of the lineage. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.

 

 

Laflamme M, Lee RW

 

Mitochondrial genome conformation among CW-group chlorophycean algae

J PHYCOL 39 (1): 213-220 FEB 2003

 

 

Abstract:

Most green algal taxa have circular-mapping mitochondrial genomes, whereas some have linear genome- or subgenomic-sized mitochondrial DNAs (mtDNA). It is not clear, however, if the circular-mapping genomes represent genome-sized circular molecules, if such circular molecules and the linear forms are the predominant in vivo mtDNA structures, or if the linear forms arose only once or multiple times among extant green algal lineages. We therefore examined the DNA components detected with homologous mtDNA probes after pulsed-field gel electrophoresis of total cellular DNA from the chlorophycean basal bodies displaced clockwise(CW)-group taxa Chlamydomonas reinhardtii and Chlamydomonas moewusii. For C. reinhardtii , the 15.8-kb linear mtDNA was the only DNA component detected, and there was no evidence of circular or large linear precursors of this DNA. In the case of C. moewusii , which is known to have a circular-mapping 22.9-kb mitochondrial genome, three DNA components were detected; these appeared to be circular (relaxed and supercoiled) and genome-sized linear DNA molecules, the latter of which likely resulted from random double-strand breaks in the circular forms during DNA isolation. In further studies, DNA from additional CW-group taxa was examined using conventional gel electrophoresis and DNA-filter blot analysis with C. reinhardtii and C. moewusii mtDNA probes. We conclude that all taxa from the "Volvox clade" (sensu Nakayama et al. 1996) of the CW-group have genome- or subgenomic-sized linear mtDNAs as their predominant mtDNA form and that these arose from a genome-sized circular form in an ancestor that existed near the base of this clade.

 

 

Hallmann A

 

Extracellular matrix and sex-inducing pheromone in Volvox

INT REV CYTOL 227: 131-+ 2003

 

 

Schmitt R, Sumper M

 

Developmental biology - How to turn inside out

NATURE 424 (6948): 499-500 JUL 31 2003

 

 

2002

 

 

Desnitski AG

 

Dormant stages of the green flagellate in Volvox in a natural habitat

 

RUSSIAN JURNAL OF DEVELOPMENTAL BIOLOGY 33(2): 107-109; 2002 (for pdf click here)

 

 

Coleman AW

 

Comparison of Eudorina/Pleodorina ITS sequences of isolates from nature with those from experimental hybrids

AM J BOT 89 (9): 1523-1530 SEP 2002

 

Abstract:

Internal transcribed spacer (ITS) regions of nuclear ribosomal repeats were compared among 50 Eudorina and Pleodorina isolates and two Volvox species known to clade with Eudorina species. Of the six major subclades found, four containing Eudorina and Pleodorina illinoisensis isolates, one containing Eudorina and Pleodorina indica, and one containing Volvox gigas and V. powersii, the basal branching order remains uncertain, but the positioning of isolates known to mate was always as nearest neighbors on the terminal branches of the tree. Four hybrid clones from a cross of E. elegans with P. illinoisensis, known from chromosome counts to be products of the failure of meiosis at zygote germination, contain both parental ITS repeat regions, as expected. However, they have in addition both crossover and other variant ITS cistrons among their many repeats of ITS. Such variation is limited to terminal regions of helices, as recognized from knowledge of RNA transcript secondary structure. Proper alignment then utilizes all of the nucleotide positions; the hybrid variants appear in positions intermediate between their parents in the tree. In fact, such variants seem to be hallmarks of recent hybridization events, since they were not found in any of the other 50 isolates.

 

 

Duncan L, Bouckaert K, Yeh F, et al.

 

Kangaroo, a mobile element from Volvox carteri, is a member of a newly recognized third class of retrotransposons

GENETICS 162 (4): 1617-1630 DEC 2002

 

Abstract:

Retrotransposons play an important role in the evolution of genomic structure and function. Here we report on the characterization of a novel retrotransposon called kangaroo front the multicellular green alga, Volvox carteri. kangaroo elements are highly mobile and their expression is developmentally regulated. The), probably integrate via double-stranded, closed-circle DNA intermediates through the action of an encoded recombinase related to the X-site-specific integrase. Phylogenetic analysis indicates that kangaroo elements are closely related to other unorthodox retrotransposons including PAT (from a nematode), DIRS-1 (from Dictyostelium), and DrDIRS1 (from zebrafish). PAT and kangaroo both contain split direct repeat (SDR) termini, and here we show that DIRS-1 and DrDIRS1 elements contain terminal features structurally related to SDRs. Thus, these mobile elements appear to define a third class of retrotransposons (the DIRS1 group) that are unified by common structural features, genes, and integration mechanisms, all of which differ from those of LTR and conventional non-LTR retrotransposons.

 

 

Berthold P, Schmitt R, Mages W

 

An engineered Streptomyces hygroscopicus aph 7" gene mediates dominant resistance against hygromycin B in Chlamydomonas reinhardtii

PROTIST 153 (4): 401-412 DEC 2002

 

Abstract:

We have developed a positively selectable marker for the green alga Chlamydomonas reinhardtii using the Streptomyces hygroscopicus aminoglycoside phosphotransferase gene (aph7"). Its expression is controlled by C. reinhardtii regulatory elements, namely, the beta2-tubulin gene promoter in combination with the first intron and the 3' untranslated region of the small subunit of ribulose bisphosphate carboxylase, rbcS2. C. reinhardtii cell-wall deficient and wild-type strains were transformed at rates up to 5 x 10(-5) with two constructs, pHyg3 and pHyg4 (intron-less). Transformants selected on plates with 10 mug/ml hygromycin B exhibited diverse levels of resistance of up to 200 mug/ml that were stably maintained for at least seven months; they contained two to five copies of the construct integrated in their genomes. Transcription of the chimeric aph7" gene, correct splicing of the rbcS2 intron, and polyadenylation of the transcripts have been verified by sequencing of RT-PCR products. Average co-transformation rates using pHyg3 and a second selectable plasmid were about 11%. This advocates the hygromycin-resistance plasmid, pHyg3, as a new versatile tool for the transformation of a broad range of C. reinhardtii strains without the sustained need for using auxotrophic mutants as recipients.

 

 

Gradmann D, Ehlenbeck S, Hegemann P

 

Modeling light-induced currents in the eye of Chlamydomonas reinhardtii

J MEMBRANE BIOL 189 (2): 93-104 SEP 15 2002

 

Abstract:

Rhodopsin-mediated electrical events in green algae have been recorded in the past from the eyes of numerous micro-algae like Haematococcus pluvialis, Chlamydomonas reinhardtii and Volvox carteri. However, the electrical data gathered by suction-pipette techniques could be interpreted in qualitative terms only. Here we present two models that allow a quantitative analysis of such results: First, an electrical analog circuit for the cell in suction pipette configuration is established. Applying this model to experimental data from unilluminated cells of C. reinhardtii yields a membrane conductance of about 3 Sm-2. Furthermore, an analog circuit allows the determination of the photocurrent fraction that is recorded under experimental conditions. Second, a reaction scheme of a rhodopsin-type photocycle with an early Ca2+ conductance and a later H+ conductance is presented. The combination of both models provides good fits to light-induced currents recorded from C. reinhardtii. Finally, it allowed the calculation of the impact of each model parameter on the time courses of observable photocurrent and of inferred transmembrane voltage. The reduction of the flash-to-peak times at increasing. light intensities are explained by superposition of two kinetically distinct rhodopsins and by assuming that the Ca2+-conducting state decays faster at more positive membrane voltages.

 

 

Saliu JK

 

The diet of Brycinus nurse (Pisces : Characidae) from Asa Reservoir, Ilorin, Nigeria

REV BIOL TROP 50 (1): 239-243 MAR 2002

 

Abstract:

From November 1991 to October 1993, 980 specimens of the characid Brycinus nurse were collected from Asa reservoir to examine its diet. The diet was analyzed using the frequency of occurrence, numerical and gravimetric methods. Two hundred and sixty nine (27.45%) of the stomachs examined were empty. The fish was an omnivore feeding extensively on a wide array of plant and animal food items. These consisted of 9 families, 10 genera and 10 species. The most extensively consumed plant food item was aquatic plant parts which occurred in 63.88% of the stomachs, and accounted for 6.06% by number and 12.10% by weight while the ephemeropteran, Povilla adusta was the most dominant animal food item, occurring in 50.92% of the stomachs, and accounting for 11.98% by number and 11.86% by weight. Conversely, the least consumed plant food item was Volvox occurring in 4.49% of the stomachs and accounting for 0.18% by number and 0.35% by weight, while the fish Barbus sp. was the least consumed animal food item occurring in 0.51% of the stomachs, accounting for 0.03% by number and 1.62% by weight. New food items not previously recorded such as a watermite, Aspatharia sinuata and Barbus callipterus were found in the stomach contents. The nonspecific feeding regime of the fish and its ability to utilize different food items effectively was what accounted for the prominence and wide distribution of the fish in the lake.

 

 

Heitzer M, Hallmann A

 

An extracellular matrix-localized metalloproteinase with an exceptional QEXXH metal binding site prefers copper for catalytic activity

J BIOL CHEM 277 (31): 28280-28286 AUG 2 2002

 

Abstract:

The extracellular matrix (ECM) of the simple multicellular organism Volvox contains many region-specific morphological elements and mediates a variety of developmental and physiological responses by modification of its components. The fact that >95% of the mature organism is ECM makes Volvox suitable as a model system for ECM investigations. VMPs are a family of Volvox genes that are homologous to zinc-dependent matrix metalloproteinases (MMPs). Here we describe the identification and purification of the first VMP protein, VMP3. The 470-kDa VMP3 glycoprotein is localized within the ECM, and its biosynthesis is induced by the sex pheromone. The metal binding motif of VMP3 is QEXXH, not HEXXH as known for 1300 other metalloproteinases. VMP3 shows proteinase activity and is inhibited by EDTA or the MMP inhibitor GM 6001, but in contrast to all known proteinases, VMP3 clearly prefers copper for activity rather than zinc. The exchange from Q to H within the QEXXH motif abolishes its copper preference. The unique properties of VMP3 suggest a novel type of metalloproteinase.

 

 

Nozaki H, Takahara M, Nakazawa A, et al.

 

Evolution of rbcL group IA introns and intron open reading frames within the colonial Volvocales (Chlorophyceae)

MOL PHYLOGENET EVOL 23 (3): 326-338 JUN 2002

 

 

Abstract:

Mobile group I introns sometimes contain an open reading frame (ORE) possibly encoding a site-specific DNA endonuclease. However, previous phylogenetic studies have not clearly deduced the evolutionary roles of the group I intron ORFs. In this paper, we examined the phylogeny of group IA2 introns inserted in the position identical to that of the chloroplast-encoded rbcL coding region (rbcL-462 introns) and their ORFs from 13 strains of five genera (Volvox, Pleodorina, Volvulina, Astrephomene, and Gonium) of the colonial Volvocales (Chlorophyceae) and a related unicellular green alga, Vitreochlamys. The rbcL-462 introns contained an intact or degenerate ORE of various sizes except for the Gonium multicoccum rbcL-462 intron. Partial amino acid sequences of some rbcL-462 intron ORFs exhibited possible homology to the endo/excinuclease amino acid terminal domain. The distribution of the rbcL-462 introns is sporadic in the phylogenetic trees of the colonial Volvocales based on the five chloroplast exon sequences (6021 bp). Phylogenetic analyses of the conserved intron sequences resolved that the G. multicoccum rbcL-462 intron had a phylogenetic position separate from those of other colonial volvocalean rbcL-462 introns, indicating the recent horizontal transmission of the intron in the G. multicoccum lineage. However, the combined data set from conserved intron sequences and ORFs from most of the rbcL-462 introns resolved robust phylogenetic relationships of the introns that were consistent with those of the host organisms. Therefore, most of the extant rbcL-462 introns may have been vertically inherited from the common ancestor of their host organisms, whereas such introns may have been lost in other lineages during evolution of the colonial Volvocales. In addition, apparently higher synonymous substitutions than nonsynonymous substitutions in the rbcL-462 intron ORFs indicated that the ORFs might evolve under functional constraint, which could result in homing of the rbcL-462 intron in cases of spontaneous intron loss. On the other hand, the presence of intact to largely degenerate ORFs of the rbcL-462 introns within the three isolates of Gonium viridistellatum and the rare occurrence of the ORF-lacking rbcL-462 intron suggested that the ORF's might degenerate to result in the spontaneous intron loss during a very short evolutionary time following the loss of the ORF function. Thus, the sporadic distribution of the rbcL-462 introns within the colonial Volvocales can be largely explained by an equilibrium between maintenance of the introns by the intron ORF and spontaneous loss of introns when the introns do not have a functional ORE. (C) 2002 Elsevier Science (USA). All rights reserved.

 

 

Aono N, Shimizu T, Inoue T, et al.

 

Palindromic repetitive elements in the mitochondrial genome of Volvox

FEBS LETT 521 (1-3): 95-99 JUN 19 2002

 

 

Abstract:

Group I introns were found in the cob and cox I genes of Volvox carteri. These introns contain tandem arrays of short palindromic sequences that are related to each other. Inspection of other regions in the mtDNA revealed that similar palindromic repetitive sequences are dispersed in the non-protein coding regions of the mitochondrial genome. Analysis of the group I intron in the cob gene of another member of Volvocaceae, Volvox aureus, has shown that its sequence is highly homologous to its counterpart in V. carteri with the exception of a cluster of palindromic sequences not found in V. carteri. This indicates that the palindromic clusters were inserted into the introns after divergence of the two species, presumably due to frequent insertions of the palindromic elements during evolution of the Volvocaceae. Possible involvement of the palindromic repetitive elements in the molecular evolution of functional RNAs is discussed. (C) 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

 

 

Ender F, Godl K, Wenzl S, et al.

 

Evidence for autocatalytic cross-linking of hydroxyproline-rich glycoproteins during extracellular matrix assembly in volvox

PLANT CELL 14 (5): 1147-1160 MAY 2002

 

Abstract:

The alga Volvox carteri is one of the simplest multicellular organisms, yet it has a surprisingly complex extracellular matrix (ECM), making Volvox suitable as a model system in which to study ECM self-assembly. Here, we analyze the primary structures and post-translational modifications of two main ECM components synthesized in response to sexual induction as well as wounding. These proteins are members of the pherophorin family with as yet unknown properties. They contain polyhydroxyproline spacers as long as 500 and 2750 residues. Even the highly purified proteins retain the capacity to self-assemble and cross-link, producing an insoluble fibrous network in an apparently autocatalytic reaction. This pherophorin-based network is located within the deep zone of the ECM. A molecular genetic search for additional members of the pherophorin family indicates that at least nine different pherophorin species can be expected to serve as precursors for ECM substructures. Therefore, the highly diversified members of the pherophorin family represent region-specific morphological building blocks for ECM assembly and cross-linking.

 

 

Shimizu T, Inoue T, Shiraishi H

 

Cloning and characterization of novel extensin-like cDNAs that are expressed during late somatic cell phase in the green alga Volvox carteri

GENE 284 (1-2): 179-187 FEB 6 2002

 

 

Abstract:

Asexual individuals of the green alga Volvox carteri consist of two cell types, somatic and reproductive cells. The somatic cells are terminally differentiated post-mitotic cells which undergo gradual senescence leading to cell death in every generation. To understand the gene expression programs associated with senescence of somatic cells, we cloned two cDNAs, LSG1 and LSG2, that are preferentially expressed during this late developmental stage. These two cDNAs were deduced to encode Pro-rich motifs characteristic of extensin proteins that are components of the extracellular in matrix. LSG1 also resembled genes encoding plant pathogenesis-related protein 1 (PR-1), while LSG2 showed similarities with genes encoding matrix metalloproteinases, including a gamete lytic enzyme of Chlamydomonas. We also found that S9, one of the late somatic cDNAs previously cloned by Tam and Kirk (Dev. Biol. 145 (1991) 51), was deduced to encode a protein with a composition similar to LSG2. The expression of PR-1 and a matrix-metalloproteinase-encoding gene has been shown to be induced during senescence in higher plants. These results indicate that some of the late somatic genes in V. carteri are related to the senescence-associated genes in higher plants. (C) 2002 Elsevier Science B.V. All rights reserved.

 

 

Miller SM

 

Taming the fierce roller: an "enhanced" understanding of cellular differentiation in Volvox

BIOESSAYS 24 (1): 3-7 JAN 2002

 

Abstract:

Few organisms offer a better opportunity to explore the mechanisms of cellular differentiation, and their origins, than Volvox. Volvox consists of just two cell types, germ and soma, and is the most complex member of a family of green algae that includes unicellular and multicellular relatives. At the heart of the cell-fate determination program of Volvox carted is the regA gene, which encodes a putative transcriptional repressor that prevents somatic cells from expressing reproductive functions. Stark et al.((1)) have dissected the regA gene to determine how its expression is restricted to somatic cells. Their results suggest that regrA expression is controlled by multiple enhancers, the most important of which prevents transcription in reproductive cells. While these findings shed light on Volvox development, they also raise a new set of questions about the mechanisms that control the germ-soma dichotomy in this organism. (C) 2002 John Wiley Sons, Inc.

 

 

Nishii I, Kirk DL

 

A kinesin-like protein encoding gene, invA, is required for the cellular movements that drive inversion of Volvox embryos

MOL BIOL CELL 13: 834 NOV 2002

 

Stark K, Schmitt R

 

Genetic control of germ-soma differentiation in Volvox carteri

PROTIST 153 (2): 99-107 JUN 2002

 

 

2001

 

 

Kirk DL, Nishii I

 

Volvox carteri as a model for studying the genetic and cytological control of morphogenesis

DEV GROWTH DIFFER 43 (6): 621-631 DEC 2001

 

Abstract:

The green alga Volvox carteri has a very simple and regular adult form that arises through a short sequence of well-defined morphogenetic steps. A mature gonidium (asexual reproductive cell) initiates a stereotyped sequence of rapid cleavage divisions that will produce all of the cells found later in an adult. A predictable subset of these divisions are asymmetric and result in production of a small set of germ cells in a precise spatial pattern. Throughout cleavage, all intracellular components are held in predictable spatial relationships by a cytoskeleton of unusually regular structure, while neighboring cells are also held in fixed spatial relationships by an extensive network of cytoplasmic bridges that form as a result of incomplete cytokinesis. As a result of these two orienting mechanisms combined, dividing cells are arranged around the anterior-posterior axis of the embryo with precise rotational symmetry. These relationships are maintained by the cytoplasmic bridge system when the embryo that was inside out at the end of cleavage turns right-side out in the gastrulation-like process of inversion. Inversion is driven by a cytoskeleton-mediated sequence of cell shape changes, cellular movements and coordinated contraction. Then, by the time the cytoplasmic bridges begin to break down shortly after inversion, a preliminary framework of extracellular matrix (ECM) has been formed. The ECM traps the cells and holds them in the rotational relationships that were established during cleavage, and that must be maintained in order for the adult to be able to swim. Transposon tagging is now being used to clone and characterize the genes regulating these morphogenetic processes.

 

 

Sineshchekov OA, Govorunova EG

 

Rhodopsin receptors of phototaxis in green flagellate algae

BIOCHEMISTRY-MOSCOW+ 66 (11): 1300-1310 NOV 2001

 

Abstract:

Green flagellate algae are capable of the active adjustment of their swimming path according to the light direction (phototaxis). This direction is detected by a special photoreceptor apparatus consisting of the photoreceptor membrane and eyespot. Receptor photoexcitation in green flagellates triggers a cascade of rapid electrical events in the cell membrane which plays a crucial role in the signal transduction chain of phototaxis and the photophobic response. The photoreceptor current is the earliest so far detectable process in this cascade. Measurement of the photoreceptor current is at present the most suitable approach to investigation of the photoreceptor pigment in green flagellate algae, since a low receptor concentration in the cell makes application of optical and biochemical methods so far impossible. A set of physiological evidences shows that the phototaxis receptor in green flagellate algae is a unique rhodopsin-type protein. It shares common chromophore properties with retinal proteins from archaea. However, the involvement of photoelectric processes in the signal transduction chain relates it to animal visual rhodopsins. The presence of some enzymatic components of the animal visual cascade in isolated eyespot preparations might also point to this relation. A retinal-binding protein has been identified in such preparations, the amino acid sequence of which shows a certain homology to sequences of animal visual rhodopsins. However, potential function of this protein as the phototaxis receptor has been questioned in recent time.

 

 

Kaiser D

 

Building a multicellular organism

ANNU REV GENET 35: 103-123 2001

 

Abstract:

Multicellular organisms appear to have arisen from unicells numerous times. Multicellular cyanobacteria arose early in the history of life on Earth. Multicellular forms have since arisen independently in each of the kingdoms and several times in some phyla. If the step from unicellular to multicellular life was taken early and frequently, the selective advantage of multicellularity may be large. By comparing the properties of a multicellular organism with those of its putative unicellular ancestor, it may be possible to identify the selective force(s). The independent instances of multicellularity reviewed indicate that advantages in feeding and in dispersion are common. The capacity for signaling between cells accompanies the evolution of multicellularity with cell differentiation.

 

 

Fuhrmann M, Stahlberg A, Govorunova E, et al.

 

The abundant retinal protein of the Chlamydomonas eye is not the photoreceptor for phototaxis and photophobic responses

J CELL SCI 114 (21): 3857-3863 NOV 2001

 

Abstract:

The chlamyopsin gene (cop) encodes the most abundant eyespot protein in the unicellular green alga Chlamydomonas reinhardtii. This opsin-related protein (COP) binds retinal and was thought to be the photoreceptor controlling photomovement responses via a set of photoreceptor currents. Unfortunately, opsin-deficient mutants are not available and targeted disruption of non-selectable nuclear genes is not yet possible in any green alga. Here we show that intron-containing gene fragments directly linked to their intron-less antisense counterpart provide efficient post-transcriptional gene silencing (PTGS) in C. reinhardtii, thus allowing an efficient reduction of a specific gene product in a green alga. In opsin-deprived transformants, Hash-induced photoreceptor currents (PC) are left unchanged. Moreover, photophobic responses as studied by motion analysis and phototaxis tested in a light-scattering assay were indistinguishable from the responses of untransformed wild-type cells. We conclude that phototaxis and photophobic responses in C. reinhardtii are triggered by an as yet unidentified rhodopsin species.

 

 

Kirk DL

 

Germ-soma differentiation in Volvox

DEV BIOL 238 (2): 213-223 OCT 15 2001

 

Abstract:

Volvox carteri is a spherical green alga with a predominantly asexual mode of reproduction and a complete germ-soma division of labor. Its somatic cells are specialized for motility, incapable of dividing, and pro-rammed to die when only a few days old, whereas its gonidia (asexual reproductive cells) are nonmotile, specialized for growth and reproduction, and potentially immortal. When a gonidium is less than 2 days old it divides to produce a juvenile spheroid containing all of the somatic cells and gonidia that will be present in an adult of the next generation. The first visible step in germ-soma differentiation is a set of asymmetric cleavage divisions in the embryo that set apart small somatic initials from their large gonidial-initial sister cells. Three types of genes have been found to play key roles in germ-soma specification. First a set of gls genes act in the embryos to shift cell-division planes, resulting in the asymmetric divisions that set apart the large-small sister-cell pairs. Then a set of lag genes act in the large cells to prevent somatic differentiation, while the regA gene acts in the small cells to prevent reproductive development. An inducible transposon was used to tag and recover some of these and other developmentally important genes. The glsA gene encodes a chaperone-like protein that, like another chaperone that is one of its putative binding partners, is associated with the cell division apparatus, although how this leads to asymmetric division remains to be elucidated. The regA gene encodes a somatic-cell-specific nuclear protein that appears to function by repressing genes required for chloroplast biogenesis, thereby preventing somatic cells from growing enough to reproduce. Somatic-cell-specific expression of regA is controlled by three intronic enhancers. (C) 2001 Academic Press.

 

Shimizu T, Inoue T, Shiraishi H

 

A senescence-associated S-like RNase in the multicellular green alga Volvox carteri

GENE 274 (1-2): 227-235 AUG 22 2001

 

Abstract:

Asexual individuals of the green alga Volvox carteri consist of only two cell types. somatic and reproductive cells. The somatic cells are terminally differentiated, post-mitotic cells which undergo gradual senescence leading to cell death in every generation. To elucidate the self-degrading process of macromolecules associated with senescence, we attempted to clone an RNase whose mRNA accumulation is increased during senescence. The corresponding cDNA clone VRN1, encoding an S-like RNase of V. carteri, is the first T-2/S-like RNase to be cloned from green algae. Semi-quantitative RT-PCR analysis revealed that a relative amount of VPN1 mRNA is more than three-fold higher in the senescent somatic cells than in young somatic cells when the mRNA of ribosomal protein S18 is used as an internal standard. VRN1 mRNA is not induced by phosphate starvation, indicating that its accumulation during senescence is not due to a self-induced defect in utilizing phosphates. Similar regulation has been reported for RNS3, which encodes the S-like RNase that is induced in senescent leaves of Arabidopsis thaliana. These observations imply that VRN1 may promote RNA degradation during senescence of somatic cells in V. carteri, and that its regulation has similarity with that of certain senescence-associated RNases in higher plants. (C) 2001 Elsevier Science B.V. All rights reserved.

 

 

Hallmann A, Amon P, Godl K, et al.

 

Transcriptional activation by the sexual pheromone and wounding: a new gene family from Volvox encoding modular proteins with (hydroxy)proline-rich and metalloproteinase homology domains

PLANT J 26 (6): 583-593 JUN 2001

 

Abstract:

The green alga Volvox represents the simplest kind of multicellular organism: it is composed of only two cell types, somatic and reproductive, making it suitable as a model system. The sexual development of males and females of Volvox carteri is triggered by a sex-inducing pheromone at a concentration of < 10(-16) M. Early biochemical responses to the pheromone involve structural modifications within the extracellular matrix (ECM). By differential screenings of cDNA libraries made from mRNAs of pheromone-treated Volvox, four novel genes were identified that encode four closely related Volvox metalloproteinases that we use to define a new protein family, the VMPs. The existence of several features common to matrix glycoproteins, such as signal peptides, a (hydroxy)proline content of 12-25%, and Ser(Pro)(2-4) repeats, suggest an extracellular localization of the VMPs within the ECM. Synthesis of VMP cDNAs is triggered not only by the sex-inducing pheromone, but also by wounding, and is restricted to the somatic cell type. Sequence comparisons suggest that the VMPs are members of the MB clan of zinc-dependent matrix metalloproteinases, although the putative zinc binding site of all VMPs is QEXXHXXGXXH rather than HEXXHXXGXXH. The presence of glutamine instead of histidine in the zinc binding motif suggests a novel family, or even clan, of peptidases. Like the matrixin family of human collagenases, Volvox VMPs exhibit a modular structure: they possess a metalloproteinase homology domain and a (hydroxy)proline-rich domain, and one of them, VMP4, also has two additional domains. Metalloproteinases seem to be crucial for biochemical modifications of the ECM during development or after wounding in the lower eukaryote Volvox with only two cell types, just as in higher organisms.

 

 

Kaczanowski S, Jerzmanowski A

 

Evolutionary correlation between linker histones and microtubular structures

J MOL EVOL 53 (1): 19-30 JUL 2001

 

Abstract:

Histones of the H1 group (linker histones) are abundant components of chromatin in eukaryotes, occurring on average at one molecule per nucleosome. The recent reports on the lack of a clear phenotypic effect of knock-out mutations as well as overexpression of histone H1 genes in different organisms have seriously undermined the long-held view that linker histones are essential for the basic functions of eukaryotic cells. In an attempt to resolve the paradox of an abundant conserved protein without a clear function, we re-examined the molecular and phylogenetic data on linker histones to see if they could reveal any correlation between the features of H1 and the functional or morphological characteristics of cells or organisms. Because of an earlier demonstration that in sea urchin the chromatin-type histone HI is also found in the flagellar microtubules (Multigner et al. 1992), we focused on the correlation between the features of H1 and those of microtubular structures. A phylogenetic tree based on multiple alignment of over 100 available H1 sequences suggests that the first divergence of the globular domain of H1 (GH1) resulted in branching into separate types characteristic for plants/Dictyostelium and for animals/ascomycetes, respectively. The GH1s of these two types differ by a short region (usually 5 amino acids) placed at a specific location within the C-terminal wing subdomain of GH1. Evolutionary analysis of the diversification of H1 mRNA into cell-cycle-dependent (polyA(-)) and independent (polyA(+)) forms showed a mosaic occurrence of these two forms in plants and animals, despite the fact that the H1 proteins of plants and animals belong to two well-distinguished groups. However, among organisms from both animal and plant kingdom, only those with H1 mRNA of a polyA- type have flagellated gametes. This correlation as well as the demonstration that in Volvox carteri the accumulation of polyA- mRNA of H1 occurs concurrently with the production of new flagella (Lindauer et al. 1993), suggests a direct link between polyA- phenotype of histone H1 mRNA and flagello-genesis.

 

 

Stark K, Kirk DL, Schmitt R

 

Two enhancers and one silencer located in the introns of regA control somatic cell differentiation in Volvox carteri

GENE DEV 15 (11): 1449-1460 JUN 1 2001

 

Abstract:

The regA gene plays a central role in germ-soma differentiation of Volvox carteri by suppressing all reproductive functions in somatic cells. Here we show that the minimal promoter of regA consists of only 42 bp immediately upstream of the transcription start site, and that it contains no discernible regulatory elements. However, introns 3 and 5 are both required for regA expression in somatic cells, and intron 7 is essential for silencing regA in gonidia (asexual reproductive cells). A regA gene lacking intron 7 rescues the normal phenotype of mutant somatic cells, but also results in gonidia that reproduce only weakly and soon die out. The same phenotype is observed when a regA gene containing intron 7 is placed under control of a constitutive promoter, suggesting that the silencing activity of intron 7 is promoter specific. Intron 7 is unusual in that it contains a potential ORE that is in frame with exons 7 and 8, and some transcripts are produced in which intron 7 is retained. However, a regulatory role for the intron 7 translation product can be ruled out, because a construct in which intron 7 must be translated, and one in which it cannot be translated, both result in wild-type development of both cell types. Furthermore, intron 7 is unable to act in trans to silence regA, but is able to exert its normal effect when placed in a different location within the gene. Therefore, it appears that intron 7 functions in gonidia as a classical cell-type-specific and promoter-specific enhancer, of the inhibitory type that is often referred to as a silencer.

 

 

Babinger P, Kobl I, Mages W, et al.

 

A link between DNA methylation and epigenetic silencing in transgenic Volvox carteri

NUCLEIC ACIDS RES 29 (6): 1261-1271 MAR 15 2001

 

Abstract:

Epigenetic silencing of foreign genes introduced into plants poses an unsolved problem for transgenic technology. Here we have used the simple multicellular green alga Volvox carteri as a model to analyse the relation of DNA methylation to transgenic silencing. Volvox DNA contains on average 1.1% Ei-methylcytosine and 0.3% N6-methyladenine, as revealed by electrospray mass spectrometry and phosphoimaging of chromatographically separated P-32-labelled nucleotides. In two nuclear transformants of V.carteri, produced in 1993 by biolistic bombardment with a foreign arylsulphatase gene (C-ars), the transgene is still expressed in one (Hill 181), but not in the other (Hill 183), after an estimated 500-1000 generations. Each transformant clone contains multiple intact copies of C-ars, most of them integrated into the genome as tandem repeats. When the bisulphite genomic sequencing protocol was applied to examine two select regions of transgenic C-ars, we found that the inactivated copies (Hill 183) exhibited a high-level methylation (40%) of CpG dinucleotides, whereas the active copies (Hill 181) displayed low-level (7%) CpG methylation. These are average values from 40 PCR clones sequenced from each DNA strand in the two portions of C-ars. The observed correlation of CpG methylation and transgene inactivation in a green alga will be discussed in the light of transcriptional silencing.

 

 

Ferris PJ, Woessner JP, Waffenschmidt S, et al.

 

Glycosylated polyproline II rods with kinks as a structural motif in plant hydroxyproline-rich glycoproteins

BIOCHEMISTRY-US 40 (9): 2978-2987 MAR 6 2001

 

Abstract:

Hydroxyproline-rich glycoproteins (HRGPs) are the major proteinaceous components of higher plant walls and the predominant components of the cell wall of the green alga Chlamydomonas reinhardtii. The GPI protein, an HRGP of the C. reinhardtii wall, is shown to adopt a polyproline II helical configuration and to carry a complex array of arabinogalactoside residues, many branched, which are necessary to stabilize the helical conformation. The deduced GP1 amino acid sequence displays two Ser-Pro-rich domains, one with a repeating (SP), motif and the other with a repeating (PPSPX)(x) motif. A second cloned gene a2 also carries the PPSPX repeat, defining a novel gene family in this lineage. The SP-repeat domains of GP1 form a 100-nm shaft with a flexible kink 28 nm from the head. The gp1 gene encodes a PPPPPRPPFPANTPM sequence at the calculated kink position, generating the proposal that this insert interrupts the PPII helix, with the resultant kink exposing amino acids necessary for GP1 to bind to partner molecules. It is proposed that similar kinks in the higher plant HRGPs called extensins may play a comparable role in wall assembly.

 

 

Kirk DL

 

Seeking the ultimate and proximate causes of Volvox multicellularity

AM ZOOL 41 (6): 1493-1493 DEC 2001

 

 

Nishii I, Kirk DL

 

The invA gene of Volvox encodes a novel kinesin that is required for inversion of the embryo.

DEV BIOL 235 (1): 115 JUL 1 2001

 

 

2000

 

 

Desnitski AG

 

Development and reproduction of two species of the genus Volvox in a shallow temporary pool

 

PROTISTOLOGY 1(4): 195-198; 2000 (for pdf click here)

 

 

Kirk DL

 

Volvox as a model system for studying the ontogeny and phylogeny of multicellularity and cellular differentiation

J PLANT GROWTH REGUL 19 (3): 265-274 SEP 2000

 

Abstract:

Volvox carteri, a spherical alga with a complete division of labor between approximately 2000 biflagellate somatic cells and 16 asexual reproductive cells called gonidia, provides a very attractive system for analyzing how a molecular-genetic program for cell-autonomous cellular differentiation may be encoded within a genome. Then, when considered in combination with a group of closely related "volvocine algae" that includes unicellular Chlamydomonas plus a series of colonial forms of increasing cell number and complexity, it also provides an attractive model system for analyzing how such a program for multicellularity and cytodifferentiation may have evolved. It is proposed that the following were some of the key steps in this evolutionary pathway: (1) The Chlamydomonas cell wall was transformed into an extracellular matrix (ECM) that joined sister cells into a colonial unit. (2) Larger organisms with more abundant ECM were favored because of the role the ECM plays in storing limiting nutrients. (3) In the V. carteri lineage the ancestral biphasic "first biflagellate and then reproductive" pathway of development bt came converted to a dichotomous pathway by introduction of two kinds of cell-type-specific negative regulators: one that blocked growth and reproduction in presumptive somatic cells and one that blocked somatic development in presumptive gonidia. Progress has been made in cloning and characterizing genes that are involved in setting apart the two cell lineages of V. carteri and in subsequently controlling their dichotomous differentiation. The strengths and weaknesses of V. carteri and its relatives as a model system for studying the evolution of multicellularity are discussed.

 

 

Hallmann A, Kirk DL

 

The developmentally regulated ECM glycoprotein ISG plays an essential role in organizing the ECM and orienting the cells of Volvox

J CELL SCI 113 (24): 4605-4617 DEC 2000

 

Abstract:

Volvox is one of the simplest multicellular organisms with only two cell types, yet it has a surprisingly complex extracellular matrix (ECM) containing many region-specific morphological components, making Volvox suitable as a model system for ECM investigations. ECM deposition begins shortly after inversion, which is the process by which the embryo turns itself right-side-out at the end of embryogenesis. It was previously shown that the gene encoding an ECM glycoprotein called ISG is transcribed very transiently during inversion. Here we show that the developmentally controlled ISG accumulates at the bases of the flagella right after inversion, before any morphologically recognizable ECM structures have yet developed. Later, ISG is abundant in the 'flagellar hillocks' that encircle the basal ends of all flagella, and in the adjacent 'boundary zone' that delimits the spheroid. Transgenic Volvox were generated which express a truncated form of ISG, These transgenics exhibit a severely disorganized ECM within which the cells are embedded in a highly chaotic manner that precludes motility, A synthetic version of the C-terminal decapeptide of ISG has a similar disorganizing effect, but only when it is applied during or shortly after inversion. We postulate that ISG plays a critical role in morphogenesis and acts as a key organizer of ECM architecture; at the very beginning of ECM formation ISG establishes an essential initial framework that both holds the somatic cells in an adaptive orientation and acts as the scaffold upon which the rest of the ECM can be properly assembled, assuring that somatic cells of post-inversion spheroids are held in orientations and locations that makes adaptive swimming behavior possible.

 

 

Goodwin PH, Li J, Jin SM

 

Evidence for sulfate derepression of an arylsulfatase gene of Colletotrichum gloeosporioides f. sp malvae during infection of round-leaved mallow, Malva pusilla

PHYSIOL MOL PLANT P 57 (4): 169-176 OCT 2000

 

 

Abstract:

An arylsulfatase gene, cgars, was cloned from Colletotrichum gloeosporioides f. sp. malvae (Cgm), a hemibiotrophic plant pathogenic fungus that causes anthlacnose disease of round-leaved mallow (Malva pusilla). The clone of cgars showed high amino acid sequence identity to ass-1(+), an arylsulfatase gene of Neurospora crassa. Arylsulfatase genes have been shown to be good reporter genes for detecting available sulfur levels in a variety of microorganisms. Expression of cgars was determined by relative RT-PCR, in which gars expression levels were compared to those of actA, a constitutively expressed actin gene of Cgm, following coamplification. In culture, expression of gars was found to be repressed by methionine as has been demonstrated for ars-1(+). In host leaf tissue, cgars expression was relatively higher than actA during penetration, similar to actA during biotrophic growth and then progressively lower than actA during necrotrophic growth. These results show that the availability of host sulfur differs depending upon the stage of infection. (C) 2000 Academic Press.

 

 

Nozaki H, Misawa K, Kajita T, et al.

 

Origin and evolution of the colonial Volvocales (Chlorophyceae) as inferred from multiple, chloroplast gene sequences

MOL PHYLOGENET EVOL 17 (2): 256-268 NOV 2000

 

Abstract:

A combined data set of DNA sequences (6021 bp) from five protein-coding genes of the chloroplast genome (rbcL, atpB, psaA, psaB, and psbC genes) were analyzed for 42 strains representing 30 species of the colonial Volvocales (Volvox and its relatives) and 5 related species of green algae to deduce robust phylogenetic relationships within the colonial green flagellates. The 4-celled family Tetrabaenaceae was robustly resolved as the most basal group within the colonial Volvocales. The sequence data also suggested that all five volvocacean genera with 32 or more cells in a vegetative colony (all four of the anisogamous/oogamous genera, Eudorina, Platydorina, Pleodorina, and Volvox, plus the isogamous genus Yamagishiella) constituted a large monophyletic group, in which 2 Pleodorina species were positioned distally to 3 species of Volvox. Therefore, most of the evolution of the colonial Volvocales appears to constitute a gradual progression in colonial complexity and in types of sexual reproduction, as in the traditional volvocine lineage hypothesis, although reverse evolution must be considered for the origin of certain species of Pleodorina. Data presented here also provide robust support for a monophyletic family Goniaceae consisting of two genera: Gonium and Astrephomene. (C) 2000 Academic Press.

 

 

Sekimoto H

 

Intercellular communication during sexual reproduction of Closterium (Conjugatophyceae)

J PLANT RES 113 (1111): 343-352 SEP 2000

 

Abstract:

Processes of intercellular communication during sexual reproduction of conjugating green algae Closterium were reviewed. In the case of Closterium peracerosum-strigosum-littorale complex, two sex-specific pheromones and their receptors were involved in sexual reproduction. These pheromones were glycoproteins and the expression of corresponding genes was critically regulated by the sex and environmental conditions. In the case of Closterium ehrenbergii, chemotactic and sexual cell division-inducing activities for mating-type plus cells were detected and characterized. Although many processes remain to be elucidated, the present results will be helpful for understanding not only the mode of sexual reproduction in Closterium but also the variety of intercellular communication in the plant kingdom especially during sexual reproduction.

 

 

Kerszberg M

 

The survival of slow reproducers

J THEOR BIOL 206 (1): 81-89 SEP 7 2000

 

Abstract:

Multicellularity, and the attendant segregation of the germ line, entails the loss of reproductive capacity by the soma: in Volvox carteri, less than 1 cell in 100 contributes to the next generation. However, compensatory advantages are unlikely to be very large (Koufopanou & Bell, 1993. Proc. R. Soc. Lond. (B) 254, 107-113). Somewhat similarly, sex implies the generation of males, hence a dramatic reproductive slowdown (Barton & Charlesworth, 1998. Science 281, 1986-1990); yet, a compensating (two-fold) advantage of sex has not been found. Here, I try to evaluate the actual cost of maintaining slow reproductive cycles, namely cycles that necessitate the production of "dead end" units such as somatic cells or males. In a quantitative model for the competition of individuals with different, heritable reproductive rates, this cost turns out to be unexpectedly small, and may even sometimes become irrelevant. The bases for this are made fairly clear: thus, when all enjoy high fecundity (e.g. a long reproductive life) the handicap of a slower reproduction vanishes; alternatively, a slight separation of ecological niches may be sufficient for survival of slower but otherwise unchanged reproducers; and finally, inherent to slow reproduction is a low rate of destabilizing genetic change. These facts are largely independent of the formal model details, and are supported by direct computer simulations. They give a quantitative basis for analysing the evolution and prevalence of slow life cycles. The implications of these findings for the evolution of multicellularity are briefly discussed. (C) 2000 Academic Press.

 

 

Matveev V, Matveeva L, Jones GJ

 

Relative impacts of Daphnia grazing and direct stimulation by fish on phytoplankton abundance in mesocosm communities

FRESHWATER BIOL 44 (3): 375-385 JUL 2000

 

Abstract:

1. Planktivorous fish were hypothesised to influence the abundance of algal biomass in lakes by changing zooplankton grazing, affecting zooplankton nutrient recycling and by direct recycling of nutrients to phytoplankton. The relative roles of direct fish effects vs. zooplankton grazing were tested in mesocosm experiments by adding to natural communities large grazing zooplankton (Daphnia carinata) and small planktivorous fish (mosquitofish or juveniles of Australian golden perch).

 

2. The addition of Daphnia to natural communities reduced the numbers of all phytoplankton less than 30 mu m in size, but did not affect total biomass of phytoplankton as large Volvox colonies predominated.

 

3. The addition of Daphnia also reduced the abundance of some small (Moina, Bosmina, Keratella) and large (adult Boeckella) zooplankton, suggesting competitive interactions within zooplankton.

 

4. The addition of mosquitofish to communities containing Daphnia further reduced the abundance of some small zooplankton (Moina, Keratella), but increased the numbers of Daphnia and adult Boeckella. In spite of the likely increase in grazing due to Daphnia, the abundance of total phytoplankton and dominant alga Volvox did not decline in the presence of mosquitofish but was maintained at a significantly higher level than in control.

 

5. The addition of juveniles of golden perch to communities containing Daphnia reduced the abundance of small zooplankton (Moina), increased the abundance of large zooplankton (adult Boeckella) but had no significant effect on Daphnia and total phytoplankton abundance.

 

6. The results of the present study suggest that some planktivorous fish can promote the growth of phytoplankton in a direct way, probably by recycling nutrients, and even in the presence of large grazers. However, the manifestation of the direct effect of fish can vary with fish species.

 

Suzuki L, Woessner JP, Uchida H, et al.

 

Zygote-specific protein with hydroxyproline-rich glycoprotein domains and lectin-like domains involved in the assembly of the cell wall of Chlamydomonas reinhardtii (Chlorophyta)

J PHYCOL 36 (3): 571-583 JUN 2000

 

 

Abstract:

The cell wall of Chlamydomonas reinhardtii zygotes, which forms rapidly after the fusion of wall-free gametes, provides a tractable system for studying the properties and assembly of hydroxyproline-rich glycoproteins, the major proteinaceous components of green algal and plant cell walls. We report the cloning of the zsp2 gene and the analysis of its ZSP-2 product, a 58.9 kDa poly-peptide that is synthesized exclusively by zygotes, The protein contains two (SP), repeats, establishing it as a member of the cell wall hydroxyproline-rich glycoproteins family. It also contains a 4-fold iteration of an amino acid sequence centered around cysteine residues, a configuration found in both plant and animal lectins, Furthermore, we report four observations on pellicle composition and production, First, cell-free preparations of the pellicle matrix are rich in hydroxyproline, arabinose, and galactose and contain bundles of very long fibrils, Second, glutathione blocks pellicle formation and results in the accumulation of long fibrils in the growth medium. Third, antibody to ZSP-8 also blocks pellicle formation, Fourth, ZSP-2 immunolocalizes to the boundary between the outer layers of the wall proper and the pellicle matrix. These observations are consistent with the possibility that the Cys-rich (glutathione-sensitive) lectin-like domains of ZSP-2 may bind to sugar residues on the long fibrils and anchor

 

 

Sumper M, Nink J, Wenzl S

 

Self-assembly and cross-linking of Volvox extracellular matrix glycoproteins are specifically inhibited by Ellman's reagent

EUR J BIOCHEM 267 (8): 2334-2339 APR 2000

 

Abstract:

A major impediment to the biochemical characterization of extracellular matrices from algae (as well as higher plants) is the extensive covalent cross-linking that exists in the matrix, rendering most components insoluble and resistant to conventional extraction procedures. In the multicellular green alga Volvox, biogenesis of the extracellular matrix (ECM) is initiated immediately after the process of embryonic inversion. At this stage of development, the sulfhydryl reagent 5,5'-dithio-bis(2-nitrobenzoic acid), known as Ellman's reagent, interferes in a highly specific manner with ECM biogenesis. Treated post-inversion embryos are no longer able to assemble an intact ECM and consequently dissociate into a suspension of single cells. Dissociated cells remain viable and continue to secrete ECM proteins into the growth medium, as documented by the identification of several members of the pherophorin family. Cross-linked ECM polymers such as sulfated surface glycoprotein 185 remain in a soluble state. Thus, treatment with Ellman's reagent opens a simple approach for the isolation and characterization of otherwise inaccessible monomeric precursors.

 

 

Wittstock U, Fischer M, Svendsen I, et al.

 

Cloning and characterization of two, cDNAs encoding sulfatases in the Roman snail, Helix pomatia

IUBMB LIFE 49 (1): 71-76 JAN 2000

 

Abstract:

The sulfatase from the snail Helix pomatia is widely used for analytical applications. We have investigated the content of sulfatases in H, pomatia, using a biochemical and a molecular approach. A 112-kDa protein from the intestinal juice of H. pomatia comigrated with sulfatase activity when chromatographed on Sephacryl S300 and concanavalin A-Sepharose. The N-terminal amino acid sequence of the protein was similar to one of three sulfatase motifs defined by sequence alignment of known sulfatases, Degenerate primers designed from the motifs and the N-terminal amino acid sequence obtained were used to generate PCR fragments and to isolate both a full-length and a 3'-truncated cDNA encoding H, pomatia sulfatases, designated SULF1 and SULF2, SULF1 consists of 503 amino acids and shows 53-55% identity to the mammalian arylsulfatase B, The amino acid sequence deduced from the 878-bp SULF2 cDNA fragment is 55% identical with SULF1, Both SULF1 and SULF2 contain the cysteine residue conserved in the active site of many sulfatases, which is known to be posttranslationally modified into formylglycine in eukaryotic sulfatases, However, the SULF1 and SULF2 cDNAs do not code for the protein purified. This indicates the presence of at least three sulfatase genes in H. pomatia.

 

 

Kirk DL, Miller SM

 

Embryonic polarity, asymmetric division,and cell fate determination in Volvox.

DEV BIOL 222 (1): 24 JUN 1 2000

 

1999

 

 

Meissner M, Stark K, Cresnar B, et al.

 

Volvox germline-specific genes that are putative targets of RegA repression encode chloroplast proteins

CURR GENET 36 (6): 363-370 DEC 1999

 

Abstract:

In Volvox carteri, regA acts as a master gene to suppress all germ cell functions in somatic cells. Its product, RegA, has features of a transcriptional repressor. Here we report cDNA sequences representing 15 nuclear genes with properties expected of RegA targets: they are expressed strongly in germ cells and in regA(-), but not regA(+), somatic cells. Two of them encode polypeptides with no recognizable features, but ten (like three previously sequenced ones) encode chloroplast proteins of known function, and the remaining three encode putative chloroplast proteins of unknown function. This suggests that RegA blocks reproductive development in somatic cells by preventing chloroplast biogenesis, thereby making it impossible for the cells to grow enough to reproduce

 

 

Ender F, Hallmann A, Amon P, et al.

 

Response to the sexual pheromone and wounding in the green alga Volvox: Induction of an extracellular glycoprotein consisting almost exclusively of hydroxyproline

J BIOL CHEM 274 (49): 35023-35028 DEC 3 1999

 

Abstract:

The extracellular matrix (ECM) of Volvox is modified during development or in response to external stimuli, like the sex-inducing pheromone. It has recently been demonstrated that a number of genes triggered by the sex-inducing pheromone are also inducible by wounding. By differential screening of a cDNA library, a novel gene was identified that is transcribed in response to the pheromone. Its gene product was characterized as an ECM glycoprotein with a striking feature: it exhibits a hydroxyproline content of 68% and therefore is an extreme member of the family of hydroxyproline-rich glycoproteins (HRGPs), HRGPs are known as constituents of higher plant ECMs and seem to function as structural barriers in defense responses. The Volvox HRGP is also found to be inducible by wounding. This indicates that the wound response scenarios of higher plants and multicellular green algae may be evolutionary related.

 

 

Kirk DL

 

Evolution of multicellularity in the volvocine algae

CURR OPIN PLANT BIOL 2 (6): 496-501 DEC 1999

 

Abstract:

Recent studies reveal that relationships among the volvocine algae are more complex than was previously believed. Nevertheless, this group still appears to provide an unrivaled opportunity to analyze an evolutionary pathway leading from unicellularity (Chlamydomonas) to multicellularity with division of labor (volvox). Significant progress in this regard was made in the past year when two genes playing key roles in volvox cellular differentiation were cloned, and clues were uncovered regarding their mechanisms of action.

 

 

Coleman AW

 

Phylogenetic analysis of "Volvocacae" for comparative genetic studies

P NATL ACAD SCI USA 96 (24): 13892-13897 NOV 23 1999

 

Abstract:

Sequence analysis based on multiple isolates representing essentially all genera and species of the classic family Volvocaeae has clarified their phylogenetic relationships. Cloned internal transcribed spacer sequences (ITS-1. and ITS-2, flanking the 5.8S gene of the nuclear ribosomal gene cistrons) were aligned, guided by ITS transcript secondary structural features, and subjected to parsimony and neighbor joining distance analysis. Results confirm the notion of a single common ancestor, and Chlamydomonas reinharditii alone among all sequenced green unicells is most similar. interbreeding isolates were nearest neighbors on the evolutionary tree in all cases. Some taxa, at whatever level, prove to be clades by sequence comparisons, but others provide striking exceptions. The morphological species Pandorina morum, known to be widespread and diverse in mating pairs, was found to encompass all of the isolates of the four species of Volvulina. Platydorina appears to have originated early and not to fall within the genus Eudorina, with which it can sometimes be confused by morphology. The four species of Pleodorina appear variously associated with Eudorina examples. Although the species of Volvox are each clades, the genus Volvox is not The conclusions confirm and extend prior, more limited, studies on nuclear SSU and LSU rDNA genes and plastid-encoded rbcL and atpB. The phylogenetic tree suggests which classical taxonomic characters are most misleading and provides a framework for molecular studies of the cell cycle-related and other alterations that have engendered diversity in both vegetative and sexual colony patterns in this classical family.

 

 

Funke RP, Kovar JL, Logsdon JM, et al.

 

Nucleus-encoded, plastid-targeted acetolactate synthase genes in two closely related chlorophytes, Chlamydomonas reinhardtii and Volvox carteri: phylogenetic origins and recent insertion of introns

MOL GEN GENET 262 (1): 12-21 AUG 1999

 

Abstract:

Acetolactate synthase (ALS catalyzes the first committed step in the synthesis of branched-chain amino acids. In green plants and fungi, ALS is encoded by a nuclear gene whose product is targeted to plastids (in plants) or to mitochondria tin fungi). In red algae, the gene is plastid-encoded. We have determined the complete sequence of nucleus-encoded ALS genes from the green algae Chlamydomonas reinhardtii and Volvox carteri. Phylogenetic analyses of the ALS gene family indicate that the ALS genes of green algae and plants are closely related, sharing a recent common ancestor. Furthermore, although these genes are clearly of eubacterial origin, a relationship to the ALS genes of red algae and cyanobacteria (endosymbiotic precursors of plastids) is only weakly indicated. The algal ALS genes are distinguished from their homologs in higher plants by the fact that they are interrupted by numerous spliceosomal introns; plant ALS genes completely lack introns. The restricted phylogenetic distribution of these introns suggests that they were inserted recently, after the divergence of these green algae from plants. Two introns in the Volvox ALS gene, not found in the Chlamydomonas gene, are positioned precisely at sites which resemble "proto-splice" sequences in the Chlamydomonas gene.

 

 

Kobayashi K, Koyanagi R, Matsumoto M, et al.

 

Switching from asexual to sexual reproduction in the planarian Dugesia ryukyuensis: Bioassay system and basic description of sexualizing process

ZOOL SCI 16 (2): 291-298 APR 1999

 

 

Abstract:

An assay system has been established for the sexual induction in the OH strain, an exclusively fissiparous (asexual) strain, of Dugesia ryukyuensis by feeding them with sexually matured worms of Bdellocephala brunnea, an exclusively oviparous (sexual) species. In this assay system, asexual worms gradually differentiated sexual organs, namely the ovary, testis, genital pore and yolk gland in this order, and eventually mated and laid cocoons filled with fertilized eggs. Although the OH strain worms were believed not to have any sexual organs, a pair of undeveloped ovaries with a few oogonia were detected by an intensive histological search. Along with the progression of sexualization, five distinct stages were histologically recognized: In the first stage, the ovaries became larger enough to be externally apparent; oocytes appeared first at stage 2; the primordial testes emerged at stage 3; a genital pore opened, yolk gland primordia developed and spermatocytes appeared at stage 4; and finally at stage 5 matured spermatozoa and yolk glands were formed. Worms in stages 1 and 2 but not in later stages returned asexual if feeding on B, brunnea was interrupted. Furthermore, when the worms at stage 3 onwards were cut posterior to the ovaries, all the tail regenerants developed eventually into fully sexualized worms. Taking these results in account, we have concluded that the process of sexualization has a point-of-no-return between stages 2 and 3. It is likely also that the testes, even the primordia, play an important role in the maintenance and development of sexuality.

 

 

Hoops HJ, Brighton MC, Stickles SM, et al.

 

A test of two possible mechanisms for phototactic steering in Volvox carteri (Chlorophyceae)

J PHYCOL 35 (3): 539-547 JUN 1999

 

Abstract:

We tested two competing models that could explain how differential flagellar activity leads to phototactic turning in spheroids of Volvox carteri f, weismannia (Powers) Iyengar. In one model, turning results from the flagella of anterior cells in the lighted and shadowed hemispheres beating at different frequencies. In a competing model, turning results from a change in beat direction in these flagella. Both models successfully explain phototactic steering under constant illumination, but they make different predictions when colonies are exposed to abrupt changes in light intensity. If turning is due to control of flagellar beat frequency, both progression and rotation rates will change in the same direction and with similar magnitudes. If spheroid turning is due to a change in flagellar beat direction, a decreased rate of progression will accompany an increased rate of rotation and vice versa. We used video-microscopy to observe the behavior of positively phototactic V. carteri spheroids exposed to 10x step-up and step-down stimuli. After a step-up stimulus, spheroids slow their progression and rotation by equal amounts, No significant changes are reported in these parameters after the reciprocal step-down response. These observations are consistent with the variable flagellar frequency model and inconsistent with the variable flagellar direction model for phototactic turning. Switching the direction of Light stimulus by 180 degrees results in reorientation of positively phototactic spheroids, The kinetics of this reorientation did not precisely match the predictions of either model.

 

 

Nishii I, Ogihara S

 

Actomyosin contraction of the posterior hemisphere is required for inversion of the Volvox embryo

DEVELOPMENT 126 (10): 2117-2127 MAY 1999

 

Abstract:

During inversion of a Volvox embryo, a series of cell shape changes causes the multicellular sheet to bend outward, and propagation of the bend from the anterior to the posterior pole eventually results in an inside-out spherical sheet of cells. We use fluorescent and electron microscopy to study the behavior of the cytoskeleton in cells undergoing shape changes. Microtubules are aligned parallel to the cell's long axis and become elongated in the bend. Myosin and actin filaments are arrayed perinuclearly before inversion. In inversion, actin and myosin are located in a subnuclear position throughout the uninverted region but this localization is gradually lost towards the bend. Actomyosin inhibitors cause enlargement of the embryo. The bend propagation is inhibited halfway and, as a consequence, the posterior hemisphere remains uninverted. The arrested posterior hemisphere will resume and complete inversion even in the presence of an actomyosin inhibitor if the anterior hemisphere is removed microsurgically. We conclude that the principal role of actomyosin in inversion is to cause a compaction of the posterior hemisphere; unless the equatorial diameter of the embryo is reduced in this manner, it is too large to pass through the opening defined by the already-inverted anterior hemisphere.

 

 

Huey RB, Berrigan D, Gilchrist GW, et al.

 

Testing the adaptive significance of acclimation: A strong inference approach

AM ZOOL 39 (2): 323-336 APR 1999

 

 

Abstract:

Acclimation is a common phenotypic response to environmental change. Acclimation is often thought to enhance performance and thus to be adaptive. This view has recently been formalized as the "Beneficial Acclimation Hypothesis" and predicts that individuals acclimated to one environment perform better in that environment than do individuals acclimated to a different environment. Although Beneficial Acclimation is appealing and widely supported, recent studies with E. coli and Drosophila have challenged its general validity. Although these challenges could be dismissed as mere exceptions, they encourage a re-evaluation of the adaptive significance of acclimation. Our philosophical approach differs from that of most previous studies of acclimation, in which the prediction derived from a Beneficial Acclimation perspective (e.g., heat tolerance is positively correlated with acclimation temperature) is tested against the null hypothesis ("single hypothesis approach"). Instead, we follow Huey and Berrigan (1996) in advocating a strong inference approach (sensu Platt, 1964), which recognizes that Beneficial Acclimation is actually one of a set of competing hypotheses that make different predictions as to how developmental temperature influences the thermal sensitivity of adults ("developmental acclimation"). Using this perspective, Huey and Berrigan proposed a factorial experimental design (3 developmental by 3 adult temperatures) designed to discriminate among all competing hypotheses. We now derive a formal statistical model (ANOVA with orthogonal polynomial contrasts) for this experimental design and use it to evaluate simultaneously the relative impact of each competing hypothesis. We then apply this model to several case studies (Drosophila, Volvox, Trichogramma), and we review also a recent study with E. coli. The influence of Beneficial Acclimation is supported (albeit often weakly) in most cases. Nevertheless, other hypotheses (especially the Optimal Developmental Temperature Hypothesis) often have a greater impact. Even so, however, Beneficial Acclimation usually predicts relative performance at extreme test temperatures. We conclude that, although rumors of its death are premature, Beneficial Acclimation cannot be viewed as the dominant expectation, at least with regard to developmental temperature acclimation. Moreover, our findings reinforce the view that a strong inference approach provides a more comprehensive portrait of complex biological responses than do single-hypothesis approaches.

 

 

Hallmann A

 

Enzymes in the extracellular matrix of Volvox: an inducible, calcium-dependent phosphatase with a modular composition

J BIOL CHEM 274 (3): 1691-1697 JAN 15 1999

 

Abstract:

The volvocine algae provide the unique opportunity for exploring development of an extracellular matrix. Volvox is the most advanced member of this family and represents the simplest multicellular organism, with differentiated cells, a complete division of labor, and a complex extracellular matrix, which serves structural and enzymatic functions. In Volvox carteri a glycosylated extracellular phosphatase was identified, which is partially released from the extracellular matrix into the growth medium. The phosphatase is synthesized in response to inorganic phosphate starvation and is strictly to inorganic phosphate starvation and is strictly calcium-dependent. The metalloenzyme has been purified to homogeneity and characterized. Its gene and cDNA have been cloned. Comparisons of genomic and cDNA sequences revealed an extremely intron-rich gene (32 introns), With an apparent molecular mass of 160 kDa the Volvox extracellular phosphatase is the largest phosphatase cloned, with no sequence similarity to any other phosphatase. This enzyme exhibits a modular composition. There are two large domains and a small one. The large domains are highly homologous to each other and therefore most likely originated from gene duplication and fusion. At least one EF-hand motif for calcium binding was identified in this extracellular protein Volvox extracellular phosphatase is the first calcium-dependent extracellular phosphatase to be cloned.

 

 

Rodriguez H, Haring MA, Beck CF

 

Molecular characterization of two light-induced, gamete-specific genes from Chlamydomonas reinhardtii that encode hydroxyproline-rich proteins

MOL GEN GENET 261 (2): 267-274 MAR 1999

 

Abstract:

Gametic differentiation in Chlamydomonas reinhardtii is a two-step process, which is controlled by the sequential action of the two extrinsic signals, nitrogen starvation and blue light. The gamete-specific genes GAS28 and GAS29 are expressed in the late phase of gametogenesis. Their light-induced expression is restricted to cells that have completed the first, nitrogen starvation-activated, phase of differentiation. A comparison of the two genes revealed striking similarities as well as differences. Their most prominent shared feature is an extended sequence homology of over 90% in their 5'-untranslated regions, suggesting a role in translational regulation. GAS28 and GAS29 both encode hydroxyproline-rich proteins (HRGPs) of very similar sizes that exhibit typical features of volvocalean cell wall constituents. GAS28 shows a high degree of homology with the Volvox pherophorin gene family, suggesting a relationship between these genes.

 

 

Bischoff F, Molendijk A, Rajendrakumar CSV, et al.

 

GTP binding proteins in plants

CELL MOL LIFE SCI 55 (2): 233-256 FEB 1999

 

Abstract:

GTP-binding proteins are found in all organisms. They are important switches that cycle between an active and an inactive state, ensuring vectorial flow of information on the expense of guanosine triphosphate (GTP). In this review, we discuss current progress in the molecular characterization and functional analysis of plant genes encoding heterotrimeric and small GTPases. An up-to-date list in eluding all cloned plant GTPase genes is given and a systematic classification is proposed.

 

 

Kirk MM, Stark K, Miller SM, et al.

 

regA, a Volvox gene that plays a central role in germ-soma differentiation, encodes a novel regulatory protein

DEVELOPMENT 126 (4): 639-647 Feb 1999

 

 

Abstract:

Volvox has two cell types: mortal somatic cells and immortal germ cells. Here we describe the transposon-tagging, cloning and characterization of regA, which plays a central role as a master regulatory gene in Volvox germsoma differentiation by suppressing reproductive activities in somatic cells. The 12.5 kb regA transcription unit generates a 6,725 nucleotide mRNA that appears at the beginning of somatic cell differentiation, and that encodes a 111 kDa RegA protein that localizes to the nucleus, and has an unusual abundance of alanine, glutamine and proline, This is a compositional feature shared by functional domains of many 'active' repressors, These findings are consistent with the hypothesis that RegA acts in somatic cells to repress transcription of genes required for growth and reproduction, including 13 genes whose products are required for chloroplast biogenesis.

 

 

Miller SM, Kirk DL

 

glsA, a Volvox gene required for asymmetric division and germ cell specification, encodes a chaperone-like protein

DEVELOPMENT 126 (4): 649-658 FEB 1999

 

Abstract:

The gls genes of Volvox are required for the asymmetric divisions that set apart cells of the germ and somatic lineages during embryogenesis. Here we used transposon tagging to clone glsA, and then showed that it is expressed maximally in asymmetrically dividing embryos, and that it encodes a 748-amino acid protein with two potential protein-binding domains. Site-directed mutagenesis of one of these, the J domain (by which Hsp40-class chaperones bind to and activate specific Hsp70 partners) abolishes the capacity of glsA to rescue mutants. Based on this and other considerations, including the fact that the GlsA protein is associated with the mitotic spindle, we discuss how it might function, in conjunction with an Hsp70-type partner, to shift the division plane in asymmetrically dividing cells.

 

 

Nozaki H, Ohta N, Takano H, et al.

 

Reexamination of phylogenetic relationships within the colonial Volvocales (Chlorophyta): An analysis of atpB and rbcL gene sequences

J PHYCOL 35 (1): 104-112 FEB 1999

 

 

Abstract:

The chloroplast-encoded atpB gene was sequenced from 33 strains representing 28 species of the colonial Volvocales (the Volvocaceae and its relatives) to reexamine phylogenetic relationships as previously deduced by morphological data and rbcL gene sequence data.1128 base pairs in the coding regions of the atpB gene were analyzed by MP, NJ, and ML analyses, Although supported with relatively low bootstrap values (75% and 65% in the NJ and ML analyses, respectively), three anisogamous/oogamous volvocacean genera-Eudorina, Pleodorina, and Volvox, excluding the section Volvox(= Euvolvox, illegitimate name), constituted a large monophyletic group (Eudorina group), Outside the Eudorina group, a robust Lineage composed of three species of Volvox sect, Volvox was resolved as in the rbcL gene trees, rejecting the hypothesis of the previous cladistic analysis based on morphological data that the genus Volvox is monophyletic, In addition, the NJ and ML trees suggested that Eudorina is a non-monophyletic genus as inferred from the morphological data and rbcL gene sequences. Although phylogenetic status of the genus Gonium is ambiguous in the rbcL gene trees and the paraphyly of this genus is resolved in the cladistic analysis based on morphological data, the atpB gene sequence data suggest monophyly of Gonium with relatively low bootstrap values (56-61%) in the NJ and ML trees. On the basis of the combined sequence data (2256 base pairs) from atpB and rbcL genes, Gonium was resolved as a robust monophyletic genus in the NJ and ML trees (with 68-86% bootstrap values), and Eudorina elegans Ehrenberg represented a paraphyletic species positioned most basally within the Eudorina group, However, phylogenetic status and relationships of the families of the colonial Volvocales were still almost ambiguous even in the combined analysis.

 

 

Braun FJ, Hegemann P

 

Two light-activated conductances in the eye of the green alga Volvox carteri

BIOPHYS J 76 (3): 1668-1678 MAR 1999

 

Abstract:

Photoreceptor currents of the multicellular green alga Volvox carteri were analyzed using a dissolver mutant. The photocurrents are restricted to the eyespot region of somatic cells. Photocurrents are detectable from intact cells and excised eyes. The rhodopsin action spectrum suggests that the currents are induced by Volvox rhodopsin. Flash-induced photocurrents are a composition of a fast Ca2+-carried current (P-F) and a slower current (P-S), which is carried by H+. P-F is a high-intensity response that appears with a delay of less than 50 mu s after flash. The stimulus-response curve of its initial rise is fit by a single exponential and parallels the rhodopsin bleaching. These two observations suggest that the responsible channel is closely connected to the rhodopsin, both forming a tight complex. At low flash energies P-S is dominating. The current delay increases up to 10 ms, and the P-S amplitude saturates when only a few percent of the rhodopsin is bleached. The data are in favor of a second signaling system, which includes a signal transducer mediating between rhodopsin and the channel. We present a model of how different modes of signal transduction are accomplished in this alga under different light conditions.

 

 

Hallmann A, Rappel A

 

Genetic engineering of the multicellular green alga Volvox: a modified and multiplied bacterial antibiotic resistance gene as a dominant selectable marker

PLANT J 17 (1): 99-109 JAN 1999

 

 

Abstract:

The green alga Volvox represents the simplest multicellular organism: Volvox is composed of only two cell types, somatic and reproductive. Volvox, therefore, is an attractive model system for studying various aspects of multicellularity. With the biolistic nuclear transformation of Volvox carteri, the powerful molecular genetic manipulation of this organism has been established, but applications have been restricted to an auxotrophic mutant serving as the DNA recipient. Therefore, a dominant selectable marker working in all strains and mutants of this organism is required. Among several gene constructs tested, the most advantageous results were obtained with a chimeric gene composed of the coding sequence of the bacterial ble gene, conferring resistance to the antibiotic zeocin, modified with insertions of two endogenous introns from the Volvox arylsulfatase gene and fused to 5' and 3' untranslated regions from the Volvox beta 2-tubulin gene. In the most suitable plasmid used, the gene dosage was increased 16-fold by a technique that allows exponential multiplication of a DNA fragment. Go-transformation of this plasmid and a non-selectable plasmid allowed the identification of zeocin resistant transformants with nuclear integration of both selectable and non-selectable plasmids. Stable expression of the ble gene and of genes from several non-selectable plasmids is demonstrated. The modified ble gene provides the first dominant marker for transformation of both wild-type and mutant strains of Volvox.

 

 

Fabry S, Kohler A, Coleman AW

 

Intraspecies analysis: Comparison of ITS sequence data and gene intron sequence data with breeding data for a worldwide collection of Gonium pectorale

J MOL EVOL 48 (1): 94-101 JAN 1999

 

Abstract:

The morphologically uniform species Gonium pectorale is a colonial green flagellate of worldwide distribution. The affinities of 25 isolates from 18 sites on five continents were assessed by both DNA sequence comparisons and sexual compatibility. Complete sequences were obtained (i) for the internal transcribed spacer ITS-1 and ITS-2 regions of ribosomal DNA and (ii) for each of three single-copy spliceosomal introns, two in a small G protein and one in the actin gene. ITS sequences appeared to homogenize sufficiently rapidly to behave as a single copy gene. Intron sequence differences between isolates in this species reached nucleotide substitution saturation, while ITS sequences did not. Parsimony and evolutionary distance analysis of the two types of DNA data gave essentially the same tree conformation. By all these criteria, the group of G. pectorale isolates fell into two main clades, A and B. Clade A, with isolates from four continents, was comprised of four subclades of quite closely related isolates, plus one strain of ambiguous affinity. Clade B was comprised of two subclades represented by South African and South American isolates, respectively; thus, only subclades of clade B showed geographical localization. With respect to mating, all isolates except one homothallic strain and one apparently sterile strain fell into either one or the other of two mating types. Pairings in all possible combinations revealed that isolates from the same site formed abundant zygotes, which germinated to produce new, sexually active organisms. Zygotes were also formed in many pairings of other combinations, including crosses of clade A with clade B organisms, but none of the latter produced viable germlings. The ability to mate and produce viable progeny that were themselves capable of sexual reproduction was restricted to members of subclades established on the basis of DNA sequence similarities. Thus, the grades of difference in both nuclear intron sequences and rDNA ITS sequences paralleled those observed in the sexual analysis.

 

 

Miller SM, Kirk DL

 

glsA, a Volvox gene required for asymmetric division and germ cell specification, encode a chaperone-like protein that co-localizes with the mitotic spindle

MOL BIOL CELL 10: 2265 Suppl. S NOV 1999

 

 

1998

 

 

Gonzalez MA, Gomez PI, Montoya R

 

Comparison of PCR-RFLP analysis of the ITS region with morphological criteria of various strains of Dunaliella

J APPL PHYCOL 10 (6): 573-580 1998

 

Abstract:

The genus Dunaliella comprises 28 species defined primarily by morphological and physiological criteria, which vary considerably depending on growth conditions. Concomitantly, the taxonomic status of various species is uncertain. To confirm the taxonomic identity and to better understand the relationship within Dunaliella, seven taxa (D. salina, D. bardawil, D. tertiolecta, D. parva, D. viridis, D. lateralis, D. peircei) were compared using RFLP analysis of the nuclear rDNA repeats, specifically the internal transcribed spacer regions, including the 5.8S rRNA gene. Volvox aureus was used as an outgroup. A single ITS PCR amplification product was obtained for each taxon. An ITS fragment of ca. 640 bp was present in all the taxa within the subgenus Dunaliella, except for D. salina CCMP 1303 (ca. 540 bp) and D. lateralis (subgenus Pascheria) (ca. 600 bp). A cluster analysis based on the presence or absence of bands generated by digestion of the PCR product with 8 restriction endonucleases (DpnI, HhaI, EcoRI, PVuII, TaqI, HaeIII, MspI, StyI) revealed no correlation between the genetic relationship inferred from the ITS-RFLP data and the morpho-physiological attributes used for taxonomy. In addition, differences in morphology, physiology and in the length and restriction fragment patterns of the ITS region of D. salina CCMP 1303 suggest that this strain does not belong to Dunaliella.

 

 

Kobl I, Kirk DL, Schmitt R

 

Quantitative PCR data falsify the chromosomal endoreduplication hypothesis for Volvox carteri (Volvocales, Chlorophyta)

J PHYCOL 34 (6): 981-988 DEC 1998

 

Abstract:

Two conflicting hypotheses for chromosome replication in the Volvocaceae, one postulating multiple rounds of replication prior to cell division (endoreduplication) and the other claiming a canonical sequence of one round of nuclear DNA replication preceding each cell division, have been tested experimentally. Competitive PCR of the single-copy actin gene (target) of Volvox carteri f. nagariensis Iyengar and a shortened gene version (competitor) containing the same primer binding sites were used to assess the genome equivalents present in a given number of cells. Determining the molar ratio of the PCR products generated from target DNA (extracted from a known number of cells) acid defined numbers of competitor molecules revealed that Volvox embryos between the one- and 16-cell stages possess an average of between one and two-but never more than two-copies of the actin gene. This led us to conclude that the number of genome equivalents per nucleus in dividing Volvox embryos varies only between one and two and that, unlike the case predicted by endoredduplication, the nuclear genome undergoes only one round of replication prior to each cell division.

 

 

Sekimoto H, Fukumoto R, Dohmae N, et al.

 

Molecular cloning of a novel sex pheromone responsible for the release of a different sex pheromone in Closterium peracerosum-strigosum-littorale complex

PLANT CELL PHYSIOL 39 (11): 1169-1175 NOV 1998

 

Abstract:

A sex pheromone, protoplast-release-inducing protein (PR-IP) inducer, of the Closterium peracerosum-strigosum-littorale complex is known to induce the release of PR-IF, from mating-type plus (mtf) cells during sexual reproduction. The purified PR-IF inducer was treated with trypsin to obtain internal peptides for determination of partial amino acid sequences. Using these sequences, oligonucleotides were synthesized and used as primers for the combined reverse transcription-PCR, A 296 bp cDNA fragment was amplified, permitting the cloning of corresponding full length cDNA (CpPI; Closterium peracerosum-strigosum-littorale complex PR-IF inducer). The deduced amino acid sequence of CpPI encodes a protein of 212 amino acid residues of M-r 23,071 whereas portion of the peptide secreted is predicted to have 142 amino acid residues of M-r 15,717 and shows no significant similarity with known proteins. The predicted protein has three possible consensus sequences for asparagine-linked glycosylation site. The CpPI gene was expressed when mating-type minus (mt(-)) cells were incubated at a low cell density in the light. Nitrogen deprivation from the medium enhances expression of the CpPI gene. An analysis by genomic Southern hybridization revealed that the cDNA probe hybridized to several DNA fragments obtained from both the genome of mt(-) and mt(+) cells. However, in mt- cells, transcripts for the PR-IF inducer could not be detected by Northern hybridization.

 

 

Schirmer A, Kolter R

 

Computational analysis of bacterial sulfatases and their modifying enzymes

CHEM BIOL 5 (8): R181-R186 AUG 1998

 

Abstract:

The sequence analysis of enzymes that might modify bacterial sulfatases should be useful in the task of identifying the human sulfatase-modifying homologs enzymes that are defective in the rare inherited disease multi sulfatase deficiency.

 

 

Gladyshev MI, Sushchik NN, Kalachova GS, et al.

 

The effect of algal blooms on the disappearance of phenol in a small forest pond

WATER RES 32 (9): 2769-2775 SEP 1998

 

Abstract:

Using experimental microecosystems the kinetics of phenol disappearance in small forest pond waters (Siberia, Russia) in the summer of 1995-96 were investigated. Despite of high variability of components of the ecosystem (plankton biomass and species composition) and two pronounced "blooms" of green algae Volvox aureus the same kinetics of the disappearance took place over the investigated period. Half-lives of the pollutant depended on water temperature only. A comparison of the self-purification of the pond with that of the Krasnoyarsk reservoir, "blooming" with blue-greens was carried out. Half-lives in the pond were significantly lower than that in the reservoir. During the periods of "blooms" of the green algae in the pond the concentrations of inorganic nutrients were comparatively high and the phenol-degrading bacteria likely were not limited by these nutrients, in contrast to the periods of "bloom" of the blue-green algae in the reservoir. (C) 1998 Elsevier Science Ltd. All rights reserved.

 

 

von Figura K, Schmidt B, Selmer T, et al.

 

A novel protein modification generating an aldehyde group in sulfatases: its role in catalysis and disease

BIOESSAYS 20 (6): 505-510 JUN 1998

 

Abstract:

In multiple sulfatase deficiency, a rare human lysosomal storage disorder, all known sulfatases are synthesized as catalytically poorly active polypeptides. Analysis of the latter has shown that they lack a protein modification that was detected in all members of the sulfatase family. This novel protein modification generates a 2-amino-3-oxopropanoic acid (C alpha-formylglycine) residue by oxidation of the thiol group of a cysteine that is conserved among all eukaryotic sulfatases, The oxidation occurs in the endoplasmic reticulum at a stage when the nascent polypeptide is not yet folded. The aldehyde is part of the catalytic site and is likely to act as an aldehyde hydrate. One of the geminal hydroxyl groups accepts the sulfate during sulfate ester cleavage leading to the formation of a covalently sulfated enzyme intermediate. The other hydroxyl is required for the subsequent elimination of the sulfate and regeneration of the aldehyde group. In some prokaryotic members of the sulfatase gene family, the DNA sequence predicts a serine residue, and not a cysteine, Analysis of one of these prokaryotic sulfatases, however, revealed the presence of the C alpha-formylglycine indicating that the aldehyde group is essential for all members of the sulfatase family and that it can be generated from either cysteine or serine, (C) 1998 John Wiley & Sons, Inc.

 

 

Arai S, Takahashi H, Takano H, et al.

 

Isolation, characterization, and chromosome mapping of an actin gene from the primitive green alga, Nannochloris bacillaris (Chorophyceae)

J PHYCOL 34 (3): 477-485 JUN 1998

 

Abstract:

Historically, the genus Nannochloris has been classified using the morphology of cell division, although the mechanics of division remain relatively poorly understood. Nannochloris bacillaris reproduces by binary fission. Microscopic observation with fluorescein isothiocyanate-phaloloidin showed that actin filaments localized near the nucleus and appeared as a ring- or beltlike structure in the septum-forming area in the middle of the cell during cell division. In primitive unicellular Chlorophyta such as N. bacillaris, actin is also thought to play important roles in nuclear migration and cell division. The N. bacillaris actin gene has three exons and two introns defined by two exon-intron junctions with splice site consensus sequences. The two introns are located at codons specifying amino acids 3/4 and 47/48. One of these, intron position 3/4, is conserved in the actin gene of Saccharomyces cerevisiae. The actin gene product was predicted to be 378 amino acids long with an estimated molecular weight of 42 kDa. There is only one copy of the actin gene in the N. bacillaris genome. Nannochloris bacillaris has 14 chromosomes that range in size from 230 kb to 3000 kb, and the total size of the genome was estimated to be 20.3 Mb. The actin gene is on either chromosome XI or XII. In a phylogenetic tree based on the actin gene sequence, N. bacillaris diverged before the divergence of Volvox, Chlamydomonas, and higher plants, and very shortly after the radiation of the Rhodophyta.

 

Amon P, Haas E, Sumper M

 

The sex-inducing pheromone and wounding trigger the same set of genes in the multicellular green alga Volvox

PLANT CELL 10 (5): 781-789 MAY 1998

 

Abstract:

The sex-inducing pheromone of the multicellular green alga Volvox carteri is a glycoprotein that triggers development of males and females at a concentration <10(-16) M. By differential screening of a cDNA library, two novel genes were identified that are transcribed under the control of this pheromone. Unexpectedly, one gene product was characterized as a lysozyme/chitinase, and the other gene product was shown to encode a polypeptide with a striking modular composition. This polypeptide has a cysteine protease domain separated by an extensin-like module from three repeats of a chitin binding domain. In higher plants, similar protein families are known to play an important role in defense against fungi. Indeed, we found that the same set of genes triggered by the sexual pheromone was also inducible in V. carteri by wounding.

 

Hallmann A, Godl K, Wenzl S, et al.

 

The highly efficient sex-inducing pheromone system of Volvox

TRENDS MICROBIOL 6 (5): 185-189 MAY 1998

 

Abstract:

The green alga Volvox is one of the simplest multicellular organisms and is capable of both asexual and sexual reproduction. Sexual development is initiated by a glycoprotein pheromone that acts at a concentration below 10(-16) M. The extracellular matrix (ECM) appears to play a key role in signal amplification: several ECM proteins contain a domain with homology to the sex-inducing pheromone.

 

El-Naggar MEE, Shaaban-Dessouki SA, Abdel-Hamid MI, et al.

 

Studies on the phytoplankton populations and physico-chemical conditions of treated sewage discharged into Lake Manzala in Egypt

MICROBIOLOGICA 21 (2): 183-196 APR 1998

 

 

Abstract:

Over a full year, the phytoplankton populations and physico-chemical conditions of treated sewage discharged into Lake Manzala in Egypt were investigated. Sixty-seven species of algae were identified, 18 Cyanophyta (Cyanobacteria), 19 Chlorophyta, 21 Bacillariophyta, 6 Euglenophyta, 2 Cryptophyta and one species Pyrrhophyta. Nitzschia (6 spp.), Scenedesmus (6 spp.), Navicula (4 spp.), Oscillatoria (4 spp.) and Euglena (4 spp.) were the most common genera.

 

A remarkable seasonal variation in species composition and standing crop of the phytoplankton populations was noted during the study. The total phytoplankton standing crop appeared to be mainly dependent on the growth of certain species viz., Oscillatoria chalybea, O. princepes, O. tenuis, Microcystis aeruginosa, Anabaena constricta (Cyanophyta), Nitzschia obtusa, Bacillaria paradoxa, Cocconeis placentula, Cyclotella meneghiniana (Bacillariophyta), Pandorina morum, Volvox sp. (Chlorophyta) and Phacus curvicauda (Euglenophyta). The continuous presence of Anabaena constricta and Nitzschia palea was recorded in the treated sewage. The least represented algal divisions were Pyrrhophyta and Cryptophyta, both in terms of quality and quantity.The data indicate that the secondary effluents were unstable in their chemical features and grossly polluted. Therefore, the treatment systems must treat the discharged sewage to a tertiary level before discharging into Lake Manzala.

 

Corrette-Bennett J, Rosenberg M, Przybylska M, et al.

 

Positional cloning without a genome map: Using 'Targeted RFLP Subtraction' to isolate dense markers tightly linked to the regA locus of Volvox carteri

NUCLEIC ACIDS RES 26 (7): 1812-1818 APR 1 1998

 

Abstract:

The ability to isolate genes defined by mutant phenotypes has fueled the rapid progress in understanding basic biological mechanisms and the causes of inherited diseases. Positional cloning, a commonly used method for isolating genes corresponding to mutations, is most efficiently applied to the small number of model organisms for which high resolution genetic maps exist. We demonstrate a new and generally applicable positional cloning method that obviates the need for a genetic map. The technique is based on Restriction Fragment Length Polymorphism (RFLP) Subtraction, a method that isolates RFLP markers spanning an entire genome, The new method, Targeted RFLP Subtraction (TRS), isolates markers from a specific region by combining RFLP Subtraction with a phenotypic pooling strategy. We used TRS to directly isolate dense markers tightly linked to the regA gene of the eukaryotic green alga Volvox, As a generally applicable method for saturating a small targeted region with DNA markers, TRS should facilitate gene isolation from diverse organisms and accelerate the process of physically mapping specific regions in preparation for sequence analysis.

 

ten Lohuis MR, Miller DJ

 

Genetic transformation of dinoflagellates (Amphidinium and Symbiodinium): expression of GUS in microalgae using heterologous promoterconstructs

PLANT J 13 (3): 427-435 FEB 1998

 

 

Abstract:

Genetic transformation of two dinoflagellates (Amphidinium sp., Symbiodinium microadriaticum) was achieved using plasmid constructs containing the neomycin phosphotransferase gene (nptll) fused to the Agrobacterium nos promoter, or the hygromycin B phosphotransferase gene (hpt) fused to the bidirectional Agrobacterium p1'2' promoter. Gene transfer into intact (walled) dinoflagellate cells was achieved by agitation in the presence of silicon carbide (SiCa) whiskers. Transformation rates of 5-24 transformants per 10(7) cells were obtained. Southern hybridization of transformants revealed stable integration of multiple copies of the constructs. Activity of integrated copies of the beta-glucoronidase (GUS) reporter gene coupled to the cauliflower mosaic virus 35S promotor or the p1'2' promoter was confirmed both histochemically and fluorometrically. This is the first report of successful application bf heterologous and widely used promoter and reporter genes in microalgae, and is the first demonstration of transformation of a dinoflagellate. There appear to be no substantial barriers to transformation of Amphidinium and Symbiodinium, which must now be considered as the first of the dinoflagellate genera accessible to genetic manipulation.

 

 

Miller SM, Kirk DL

 

glsA, a Volvox gene required for asymmetric division and germ cell specification encodes a chaperone-like protein

MOL BIOL CELL 9: 1694 Suppl. S NOV 1998

 

 

Bell G

 

Volvox - Molecular-genetic origins of multicellularity and cellular differentiation

SCIENCE 282 (5387): 248-248 OCT 9 1998

 

 

Sumper M, Hallmann A

 

Biochemistry of the extracellular matrix of Volvox

INT REV CYTOL 180: 51-85 1998

 

 

1997

 

 

Kirk DL

 

The genetic program for germ-soma differentiation in Volvox

ANNU REV GENET 31: 359-380 1997

 

Abstract:

Volvox carteri possesses only two cell types: mortal somatic cells and potentially immortal asexual reproductive cells called gonidia. Mutational analysis indicates that three categories of genes play central roles in programming this germ-soma division of labor: First the gls genes function during embryogenesis to cause asymmetric divisions that produce large and small cells. Then the lag genes act in the large cells (gonidial initials) to repress functions required for somatic development while the regA locus acts in the small cells (somatic initials) to repress functions required for reproductive development. Transposon tagging and DNA transformation have recently been used to recover and characterize the glsA and regA genes, and the sequences of these genes lead to testable hypotheses about how they play their roles in germ-soma differentiation.

 

 

Kroger N, Lehmann G, Rachel R, et al.

 

Characterization of a 200-kDa diatom protein that is specifically associated with a silica-based substructure of the cell wall

EUR J BIOCHEM 250 (1): 99-105 NOV 15 1997

 

 

Abstract:

The cell wall of a diatom is made up of a silica-based scaffold and organic macromolecules. Proteins located in the cell wall are believed to control morphogenesis of the species-specific silica structures of the scaffold. However, data that correlate distinct silica elements and specific proteins within the diatom cell wall have not been reported. Here, the cell wall protein HEP2OO (200-kDa HE-extractable protein) from the diatom Cylindrotheca fusiformis is identified and characterized. HEP200 is tightly associated with a substructure of the silica scaffold. It is a member of a new protein family, of which two more members are identified. Each member displays the same bipartite structure. The N-terminal part consists of a variable number of a repeated sequence motif (PSCD domain), whereas the C-terminal part is unique, Immunolocalization experiments revealed the arrangement of different proteins within the cell wall. Frustulins, a previously described group of glycoproteins, constitute the outer coat of the cell wall and exhibit a ubiquitous distribution. In contrast, HEP200 is specifically located at a subset of about six silica strips in intact cell walls, shielded by frustulins. This study therefore identifies a diatom cell wall protein (HEP200) that is associated with a distinct substructure of the silica scaffold.

 

 

Kurvari V

 

Cell wall biogenesis in Chlamydomonas: molecular characterization of a novel protein whose expression is up-regulated during matrix formation

MOL GEN GENET 256 (5): 572-580 NOV 1997

 

 

Abstract:

In the unicellular eukaryote Chlamydomonas, disruption of cell-matrix interactions by treatment with a periplasmic matrix metalloproteinase, g-lysin, activates a signal transduction pathway that results in the rapid synthesis and secretion of matrix molecules, followed by their assembly into a new matrix. I have identified and partially characterized several cDNA clones for transcripts that are dramatically up-regulated following treatment of cells with g-lysin. Here I report the complete nucleotide sequence and preliminary characterization of a matrix-related molecule termed Mrp47. The cDNA clone for Mrp47 contained an insert of 2.5 kb, corresponding to a transcript of 3.0 kb that is encoded by a single-copy gene. Sequence analysis indicated that Mrp47 cDNA contains an open reading frame (ORF) that encodes a 46-kDa polypeptide. The putative polypeptide is unusually rich in the amino acids proline, alanine and serine, with prolines clustered together in a 30-amino acid N-terminal region and a 80-amino acid C-terminal region. Further analysis of the predicted amino acid sequence suggested that Mrp47 is likely to be a secreted glycoprotein. Southern hybridization analysis indicated that Mrp47 is encoded by a single-copy gene in the Chlamydomonas genome. Database searches suggested that Mrp47 shows homology to other proline-rich proteins including a surface glycoprotein in Volvox and verprolin from yeast.

 

 

Hoops HJ

 

Motility in the colonial and multicellular Volvocales: structure, function, and evolution

PROTOPLASMA 199 (3-4): 99-112 1997

 

Abstract:

The colonial Volvocales are often said to be composed of Chlamydomonas-like cells, but there are substantial differences in motility and flagellar apparatus construction between the unicellular forms and the individual members of a colony or spheroid. These changes appear to be required for effective organismal motion and might possibly limit the rate at which new colonial forms evolve from unicellular ones. The flagellar-beat envelopes in colonial members are modified such that they beat in the same direction and in parallel planes with their effective strokes at right angles to the cellular anterior-posterior axis. These changes result from a series of developmental events of the flagellar apparatus of the colonial forms while the colony is still an embryo. Differences in the flagellar-apparatus structure in the members of the Goniaceae and Volvocaceae are not obviously correlated with the traditional placement of these algae in a simple volvocine lineage. Effective colonial motion clearly requires precise positioning and rotational orientation of the cells within the colony. Almost any arrangement where the cells are placed with rotational symmetry within the colony results in colonial progression with rotation. Such rotational symmetry is present from the time of embryogenesis. The mechanism that leads to organismal steering in behavioral responses (e.g., phototaxis) must likewise differ between colonial and unicellular forms. Ln at least some cases, this appears to result from changes in beat frequency in some parts of the spheroid, but changes in beat direction cannot be ruled out for all forms.

 

 

Hegemann P

 

Vision in microalgae

PLANTA 203 (3): 265-274 NOV 1997

 

Abstract:

Flagellate green algae such as Chlamydomonas and related genera are guided by their eyes to places where light conditions are optimal for photosynthetic growth. These eyes constitute the simplest and most common visual system found in nature. The eyes contain optics, photoreceptors and the elementary components of a signal-transduction chain. Rhodopsin serves as the photoreceptor, as it does in animal vision. Upon light stimulation, its all-trans-retinal chromophore isomerizes into 13-cis and activates a photoreceptor channel which leads to a rapid Ca2+ influx into the eyespot region. At low light levels, the depolarization activates small flagellar currents which induce in both flagella small but slightly different beating changes resulting in distinct directional changes. In continuous light, Ca2+ fluxes serve as the molecular basis for phototaxis. In response to flashes of higher energy the larger photoreceptor currents trigger a massive Ca2+ influx into the flagella which causes the well-known phobic response. The identification of proteins contributing to this signalling system has just begun with the isolation and cloning of the opsins from Chlamydomonas and Volvox. These plant opsins are highly charged, are not typical seven-helix receptors, and are believed to form a protein complex with the photoreceptor channel. In Spermatozopsis, a G-protein has been found which interacts either directly with the rhodopsin or with the rhodopsin-ion channel complex. By using insertional mutagenesis, genes coding for proteins that are involved in signalling have been tagged. One of them is connected to the flagellar channel and crucial for the flagellar action potential. Elucidation of photoreception in flagellated algae will provide deeper insight into the development of visual systems, starting from single-celled organisms and moving up through higher animals.

 

 

Nozaki H, Ito M, Uchida H, et al.

 

Phylogenetic analysis of Eudorina species (Valvocaceae, Chlorophyta) based on rbcL gene sequences

J PHYCOL 33 (5): 859-863 OCT 1997

 

Abstract:

Species and varieties in the genus Eudorina Ehrenberg (Volvocaceae, Chlorophyta) were evaluated on the basis of phylogenetic analyses of the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) gene sequence from 14 strains of four Eudorina species, as well as from nine species of Pleodorina and Volvox. The sequence data suggested that 10 of the 14 Eudorina strains form three separate and robust monophyletic groups within the nonmonophyletic genus Eudorina. The first group comprises ail three strains off. unicocca G. M. Smith; the second group consists of one of the E, elegans Ehrenberg var elegans strains, the E. cylindrica Korshikov strain, and both E. illinoisensis (Kofoid) Pascher strains; and the third group consists of two monoecious varieties off, elegans [two strains of E. elegans var synoica Goldstein and one strain of E. elegans var. carteri (G. hi. Smith) Goldstein]. In addition, E. illinoisensis represents a poly- or paraphyletic species within the second group. The remaining four strains, all of which are assigned to E. elegans var. elegans, are nonmonophyletic. Although their position in the phylogenetic trees is more or less ambiguous, they are ancestral to other taxa ill the large anisogamous/oogamous monophyletic group including Eudorina, Pleodorina, and Volvox (except for sect. Volvox). Thus, the four Eudorina groups resolved in the present molecular phylogeny do not correspond with the species concepts of Eudorina based on vegetative morphology, but they do reflect the results Of the previous intercrossing experiments and modes of monoecious and dioecious sexual reproduction.

 

 

Dierks T, Schmidt B, VonFigura K

 

Conversion of cysteine to formylglycine: A protein modification in the endoplasmic reticulum

P NATL ACAD SCI USA 94 (22): 11963-11968 OCT 28 1997

 

Abstract:

In sulfatases a C-alpha-formylglycine residue is found at a position where their cDNA sequences predict a cysteine residue. In multiple sulfatase deficiency, an inherited lysosomal storage disorder, catalytically inactive sulfatases are synthesized which retain the cysteine residue, indicating that the C,-formylglycine residue is required for sulfatase activity. Using in vitro translation in the absence or presence of transport competent microsomes we found that newly synthesized sulfatase polypeptides carry a cysteine residue and that the oxidation of its thiol group to an aldehyde is catalyzed in the endoplasmic reticulum. A linear sequence of 16 residues surrounding the Cys-69 in arylsulfatase A is sufficient to direct the oxidation, This novel protein modification occurs after or at a late stage of cotranslational protein translocation into the endoplasmic reticulum when the polypeptide is not yet folded to its native structure.

 

 

Hallmann A, Rappel A, Sumper M

 

Gene replacement by homologous recombination in the multicellular green alga Volvox carteri

P NATL ACAD SCI USA 94 (14): 7469-7474 JUL 8 1997

 

Abstract:

With only two different cell types, the haploid green alga Volvox represents the simplest multicellular model system. To facilitate genetic investigations in this organism, the occurrence of homologous recombination events was investigated with the intent of developing methods for gene replacement and gene disruption. First, homologous recombination between two plasmids was demonstrated by using overlapping nonfunctional fragments of a recombinant arylsulfatase gene (tubulin promoter/arylsulfatase gene). After bombardment of Volvox reproductive cells with DNA-coated gold microprojectiles, transformants expressing arylsulfatase constitutively were recovered, indicating the presence of the machinery for homologous recombination in Volvox. Second, a well characterized loss-of-function mutation in the nuclear nitrate reductase gene (nitA) with a single G --> A nucleotide exchange in a 5'-splice site was chosen as a target for gene replacement. Gene replacement by homologous recombination was observed with a reasonably high frequency only if the replacement vector containing parts of the functional nitrate reductase gene contained only a few nucleotide exchanges. The ratio of homologous to random integration events ranged between 1:10 and 1:50, i.e., homologous recombination occurs frequently enough in Volvox to apply the powerful tool of gene disruption for functional studies of novel genes.

 

 

Raven JA

 

Multiple origins of plasmodesmata

EUR J PHYCOL 32 (2): 95-101 MAY 1997

 

Abstract:

Plasmodesmata in photosynthetic eukaryotes are found in all embryophytes, in many members of the Chlorophyta, and in the Phaeophyceae. The Phaeophyceae and the Chlorophyta clearly developed cell walls and multicellularity independently, sc that (in the absence of lateral gene transfer) plasmodesmata evolved independently in these groups. The minimum number of independent origins of plasmodesmata in the Chlorophyta based on molecular phylogenies is two (Chlorophyceae sensu late, Charophyceae sensu late). Other intercellular connections in members of the Chlorophyta (Ctenocladus, Smithsoniella, Volvox) are structurally very different from true plasmodesmata. Recently published taxonomies of the Chlorophyta have five classes (Chlorophyceae, Oedegoniophyceae, Trentepohliophyceae, Klebsormidiophyceae and Charophyceae sensu stricto) with plasmodesmata out of a total of thirteen. However, it is by no means clear that these classes all acquired plasmodesmata independently.

 

 

Nozaki H, Ito M, Sano R, et al.

 

Phylogenetic analysis of Yamagishiella and Platydorina (Volvocaceae, Chlorophyta) based on rbcL gene sequences

J PHYCOL 33 (2): 272-278 APR 1997

 

Abstract:

Yamagishiella, based on Pandorina unicocca Rayburn et Starr is distinguished from Eudorina by its isogamous sexual reproduction, whereas Platydorina exhibits anisogamous sexual reproduction. In the present study, rue sequenced the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) genes from five Japanese and North American strains of Y. unicocca (Rayburn et Stair) Nozaki, true Platydorina caudata Kofoid strains, and two strains of Eudorina unicocca G. M. Smith, as well as eight related colonial and unicellular species. Phylogenetic trees were constructed based on these sequence data and on previously published rbcL gene sequences from 23 volvocalean species in order to deduce phylogenetic relationships within the colonial Volvocales, with particular regard to the phylogenetic positions and status of the genera Yamagishiella and Platydorina. Two robust monophyletic groups of the anisogamous/oogamous volvocacean species were resolved in the maximum-parsimony tree as well as in the neighbor-joining distance tree. One of the two groups comprises three species of Volvox section Volvox, whereas the other is composed of other sections of Volvox as well as of all the species of Eudorina and Pleodorina. Platydorina, however, was positioned outside these two monophyletic groups. Therefore, derivation of the Platydorina lineage may be earlier than that of such anisogamous/oogamous groups, or origin of anisogamy with sperm, packets in Platydorina may De independent of sperm packet evolution in Eudorina, Pleodorina, and Volvox. It was also resolved with high bootstrap values that all of the Y. unicocca strains form a monophyletic group positioned outside the large monophyletic group including Eudorina and Pleodorina. These reject the possibility of the reverse evolution of isogamy from anisogamy to give rise to Yamagishiella within the lineage of Eudorina.

 

 

Liss M, Kirk DL, Beyser K, et al.

 

Intron sequences provide a tool for high-resolution phylogenetic analysis of volvocine algae

CURR GENET 31 (3): 214-227 MAR 1997

 

 

Abstract:

Three nuclear spliceosomal introns in conserved locations were amplified and sequenced from 28 strains representing 14 species and 4 genera of volvocalean green algae. Data derived from the three different introns yielded congruent results in nearly all cases. In pairwise comparisons, a spectrum of taxon-specific sequence differences ranging from complete identity to no significant similarity was observed, with the most distantly related organisms lacking any conserved elements apart from exon-intron boundaries and a pyrimidine-rich stretch near the 3' splice site. A metric (SI50), providing a measure of the degree of similarity of any pair of intron sequences, was defined and used to calculate phylogenetic distances between organisms whose introns displayed statistically significant similarities. The rate of sequences divergence in the introns was great enough to provide useful information about relationships among different geographical isolates of a single species, but in most cases was too great to provide reliable guides to relationships above the species level. A substitution rate of approximately 3 x 10(-8) per intron position per year was estimated, which is about 150-fold higher than in nuclear genes encoding rRNA and about 10-fold higher than the synonymous substitution rate in protein-coding regions. Thus, these homologous introns not only provide useful information about intraspecific phylogenetic relationships, but also illustrate the concept that different parts of a gene may be subject to extremely different intensities of selection. The intron data generated here (1) reliably resolve for the first;time the relationships among the five most extensively studied strains of Volvox, (2) reveal that two other Volvox species may be more closely related than had previously been suspected, (3) confirm prior evidence that particular isolates of Eudorina elegans and Pleodorina illinoisensis appear to be sibling taxa, and (4) contribute to the resolution of several hitherto unsettled issues in Chlamydomonas taxonomy.

 

 

Godl K, Hallmann A, Wenzl S, et al.

 

Differential targeting of closely related ECM glycoproteins: The pherophorin family from Volvox

EMBO J 16 (1): 25-34 JAN 2 1997

 

Abstract:

The alga Volvox carteri represents one of the simplest multicellular organisms. Its extracellular matrix (ECM) is modified under developmental control, e.g. under the influence of the sex-inducing pheromone that triggers development of males and females at a concentration below 10(-16) M. A novel ECM glycoprotein (pherophorin-S) synthesized in response to this pheromone was identified and characterized. Although being a typical member of the pherophorins, which are identified by a C-terminal domain with sequence homology to the sex-inducing pheromone, pherophorin-S exhibits a completely novel set of properties. In contrast to the other members of the family, which are found as part of the insoluble ECM structures of the cellular zone, pherophorin-S is targeted to the cell-free interior of the spherical organism and remains in a soluble state. A main structural difference is the presence of a polyhydroxyproline spacer in pherophorin-S that is linked to a saccharide containing a phosphodiester bridge between two arabinose residues. Sequence comparisons indicate that the self-assembling proteins that create the main parts of the complex Volvox ECM have evolved from a common ancestral gene.

 

 

1996

 

Stratmann J, Paputsoglu G, Oertel W

 

Differentiation of Ulva mutabilis (Chlorophyta) gametangia and gamete release are controlled by extracellular inhibitors

J PHYCOL 32 (6): 1009-1021 DEC 1996

 

Abstract:

Blade cells of Ulva mutabilis Foyn (Chlorophyta) excrete regulatory factors into their cell walls and into the environment. These factors are essential for the maintenance of the vegetative state. Sporulation inhibitor-1a (SI-1a) is a glycoprotein that was isolated from the culture medium of axenic Ulva growing as an undifferentiated callus. This protein was unusually stable to denaturing treatments and showed an extremely high apparent molecular mass (M(r)) of 1-4 X 10(7) daltons estimated by size exclusion chromatography. The glycosylation was not essential for activity. SI-1a suppressed gametogenesis completely at concentrations lower than 10(-14) M. When Ulva developed normally in the presence of their symbiotic bacteria, smaller forms of SI-1 accumulated in the medium (10(4) - 10(6) daltons). Sporulation inhibitors of the same size spectrum and with similar properties were also extracted from crude cell walls of nonaxenic Ulva. A class of different nonprotein sporulation inhibitors (SI-2) of very low M(r) and yet unknown structure was isolated from the inner space between the two blade cell layers. Excretion of all SI-1 forms decreased with maturation of the thallus, whereas the overally concentration of SI-2 in the thallus stayed constant throughout the life cycle. The SI-2 affected different Ulva species whereas SI-1 was species-specific. Gametogenesis was induced upon removal of both sporulation inhibitors from small single-layered fragments of mature blades. After a determination phase of 23-46 h, dependent on the time of induction within the cell cycle, the cells became irreversibly committed to differentiation and were no longer susceptible to SI-1 or SI-2. Subsequently, during a 28-h differentiation phase, 16 progametes were formed by synchronous genome doublings and cell divisions and differentiated into mature gametes. These became motile and were released from the gametangia when the concentration of a swarming inhibitor of low M(r), excreted mainly during the determination phase, declined below a threshold concentration. The biochemical properties of these regulatory factors and their effects on gametogenesis and gamete release are described.

 

 

Ichimura T

 

Genome rearrangement and speciation in freshwater algae

HYDROBIOLOGIA 336 (1-3): 1-17 OCT 25 1996

 

Abstract:

Speciation problems are reviewed in the context of biogeography of fresh-water algae. Currently accepted species concept in phycology is based on morphological characters, and according to this concept, most freshwater algal species are considered cosmopolitan. This implies whether they have a highly efficient means of dispersal or their morphological characters are very static through a long evolutionary time. Recent studies of reproductive isolation show that some biological species of fresh-water algae are not so static or may not have such a high power of dispersal means, though some are indeed very static in morphological characters. The life cycle of most freshwater algae is composed of a vegetative cycle of growth and reproduction and a sexual cycle of gametic fusion and meiosis in the zygote, which forms a dormant spore-like structure. Since any freshwater habitat is ephemeral in terms of evolutionary time scale, each species has a capacity of forming germlings from a dormant cell in order to recycle its life history. The genome of freshwater algae, therefore, contains various coadapted gene systems, at least two, for the vegetative and for the sexual cycle. Homothallism and heterothallism are two contrasting mating systems that represent two opposing ways of life to harmonize antagonism between the vegetative stage of growth and reproduction and the sexual and dormant stage. Geographic and ecological distribution, polyploidy, and sex determination are discussed in conjunction with sexual and postzygotic isolating mechanisms.

 

Nozaki H

 

Morphology and evolution of sexual reproduction in the Volvocaceae (Chlorophyta)

J PLANT RES 109 (1095): 353-361 SEP 1996

 

 

Abstract:

Morphological features of sexual reproduction in the Volvocaceae are reviewed, focusing particularly on gametic union and zygote germination. Both of the two conjugating gametes of the isogamous genera Pandorina, Volvulina and Yamagishiella bear a tubular mating structure (mating papilla), and plasmogamy is initiated by union of the papillae tips. On zygote germination, a single biflagellate gone cell is released from the zygote wall. Although all the anisogamous and oogamous genera of the Volvocaceae produce sperm packets during gametogenesis and a single gone cell at zygote germination, some difference can be recognized in the male gametes. The male gametes of Eudorina bear a tubular cytoplasmic protuberance (putative mating papilla) near the base of the flagella, whereas such a structure recognized at the light microscopic level is not evident in Pleodorina and Volvox, Evolution of the sexual reproduction characteristics of volvocacean algae is discussed on the basis of recent cladistic analysis of morphological data as well as of the ribosomal (r) RNA phylogeny and large subunit of the ribulose-1,5-biphosphate carboxylase/oxygenase(rbcL) gene trees.

 

 

Beyser K, Fabry S

 

Identification and characterization of a lower plant Ypt/Rab guanosine dissociation inhibitor (GDI)

FEBS LETT 396 (2-3): 298-304 NOV 4 1996

 

Abstract:

The cDNA encoding a Ypt/Rab guanosine dissociation inhibitor (Ypt-GDI) was isolated from the multicellular green alga Volvox carteri, representing the first complete plant gdi gene described. The gdiV1 gene occurs as a single copy in the algal genome, indicating that its product regulates all YptV proteins from Volvox. The derived GDI protein (GDIV1p) shows high similarity to animal and fungal GDIs. A specific antibody developed against GDIV1p detected the protein throughout the whole Volvox life-cycle. GDIV1p was localized in the cytoplasm and in the algal flagellum. This is in line with earlier findings of a dual localization of Ypt proteins both in the cell body and in the motility organelle, and indicates a novel role of the GDI/Ypt system, possibly in intraflagellar transport.

 

 

Choi G, Przybylska M, Straus D

 

Three abundant germ line-specific transcripts in Volvox carteri encode photosynthetic proteins

CURR GENET 30 (4): 347-355 SEP 1996

 

 

Abstract:

Volvox carteri is a multicellular eukaryotic green alga composed of about 2000 cells of only two differentiated types: somatic and germ line. To understand how embryonic cells are assigned either to somatic or germ line fates, we are investigating the regulation of transcripts that are abundant in only one cell type. Here we report the identity of three

 

transcripts that are coordinately expressed at high levels in germ line cells but not in somatic cells. Surprisingly, all three transcripts encode photosynthetic chloroplast proteins (light-harvesting complex protein. oxygen-evolving enhancer protein 3, and ferredoxin-NADP(+) reductase) that are transcribed from nuclear genes. We discuss why these mRNAs might be required at high levels in germ line cells and present a hypothesis, suggested by our results, on the evolution of cell specialization in the Volvocales.

 

 

Ortega MA, DiazGuerra M, Sastre L

 

Actin gene structure in two Artemia species, A-franciscana and A-parthenogenetica

J MOL EVOL 43 (3): 224-235 SEP 1996

 

Abstract:

Genomic clones coding for actin have been isolated from two species of the crustacean Artemia, A. parthenogenetica and A. franciscana. The Act211 isoform gene was isolated from A. parthenogenetica, and the two other isoform genes, Act302 and Act403, were isolated from A. franciscana. The comparison of the nucleotide sequence of genomic and cDNA clones showed an interspecific divergence of 4% in translated and 6.1% in untranslated regions. However, the establishment of the partial structure of the Act211 gene in A. franciscana and of the Act302 gene in A. parthenogenetica suggests their similarity in the two species. The Act211 gene is divided into four exons, the Act302 gene into six exons, and the Act403 gene into seven exons. The three genes have introns in the 5' untranslated region and between codons 41 and 42. The Act211 and 403 genes have one common intron in codon 168. The Act302 and 403 genes have common introns between codons 121-122, 246-247, and within codon 301. While introns in the 5' untranslated region and between codons 41-42 and 121-122 are present in many organisms, the introns in positions 168 and 246-247 had only been found previously in actin genes from the nematode Onchocerca volvulus and the green alga Volvox carterii, respectively. The intron in position 301 had not been reported before. The transcription initiation sites of these three genes as well as the nucleotide sequences of the promoter regions have been also determined.

 

 

Huber H, Beyser K, Fabry S

 

Small G proteins of two green algae are localized to exocytic compartments and to flagella

PLANT MOL BIOL 31 (2): 279-293 MAY 1996

 

Abstract:

The Ypt/Rab proteins are small GTPases, which belong to the Ras superfamily and have been shown to be involved in endo- and exocytosis in mammalian cells and yeast. Using affinity-purified antibodies specific for four Ypt proteins, namely Ypt1p, Ypt4p, Ypt5p and Ypt6p, of the multicellular green alga Volvox carteri (YptVp) and its close unicellular relative Chlamydomonas reinhardtii (YptCp), we examined the abundance of the corresponding antigens during the asexual life cycle of Volvox, and their intracellular localization. The YptV proteins were found in all stages throughout the asexual life cycle and are tightly associated with intracellular membranes. Indirect immunofluorescence revealed that YptV4p, YptV5p and YptV6p are present in perinuclear regions of the cell, indicating an association with the Golgi region. Golgi localization of YptV4p and YptV6p in Volvox was confirmed by immunogold electron microscopy. In contrast, we found Ypt1p associated with the contractile vacuole in both V. carteri and C. reinhardtii. Furthermore, the YptV proteins were also detected along the entire length of the flagella of somatic Volvox cells. This flagellar location was substantiated by western blot analysis of extracts prepared from isolated flagella of both algae. While localization to exocytic compartments is in agreement with the established Ypt/Rab function in intracellular vesicle transport of eukaryotic cells, presence in the algal flagellum is the first hint of a possible role for small G proteins also in motility organelles.

 

 

Ferris PJ, Woessner JP, Goodenough UW

 

A sex recognition glycoprotein is encoded by the plus mating-type gene fus1 of Chlamydomonas reinhardtii

MOL BIOL CELL 7 (8): 1235-1248 AUG 1996

 

Abstract:

Sexual fusion between plus and minus gametes of the unicellular green alga Chlamydomonas reinhardtii entails adhesion between plus-specific and minus-specific fringe proteins displayed on the plasma membrane of gametic mating structures. We report the identification of the gene (fus1) encoding the plus fringe glycoprotein, which resides in a unique domain of the mating-type plus (mt(+)) locus, and which was identified by transposon insertions in three fusion-defective mutant strains. Transformation with fus1(+) restores fringe and fusion competence to these mutants and to the pseudo-plus mutant imp11 mt(-), defective in minus differentiation. The fus1 gene is remarkable in lacking the codon bias found in all other nuclear genes of C. reinhardtii.

 

 

Gruber H, Kirzinger SH, Schmitt R

 

Expression of the Volvox gene encoding nitrate reductase: Mutation-dependent activation of cryptic splice sites and intron-enhanced gene expression from a cDNA

PLANT MOL BIOL 31 (1): 1-12 APR 1996

 

Abstract:

Use of the nitrate reductase encoding gene (nitA) as selection marker has facilitated the successful nuclear transformation of Volvox carteri. The Volvox nitA gene contains 10 introns. A stable nitA mutation in the Volvox recipient strain 153-81 resides in a G-to-A transition of the first nucleotide in the 5' splice site of nitA intron 2. This mutation resulted in at least three non-functional splice variants, namely: (1) intron 2 was not spliced at all; (2) a cryptic 5' splice site 60 nt upstream or (3) a cryptic 5' splice site 16 nt downstream of the mutation were activated and used for splicing. When we used nitA cDNA (pVcNR13) for transformation of V. carteri 153-81, a low efficiency of about 5 x 10(-5) transformants per reproductive cell was observed. Re-integration of either intron 1 (pVcNR15) or introns 9 and 10 (pVcNR16) in the transforming cDNA increased transformation rates to 5 x 10(-4). In parallel, pVcNR15-transformed Volvox exhibited growth rates that were 100-fold increased over the pVcNR13-transformed alga. This intron-enhancement of nitA gene expression appears to be associated with post-transcriptional processing and 'channelling' of the message. These data suggest an important role of splicing for gene expression in V. carteri.

 

 

Agrawal SC, Sharma UK

 

Chemical and biological properties of culture filtrates of Westiellopsis prolifica and Chaetophora attenuata

ISRAEL J PLANT SCI 44 (1): 43-48 1996

 

Abstract:

Westiellopsis prolifica Janet and Chaetophora attenunta Hazen cultures released sugars (glucose, fructose, and sucrose), organic acids (oxaloacetic acid and oxalic acid), amino acids, and protein. W. prolifica cultures released the amino acids glycine, serine, cystine, glutamic acid, aspartic acid, and cc-alanine, while C. attenuata cultures released glycine, serine, aspartic acid, and cr-alanine. W. prolifica and C. attenuata cultures of all ages released more extracellular protein than total free amino acids. Cultures of C. attenuata released more protein than cultures of the same age of W. prolifica. The filtrates from old cultures of W. prolifica and C. attenunta decreased the total chlorophyll content of all algae tested, totally suppressed conjugation in Spirogyra decimina and zoospore formation in C. attenuata, and drastically decreased spore germination in W. prolifica, thus producing stressful conditions affecting the growth and reproduction of these and other algae.

 

 

Selmer T, Hallmann A, Schmidt B, et al.

 

The evolutionary conservation of a novel protein modification, the conversion of cysteine to serinesemialdehyde in arylsulfatase from Volvox carteri

EUR J BIOCHEM 238 (2): 341-345 JUN 1 1996

 

 

Abstract:

A novel post-translational protein modification has recently been described in two human sulfatases, by which a cysteine is replaced by a serinesemialdehyde (2-amino-3-oxopropionic acid) residue [Schmidt, B., Selmer, T., Ingendoh, A. & von Figura, K. (1995) Cell 82, 271-278]. This cysteine is conserved among all known eukaryotic sulfatases. Here we report the presence of this modification in arylsulfatase from the green alga Volvox carteri. The evolutionary conservation of this novel protein modification between sulfatases of V. carteri and man lends further support to the assumption that this modification is required for the catalytic activity of sulfatases and may be present in all sulfatases of eukaryotic origin.

 

 

Sugase Y, Hirono M, Kindle KL, et al.

 

Cloning and characterization of the actin-encoding gene of Chlamydomonas reinhardtii

GENE 168 (1): 117-121 FEB 2 1996

 

Abstract:

The genomic and complementary DNA sequences were determined for the unique actin-encoding gene in Chlamydomonas reinhardtii (Cr). The deduced amino acid (aa) sequence of this actin was similar to most known actin sequences, with the highest identity (98.1%) being with that of Volvox carteri actin. The Cr actin-encoding gene has one intron in the 5'-untranslated region and eight introns in the coding region. The latter eight introns occur at the same positions as those in the V. casteri actin-encoding gene. The 5'-upstream region contains four short stretches of sequence similar to the so-called 'tub box', a characteristic sequence proposed to be responsible for the regulation of synthesis of various axonemal proteins upon deflagellation and during the cell cycle, Southern blot analysis indicated that the Cr genome has only a single actin-encoding gene. An antibody specific for the 11-aa peptide corresponding to the N-terminal sequence of this actin was found to react with a 43-kDa protein associated with flagellar inner-arm dynein. These findings indicate that a single actin functions in both the cytoplasm and flagella of this organism.

 

 

Fabry S, Beyser K

 

YptV2p, a membrane-associated small G protein abundant during embryogenesis in the green alga Volvox carteri

PROTOPLASMA 190 (1-2): 79-87 1996

 

Abstract:

The multicellular fresh-water alga Volvox carteri contains at least six small G protein-encoding genes (ypt genes) whose products are probably involved in intracellular vesicle transport. Four of them, YptV1, YptV3, YptV4, and YptV5, have been isolated and characterized previously. Here we report the cloning of yptV2 cDNA, the production of recombinant His-tagged YptV2p protein (reYptV2p) in E. coli, and the analysis of its GTPase activity and intracellular localization. YptV2p is predominantly present in dividing Volvox embryos. It is a membrane-associated protein which is localized to the cell periphery (plasma membrane or plasma-membrane-associated vesicles), probably by a lipid moiety. Purified, E. coli-expressed YptV2p binds GTP specifically, and has a typically low intrinsic GTPase activity (k(cat) = 0.004/min), which is enhanced by a GTPase activating protein activity present in Volvox. Our observations suggest a role of YptV2p in secretion, with a peak during the rapid cleavages of the Volvox embryo.

 

 

Hallmann A, Sumper M

 

The Chlorella hexose H+ symporter is a useful selectable marker and biochemical reagent when expressed in Volvox

P NATL ACAD SCI USA 93 (2): 669-673 JAN 23 1996

 

Abstract:

The multicellular obligately photoautotrophic alga Volvox is composed of only two types of cells, somatic and reproductive, Therefore, Volvox provides the simplest model system for the study of multicellularity. Metabolic labeling experiments using radioactive precursors are crucial for the detection of stage- and cell-type-specific proteins, glycoproteins, lipids, and carbohydrates. However, wild-type Volvox lacks import systems for sugars or amino acids. To circumvent this problem, the hexose/H+ symporter (HUP1) gene from the unicellular alga Chlorella was placed under the control of the constitutive Volvox beta-tubulin promoter. The corresponding transgenic Volvox strain synthesized the sugar transporter in a functional state and was able to efficiently incorporate C-14 from labeled glucose or glucosamine. Sensitivity toward the toxic glucose/mannose analogue 2-deoxyglucose increased by orders of magnitude in transformants. Thus we report the successful transformation of Volvox with a gene of heterologous origin. The chimeric gene may be selected for in either a positive or a negative manner, because transformants exhibit both prolonged survival in the dark in the presence of glucose and greatly increased sensitivity to the toxic sugar 2-deoxyglucose. The former trait may make the gene useful as a dominant selectable marker for use in transformation studies, whereas the latter trait may make it useful in development of a gene-targeting system.

 

 

Nishii I, Ogihara S

 

Role of actomyosin in multicellular deformation: Inversion of Volvox embryos.

MOL BIOL CELL 7: 2219-2219 Suppl. S DEC 1996

 

Girardin HM, Pelletier JA, Jovanovic L, et al.

 

Translational control during the development of Volvox.

MOL BIOL CELL 7: 624-624 Suppl. S DEC 1996

 

 

1995

 

 

Nozaki H, Itoh M, Sano R, et al.

 

Phylogenetic relationships within the colonial volvocales (Chlorophyta) inferred from rbcL gene sequence data

J PHYCOL 31 (6): 970-979 DEC 1995

 

Abstract:

The chloroplast-encoded large subunit of the ribulose-1, 5-bisphosphate carboxylase/oxygenase (rbcL) gene was sequenced from 20 species of the colonial Volvocales (the Volvacaceae, Goniaceae, and Tetrabaenaceae) in order to elucidate phylogenetic relationships within the colonial Volvocales. Eleven hundred twenty-eight base pairs In the coding regions of the (rbcL) gene were analyzed by the neighbor-joining (NJ) method using three kinds of distance estimations, as well as by the maximum parsimony (MP) method. A large group comprising all the anisogamous and oogamous volvocacean species was resolved in the MP tree as well as in the NJ trees based on overall and synonymous substitutions. In all the trees constructed, Basichlamys and Tetrabaena (Tetrabaenaceae) constituted a very robust phylogenetic group. Although not supported by high bootstrap values, the MP tree and the NJ tree based on nonsynonymous substitutions indicated that the Tetrabaenaceae is the sister group to the large group comprising the Volvocaceae and the Goniaceae. In addition, the present analysis strongly suggested that Pandorina and Astrephomene are monophyletic genera whereas Eudorina is nonmonophyletic. These results are essentially consistent with the results of the recent cladistic analyses of morphological data. However, the monophyly of the Volvocaceae previously supported by four morphological synapomorphies is found only in the NJ tree based on nonsynonymous substitutions (with very low bootstrap values). The genus Volvox was clearly resolved as a polyphyletic group with V. rousseletii Pocock separated from other species of volvox in the rbcL gene comparisons, although this genus represents a monophyletic group in the previous morphological analyses. Furthermore, none of the rbcL gene trees supported the monophyly of the Goniaceae; Astrephomene was placed in various phylogenetic positions.

 

 

Memon A, Hwang SB, Deshpande N, et al.

 

Novel aspects of the regulation of a cDNA (Arf1) from Chlamydomonas with high sequence identity to animal ADP-ribosylation factor 1

PLANT MOL BIOL 29 (3): 567-577 NOV 1995

 

Abstract:

ADP-ribosylation factor (ARF) is a highly conserved, low molecular mass (ca. 21 kDa) GTP-binding protein that has been implicated in vesicle trafficking and signal transduction in yeast and mammalian cells. However, little is known of ARF in plant systems. A putative ARF polypeptide was identifed in subcellular fractions of the green alga Chlamydomonas reinhardtii, based on P-32GTP binding and immunoblot assays. A cDNA clone was isolated from Chlamydomonas (Arfl), which encodes a 20.7 kDa protein with 90% identity to human ARF1. Northern blot analyses showed that levels of Arfl mRNA are highly regulated during 12 h/12 h light/dark (LD) cycles. A biphasic pattern of expression was observed: a transient peak of Arfl mRNA occurred at the onset of the light period, which was followed ca. 12 h later by a more prominent peak in the early to mid-dark period. When LD-synchronized cells were shifted to continuous darkness, the dark-specific peak of Arfl mRNA persisted, indicative of a circadian rhythm. The increase in Arfl mRNA at the,beginning of the light period, however, was shown to be light-dependent, and, moreover, dependent on photosynthesis, since it was prevented by DCMU. We conclude that the biphasic pattern of Arfl mRNA accumulation during LD cycles is due to regulation by two different factors, light (which requires photosynthesis) and the circadian clock. Thus, these studies identify a novel pattern of expression for a GTP-binding protein gene.

 

 

Imaizumi M, Doida Y

 

Cyclic AMP is a signal for repression of differentiation into gametes in Micrasterias thomasiana var notata

PLANT SCI 112 (1): 33-42 NOV 24 1995

 

Abstract:

This study investigates the effects of adenosine 3':5'-cyclic monophosphate (cAMP) and several chemicals which elevate the intracellular level of cAMP on the induction of zygote formation in Micrasterias thomasiana var. notata. When added at a concentration of 0.5-3 mM, cAMP repressed the induction of zygotes and simultaneously promoted cell proliferation, although at a concentration of 0.1 mM it merely delayed the initiation of zygote induction. Methylxanthines caffeine (0.05-1 mM) and theophylline (0.05-1 mM), forskolin (10 mu M), which is a potent activator of adenylate cyclase, and a membrane-permeable cAMP analog, 8-bromo cAMP (0.1-3 mM), also repressed the induction of zygotes and simultaneously promoted cell proliferation. In contrast, another cAMP analog used in this study, N-6,O-2'-dibutyryl cAMP (2-3 mM), repressed the induction of zygotes but did not cause promotion of cell proliferation. This analog also specifically blocked the cell division directly involved with gamete formation. The results obtained suggest that intracellular cAMP may function as a signal which simultaneously represses zygote induction and causes proliferation of cells in Micrasterias.

 

 

DESNITSKI AG

 

On the origin of Metazoa

ZH OBSHCH BIOL 56 (5): 629-631 SEP-OCT 1995

 

Abstract:

Under consideration is a new version of the phagocytella conception. It is suggested to consider blastea not a particular organism but a morphologically variable taxon of mixotrophic flagellates. Some of its subtaxa might have made a transition to the true heterotrophy, thus having become direct metazoan ancestors.

 

 

WALTHER Z, HALL JL

 

The uni chromosome of chalmydomonas – histone genes and nucleosome structure.

NUCLEIC ACIDS RES 23 (18): 3756-3763 SEP 25 1995

 

Abstract:

The uni linkage group (ULG) of Chlamydomonas reinhardtii contains many genes involved in the basal body-flagellar system, Recent evidence suggests that the corresponding uni chromosome is located in close proximity to the basal body complex. In the course of studies into its molecular organization, we have found a cluster of four histone genes on the ULG. The genes are arranged as divergently-transcribed pairs: H3-H4 and H2B-H2A. Genomic sequencing reveals that these genes lack introns and contain characteristic 3' palindromes similar to those of animals, The predicted amino acid sequences are highly conserved across species, with greatest similarities to the histone genes of Volvox. Southern analysis shows that each histone gene is present in 15-20 copies in Chlamydomonas and suggests a dispersed genomic organization. Northern analysis of mitotically-synchronized cells shows that, like the replication-dependent histones of higher eukaryotes, Chlamydomonas histone genes are expressed during S-phase. Using a gene-specific probe on Northern blots, we provide evidence that the ULG H4 gene is regulated in the same manner as other Chlamydomonas histone genes. Finally, micrococcal nuclease protection experiments show that the uni chromosome itself associates with histone proteins and displays a conventional nucleosomal banding pattern.

 

 

FABRY S, MULLER K, LINDAUER A, et al.

 

THE ORGANIZATION STRUCTURE AND REGULATORY ELEMENTS OF CHLAMYDOMONAS HISTONE GENES REVEAL FEATURES LINKING PLANT AND ANIMAL GENES

CURR GENET 28 (4): 333-345 SEP 1995

 

 

Abstract:

The genome of the green alga Chlamydomonas reinhardtii contains approximately 15 gene clusters of the nucleosomal (or core) histone H2A, H2B, H3 and H4 genes and at least one histone H1 gene. Seven non-allelic histone gene loci were isolated from a genomic library, physically mapped, and the nucleotide sequences of three isotypes of each core histone gene species and one linked H1 gene determined. The core histone genes are organized in clusters of H2A-H2B and H3-H4 pairs, in which each gene pair shows outwardly divergent transcription from a short (< 300 bp) intercistronic region. These intercistronic regions contain typically conserved promoter elements, namely a TATA-box and the three motifs TGGCCAGG(G/C)-CGAG, CGTTGACC and CGGTTG. Different from the genes of higher plants, but like those of animals and the related alga Volvox, the 3' untranslated regions contain no poly A signal, but a palindromic sequence (3' palindrome) essential for mRNA processing is present. One single H1 gene was found in close linkage to a H2A-H2B pair. The H1 upstream region contains the octameric promoter element GGTTGACC (also found upstream of the core histone genes) and two specific sequence motifs that are shared only with the Volvox H1 promoters. This suggests differential transcription of the H1 and the core histone genes. The H1 gene is interrupted by two introns. Unlike Volvox H3 genes, the three sequenced H3 isoforms are intron-free. Primer-directed PCR of genomic DNA demonstrated, however, that at least 8 of the about 15 H3 genes do contain one intron at a conserved position. In synchronized C. reinhardtii cells, H4 mRNA levels (representative of all core histone mRNAs) peak during cell division, suggesting strict replication-dependent gene control. The derived peptide sequences place C. reinhardtii core histones closer to plants than to animals, except that the H2A histones are more animal-like. The peptide sequence of histone H1 is closely related to the V. carteri VH1-II (66% identity). Organization of the core histone gene in pairs, and non-polyadenylation of mRNAs are features shared with animals, whereas peptide sequences and enhancer elements are shared with higher plants, assigning the volvocalean histone genes a position intermediate between animals and plants.

 

 

DESNITSKI AG

 

A REVIEW ON THE EVOLUTION OF DEVELOPMENT IN VOLVOX - MORPHOLOGICAL AND PHYSIOLOGICAL-ASPECTS

EUR J PROTISTOL 31 (3): 241-247 AUG 25 1995

 

Abstract:

This paper presents a morphophysiological concept of the evolution of Volvox development. We use published data concerning differences in size of the mature gonidia, rates of their division and peculiarities in segregation of somatic and reproductive cell lines. Based on this, four programmes (types) of asexual development of Volvox are recognized, and the evolutionary relationships among these programmes (but not among any concrete species of Volvox) are elucidated. The first developmental programme (Volvox powersii - V. pocockiae) is clearly primitive for the genus. This programme is characterized by ancestral features: large gonidia, division is fast, and there is no unequal (asymmetric) division into two cellular types. The second developmental programme(V. carteri), the third programme (V. tertius) and the fourth programme (V. aureus) are all derived, but constitute different phylogenetic trends. They each have some derived features: the second programme involves asymmetric division, the third programm involves slow division, while the fourth programme involves small gonidia and slow division. The evolutionary concept is supplemented by data on sexual reproduction in various species of Volvox.

 

 

GODL K, HALLMANN A, RAPPEL A, et al.

 

PHEROPHORINS - A FAMILY OF EXTRACELLULAR-MATRIX GLYCOPROTEINS FROM VOLVOX STRUCTURALLY RELATED TO THE SEX-INDUCING PHEROMONE

PLANTA 196 (4): 781-787 JUL 1995

 

Abstract:

Pherophorins are extracellular matrix (ECM) glycoproteins from Volvox that share homology with the sex-inducing pheromone. A novel pherophorin (pherophorin III) was characterized both with respect to expression pattern and proteolytic processing in vivo. Furthermore, it was shown that the pherophorins represent a protein family of ECM glycoproteins exhibiting a modular composition: their N-terminally located domain is a homolog of a domain found in the ECM glycoprotein SSG 185. Together with SSG 185, pherophorin I is a main component of the cellular zone within the ECM. The Volvox genome contains a tandem arrangement of genes encoding pherophorin II-related polypeptides. Inhibition of proteolytic processing of pherophorin II and III in vivo appears to result in the suppression of sexual induction.

 

 

DIETMAIER W, FABRY S, HUBER H, et al.

 

ANALYSIS OF A FAMILY OF YPT GENES AND THEIR PRODUCTS FROM CHLAMYDOMONAS-REINHARDTII

GENE 158 (1): 41-50 MAY 26 19

 

 

Abstract:

Small G-proteins encoded by the ras-like ypt genes are ubiquitous in eukaryotic cells. They have been shown to play an essential role in membrane vesicle transport. We have isolated four ypt genes, yptC1, yptC4, yptC5 and yptC6, from Chlamydomonas reinhardtii (Cr) genomic and cDNA libraries. Three of them, yptC1, yptC4 and yptC5, are close homologues of ypt genes previously found in the multicellular alga Volvox carteri (Vc), the fourth, yptC6, is new. Each yptC gene is present as a single copy in the genome. Comparisons of genomic and cDNA sequences revealed that the coding regions are interrupted by five (yptC5), six (yptC6), seven (yptC4) and eight (yptC1) introns, respectively. Cr ypt genes and the closely related Vc ypt genes have identical exon-intron structures, but the corresponding intron sequences are completely different. Polyadenylation is signalled by UAUAA, UGUAG and UGUAA. The deduced amino acid (aa) sequence of YptC6 exhibited 79% identity with HRab2; YptC1, YptC4 and YptC5 exhibited over 90% identity with their Vc homologues. Primary structures of the 9-aa 'effector domain' and the contiguous 'helix3-loop7' motif (approx. 30 aa) are 'diagnostic' features for functional assignment. Recombinant YptC proteins, overproduced in Escherichia coli and purified to near homogeneity, displayed strong and specific binding of GTP, but not of GMP or ATP. The four Cr Ypt proteins showed immunochemical cross reactions to their Vc counterparts. Moreover, Western blots demonstrated at least six types of Ypt in both Cr and Vc, suggesting that these Ypt are used for household functions responsible for vesicle transport rather than for cellular differentiation.

 

 

VOIGT J, VOGELER HP, KONIG WA, et al.

 

CHAOTROPE-SOLUBLE CELL-WALL GLYCOPROTEINS OF VOLVOX AND SOME MEMBERS OF THE ZYGNEMATOPHYCEAE IMMUNOLOGICALLY RELATED TO THE 150 KDA CELL-WALL GLYCOPROTEIN OF CHLAMYDOMONAS-REINHARDTII

MICROBIOL RES 150 (2): 129-137 MAY 1995

 

Abstract:

As previously described, the cell wall of Chlamydomonas reinhardtii contains several chaotrope-soluble glycoproteins with similar sugar compositions, but considerably different proportions of hydroxyproline. All these hydroxyproline-containing cell wall glycoproteins are recognized by a polyclonal antibody raised against the purified '150 kDa' cell wall glycoprotein of Chlamydomonas reinhardtii. This antibody also cross-reacts with some polypeptides present in the LiCl-extracts from intact cells of Spirotaenia erythrocephala, Spirotaenia obscura, Volvox aureus, and Volvox globator as revealed by Western blot analyses. Therefore, an Ige fraction of this particular antibody coupled to CNBr-activated Sepharose was used to isolate the immunologically related polypeptides extracted by aqueous LiCl from intact cells or cell wall preparations of different green algae belonging to the Volvocales or to the Zygnematophycene. Different and more or less complex polypeptide patterns were observed by comparative SDS-PAGE analyses of the polypeptide fractions isolated by immunoaffinity chromatography from extracts of Chlamydamonas reinhardtii, Volvox aureus, Micrasterias rotata, Gonatozygon brebissonii and Netrium digitus, respectively, whereas the corresponding fraction prepared from Spirotaenia erythrocephala contained a predominant '160 kDa' component. Amino acid and sugar analyses revealed that all these polypeptide fractions contained hydroxyproline (1.0-4.5 mol%) and the same sugars as the Chlamydomonas cell wall glycoproteins. However, the relative amounts of these sugars (arabinose, galactose, glucose, mannose and xylose) were found to be rather different. The highest proportion of hydroxyproline (4.5 mol%) and the highest ratio of arabinose:galactose (4.75:1) were determined for the glycoprotein fraction isolated from Spirotaenia erythrocephala indicating that at least the predominant '160 kDa' component is an intrinsic cell wall glycoprotein containing hydroxyproline and oligo-arabinosyl side chains. All the polypeptide fractions isolated from the other green algae obviously also contained chaotropesoluble cell wall glycoproteins as revealed by the presence of arabinose and hydroxyproline. These findings show that all the investigated green algae contain chaotrope-soluble cell wall glycoproteins immunologically related to the '150 kDa' cell wall glycoprotein of Chlamydomonas reinhardtii.

 

 

FABRY S, STEIGERWALD R, BERNKLAU C, et al.

 

STRUCTURE-FUNCTION ANALYSIS OF SMALL G-PROTEINS FROM VOLVOX AND CHLAMYDOMONAS BY COMPLEMENTATION OF SACCHAROMYCES-CEREVISIAE YPT/SEC MUTATIONS

MOL GEN GENET 247 (3): 265-274 MAY 10 1995

 

 

Abstract:

cDNAs representing nine small G protein genes encoding Ypt proteins from the green algae Volvox carteri (YptV) and Chlamydomonas reinhardtii (YptC) were tested for their ability to complement mutations in the YPT1, SEC4, and YPT7 genes of Saccharomyces cerevisiae strains defective in different steps of intracellular vesicle transport. None of the heterologously expressed algal genes was able to complement mutations in SEC4 or YPT7, but three of them, yptV1, yptC1, and yptV2, restored a YPT1 null mutation. On the amino acid sequence level, and particularly with respect to known small G protein specificity domains. YptV1p and YptC1p are the closest algal analogs of yeast Ypt1p, with 70% overall identity and identical effector regions, but YptV2p is only 55% identical to Ypt1p, and its effector domain resembles that of Sec4p. To define more precisely the regions that supply Ypt1p function, six chimeras were constructed by reciprocal exchange of 68/72-, 122/123-, and 162/163-amino acid segments of the C-terminal regions between YptV1p (complementing) and YptV3p (non-complementing). Segments containing 68 amino acids of the hypervariable C-terminal, and 41 residues of the N-terminal region including the effector region, of YptV1p could be replaced by the corresponding parts of YptV3p without loss of function in yeast, but exchanges within the central core destroyed the ability to rescue the YPT1 mutation. Sequence analysis of ypt1-complementing and -noncomplementing Ypt types suggests that surface loop3 represents a novel specificity domain of small G proteins.

 

 

FELDWISCH O, LAMMERTZ M, HARTMANN E, et al.

 

PURIFICATION AND CHARACTERIZATION OF A CAMP-BINDING PROTEIN OF VOLVOX-CARTERI F NAGARIENSIS IYENGAR

EUR J BIOCHEM 228 (2): 480-489 MAR 1 1995

 

Abstract:

Two cAMP-binding proteins, cbp1 and cbp2, were purified from the cytoplasm of the green alga Volvox carteri. Both proteins have a native molecular mass of 90 kDa as determined by gel filtration. cbp2 was purified to apparent electrophoretic homogeneity, having a subunit molecular mass of 42 kDa as determined by SDS/PAGE. The cbp1 preparation contains a 42-kDa and a 44-kDa band. The cAMP-binding activity is not associated with protein kinase activity. Tryptic peptides of cbp2 were sequenced by automated Edman degradation. Two pairs of peptides differ in one amino acid only, thus pointing to the presence of isoforms of cbp2. Both binding proteins differed from the cAMP-specific phosphodiesterases of V. carteri with respect to charge, molecular mass and binding affinity to N-6-cAMP-agarose, Reverse-phase chromatography of the bound ligand revealed that the two binding proteins hydrolyse cAMP to 5'AMP. The binding specificity of purified cbp1 and cbp2 was probed by a set of modified cAMP derivatives. Both proteins bind cAMP strictly specifically in the anti conformation; position 1 and 6 of the adenine moiety and at least one of the exocyclic O atoms of the ribose cyclic phosphate moiety are essential. 3-Isobutyl-1-methylxanthine is an effective inhibitor of binding but the natural methylxyanthines are not. At present it is not clear whether cbp1 and cbp2 are individual proteins or isoforms of one another.

 

 

MILLER SM, KIRK DL

 

CHARACTERIZATION OF A VOLVOX GENE REGULATING ASYMMETRIC CELL-DIVISION

MOL BIOL CELL 6: 501-501 Suppl. S NOV 1995

 

 

1994

 

 

MA H

 

GTP-BINDING PROTEINS IN PLANTS - NEW MEMBERS OF AN OLD FAMILY

PLANT MOL BIOL 26 (5): 1611-1636 DEC 1994

 

Abstract:

Regulatory guanine nucleotide-binding proteins (G proteins) have been studied extensively in animal and microbial organisms, and they are divided into the heterotrimeric and the small (monomeric) classes. Heterotrimeric G proteins are known to mediate signal responses in a variety of pathways in animals and simple eukaryotes, whiole small G proteins perform diverse functions including signal transduction, secretion, and regulation of cytoskeleton. In recent years, biochemical analyses have produced a large amount of information on the presence and possible functions of G proteins in plants. Further, molecular cloning has clearly demonstrated that plants have both heterotrimeric and small G proteins. Although the functions of the plant heterotrimeric G proteins are yet to be determined, expression analysis of an Arabidopsis Ga protein suggests that it may be involved in the regulation of cell division and differentiation. In contrast to the very few genes cloned thus far that encode heterotrimeric G proteins in plants, a large number of small G proteins have been identified by molecular cloning from various plants. In addition, several plant small G proteins have been shown to be functional homologues of their counterparts in animals and yeasts. Future studies using a number of approaches are likely to yield insights into the role plant G proteins play.

 

 

VALIN P, GOULARD B, SANIELEVICI M

 

TOPOLOGY DEPENDENCE IN LATTICE SIMULATIONS OF NONLINEAR PDES ON A MIMD COMPUTER

INT J MOD PHYS C 5 (6): 957-971 DEC 1994

 

 

Abstract:

We tested the parallelization of explicit schemes for the solution of non-linear classical field theories of complex scalar fields which are capable of simulating; hadronic collisions. Our attention focused on collisions in a fractional model with a particularly rich inelastic spectrum of final states. Relativistic collisions of all types were performed by computer on large lattices (64 to 256 sites per dimension). The stability and accuracy of the objects were tested by the use of two other methods of solutions: Pseudo-spectral and semi-implicit. Parallelization of the Fortran code on a 64-transputer MIMD Volvox machine revealed, for certain topologies, communication deadlock and less-than-optimum routing strategies when the number of transputers used was less than the maximum. The observed speedup, for N transputers in an appropriate topology, is shown to scale approximately as N, but the overall gain in execution speed, for physically interesting problems, is a modest 2-3 when compared to state-of-the-art workstations.

 

 

SCHULZE E, NAGEL S, GAVENIS K, et al.

 

STRUCTURALLY DIVERGENT HISTONE H1 VARIANTS IN CHROMOSOMES CONTAINING HIGHLY CONDENSED INTERPHASE CHROMATIN

J CELL BIOL 127 (6): 1789-1798 Part 2 DEC 1994

 

Abstract:

Condensed and late-replicating interphase chromatin in the Dipertan insect Chironomus contains a divergent type of histone H1 with an inserted KAPKAP repeat that is conserved in single H1 variants of Caenorhabditis elegans and Volvox carteri. H1 peptides comprising the insertion interact specifically with DNA. The Chironomid Glyptotendipes exhibits a corresponding correlation between the presence of condensed chromosome sections and the appearance of a divergent H1 subtype. The centromere regions and other sections of Glyptotendipes barbipes chromosomes are inaccessible to immunodecoration by anti-H2B and anti-H1 antibodies one of which is known to recognize nine different epitopes in all domains of the H1 molecule. Microelectrophoresis of the histones from manually isolated unfixed centromeres revealed the presence of H1 and core histones. H1 genes of G. barpipes were sequenced and found to belong to two groups. H1 II and H1 III are rather similar but differ remarkably from H1 I. About 30% of the deduced amino acid residues were found to be unique to H1 I. Most conspicuous is the insertion, SPAKSPGR, in H1 I that is lacking in H1 II and H1 III and at its position gives rise to the sequence repeat SPAKSPAKSPGR. The homologous H1 I gene in Glyptotendipes salinus encodes the very similar repeat TPAKSPAKSPGR. Both sequences are structurally related to the KAPKAP repeat in H1 I-1 specific for condensed chromosome sites in Chironomus and to the SPKKSPKK repeat in sea urchin sperm H1, lie at almost the same distance from the central globular domain, and could interact with linker DNA in packaging condensed chromatin.

 

 

WOESSNER JP, MOLENDIJK AJ, VANEGMOND P, et al.

 

DOMAIN CONSERVATION IN SEVERAL VOLVOCALEAN CELL-WALL PROTEINS

PLANT MOL BIOL 26 (3): 947-960 NOV 1994

 

Abstract:

Based on our previous work demonstrating that (SerPro)(x) epitopes are common to extensin-like cell wall proteins in Chlamydomonas reinhardtii, we looked for similar proteins in the distantly related species C. euganzetos. Using a polyclonal antiserum against a (SerPro)(10) oligopeptide, we found distinct sets of stage-specific polypeptides immunoprecipitated from in vitro translations of C. eugametos RNA. Screening of a C. eugametos cDNA expression library with the antiserum led to the isolation of a cDNA (WP6) encoding a (SerPro)(x)-rich multidomain wall protein. Analysis of a similarly selected cDNA (VSP-3) from a C. reinhardtii cDNA expression library revealed that it also coded for a (SerPro)(x)-rich multidomain wall protein. The C-terminal rod domains of VSP-3 and WP6 are highly homologous, while the N-terminal domains are dissimilar; however, the N-terminal domain of VSP-3 is homologous to the globular domain of a cell wall protein from Volvox carteri. Exon shuffling might be responsible for this example of domain conservation over 350 million years of volvocalean cell wall protein evolution.

 

 

DIETMAIER W, FABRY S

 

ANALYSIS OF THE INTRONS IN GENES ENCODING SMALL G-PROTEINS

CURR GENET 26 (5-6): 497-505 NOV-DEC 19

 

 

Abstract:

Because all small G proteins (SGPs) possess a very similar array of structural and functional domains, they are obvious candidates for examining the relationships postulated to exist between the exon-intron structure of genes and the domain structure of the encoded proteins. To address this issue, and to possibly gain insight into the evolution of their introns, we have analyzed positions, sizes, and sequences of 125 introns from 28 SGP genes. These introns were found to be distributed in 60 different locations throughout the aligned sequences, with a preference for the 5'-half of the genes. More than 50% of the positions were found to be shared by two or more genes, and genes encoding SGPs of very similar amino acid sequence (i.e., isotypes) in quite closely related species tend to have most, or all, of their introns in identical locations, indicating a common evolutionary origin (homologous introns). However, with few exceptions, no statistically significant sequence similarity or common folding motif was found between homologous intron pairs. Only three intron positions are shared between members of distantly related SGP subfamilies. These three potentially ancient intron locations fall between regions encoding alpha-helices or beta-sheets, but two of them interrupt regions encoding known functional (guanosine-nucleotide-binding) modules. Intron positions that are occupied only in single genes, or in genes encoding very similar SGPs, do not show any preferential distribution with respect to regions encoding structural or functional motifs. This discordance between exon modules and structural and/or functional protein domains suggests that most, if not all, introns in modern SGP genes arose by independent insertion events after diversification of the various SGP subfamilies, and therefore probably did not participate in the early evolution of these genes.

 

 

HALLMANN A, SUMPER M

 

REPORTER GENES AND HIGHLY REGULATED PROMOTERS AS TOOLS FOR TRANSFORMATION EXPERIMENTS IN VOLVOX-CARTERI

P NATL ACAD SCI USA 91 (24): 11562-11566 NOV 22 1994

 

Abstract:

The multicellular alga Volvox is an attractive model for the study of developmental processes. With the recent report of successful transformation, regulated promoters as well as reporter genes working in this organism are now required. The Volvox genes encoding arylsulfatase and the extracellular glycoprotein ISG are strictly regulated. The former is transcribed only under conditions of sulfur starvation, whereas the latter operates under extreme developmental control-i.e., it is transcribed for only a few minutes in Volvox embryos at the stage of embryonic inversion. The gene encoding the sexual pheromone of Volvox carteri was placed under the control of the arylsulfatase promoter. In response to sulfur deprivation, V. carteri transformed by this construct synthesized and secreted biologically active pheromone. In addition, the gene encoding Volvox arylsulfatase was placed under the control of the ISG promoter. Transformed algae synthesized arylsulfatase mRNA only during embryonic inversion. These experiments demonstrate the usefulness of both the arylsulfatase and the sexual.

 

 

WOESSNER JP, GOODENOUGH UW

 

VOLVOCINE CELL-WALLS AND THEIR CONSTITUENT GLYCOPROTEINS - AN EVOLUTIONARY PERSPECTIVE

PROTOPLASMA 181 (1-4): 245-258 1994

 

 

Abstract:

Similarities in the composition of the extracellular matrix suggest that only some species of the unicellular Chlamydomonas are closely related to the colonial and multicellular flagellated members of the family Volvocaceae. The cell walls from all of the algae in this volvocine group contain a crystalline layer. This lattice structure can be used as a phylogenetic marker to divide Chlamydomonas species into distinct classes, only one of which includes the volvocacean algae. Similarly, not all species of Chlamydomonas are sensitive to each other's cell wall lytic enzymes, implying divergence of the enzyme's inner wall substrate. Interspecific reconstitution of the crystalline layer is possible between C. reinhardtii and the multicellular Volvox carteri, but not between C. reinhardtii and C. eugametos. The hydroxyproline-rich glycoproteins (HRGPs) which make up the crystalline layer in genera which have a similar crystal structure exhibit many homologies. Interestingly, the evolutionarily distant cell walls of C. reinhardtii and C. eugametos also contain some HRGPs displaying a few morphological and amino acid sequence homologies. The morphological similarities between the flagellar agglutinins (HRGPs responsible for sexual recognition and adhesion during the mating reaction) and the cell wall HRGPs leads to the proposal of a superfamily from which novel HRGPs (designed for self-assembly/recognition) can constantly evolve. Just as Variations in the wall HRGPs can lead to unique wall structures, new agglutinins facilitate sexual isolation of new species. Thus, the HRGPs could emerge as Valuable phylogenetic markers.

 

 

HUBER O, SUMPER M

 

ALGAL-CAMS - ISOFORMS OF A CELL-ADHESION MOLECULE IN EMBRYOS OF THE ALGA VOLVOX WITH HOMOLOGY TO DROSOPHILA FASCICLIN-I

EMBO J 13 (18): 4212-4222 SEP 15 1994

 

Abstract:

Proof that plants possess homologs of animal adhesion proteins is lacking. In this paper we describe the generation of monoclonal antibodies that interfere with cell-cell contacts in the 4-cell embryo of the multicellular alga Volvox carteri, resulting in a hole between the cells. The number of following cell divisions is reduced and the cell division pattern is altered drastically. Antibodies given at a later stage of embryogenesis specifically inhibit inversion of the embryo, a morphogenetic movement that turns the embryo inside out. Immunofluorescence microscopy localizes the antigen (Algal-CAM) at cell contact sites of the del eloping embryo. Algal-CAR I is a protein with a three-domain structure: an N-terminal extensin-like domain characteristic for plant cell walls and two repeats with homology to fasciclin I, a cell adhesion molecule involved in the neuronal development of Drosophila. Alternatively spliced variants of Algal-CAM mRNA were detected that are produced under developmental control. Thus, Algal-CAM is the first plant homolog of animal adhesion proteins.

 

 

NASS N, MOKA R, JAENICKE L

 

ADENYLYL-CYCLASE FROM THE GREEN-ALGA VOLVOX-CARTERI F NAGARIENSIS - PARTIAL-PURIFICATION AND CHARACTERIZATION

AUST J PLANT PHYSIOL 21 (5): 613-622 1994

 

Abstract:

In order to understand changes in cyclic adenylate levels of Volvox carteri during the process of sexual induction, we investigated the biochemical properties of its membrane-bound adenylyl cyclase. Membrane preparations possess low levels of Mg2+-dependent or Mn2+-dependent adenylyl cyclase activity. This activity was solubilised and then purified 7800-fold. The enzyme detergent complex has an apparent molecular mass of 100 kDa. Purified preparations contain a major ATP-binding protein of 33 kDa as shown by affinity labelling. The Mg2+-dependent basal enzyme activity is regulated by Ca2+, and is highest in the presence of 10(-7) M Ca2+, but is inhibited by Ca2+ above 10(-5) M. La3+ at 10(-4) M also blocks activity. Neither calmodulin nor its antagonists affect the enzyme activity, nor do the purified preparations interact with immobilised calmodulin. Further mediators of G-protein action (NaF, or GTP and its derivatives) and forskolins have no influence on the basal activity of this plant enzyme. The function of adenylyl cyclase in sexual induction of Volvox is discussed.

 

 

HOOPS HJ, LONG JJ, HILE ES

 

FLAGELLAR APPARATUS STRUCTURE IS SIMILAR BUT NOT IDENTICAL IN VOLVULINA-STEINII, EUDORINA-ELEGANS, AND PLEODORINA-ILLINOISENSIS (CHLOROPHYTA) - IMPLICATIONS FOR THE VOLVOCINE EVOLUTIONARY LINEAGE

J PHYCOL 30 (4): 679-689 AUG 1994

 

Abstract:

The colonial and multicellular members of the Volvocales can be arranged in order of increasing size and complexity as the volvocine series. This series is often assumed to reflect an evolutionary progression. The flagellar apparatuses of previously examined algae are not consistent with a simple lineage. The flagellar apparatuses of Astrephomene gubernaculifera Pocock, Gonium pectorale Muller, Platydorina caudata Kofoid, Volvox rousseletii G. S. West, and V. carteri f. weismannia (Powers) Iyengar differ from one another, and there is no apparent progression in flagellar apparatus features from the simple to complex colonial forms. We examined the flagellar apparatuses of Volvulina steinii Playfair, Eudorina elegans Ehr., and Pleodorina illinoisensis Kofoid and found then to be similar to one another. The basal bodies ave connected by a distal fiber that is offset to the anti side of the cell. Two microtubular rootlets originate on the inside of the basal bodies and extend toward the syn side. The other two rootlets are oriented perpendicular to the first two and are anti-parallel to each other. A coarsely striated component underlies the four-membered rootlets and extends to the basal bodies. A proximal fiber complex connects the two basal bodies. This complex consists of a branched striated component on the cis side of each basal body. One part extends toward the anti side of the cell, while the other extends into a fibrous component that runs between basal bodies. An additional structure extends in the anti direction from the trans side of each basal body. A fibrous component extends past one basal body in all four species. This component goes past the trans basal body in Volvulina steinii and the cis basal body in E. elegans and P. illinoisensis. The flagellar apparatuses of these organisms are similar to those of G. pectorale and Volvox carteri but different from the other colonial volvocalean algae examined. The algae examined in this study plus G. pectorale and V. carteri probably share a common evolutionary history that postdates the transition from the unicellular to colonial habit. Such a shared evolutionary history is a requirement of the volvocine hypothesis. However, we have not observed progressive changes in the flagellar apparatus correlated with increasing cell number, differentiation, and sexual specialization. Thus, it is possible, but not certain, that G. pectorale, Volvulina steinii, E. elegans, P. illinoisensis, and Volvox carteri may form part of a volvocine lineage.

 

 

KIRK DL

 

GERM-CELL SPECIFICATION IN VOLVOX-CARTERI

CIBA F SYMP 182: 2-15 1994

 

 

Abstract:

Volvox carteri illustrates with diagrammatic clarity Weismann's concept of an immortal germline that produces a mortal soma that will carry it for a time, but then perish. Each V. carteri adult consists of about 16 asexual reproductive cells (gonidia) in the interior of a sphere that consists at its surface of about 2000 biflagellate somatic cells. When mature, each gonidium divides to form a juvenile with this same cellular composition. Half-way through their maturation, juveniles hatch out of the parenteral spheroid, whereupon parental somatic cells undergo programmed death while juvenile gonidia prepare for a new round of reproduction. The first visible step in V. carteri germ-soma differentiation is asymmetric cleavage, which sets apart large gonidial initials from small somatic initials. Experimental analysis indicates that it is a difference in size, not any difference in cytoplasmic quality, that determines whether a cell will become germinal or somatic. Mutational and molecular studies lead to the following model for the genetic control of the germ-soma dichotomy: first, the gls locus acts to cause asymmetric division; then large cells activate a set of lag loci that suppress expression of somatic genes, while small cells activate the regA locus that suppresses gonidial genes.

 

 

SCHIEDLMEIER B, SCHMITT R, MULLER W, et al.

 

NUCLEAR TRANSFORMATION OF VOLVOX-CARTERI

P NATL ACAD SCI USA 91 (11): 5080-5084 MAY 24 1994

 

Abstract:

Stable nuclear transformation of Volvox carteri was achieved using the cloned V. carteri nitA(+) gene (which encodes nitrate reductase) to complement a nitA(-) mutation. Following bombardment of mutant cells with plasmid-coated gold particles, putative transformants able to utilize nitrate as a nitrogen source were recovered with an efficiency of approximate to 2.5 x 10(-5). DNA analysis indicated that the plasmid integrated into the genome, often in multiple copies, at sites other than the nitA locus. Cotransformants were recovered with a frequency of 40-80% when cells were cobombarded with a selected and an unselected marker. Thus, V. carteri becomes one of the simplest multicellular organisms that is accessible to detailed molecular studies of genes regulating cellular differentiation and morphogenesis.

 

 

KOUFOPANOU V

 

THE EVOLUTION OF SOMA IN THE VOLVOCALES

AM NAT 143 (5): 907-931 MAY 1994

 

 

Abstract:

The presence of soma and the manner in which it segregates from the germ line is a fundamental aspect of development. This article examines the origin and evolution of soma in the Volvocales, the flagellated forms of green algae by analyzing data on cell division and development of 370 species. Phylogenetic analysis suggests that the cell wall is a preadaptation for the evolution of large multicellular colonies with deterministic development. The allometry of soma and germ supports the idea that soma functions to provide functional flagella during the embryogenesis of large colonies (Volvocaceae). The need for soma arises from a constraint that prevents simultaneous flagellation and cell division of cells surrounded by rigid walls: basal bodies cannot remain attached to their flagella while migrating to the mitotic poles. The con-straint is different from those that may cause the separation of flagellation and cell division in metazoan cells. Apart from a few developmental variations, which may represent adaptations to larger size, the Volvocaceae can be obtained by heterochronic changes in the timing of cell division. Their small size compared to the size of nonflagellated relatives can be attributed to their locomotion by flagella, which limits the maximum amount of germ that can be carried by the soma. This limitation is manifested in a negative correlation between size and number of germ cells among the largest species of Volvocaceae (Volvox). the opposite of a positive one among the smaller species.

 

 

NOZAKI H, ITOH M

 

PHYLOGENETIC-RELATIONSHIPS WITHIN THE COLONIAL VOLVOCALES (CHLOROPHYTA) INFERRED FROM CLADISTIC-ANALYSIS BASED ON MORPHOLOGICAL DATA

J PHYCOL 30 (2): 353-365 APR 1994

 

Abstract:

 

A cladistic analysis was used to deduce the phylogenetic relationships within the colonial Volvocales. Forty-one pairs of characters related to gross morphology and ultrastructure of vegetative colonies as well as asexual and sexual reproduction were analyzed based on parsimony, using the PAUP 3.0 computer program, for 25 species belonging to nine volvocacean and goniacean genera of the colonial Volvocales. Chlamydomonas reinhardtii Dangeard was the outgroup. The strict consensus tree indicated the presence of two monophyletic groups, one composed of all the volvocacean species analyzed in this study and the other containing the goniacean species except for the four-celled species Gonium sociale (Dujardin) Warming. In addition, these two groups constitute a large monophyletic group, to which G. sociale is a sister group. A new combination Tetrabaena socialis (Dujardin) Nozaki et Itoh and a new family Tetrabaenaceae Nozaki et Itoh are thus proposed for G. sociale. In addition, the analysis suggests that the volvocacean genera Eudorina and Pleodorina are paraphyletic groups, respectively, and that the monotypic genus Yamagishiella has no autapomorphic characters and represents primitive features of the anisogamous and oogamous genera of the Volvocaceae. Phylogenetic relationships within the Volvocaceae and the Goniaceae, as well as the various modes of sexual reproduction exhibited by these organisms, are discussed on the basis of the analysis.

 

 

HALLMANN A, SUMPER M

 

AN INDUCIBLE ARYLSULFATASE OF VOLVOX-CARTERI WITH PROPERTIES SUITABLE FOR A REPORTER-GENE SYSTEM - PURIFICATION, CHARACTERIZATION AND MOLECULAR-CLONING

EUR J BIOCHEM 221 (1): 143-150 APR 1 1994

 

 

Abstract:

The multicellular green flagellate Volvox carteri synthesizes a periplasmic arylsulfatase in response to sulfur deprivation. The inducible enzyme has been purified to homogeneity and characterized. The corresponding gene and cDNA have been cloned. Determination of the sequence of genomic clones and comparisons to the cDNA sequence, revealed sixteen introns and seventeen a exons that encode a 649-amino-acid polypeptide chain. Since the arylsulfatase enzyme is readily assayed using chromogenic substrates, but is not detectable in cells grown in sulfate-containing medium, the gene encoding arylsulfatase may be useful as a reporter gene in V. carteri. In addition, the highly regulated promoter of the arylsulfatase gene suggests its suitability as a tool for producing inducible expression vectors for cloned genes.

 

 

SEKIMOTO H, SONE Y, FUJII T

 

REGULATION OF EXPRESSION OF THE GENES FOR A SEX-PHEROMONE BY AN INDUCER OF THE SEX-PHEROMONE IN THE CLOSTERIUM PERACEROSUM-STRIGOSUM-LITTORALE COMPLEX

PLANTA 193 (1): 137-144 MAR 1994

 

Abstract:

A sex pheromone, protoplast-release-inducing protein (PR-IP), of the Closterium peracerosum-strigosum-littorale complex is known to induce the release of protoplasts from mating-type minus (Mt(-)) cells during sexual reproduction and to have two subunit polypeptides of 19 and 42 kDa. Here, we describe the regulation mechanism for the release of the PR-IP. The sex pheromone was fractionated to yield subunits of 19 and 42 kDa, respectively, and each subunit was treated with V8 protease and with CNBr. By reference to the partial amino-acid sequences of the digested polypeptides, oligo nucleotides were synthesized and used as primers for the combined reverse transcription-polymerase chain reaction. Amplified fragments of DNA, of 130 bp in the case of the 19-kDa subunit and of 330 bp in the case of the 42-kDa subunit, were obtained, sequenced, and used as probes to identify the respective transcripts. From the results of Northern hybridization, the sizes of transcripts were estimated to be 1.2 kb for the 18-kDa subunit and 1.4 kb for the 42-kDa subunit. These transcripts appeared transiently only when mating-type plus (mt(+)) cells were treated with another sex pheromone (PR-IP Inducer) for more than 4h in the light. By immunoblotting with anti-42-kDa-subunit antiserum, it was shown that PR-IP accumulated gradually in the medium but not in the mt(+) cells after treatment with PR-IP Inducer in the light. We suggest that PR-IP is synthesized de novo and secreted from mt(+) cells only after the perception of PR-IP Inducer that has been released from mt(-) cells in the light during the sexual reproduction of Closterium, An analysis by genomic Southern hybridization revealed that probes for the 19-kDa and 42-kDa peptides hybridized to 6.8-kb and 5.1-kb DNA fragments, respectively, after the digestion of the genome with EcoRI. These hybridized DNA fragments were obtained not only from the genome of mt(+) cells but also from the genome of mt(-) cells, in which no transcripts for PR-IP could be detected by Northern hybridization. On the basis of these results, we discuss the possibility that the expression of the gene for the two subunits of PR-IP might be critically dependent upon the action of putative sex-determining genes.

 

 

SCHIEDLMEIER B, SCHMITT R

 

REPETITIOUS STRUCTURE AND TRANSCRIPTION CONTROL OF A POLYUBIQUITIN GENE IN VOLVOX-CARTERI

CURR GENET 25 (2): 169-177 FEB 1994

 

 

Abstract:

Southern analysis indicated the presence of at least four ubiquitin gene loci in the Volvox carteri genome. Three of these, a polyubiquitin gene described here and a non-segregating ubiquitin gene pair, were assigned to two different linkage groups by RFLP mapping; the non-polymorphic fourth gene locus remained unassigned. The polyubiquitin gene was cloned and its 2,116-bp sequence determined. It contains six exons each interrupted by an intron at Gly35, and it encodes a pentameric polyubiquitin polypeptide consisting of five runs of 76 identical amino-acid residues and a C-terminal extension of one leucine. The five tandem repeats of coding units plus introns exhibit an unusually high degree of overall sequence identity indicating an efficient process of gene homogenization in this region of the V. carteri genome. S1 mapping revealed two closely-spaced transcription starts, 24 and 28 nucleotides downstream from a putative TATA sequence. Preceding the TATA box are two 14-bp conserved heat-shock elements (HSEs) and two octameric sequences closely resembling an yeast HSE. Consistent with a 1.6-kb transcript seen on Northern blots are two polyadenylation signals (TGTAA) located 99 bp and 169 bp downstream from the TGA translational stop. The polyubiquitin gene was transcribed throughout the Volvox life cycle with peaks in the 1.6-kb mRNA levels during pre-cleavage, cleavage, and post-inversion. In contrast, an 0.6-kb monoubiquitin transcript was abundant only at the pre-cleavage stage suggesting a different type of gene control. Heat shock increased the level of polyubiquitin mRNA, whereas the level of monoubiquitin mRNA was down-regulated.

 

 

1993

 

 

KOUFOPANOU V, BELL G

 

SOMA AND GERM - AN EXPERIMENTAL APPROACH USING VOLVOX

P ROY SOC LOND B BIO 254 (1340): 107-113 NOV 22 1993

 

Abstract:

The separation of soma from germ may have originated as a result of a specialization in source and sink, with somatic cells acting as sources, gathering nutrients from the external environment and germ cells as sinks, utilizing nutrients to grow and reproduce. This hypothesis can be tested in an organism, such as Volvox, where single germ cells can be cultured in isolation from the soma, thus serving both as source and sink, and their growth compared with that of germ cells with an intact soma where source and sink are separated into different cells. Results from such an experiment show that germ cells grown with an intact soma had greater rates of increase than those grown with disrupted soma or that were completely isolated, but the difference became greater as nutrient concentration increased, as predicted by the source-and-sink hypothesis. The advantage, however, was not sufficient to compensate fully for the initial investment in soma, especially at low nutrients, perhaps due to the energetic cost of swimming. In nature, species with segregated soma are found in nutrient-rich lakes and ponds. In experimental farm ponds, the biomass of such species increases with eutrophication more than the biomass of related species without division of labour, suggesting an advantage consistent with the source-and-sink.

 

 

MAIER I

 

GAMETE ORIENTATION AND INDUCTION OF GAMETOGENESIS BY PHEROMONES IN ALGAE AND PLANTS

PLANT CELL ENVIRON 16 (8): 891-907 NOV 1993

 

Abstract:

This review attempts to give a concise overview of the widespread occurrence and the significance, structure and function of pheromones in the chemical communication between individuals of the same species during sexual reproduction in algae and plants. Also included is information on the Oomyctes and the chytridiomycete Allomyces. The terminology in respect of pheromone function and pheromone-induced reactions is discussed.

 

 

VONGROMOFF ED, BECK CF

 

GENES EXPRESSED DURING SEXUAL-DIFFERENTIATION OF CHLAMYDOMONAS-REINHARDTII

MOL GEN GENET 241 (3-4): 415-421 NOV 1993

 

Abstract:

Four genes specifically expressed during gametogenesis of Chlamydomonas reinhardtii have been cloned and their expression patterns analyzed. mRNAs encoded by these gamete-specific genes (gas) were absent or present only at very low levels in vegetative cells and mature zygotes. In young zygotes 2 h after gamete fusion, the mRNAs of three gas genes still persisted. The gas mRNAs accumulated during gametic differentiation. The temporal patterns of accumulation of individual mRNAs differed; some started to increase early during gametogenesis, others accumulated in the late phase. The accumulation of one of the late mRNAs (gas28) was stricly light-dependent. To illustrate the utility of the genes cloned in the analysis of sexual differentiation in Chlamydomonas reinhardtii we show that in a gametogenesis-defective mutant, the expression of late genes is prevented while that of early genes is normal.

 

 

MEMON AR, HERRIN DL, THOMPSON GA

 

INTRACELLULAR TRANSLOCATION OF A 28-KDA GTP-BINDING PROTEIN DURING OSMOTIC SHOCK-INDUCED CELL-VOLUME REGULATION IN DUNALIELLA-SALINA

BIOCHIM BIOPHYS ACTA 1179 (1): 11-22 OCT 7 1993

 

Abstract:

The primary aim of this study was to determine if small GTP-binding proteins play a role in the conspicuous and much-examined volume control process in Dunaliella salina. We confirmed the previous identification by Rodriguez et al. (Rodriguez Rosales, M.P., Herrin, D.L. and Thompson, G.A., Jr. (1992) Plant Physiol. 98, 446-451) of small GTP-binding proteins in the green alga Dunaliella salina and revealed the presence of at least five such proteins, having molecular masses of approx. 21, 28, 28.5, 29 and 30 kDa. These proteins were concentrated largely in the endoplasmic reticulum (ER) and in an intermediate density organelle fraction (GA) containing mainly Golgi vesicles, mitochondria and flagella. The chloroplast fraction and plasma membrane contained the 28-kDa GTP-binding protein exclusively, while the cytosol contained both the 28-kDa component and small amounts of a 21-kDa GTP-binding protein. Immunodetection analysis showed that the D. salina 28-kDa protein cross-reacted strongly with a polyclonal antibody raised against a Volvox carteri yptV1 type GTP-binding protein. This antibody was utilized for quantitative GTP-binding protein measurements as described below. Certain anti-GTP-binding protein antibodies derived from non-plant sources, namely, monoclonal antibodies raised against yeast and mouse ypt1 GTP-binding proteins, cross-reacted not only with the D. salina 28-kDa protein but also the 29-kDa component. The 30-kDa GTP-binding protein of D. salina did not bind the antibodies mentioned above but did cross-react with an anti-yeast ypt1 polyclonal antibody. None of the D. salina GTP-binding proteins reacted positively with polyclonal antibodies raised against SEC4, rab1 or rab6 proteins. When D. salina cells were subjected to hypoosmotic swelling by abruptly reducing the NaCl concentration of their medium from 1.7 M to 0.85 M, the increase in cell surface area was accompanied by a substantial translocation of the 28-kDa GTP-binding protein from the ER and GA fractions to the plasma membrane, chloroplast and cytosolic fractions, as determined by quantitative P-32GTP binding and I-125antibody binding on nitrocellulose blots. This translocation increased the content of the 28-kDa component in the plasma membrane, chloroplast and cytosol by 3-4-fold. No net movement of the 30-kDa GTP-binding protein from either the ER or GA fractions was observed following hypoosmotic shock. We also examined the behavior of D. salina small GTP-binding proteins following exposure of cells to hyperosmotic shock. Increasing the NaCl concentration from 1.7 M to 3.4 M led within 8 min to a decrease in 28-kDa GTP-binding protein content in ER, GA, plasma membrane and chloroplasts, and a concurrent increase in the cytosol. The pattern of change differed from that seen following hypoosmotic shock, where the plasma membrane and chloroplast fractions, as well as the cytosol gained 28-kDa GTP-binding protein during accelerated membrane vesicle trafficking. It appears that hyperosmotic shock, by interrupting vesicular trafficking, releases the 28-kDa GTP-binding proteins from their membrane associations. Two less abundant GTP-binding proteins were also redistributed following hyperosmotic shock. A 30-kDa component of microsomes decreased in amount, but only after 8 min of shock. And a barely detectable 21-kDa band present in organelle fractions was slowly released into the cytosol, becoming relatively prominent there by 30 min. Our findings suggest a role for small GTP-binding proteins in osmoregulatory volume control by D. salina.

 

 

KIRK MM, RANSICK A, MCRAE SE, et al.

 

THE RELATIONSHIP BETWEEN CELL-SIZE AND CELL FATE IN VOLVOX-CARTERI

J CELL BIOL 123 (1): 191-208 OCT 199

 

 

Abstract:

In Volvox carteri development, visibly asymmetric cleavage divisions set apart large embryonic cells that will become asexual reproductive cells (gonidia) from smaller cells that will produce terminally differentiated somatic cells. Three mechanisms have been proposed to explain how asymmetric division leads to cell specification in Volvox: (a) by a direct effect of cell size (or a property derived from it) on cell specification, (b) by segregation of a cytoplasmic factor resembling germ plasm into large cells, and (c) by a combined effect of differences in cytoplasmic quality and cytoplasmic quantity. In this study a variety of V carteri embryos with genetically and experimentally altered patterns of development were examined in an attempt to distinguish among these hypotheses. No evidence was found for regionally specialized cytoplasm that is essential for gonidial specification. In all cases studied, cells with a diameter > approximately 8 mum at the end of cleavage-no matter where or how these cells had been produced in the embryo-developed as gonidia. Instructive observations in this regard were obtained by three different experimental interventions. (a) When heat shock was used to interrupt cleavage prematurely, so that presumptive somatic cells were left much larger than they normally would be at the end of cleavage, most cells differentiated as gonidia. This result was obtained both with wild-type embryos that had already divided asymmetrically (and should have segregated any cytoplasmic determinants involved in cell specification) and with embryos of a mutant that normally produces only somatic cells. (b) When individual wild-type blastomeres were isolated at the 16-cell stage, both the anterior blastomeres that normally produce two gonidia each and the posterior blastomeres that normally produce no gonidia underwent modified cleavage patterns and each produced an average of one large cell that developed as a gonidium. (c) When large cells were created microsurgically in a region of the embryo that normally makes only somatic cells, these large cells became gonidia. These data argue strongly for a central role of cell size in germ/soma specification in Volvox carteri, but leave open the question of how differences in cell size are actually transduced into differences in gene expression.

 

 

FABRY S, JACOBSEN A, HUBER H, et al.

 

STRUCTURE, EXPRESSION, AND PHYLOGENETIC-RELATIONSHIPS OF A FAMILY OF YPT GENES ENCODING SMALL G-PROTEINS IN THE GREEN-ALGA VOLVOX-CARTERI

CURR GENET 24 (3): 229-240 SEP 1993

 

 

Abstract:

In addition to the previously described gene yptV1 encoding a small G-protein we have now identified and sequenced four more ras-related ypt genes (yptV2-yptV5) from the green alga Volvox carteri. The four new genes encode polypeptides consisting of 203 to 217 amino-acid residues that contain the typical sequence elements (GTP-binding domains, effector domain) of the ypt/rab subgroup of the Ras superfamily. Comparison of the derived amino-acid sequences from the V carteri ypt gene products and their Ypt homologs from other species revealed similarity values ranging from 60% to 85%, whereas intraspecies similarities were found to approach only 55%. The coding sequences are interrupted by 5-7 introns of variable size (70-1000 nucleotides) occupying different positions in the genes. Reverse-transcribed samples of stage-specific RNAs were PCR-amplified with primers specific to yptV1, yptV3, yptV4, and yptV5 to determine if yptV transcription might be restricted to either cell type or to a specific stage of the life cycle. These experiments demonstrated that each of these genes is expressed throughout the entire Volvox life cycle and in both the somatic and the reproductive cells of the alga. The transcription start sites of yptV1 and yptV5 were mapped by primer extension. Expression of recombinant yptV cDNA in E. coli yielded recombinant proteins that bound GTP specifically, demonstrating a property which is typical for small G-proteins. The derived YptV polypeptide sequences were used to group them into four distinct classes of Ras-like proteins. These are the first proteins of the Ras superfamily to be identified in a green alga. We discuss the possible. role of the YptV-proteins in the intracellular vesicle transport of Volvox.

 

 

MILLER SM, SCHMITT R, KIRK DL

 

JORDAN, AN ACTIVE VOLVOX TRANSPOSABLE ELEMENT SIMILAR TO HIGHER-PLANT TRANSPOSONS

PLANT CELL 5 (9): 1125-1138 SEP 1993

 

 

Abstract:

We have isolated a 1595-bp transposable element from the multicellular green alga Volvox carteri following its insertion into the nitrate reductase (nitA) locus. This element, which we have named Jordan, has short (12-bp) terminal inverted repeats and creates a 3-bp target site duplication, like some higher plant transposons of the classic type. Contained within the first 200 bp of one end of the element are 55-bp inverted repeats, one of which begins with the terminal inverted repeat. Revertants of the transposon insertion into the nitA locus were obtained at a rate of approximately 10(-4) per Volvox embryo per generation. In each revertant examined, all transposon sequences were completely excised, but footprints containing both sets of duplicated bases, in addition to three to nine extra bases, were left behind. Jordan contains no significant open reading frames and so appears to be nonautonomous. DNA gel blot analysis indicates that Jordan is a member of a large family of homologous elements in the Volvox genome. We have isolated and characterized several of these homologs and found that they contain termini very similar to those of Jordan. Efforts to utilize Jordan and its homologs as tools to tag and clone developmentally interesting genes of Volvox are discussed.

 

 

HSU JP, HSU WC, TSAO HK

 

DIFFUSION-ENHANCED BIOREACTIONS - A HYPOTHETICAL MECHANISM FOR PLANT-CELL AGGREGATION

B MATH BIOL 55 (5): 869-889 SEP 1993

 

Abstract:

We show that the existence of diffusional resistance due to the presence of a solid phase can have a positive effect on the metabolic reactions of plant cells. In this case the efficiency of metabolic reactions, defined as the ratio of rate of production of biomass of aggregated cells/rate of production of biomass of dispersed cells. can be greater than unity for a certain range of aggregate sizes for both so[id spheres (common plant cell aggregates) and hollow spheres (e.g. Volvox aggregates). This means that, under appropriate conditions, plant cells tend to stay in the aggregated form to improve the efficiency of their metabolic reactions. The result of the present analysis provides an explanation as to why aggregates of plant cells are observed under typical culture conditions.

 

 

LINDAUER A, MULLER K, SCHMITT R

 

2 HISTONE H1-ENCODING GENES OF THE GREEN-ALGA VOLVOX-CARTERI WITH FEATURES INTERMEDIATE BETWEEN PLANT AND ANIMAL GENES

GENE 129 (1): 59-68 JUL 15 1993

 

Abstract:

Southern hybridization indicated the presence of at least two and possibly four histone H1-encoding genes occurring as singlets in the Volvox carteri genome. Two of these genes, H1-I and H1-II, have been cloned and characterized. Their coding sequences are each interrupted by three introns, but only the position of the second intron is identically conserved in both H1-I and H1-II. The encoded 260-amino-acid (aa) (H1-1) and 240-aa (H1-II) polypeptides possess the typical tripartite organization of animal H1 histones, with variable N- and C-terminal domains flanking a conserved 'globular' DNA-binding domain. Extensive differences in their variable regions suggest that H1-I and H1-II(62% identity) represent two isotypes with different functions. A prominent KAPKAP-KAA motif in the H1-I N-terminal region, similarly seen in single H1 variants of a mosquito and a nematode, has a putative function in packing condensed subtypes of chromatin. Different from higher plants, but like animals, the H1 genes of V. carteri possess a typical 3' palindrome for mRNA processing, resulting in non-polyadenylated mRNAs. Transcription initiates 33 nucleotides (nt) (H1-I) and 26 nt (H1-II) downstream of typical TATA boxes. A putative 20-bp conserved enhancer element upstream of each TATA box closely resembles the consensus sequence associated with the nucleosomal histone-encoding genes in V. carteri [Muller et al., Gene 93 (1990) 167-175] and suggests stringent regulation. Accordingly, transcription of H1 was shown to be restricted to late embryogenesis, when new flagella are produced. We discuss the inferred accessory role of histone H1 proteins in stabilizing axonemal microtubules, as has been recently observed in sea urchin flagella [Multigner et al., Nature 360 (1992) 33-39].

 

 

WAFFENSCHMIDT S, WOESSNER JP, BEER K, et al.

 

ISODITYROSINE CROSS-LINKING MEDIATES INSOLUBILIZATION OF CELL-WALLS IN CHLAMYDOMONAS

PLANT CELL 5 (7): 809-820 JUL 1993

 

Abstract:

Enzymatic removal of the cell wall vegetative Chlamydomonas reinhardtii cells to transcribe wall genes and synthesize new hydroxyproline-rich glycoproteins (HRGPs) related to the extensins found in higher plant cell walls. A cDNA expression library made from such induced cells was screened with antibodies to an oligopeptide containing the (SP)x repetitive domains found in Chlamydomonas wall proteins. One of the selected cDNAs encodes an (SP)x-rich polypeptide that also displays a repeated YGG motif Ascorbate, a peroxidase inhibitor, and tyrosine derivatives were shown to inhibit insolubilization of both the vegetative and zygotic cell walls of Chlamydomonas, suggesting that oxidative cross-linking of tyrosines is occurring. Moreover, insolubilization of both walls was concomitant with a burst in H2O2 production and in extracellular peroxidase activity. Finally, both isodityrosine and dityrosine were found in hydrolysates of the insolubilized vegetative wall layer. We propose that the formation of tyrosine cross-links is essential to Chlamydomonas HRGP insolubilization.

 

 

DESNITSKI AG

 

ON THE ORIGINS AND EARLY EVOLUTION OF MULTICELLULARITY

BIOSYSTEMS 29 (2-3): 129-132 1993

 

Abstract:

In this paper an attempt is made to consider the significance of recent data on the organization and development of Volvox, a multicellular spheroidal green alga, for the unsolved problem of metazoan origins. A brief analysis is made of differences and similarities in some trends and principles during the establishment of metazoan and volvocalean multicellularity.

 

 

FODINGER M, ORTNER S, PLAIMAUER B, et al.

 

PATHOGENIC ENTAMOEBA-HISTOLYTICA - CDNA CLONING OF A HISTONE H3 WITH A DIVERGENT PRIMARY STRUCTURE

MOL BIOCHEM PARASIT 59 (2): 315-322 JUN 1993

 

Abstract:

Entamoeba histolytica has an unusual nuclear structure characterized by a low degree of chromatin condensation and the absence of stainable metaphase chromosomes. Although nucleosome-like particles were observed, no information about histones was available so far. In this paper we describe a cDNA clone with significant homology to H3 histones that was isolated from a library of pathogenic E. histolytica.

 

The complete cDNA encodes a 15-kDa polypeptide, which like the histone sequence from Volvox carteri is shorter by one residue than the human homologue. The amino acid sequence has only 69% identity with human H3.3 histone and 67% identity with the human H3.1 histone. This is the highest degree of sequence divergence observed for any eukaryote H3 histone sequence. Our results indicate that this divergence may contribute to the unusual chromatin structure of E. histolytica.

 

JOSHI S, MILLER MI

 

MAXIMUM A POSTERIORI ESTIMATION WITH GOOD ROUGHNESS FOR 3-DIMENSIONAL OPTICAL-SECTIONING MICROSCOPY

J OPT SOC AM A 10 (5): 1078-1085 MAY 1993

 

Abstract:

The three-dimensional image-reconstruction problem solved here for optical-sectioning microscopy is to estimate the fluorescence intensity lambda(x), where x is-an-element-of R3, given a series of Poisson counting process measurements {M(j)(dx)}j=1J, each with intensity s(j)(y) integral(R3)p(j)(y\x)lambda(x)dx, with p(j)(y\x) being the point spread of the optics focused to the jth plane and s(j)(y) the detection probability for detector point y at focal depth j. A maximum a posteriori reconstruction generated by inducing a prior distribution on the space of images via Good's three-dimensional rotationally invariant roughness penalty integral(R3)[\DELTAlambda(x)\2/lambda(x)]dx. It is proven that the sequence of iterates that is generated by using the expectation maximization algorithm is monotonically increasing in posterior probability, with stable points of the iteration satisfying the necessary maximizer conditions of the maximum a posteriori solution. The algorithms were implemented on the DECmpp-SX, a 64 x 64 parallel processor, running at <2 s/(64(3), 3-D iteration). Results are demonstrated from simulated as well as amoebae and volvox data. We study performance comparisons of the algorithms for the missing-data problems corresponding to fast data collection for rapid motion studies in which every other focal plane is removed and for imaging with limited detector areas and efficiency.

 

 

LINDAUER A, FRASER D, BRUDERLEIN M, et al.

 

REVERSE-TRANSCRIPTASE FAMILIES AND A COPIA-LIKE RETROTRANSPOSON, OSSER, IN THE GREEN-ALGA VOLVOX-CARTERI

FEBS LETT 319 (3): 261-266 MAR 22 1993

 

Abstract:

By using the polymerase chain reaction (PCR) we have isolated and sequenced two distinct families of reverse transcriptase (RT) sequences from the genome of the colonial alga, Volvox carteri. Probing a genomic library with these RT clones revealed copia-like retrotransposons. One of these elements, named Osser, is 4,875 bp long, bordered by 197-bp identical long terminal repeats (LTRs), and shows the typical organization of retrotransposons belonging to the copia-Ty1 group. This is the first complete copia-like retrotransposon sequence described in a green alga.

 

 

SUMPER M, BERG E, WENZL S, et al.

 

HOW A SEX-PHEROMONE MIGHT ACT AT A CONCENTRATION BELOW 10(-16) M

EMBO J 12 (3): 831-836 MAR 1993

 

Abstract:

The sex-inducing pheromone of Volvox carteri is a glycoprotein that triggers development of males and females at a concentration below 10(-16) M. Evidence is presented for the existence of a novel mechanism of signal amplification operating within the extracellular matrix of this multicellular organism. A family of 70 kDa matrix glycoproteins denoted pherophorins bear a C-terminal domain being homologous to the sex-inducing pheromone. Under the influence of the pheromone, this domain is liberated by highly specific proteolysis.

 

 

SEKIMOTO H, SATOH S, FUJII T

 

ANALYSIS OF BINDING OF BIOTINYLATED PROTOPLAST-RELEASE-INDUCING PROTEIN THAT INDUCES RELEASE OF GAMETIC PROTOPLASTS IN THE CLOSTERIUM-PERACEROSUM-STRIGOSUM-LITTORALE COMPLEX

PLANTA 189 (3): 468-474 MAR 1993

 

Abstract:

A protoplast-release-inducing protein (PR-IP) which is released from mating-type plus (mt+) cells and induces the release of gametic protoplasts from mating-type minus (mt-) cells of Closterium was biotinylated and then used to examine the interaction of this protein with mt- cells. The protoplast-release-inducing activity of PR-IP was not altered after the biotinylation. When mt- cells that had been pre-cultured for 24 h were incubated with biotinylated PR-IP for 6 h in nitrogen-deficient medium that contained 1 % (w/v) bovine serum albumin, and then washed with the same medium, only a 19-kDa polypeptide, the smaller subunit of PR IP, was detected in cells by the avidin and biotinylated horseradish-peroxidase macromolecular complex system. The amount of bound 19-kDa polypeptide increased with increasing doses of PR-IP and reached a maximum at around 10 nM, reflecting the protoplast-release-inducing activity. From a Scatchard plot, the dissociation constant of the polypeptide was calculated to be 2.7 . 10(-8) M. The binding of the polypeptide proceeded only after an appropriate period of pre-culture in the light, and the polypeptide was competitively displaced by non-biotinylated PR-IP. From these results, it appears that the PR-IP induces the release of protoplasts from mt- cells by binding of a polypeptide of relative molecular mass 19000 to the receptor on the cell surface in a manner analogous to the binding of peptide hormones in animals.

 

 

KIM GH, FRITZ L

 

A SIGNAL GLYCOPROTEIN WITH ALPHA-D-MANNOSYL RESIDUES IS INVOLVED IN THE WOUND-HEALING RESPONSE OF ANTITHAMNION-SPARSUM (CERAMIALES, RHODPHYTA)

J PHYCOL 29 (1): 85-90 FEB 1993

 

 

Abstract:

A variety of fluorescein isothiocyanate-labeled lectins specific for different sugar moieties were examined as probes for the wound-healing response in the filamentous red alga Antithamnion sparsum Tokida. Among them, only concanavalin A (ConA) and Lens culrinaris agglutinin (LCA), which have specificity to alpha-D-mannosyl residues, bound specifically to repair cells during the wound-healing process. When ConA or LCA was added at various time intervals after wounding, it first bound (3 h post-wounding) as a thin layer at the tips of the adjacent cells. Later (4-5 h post-wounding) labeling also appeared at the tips of the repair cells. Intense labeling at these sites continued throughout the healing process until repair cell fusion, at which time the lectin labeling was reduced to a narrow ring around the area of fusion. When added to plants prior to wounding and continually monitored, these same lectins acted as inhibitors to the wound-healing response. Other control lectins showed no inhibitory effects. A crude extract solution obtained from decapitated filaments stimulated the wound-healing response, and a lectin-binding component bound strongly to a protein-binding transfer membrane. These results suggest that the labeled compound is a glycoprotein that has alpha-D-mannosyl residues and is similar to the repair hormone rhodomorphin found in Griffithsia pacifica Kylin.

 

 

HOOPS HJ

 

FLAGELLAR, CELLULAR AND ORGANISMAL POLARITY IN VOLVOX-CARTERI

J CELL SCI 104: 105-117 Part 1 JAN 1993

 

Abstract:

It has previously been shown that the flagellar apparatus of the mature Volvox carteri somatic cell lacks the 180-degrees rotational symmetry typical of most unicellular green algae. This asymmetry has been postulated to be the result of rotation of each half of the flagellar apparatus. Here it is shown that V. carteri axonemes contain polarity markers that are similar to those found in Chlamydomonas, except that in V. carteri the number one doublets do not face each other as they do in Chlamydomonas but are oriented in parallel and at approximately right angles to the line that connects the flagella. Thus, the rotational orientations of the axonemes are consistent with the postulate that the flagella of V. carteri have rotated in opposite directions, as was predicted earlier from the positions of the basal fibers and microtubular rootlets. Moreover, high-speed cinephotomicrographic analysis shows that the V. carteri flagellar effective strokes are also oriented in approximately the same direction, and in parallel planes. These results suggest that the direction of the effective stroke in both Chlamydomonas and Volvox is fixed, and that rotation of the axoneme is the cause of the differences in flagellar motility observed between Chlamydomonas and Volvox. These differences are probably essential for effective organismal motility. Cellular polarity of V. carteri can be related to that of Chlamydomonas after taking into account the developmental reorientation of flagellar apparatus components. This reorientation also results in the movement of the eye-spot from a position nearer one of the flagellar bases to a position approximately equidistant between them. By analogy to Chlamydomonas, the anti side of the V. carteri somatic cell faces the spheroid anterior, the syn side faces the spheroid posterior. The cis side of the cell is to the cell's left (the right to an outside observer), although it cannot be described solely on the basis of eyespot position as it can in Chlamydomonas, while the trans side is to the cell's right It follows that if the direction of the effective flagellar stroke is specified by structural features, then effective organismal motility in V. carteri, will be accomplished only if the cells are held in the proper orientation with respect to one another. The simplest arrangement that will yield both progression and rotation in ovoid or spherical colonies composed of biflagellate isokont cells is one in which the cells are arranged with rotational symmetry about the anterior-posterior axis of the spheroid. Analysis of the polarity of somatic cells from throughout the spheroid shows that it is constructed with just such symmetry. This symmetry probably originates with the very first divisions.

 

 

JAENICKE L, FELDWISCH O, MERKL B, et al.

 

EXPRESSION OF HIGHLY-ACTIVE SEX-INDUCING PHEROMONE OF VOLVOX-CARTERI F NAGARIENSIS IN A MAMMALIAN-CELL SYSTEM

FEBS LETT 316 (3): 257-260 FEB 1 1993

 

Abstract:

A cDNA fragment coding for the sex-inducing glycoprotein of Volvox carteri f. nagariensis was expressed in a mammalian cell system (baby hamster kidney (BHK) cells). The transfection product exhibited a specific biological activity intermediate between the natural pheromone of the strains Volvox carteri f. nagariensis and Volvox carteri f. weismannia. Immunoblot analysis showed that the sex-inducing activity was expressed as a set of three iso-glycoproteins (35, 34 and 31 kDa).

 

 

DENIS H, LACROIX JC

 

THE DICHOTOMY BETWEEN GERM LINE AND SOMATIC LINE, AND THE ORIGIN OF CELL MORTALITY

TRENDS GENET 9 (1): 7-11 JAN 1993

 

Abstract:

The germ cells of extant animals are potentially immortal, whereas somatic cells are mortal, that is, they are able to carry out only a finite number of divisions. In this article we propose an evolutionary interpretation of these differences. We assume that germ cells of the earliest metazoans inherited immortality from their unicellular ancestor, while somatic cells acquired mortality by gaining new functions. It follows that cell mortality was under genetic control from the beginning of metazoan life.

 

 

HOLLOWDAY ED

 

CEPHALODELLA-EDAX SP-NOV A ROTIFER PARASITIC IN THE MOTILE COLONIAL ALGA UROGLENA-VOLVOX EHRENBERG

HYDROBIOLOGIA 255: 445-448 APR 16 1993

 

 

1992

 

 

DUBOUX T, FERREIRA A, GASTALDO M

 

MIMD DICTIONARY MACHINES - FROM THEORY TO PRACTICE

LECT NOTES COMPUT SC 634: 545-550 1992

 

 

Abstract:

We describe the implementation of a dictionary structure on a distributed memory parallel computer. The dictionary is an important data structure used in applications such as sorting and searching, symbol-table and index-table implementations. Theoretical as well as practical aspects of the development of the application are discussed. Our target machine was a Volvox IS860 with 8 nodes, each composed of one Transputer T800 from INMOS plus an Intel i860. Extensive testing was carried out and the results reported. We also address problems and solutions connected to the programming environment of such a machine

 

 

BOWSER SS, ALEXANDER SP, STOCKTON WL, et al.

 

EXTRACELLULAR-MATRIX AUGMENTS MECHANICAL-PROPERTIES OF PSEUDOPODIA IN THE CARNIVOROUS FORAMINIFERAN ASTRAMMINA-RARA - ROLE IN PREY CAPTURE

J PROTOZOOL 39 (6): 724-732 NOV-DEC 1992

 

Abstract:

The seemingly delicate, strand-like pseudopodia of Astrammina rara, a camivorous benthic foraminiferan, adhere to and withstand the rigorous movements of meiofaunal prey. Previous electron microscopic studies identified two novel structures that might account for the unusual tensile properties of these pseudopodia: 1) an extensive, coiled microtubule cytoskeleton and 2) a fibrous extracellular matrix vesting the pseudopodial surface. In the present study, we found that pseudopodial networks microsurgically removed from A. rara's cell body captured Artemia metanauplii as efficiently as intact organisms, and therefore used them to test the role of microtubules and extracellular matrix components in augmenting pseudopodial strength. Agents that specifically disassemble microtubules (1 mM colchicine or 20 muM nocodazole) or generally disrupt pseudopodial integrity (heat, 10 mM formaldehyde, 1 mg/ml saponin) failed to inhibit prey capture. All of these treatments left the extracellular matrix intact as revealed by immunofluorescence and scanning electron microscopy. The elastic and tensile properties of the extracellular matrix, isolated by solubilization of pseudopodial cytoplasm using the nonionic detergent Triton X-100, were similar to those of intact pseudopodial networks when assayed with calibrated microneedles or a flexible rubber substrate. These observations indicate that A. rara uses a fibrous extracellular matrix to augment cytoplasmic tensile properties.

 

 

MISHRA SR, SHARMA S, YADAV RK

 

PHYTOPLANKTONIC COMMUNITIES IN RELATION TO ENVIRONMENTAL-CONDITIONS OF LENTIC WATERS AT GWALIOR (MP)

J ENVIRON BIOL 13 (4): 291-296 OCT 1992

 

Abstract:

A study was undertaken to determine the distribution of phytoplanktonic communities in two lentic water bodies of variable nature in Gwalior city. The study revealed that the water quality at Cotton mill waste water pond was severely destructed. In this pond the abundance of Arthrospira platensis, Volvox sp., Scenedesmus sp., Phacus sp., Euglena gracilis and E. acus was observed, which depicts their possible sustainance power in stressed habitats.

 

 

FABRY S, NASS N, HUBER H, et al.

 

THE YPTV1 GENE ENCODES A SMALL G-PROTEIN IN THE GREEN-ALGA VOLVOX-CARTERI - GENE STRUCTURE AND PROPERTIES OF THE GENE-PRODUCT

GENE 118 (2): 153-162 SEP 10 1992

 

 

Abstract:

Small G-proteins encoded by ras-like genes are ubiquitous in eukaryotic cells. These G-proteins are believed to play a role in central processes, such as signal transduction, cell differentiation and membrane vesicle transport. By screening genomic and cDNA libraries of the colonial alga, Volvox carteri f. nagariensis, with ypt DNA probes from Zea mays, we have identified the first member of a ypt gene family, yptV1, within a green alga. The 1538-bp yptV1 gene of V. carteri consists of nine exons and eight introns and has three potential polyadenylation sites 210, 420 and 500 bp downstream from the UGA stop codon. The derived 203-amino-acid polypeptide, YptV1, exhibits 81% similarity with Ypt1 from mouse, with the corresponding genes sharing four identical intron positions. Recombinant YptV1 (reYptV1) produced in Escherichia coli retains the ability to bind GTP after SDS-PAGE and immobilization on nitrocellulose. Immunological studies using polyclonal antibodies against reYptV1 indicate that the protein is present in the membrane fraction of a V. carteri extract and is expressed throughout the whole life-cycle of the alga. Similar to other Ras-like proteins, YptV1 contains two conserved C-terminal cysteine residues suggesting post-translational modification(s), such as isoprenylation or palmitoylation, required for membrane anchoring. The presumptive role of YptV1 in cytoplasmic vesicle transport is briefly discussed.

 

 

VOYTAS DF, CUMMINGS MP, KONIECZNY A, et al.

 

COPIA-LIKE RETROTRANSPOSONS ARE UBIQUITOUS AMONG PLANTS

P NATL ACAD SCI USA 89 (15): 7124-7128 AUG 1 1992

 

Abstract:

Transposable genetic elements are assumed to be a feature of all eukaryotic genomes. Their identification, however, has largely been haphazard, limited principally to organisms subjected to molecular or genetic scrutiny. We assessed the phylogenetic distribution of copia-like retrotransposons, a class of transposable element that proliferates by reverse transcription, using a polymerase chain reaction assay designed to detect copia-like element reverse transcriptase sequences. copia-like retrotransposons were identified in 64 plant species as well as the photosynthetic protist Volvox carteri. The plant species included representatives from 9 of 10 plant divisions, including bryophytes, lycopods, ferns, gymnosperms, and angiosperms. DNA sequence analysis of 29 cloned PCR products and of a maize retrotransposon cDNA confirmed the identity of these sequences as copia-like reverse transcriptase sequences, thereby demonstrating that this class of retrotransposons is a ubiquitous component of plant genomes.

 

DOMOZYCH DS, WELLS B, SHAW PJ

 

THE CELL-WALL OF THE CHLAMYDOMONAD FLAGELLATE, GLOEOMONAS-KUPFFERI (VOLVOCALES, CHLOROPHYTA)

PROTOPLASMA 168 (3-4): 95-106 1992

 

Abstract:

The large unicellular flagellate, Gloeomonas kupfferi, has recently been used as an important tool in chlamydomonad cell biology research, especially in studies dealing with the structure and function of the endomembrane system. However, little is known about the main secretory product, the cell wall. This study presents structural, chemical and immunological information about this wall. This 850-900 nm thick matrix is highly elaborate and consists of three distinct layers: an inner stratum (325 nm thick) consisting of tightly interwoven fibers, a medial crystalline layer consisting of 22-23 nm subunits and an outer wall layer (500 nm thick) of outwardly-radiating fibrils. Rapid freeze-deep etch analysis reveals that the 35-40 nm fibers of the outer layer form a quasi-lattice of 160 nm subunits. The outer wall can be removed from whole pellets using the chelator, CDTA. The medial wall complex can be solubilized by perchlorate. SDS-gel electrophoresis reveals that the perchlorate soluble-material consists of five high molecular weight glycoproteins and five major low molecular weight glycoproteins. The electrophoretic profile is roughly similar to that of Chlamydomonas reinhardtii. Antibodies were successfully raised against the outer wall component and were shown to label the outer wall layer.

 

BUCHHEIM MA, CHAPMAN RL

 

PHYLOGENY OF CARTERIA (CHLOROPHYCEAE) INFERRED FROM MOLECULAR AND ORGANISMAL DATA

J PHYCOL 28 (3): 362-374 JUN 1992

 

Abstract:

Comparative ultrastructural data have shown that at least two distinct groups exist within Carteria. Similarly, interpretations of variation in gross morphological features have led to the discovery of morphologically distinct groups within the genus. Partial sequences from the nuclear-encoded small- and large-subunit ribosomal RNA molecules of selected Carteria taxa were studied as a means of 1) testing hypotheses that distinct groups of species exist within the genus and 2) assessing monophyly of the genus. Parsimony analysis of the sequence data suggests that three Carteria species, C. lunzensis, C. crucifera, and C. olivieri, form a monopkyletic group that is the basal sister group to all other ingroup flagellate taxa (including species of Chlamydomonas, Haematococcus, Stephanosphaera, Volvox, and Eudorina). Two other Carteria taxa, C. radiosa and Carteria sp. (UTEX isolate LB 762), form a clade that is the sister group to a clade that includes Haematococcus spp., Chlamydomonas spp., and Stephanosphaera. Thus, the sequence data support the interpretations of ultrastructural evidence that described two distinct Carteria lineages. Moreover, the sequence data suggest that these two Carteria groups do not form a monophyletic assemblage. Parsimony analysis of a suite of organismal (morphological, ultrastructural, life history, and biochemical) character data also suggest two distinct lineages among the five Carteria taxa; however, the organismal data are ambiguous regarding monophyly of these Carteria taxa. When the two independent data sets are pooled, monophyly of Carteria is not supported; therefore, the weight of available evidence, both molecular and organismal, fails to support the concept of Carteria as a natural genus.

 

 

BLAKEFIELD MK, CALKINS J

 

INHIBITION OF PHOTOTAXIS IN VOLVOX-AUREUS BY NATURAL AND SIMULATED SOLAR ULTRAVIOLET-LIGHT

PHOTOCHEM PHOTOBIOL 55 (6): 867-872 JUN 1992

 

Abstract:

Exposure to artificial UV wavelengths and the UV component of sunlight delays positive phototaxis in the green alga Volvox aureus. Broad band wavelength filters were used to modify the Output from UV-B sources (280-320 nm) and natural sunlight. The delay in phototaxis by artificial UV is increased with exposure to shorter UV-B wavelengths. Natural sunlight experiments were performed with exposure to full sunlight and to its UV component only. The UV component present in summer sunlight Produced long periods of inhibition in phototaxis and even lethality, while exposure to the total spectrum of sunlight had no significant effects on movement or survival. The data indicate that although this species of alga is well equipped to deal with present levels of UV exposure, increases in the short UV-B wavelengths in sunlight may force an alteration in patterns of photomovement.

 

ERTL H, HALLMANN A, WENZL S, et al.

 

A NOVEL EXTENSIN THAT MAY ORGANIZE EXTRACELLULAR-MATRIX BIOGENESIS IN VOLVOX-CARTERI

EMBO J 11 (6): 2055-2062 JUN 1992

 

Abstract:

ISG is a sulphated, extracellular glycoprotein synthesized for only a few minutes in inverting Volvox embryos and inverting sperm cell packets. This control operates at the level of transcription. ISG has been characterized by studies of protein chemistry and electron microscopy. The primary structure of ISG has been derived from genomic DNA and cDNA. ISG is composed of a globular and a rod-shaped domain. The rod-shaped domain represents a member of the extensin family with numerous repeats of Ser-(Hyp)4-6 motifs. A synthetic decapeptide matching the C-terminal sequence is able to disaggregate the organism into individual cells. Immunofluorescence microscopy localizes ISG within the boundary zone of the ECM.

 

DESNITSKI AG

 

CELLULAR MECHANISMS OF THE EVOLUTION OF ONTOGENY IN VOLVOX

ARCH PROTISTENKD 141 (3): 171-178 APR 1992

 

Abstract:

The green flagellates of the genus Volvox can be conditionally subdivided into two groups according to the size of gonidia (asexual reproductive cells) at the onset of cleavage. In Volvox carteri and several other species the gonidium undergoes an extended period of hypertrophied growth, after which a series of rapid fissions occurs. Embryonic cells do not grow during the intervals between consecutive divisions. In representatives of the second group (e.g., V. aureus) the period of gonidial enlargement is comparatively nondurable; thus the cleavage begins when the gonidium is relatively small, and each division is followed by a period of cellular growth.

 

In this paper the evolutionary relationships between two types of asexual life cycle in Volvox are analysed on the basis of literary and our own data. It is supposed that the V. aureus type of development with slow divisions of small gonidia is more advanced in the evolutionary respect than the V. carteri type of development with rapid divisions of large gonidia.

 

Experimental analysis of the role of light and dark for embryonic cleavage progression in V. aureus, V. carteri f. nagariensis and V. tertius as well as the experiments with several metabolic inhibitors (aminopterin, actinomycin D, cycloheximide and streptomycin) have enabled us to elucidate cellular mechanisms of the evolution of ontogenesis in Volvox.

 

MENGELE R, SUMPER M

 

GULOSE AS A CONSTITUENT OF A GLYCOPROTEIN

FEBS LETT 298 (1): 14-16 FEB 17 1992

 

Abstract:

The aldohexose gulose was identified as a constituent of a hydroxyproline-rich glycopeptide derived from the glycoprotein SSG 185. This glycoprotein is part of the extracellular matrix of the green alga Volvox carteri. The gulose residue occupies a terminal position in the corresponding saccharide.

 

ALHASANI H, JAENICKE L

 

CHARACTERIZATION OF THE SEX-INDUCER GLYCOPROTEIN OF VOLVOX-CARTERI F WEISMANNIA

SEX PLANT REPROD 5 (1): 8-12 JAN 1992

 

Abstract:

Sexual inducer pheromones from Volvox carteri f. weismannia, strains 65-30(12) and 1B were purified and characterized as glycoproteins with apparent molecular weights of 27 kDa and 28.5 kDa, respectively. This subspecies yielded 20-40 times more pheromone based on weight per spheroid than Volvox carteri f. nagariensis, but its specific activity (threshold dilution) is four to five orders of magnitude less (10(-12) to 10(-13) M). Gas-chromatographic sugar analysis revealed quantitative differences in the composition of the O- and N-glucans compared with the V. carteri f. nagariensis inducer. The V. carteri f. weismannia pheromones showed antigenic cross-reaction with an antiserum directed against chemically deglycosylated inducer from V. carteri f. nagariensis. However, there is only unilateral biological cross-induction. The V. carteri f. nagariensis inducer is strictly competent for its own gonidia only; the inducers from V. carteri f. weismannia also cross-induce V. carteri f. nagariensis. This pattern of cross-induction suggests the existence of related pheromone receptors but with different ligand specificities.

 

LARSON A, KIRK MM, KIRK DL

 

MOLECULAR PHYLOGENY OF THE VOLVOCINE FLAGELLATES

MOL BIOL EVOL 9 (1): 85-105 JAN 1992

 

Abstract:

Phylogenetic studies of approximately 2,000 bases of sequence from the large and small nuclear-encoded ribosomal RNAs are used to investigate the origins of the genus Volvox. The colonial and multicellular genera currently placed in the family Volvocaceae form a monophyletic group that is significantly closer phylogenetically to Chlamydomonas reinhardtii than it is to the other unicellular green flagellates that were tested, including Chlamydomonas eugametos, Chlorella pyrenoidosa, and Haematococcus lacustris. Statistical analysis of 251 phylogenetically informative nucleotide positions rejects the "volvocine lineage" hypothesis, which postulates a monophyletic evolutionary progression from unicellular organisms (such as Chlamydomonas), through colonial organisms (e.g., Gonium, Pandorina, Eudorina, and Pleodorina) demonstrating increasing size, cell number, and tendency toward cellular differentiation, to multicellular organisms having fully differentiated somatic and reproductive cells (in the genus Volvox). The genus Volvox appears not to be monophyletic. Volvox capensis falls outside a lineage containing other representatives of Volvox(V. aureus, V. carteri, and V. obversus), and both of these Volvox lineages are more closely related to certain colonial genera than they are to each other. This implies either a diphyletic origin of Volvox from different colonial volvocacean ancestors, a phylogenetic derivation of some of the colonial genera from a multicellular (i.e., Volvox) ancestor, or both. Considered together with previously published observations, these results suggest that the different levels of organizational and developmental complexity found in the Volvocaceae represent alternative stable states, among which evolutionary transitions have occurred several times during the phylogenetic history of this group.

 

SCHMITT R, FABRY S, KIRK DL

 

IN SEARCH OF MOLECULAR-ORIGINS OF CELLULAR-DIFFERENTIATION IN VOLVOX AND ITS RELATIVES

INT REV CYTOL 139: 189-265 1992

 

 

MENGELE R, SUMPER M

 

GULOSE AS A CONSTITUENT OF A GLYCOPROTEIN

FEBS LETT 298 (1): 14-16 FEB 17 1992

 

 

1991

 

 

KOUFOPANOU V, BELL G

 

DEVELOPMENTAL MUTANTS OF VOLVOX - DOES MUTATION RECREATE THE PATTERNS OF PHYLOGENETIC DIVERSITY

EVOLUTION 45 (8): 1806-1822 DEC 1991

 

Abstract:

The nature of the variation which is created by mutation can show how the direction of evolution is constrained by internal biases arising from development and pre-existing design. We have attempted to quantify these biases by measuring eight life history characters in developmental mutants of Volvox carteri. Most of the mutants in our sample were inferior to the wild type, but deviated by less than tenfold from the wild-type mean. Characters differed in mutability, suggesting different levels of canalisation. Most correlations between life history characters among strains were positive, but there was a significant negative correlation between the size and the number of reproductive cells, suggesting an upper limit to the total quantity of germ produced by individuals. The most extreme phenotypes in our sample were very vigorous, showing that not all mutations of large effect are unconditionally deleterious. We investigated the effect of developmental constraints on the course of evolution by comparing the variance and covariance patterns among mutant strains with those among species in the family Volvocaceae. A close correspondence between patterns at these two levels would suggest that pre-existing design has a strong influence on evolution, while little or no correspondence shows the action of selection. The variance generated by mutation was equal to that generated by speciation in the family Volvocaceae, the genus Volvox, or the section Merillosphaera, depending on the character considered. We found that mutation changes the volume of somatic tissue independently of the quantity of germ tissue, so that the interspecific correlation between soma and germ can be attributed to selection. The negative correlation between size and number of germ cells among mutants of V. carteri is also seen among the larger members of the family (Volvox spp.), but not among the smaller members, suggesting a powerful design constraint that may be responsible for the absence of larger forms in the entire group.

 

 

HAAS E, SUMPER M

 

THE SEXUAL INDUCER OF VOLVOX-CARTERI - ITS LARGE-SCALE PRODUCTION AND SECRETION BY SACCHAROMYCES-CEREVISIAE

FEBS LETT 294 (3): 282-284 DEC 9 1991

 

Abstract:

The DNA sequence coding for the sexual inducer glycoprotein of Volvox carteri and its N-terminal signal peptide was placed under the control of the repressible acid phosphatase promoter of the yeast Saccharomyces cerevisiae in a yeast-E. coli shuttle vector. Yeast transformed by this construct synthesized and secreted into the culture medium biologically active inducer in amounts two to three orders of magnitude higher than observed in the Volvox system.

 

 

JAENICKE L, VANLEYEN K, SIEGMUND HU

 

DOLICHYL PHOSPHATE-DEPENDENT GLYCOSYLTRANSFERASES UTILIZE TRUNCATED COFACTORS

BIOL CHEM H-S 372 (11): 1021-1026 NOV 1991

 

 

Abstract:

Synthetic truncated dolichyl phosphates of chain lengths from four to thirteen isoprene units (Jaenicke L. and Siegmund H.-U., Chem. Phys. Lipids 51 (1989) 159-170) were assayed for their cofactor activity in the enzymatic transfer of hexoses and hexosamines. The enzymes were microsomal preparations from the green alga Volvox carteri, baker's yeast, and mammalian liver cells. Under saturating conditions, the acceptor activities of the truncated dolichyl phosphates increased from zero to full strength as compared to the mixture of long-chain dolichyl phosphates from natural sources with growing chain length from five to nine isoprene units. K(m) determinations confirmed the results. Of the geometric isomers of dolichyl 7-phosphate (35 carbon atoms), the 14-trans compound has unchanged acceptor activity; all-trans dolichyl 7-phosphate, however, was almost inactive. The data suggest that hydrophobicity may be an important, but not the only criterion for the binding of the isoprene moiety to the active sites of the transferase enzyme(s) and that the geometry of more than only one double bond in the dolichols is recognized.

 

 

KIRK DL, KAUFMAN MR, KEELING RM, et al.

 

GENETIC AND CYTOLOGICAL CONTROL OF THE ASYMMETRIC DIVISIONS THAT PATTERN THE VOLVOX EMBRYO

DEVELOPMENT : 67-82 Suppl. 1 1991

 

 

Abstract:

The highly regular pattern in which approximately 2000 small somatic cells and 16 large reproductive cells (or 'gonidia') are arranged in a typical asexual adult of Volvox carteri can be traced back to a stereotyped program of embryonic cleavage divisions. After five symmetrical divisions have produced 32 cells of equal size, the anterior 16 cells cleave asymmetrically, to produce one small somatic cell initial and one larger gonidial initial each. The gonidial initials then cease dividing before the somatic cell initials do. The significance of the visibly asymmetric divisions is underscored by genetic and experimental evidence that differences in size - rather than differences in cytoplasmic quality - are causally important in activating the programs that cause small cells to become mortal somatic cells and large cells to differentiate as reproductive cells. A number of loci, including at least five mul ('multiple gonidia') loci, appear to be responsible for determining where and when asymmetric divisions will occur, since mutations at these loci result in modified temporal and/or spatial patterns of asymmetric division in one or more portions of the life cycle. But the capacity to divide asymmetrically at all appears to require a function encoded by the gls (gonidialess) locus, since gls mutants fail to execute any asymmetric divisions. Second-site suppressors of gls that have been identified may encode other functions required for asymmetric division. Cytological and immunocytochemical studies of dividing embryos are being undertaken in an attempt to elucidate the mechanisms by which cell-division planes are established - and shifted - under the influence of such pattern-specifying genes. Studies to date clearly indicate a central role for the basal body apparatus, and particularly its microtubular rootlets, in establishing the orientation of both the mitotic spindle and the cleavage furrow; but it remains to be determined how behavior of the division apparatus becomes modified during asymmetric division.

 

 

WAYNE R, KADOTA A, WATANABE M, et al.

 

PHOTOMOVEMENT IN DUNALIELLA-SALINA - FLUENCE RATE-RESPONSE CURVES AND ACTION SPECTRA

PLANTA 184 (4): 515-524 1991

 

Abstract:

We determined the action spectra of the photophobic responses as well as the phototactic response in Dunaliella salina (Volvocales) using both single cells and populations. The action spectra of the photophobic responses have maximum at 510 nm, the spectrum for phototaxis has a maximum at 450-460 nm. These action spectra are not compatible with the hypothesis that flavoproteins are the photoreceptor pigments, and we suggest that carotenoproteins or rhodopsins act as the photoreceptor pigments. We also conclude that the phototactic response in Dunaliella is an elementary response, quite independent of the step-up and step-down photophobic responses. We also determined the action spectra of the photoaccumulation response in populations of cells adapted to two different salt conditions. Both action spectra have a peak a 490 nm. The photoaccumulation response may be a complex response composed of the phototactic and photophobic responses. Blue or blue-green light does not elicit a photokinetic response in Dunaliella.

 

 

TAM LW, KIRK DL

 

THE PROGRAM FOR CELLULAR-DIFFERENTIATION IN VOLVOX-CARTERI AS REVEALED BY MOLECULAR ANALYSIS OF DEVELOPMENT IN A GONIDIALESS SOMATIC REGENERATOR MUTANT

DEVELOPMENT 112 (2): 571-580 JUN 1991

 

Abstract:

Development of a 'gonidialess'/'somatic regenerator' double mutant of Volvox carteri was analyzed with a number of cell-type-specific cDNA probes that had been identified in a previous study. Whereas in wild-type strains somatic cells and gonidia (asexual reproductive cells) constitute two distinct cell lineages, in this mutant all cells first differentiate as somatic cells and then redifferentiate as gonidia. During the initial period of somatic differentiation, we found that both gonidial and 'early' somatic transcripts were accumulated in the mutant, consistent with the idea that it is the regA gene product (which is defective in this mutant) that normally acts to suppress gonidial gene expression in somatic cells. Later in development, levels of early somatic transcripts fell abruptly, levels of the late somatic transcripts remained extremely low, and levels of gonidial transcripts rose as the cells redifferentiated. Thus it appears that in the mutant cells the gonidial program of development takes over and somatic differentiation is aborted before the stage at which late somatic genes are normally activated. These results provide molecular genetic support for a model which postulates that three types of genes (including the two that are defective in the strain studied here) are crucial for converting the sequential program of differentiation seen in more primitive volvocalean algae to the dichotomous program of germ-soma differentiation that occurs in wild-type V. carteri.

 

 

ROSATI G, VERNI F

 

SEXUAL RECOGNITION IN PROTOZOA - CHEMICAL SIGNALS AND TRANSDUCTION MECHANISMS

ZOOL SCI 8 (3): 415-429 JUN 1991

 

 

TAM LW, STAMER KA, KIRK DL

 

EARLY AND LATE GENE-EXPRESSION PROGRAMS IN DEVELOPING SOMATIC-CELLS OF VOLVOX-CARTERI

DEV BIOL 145 (1): 67-76 MAY 1991

 

 

RANSICK A

 

REPRODUCTIVE CELL SPECIFICATION DURING VOLVOX-OBVERSUS DEVELOPMENT

DEV BIOL 143 (1): 185-198 JAN 1991

 

1990

 

BUCHHEIM MA, TURMEL M, ZIMMER EA, et al.

 

PHYLOGENY OF CHLAMYDOMONAS (CHLOROPHYTA) BASED ON CLADISTIC-ANALYSIS OF NUCLEAR 18S RIBOSOMAL-RNA SEQUENCE DATA

J PHYCOL 26 (4): 689-699 DEC 1990

 

Abstract:

The genus Chlamydomonas Ehrenberg may contain as many as 450 described species. Morphological, physiological and molecular data show that variation among some Chlamydomonas species can be great, leading to speculation that multiple, generic-level lineages exist within this genus. The most recent systematic studies of Chlamydomonas have led to proposals of nine distinct morphological and 15 distinct sporangial autolysin groups. Partial sequences from the nuclear small subunit rNAs from 14 Chlamydomonas species representing 12 autolysin and four morphological groups, and from three flagellates thought to be related to Chlamydomonas were determined in a phylogenetic study of relationships among these algae. Sequence comparisons among some Chlamydomonas species revealed differences comparable to the sequence divergence between soybeans and cycads. Cladistic analysis of the sequence data suggests that multiple lineages exist among species of Chlamydomonas. Some of these lineages represent alliances of both Chlamydomonas and non-Chlamydomonas taxa; thus, the current taxonomy does not reflect natural, or monophyletic, groups. Collectively, these lineages may represent distinct families or even orders.

 

CRESNAR B, MAGES W, MULLER K, et al.

 

STRUCTURE AND EXPRESSION OF A SINGLE ACTIN GENE IN VOLVOX-CARTERI

CURR GENET 18 (4): 337-346 NOV 1990

 

MULLER K, LINDAUER A, BRUDERLEIN M, et al.

 

ORGANIZATION AND TRANSCRIPTION OF VOLVOX HISTONE-ENCODING GENES - SIMILARITIES BETWEEN ALGAL AND ANIMAL GENES

GENE 93 (2): 167-175 SEP 14 1990

 

BALSHUSEMANN D, JAENICKE L

 

THE OLIGOSACCHARIDES OF THE GLYCOPROTEIN PHEROMONE OF VOLVOX-CARTERI F NAGARIENSIS IYENGAR (CHLOROPHYCEAE)

EUR J BIOCHEM 192 (1): 231-237 AUG 28 1990

 

 

ADAMS CR, STAMER KA, MILLER JK, et al.

 

PATTERNS OF ORGANELLAR AND NUCLEAR INHERITANCE AMONG PROGENY OF 2 GEOGRAPHICALLY ISOLATED STRAINS OF VOLVOX-CARTERI

CURR GENET 18 (2): 141-153 AUG 1990

 

BALSHUSEMANN D, JAENICKE L

 

TIME AND MODE OF SYNTHESIS OF THE SEXUAL INDUCER GLYCOPROTEIN OF VOLVOX-CARTERI

FEBS LETT 264 (1): 56-58 MAY 7 1990

 

WAFFENSCHMIDT S, KNITTLER M, JAENICKE L

 

CHARACTERIZATION OF A SPERM LYSIN OF VOLVOX-CARTERI

SEX PLANT REPROD 3 (1): 1-6 FEB 1990

 

 

1989

 

ERTL H, MENGELE R, WENZL S, et al.

 

THE EXTRACELLULAR-MATRIX OF VOLVOX-CARTERI - MOLECULAR-STRUCTURE OF THE CELLULAR COMPARTMENT

J CELL BIOL 109 (6): 3493-3501 Part 2 DEC 1989

 

 

BALSHUSEMANN D, GILLES R, JAENICKE L

 

THE BIOCHEMISTRY OF THE SEX INDUCER OF VOLVOX-CARTERI

BIOL CHEM H-S 370 (9): 873-874 SEP 1989

 

FELDWISCH O, ERK H, JAENICKE L

 

CYCLIC-AMP BINDING-PROTEIN AND PHOSPHODIESTERASES IN VOLVOX-CARTERI

BIOL CHEM H-S 370 (9): 895-895 SEP 1989

 

 

FELDWISCH O, ERK H, JAENICKE L

 

CYCLIC-AMP BINDING-PROTEIN AND PHOSPHODIESTERASES IN VOLVOX-CARTERI

BIOL CHEM H-S 370 (9): 895-895 SEP 1989

 

HOLST O, CHRISTOFFEL V, FRUND R, et al.

 

A PHOSPHODIESTER BRIDGE BETWEEN 2 ARABINOSE RESIDUES AS A STRUCTURAL ELEMENT OF AN EXTRACELLULAR GLYCOPROTEIN OF VOLVOX-CARTERI

EUR J BIOCHEM 181 (2): 345-350 MAY 1 1989

 

1988

 

KASKA DD, MYLLYLA R, GUNZLER V, et al.

 

PROLYL 4-HYDROXYLASE FROM VOLVOX-CARTERI - A LOW-MR ENZYME ANTIGENICALLY RELATED TO THE ALPHA-SUBUNIT OF THE VERTEBRATE ENZYME

BIOCHEM J 256 (1): 257-263 NOV 15 1988

 

 

HARPER JF, MAGES W

 

ORGANIZATION AND STRUCTURE OF VOLVOX BETA-TUBULIN GENES

MOL GEN GENET 213 (2-3): 315-324 AUG 1988

 

MAGES W, SALBAUM JM, HARPER JF, et al.

 

ORGANIZATION AND STRUCTURE OF VOLVOX ALPHA-TUBULIN GENES

MOL GEN GENET 213 (2-3): 449-458 AUG 1988

 

GOODENOUGH UW, HEUSER JE

 

MOLECULAR-ORGANIZATION OF CELL-WALL CRYSTALS FROM CHLAMYDOMONAS-REINHARDTII AND VOLVOX-CARTERI

J CELL SCI 90: 717-733 Part 4 AUG 1988

 

 

MAGES HW, TSCHOCHNER H, SUMPER M

 

THE SEXUAL INDUCER OF VOLVOX-CARTERI PRIMARY STRUCTURE DEDUCED FROM CDNA SEQUENCE

FEBS LETT 234 (2): 407-410 JUL 18 1988

 

 

NOZAKI H

 

MORPHOLOGY, SEXUAL REPRODUCTION AND TAXONOMY OF VOLVOX-CARTERI F KAWASAKIENSIS F NOV (CHLOROPHYTA) FROM JAPAN

PHYCOLOGIA 27 (2): 209-220 JUN 1988

 

MULLER K, SCHMITT R

 

HISTONE GENES OF VOLVOX-CARTERI - DNA-SEQUENCE AND ORGANIZATION OF 2 H3-H4 GENE LOCI

NUCLEIC ACIDS RES 16 (9): 4121-4136 MAY 11 1988

 

 

KIRK DL

 

THE ONTOGENY AND PHYLOGENY OF CELLULAR-DIFFERENTIATION IN VOLVOX

TRENDS GENET 4 (2): 32-36 FEB 1988

 

1987

 

ADAIR WS, STEINMETZ SA, MATTSON DM, et al.

 

NUCLEATED ASSEMBLY OF CHLAMYDOMONAS AND VOLVOX CELL-WALLS

J CELL BIOL 105 (5): 2373-2382 NOV 1987

 

MULLER K, RAUSCH H, SCHMITT R

 

MOLECULAR EVOLUTION OF VOLVOX CARTERI PROBED WITH HISTONE AND RDNA GENES

BIOL CHEM H-S 368 (9): 1084-1084 SEP 1987

 

 

GUNTHER R, BAUSE E, JAENICKE L

 

UDP-L-ARABINOSE-HYDROXYPROLINE-O-GLYCOSYLTRANSFERASES IN VOLVOX-CARTERI

FEBS LETT 221 (2): 293-298 SEP 14 1987

 

 

HARPER JF, HUSON KS, KIRK DL

 

USE OF REPETITIVE SEQUENCES TO IDENTIFY DNA POLYMORPHISMS LINKED TO REGA, A DEVELOPMENTALLY IMPORTANT LOCUS IN VOLVOX

GENE DEV 1 (6): 573-584 AUG 1987

 

 

TSCHOCHNER H, LOTTSPEICH F, SUMPER M

 

THE SEXUAL INDUCER OF VOLVOX-CARTERI - PURIFICATION, CHEMICAL CHARACTERIZATION AND IDENTIFICATION OF ITS GENE

EMBO J 6 (8): 2203-2207 AUG 1987

 

 

KIRK DL, BARAN GJ, HARPER JF, et al.

 

STAGE-SPECIFIC HYPERMUTABILITY OF THE REGA LOCUS OF VOLVOX, A GENE REGULATING THE GERM SOMA DICHOTOMY

CELL 48 (1): 11-24 JAN 16 1987

 

 

1986

 

SCHLIPFENBACHER R, WENZL S, LOTTSPEICH F, et al.

 

AN EXTREMELY HYDROXYPROLINE-RICH GLYCOPROTEIN IS EXPRESSED IN INVERTING VOLVOX EMBRYOS

FEBS LETT 209 (1): 57-62 DEC 1 1986

 

 

KIRK DL, KIRK MM

 

HEAT-SHOCK ELICITS PRODUCTION OF SEXUAL INDUCER IN VOLVOX

SCIENCE 231 (4733): 51-54 JAN 3 1986

 

COGGIN SJ, KOCHERT G

 

FLAGELLAR DEVELOPMENT AND REGENERATION IN VOLVOX-CARTERI (CHLOROPHYTA)

J PHYCOL 22 (3): 370-381 SEP 1986

 

WENZL S, SUMPER M

 

A NOVEL GLYCOSPHINGOLIPID THAT MAY PARTICIPATE IN EMBRYO INVERSION IN VOLVOX CARTERI

CELL 46 (4): 633-639 AUG 15 1986

 

SOMMER U, GLIWICZ ZM

 

LONG-RANGE VERTICAL MIGRATION OF VOLVOX IN TROPICAL LAKE CAHORA BASSA (MOZAMBIQUE)

LIMNOL OCEANOGR 31 (3): 650-653 MAY 1986

 

 

KIRK DL, HARPER JF

 

GENETIC, BIOCHEMICAL, AND MOLECULAR APPROACHES TO VOLVOX DEVELOPMENT AND EVOLUTION

INT REV CYTOL 99: 217-293 1986

 

WENZL S, SUMPER M

 

EARLY EVENT OF SEXUAL INDUCTION IN VOLVOX - CHEMICAL MODIFICATION OF THE EXTRACELLULAR-MATRIX

DEV BIOL 115 (1): 119-128 MAY 1986

 

BARAN GJ, HUSKEY RJ

 

DEVELOPMENTAL-CHANGES IN THE SENSITIVITY OF VOLVOX TO ULTRAVIOLET-LIGHT

DEV GENET 6 (4): 269-280 1986

 

KIRK DL, KIRK MM

 

GENETIC AND ENVIRONMENTAL-REGULATION OF DETERMINATION AND DIFFERENTIATION IN VOLVOX

J CELL BIOCHEM : 37-37 Suppl. 10D 1986

 

SCHMITT R, MULLER K, RAUSCH H, et al.

 

HOUSEKEEPING GENES AND THEIR EXPRESSION IN THE GENERATION CYCLE OF VOLVOX-CARTERI

J CELL BIOCHEM : 43-43 Suppl. 10D 1986

 

KIRK DL, BIRCHEM R, KING N

 

THE EXTRACELLULAR-MATRIX OF VOLVOX - A COMPARATIVE-STUDY AND PROPOSED SYSTEM OF NOMENCLATURE

J CELL SCI 80: 207-231 FEB 1986

 

1985

 

JAENICKE L, GILLES R

 

GERM-CELL DIFFERENTIATION IN VOLVOX-CARTERI

DIFFERENTIATION 29 (3): 199-206 1985

 

 

GILLES R, MOKA R, JAENICKE L

 

THE EXTRACELLULAR-MATRIX PLAYS A FUNCTIONAL-ROLE IN SEXUAL-DIFFERENTIATION OF VOLVOX CARTERI

BIOL CHEM H-S 366 (9): 793-794 1985

 

 

KIRK MM, KIRK DL

 

TRANSLATIONAL REGULATION OF PROTEIN-SYNTHESIS, IN RESPONSE TO LIGHT, AT A CRITICAL STAGE OF VOLVOX DEVELOPMENT

CELL 41 (2): 419-428 1985

 

 

GILLES R, MOKA R, GILLES C, et al.

 

CYCLIC-AMP AS AN INTRASPHEROIDAL DIFFERENTIATION SIGNAL IN VOLVOX-CARTERI

FEBS LETT 184 (2): 309-312 1985

 

 

KOPAN R, KURN N, OVADIA M

 

SYNTHESIS AND POSSIBLE ROLE OF PROTEOGLYCANS DURING VOLVOX DEVELOPMENT

CELL DIFFER DEV 16 (2): 119-132 1985

 

 

1984

 

WEISSHAAR B, GILLES R, MOKA R, et al.

 

A HIGH-FREQUENCY MUTATION STARTS SEXUAL REPRODUCTION IN VOLVOX-CARTERI

Z NATURFORSCH C 39 (11-1): 1159-1162 1984

 

 

HOFFMAN JL

 

MONOCLONAL-ANTIBODIES TO SURFACE COMPONENTS OF VOLVOX

J CELL BIOL 99 (4): A243-A243 1984

 

 

GILLES R, JAENICKE L

 

EXTRACELLULAR PHOSPHOPROTEINS ARE INVOLVED IN SEXUAL-DIFFERENTIATION OF VOLVOX-CARTERI

H-S Z PHYSIOL CHEM 365 (9): 990-990 1984

 

GILLES R, GILLES C, JAENICKE L

 

PHEROMONE-BINDING AND MATRIX-MEDIATED EVENTS IN SEXUAL INDUCTION OF VOLVOX-CARTERI

Z NATURFORSCH C 39 (6): 584-592 1984

 

WENZL S, THYM D, SUMPER M

 

DEVELOPMENT-DEPENDENT MODIFICATION OF THE EXTRACELLULAR-MATRIX BY A SULFATED GLYCOPROTEIN IN VOLVOX-CARTERI

EMBO J 3 (4): 739-744 1984

 

 

HOOPS HJ

 

SOMATIC-CELL FLAGELLAR APPARATUSES IN 2 SPECIES OF VOLVOX (CHLOROPHYCEAE)

J PHYCOL 20 (1): 20-27 1984

 

MULLER T, BAUSE E, JAENICKE L

 

EVIDENCE FOR AN INCOMPLETE DOLICHYL-PHOSPHATE PATHWAY OF LIPOGLYCAN FORMATION IN VOLVOX-CARTERI F NAGARIENSIS

EUR J BIOCHEM 138 (1): 153-159 1984

 

 

1983

 

REYNOLDS CS PENTECOST A

 

THE DISTRIBUTION OF DAUGHTER COLONIES AND CELL NUMBERS IN A NATURAL-POPULATION OF VOLVOX-AUREUS EHRENB

ANN BOT-LONDON 52 (5): 769-776 1983

 

GROWTH-RATE RESPONSES OF VOLVOX-AUREUS EHRENB (CHLOROPHYTA, VOLVOCALES) TO VARIABILITY IN THE PHYSICAL-ENVIRONMENT

BRIT PHYCOL J 18 (4): 433-442 1983

 

GILLES R, GILLES C, JAENICKE L

 

SEXUAL-DIFFERENTIATION OF THE GREEN-ALGA VOLVOX-CARTERI - INVOLVEMENT OF EXTRACELLULAR PHOSPHORYLATED PROTEINS

NATURWISSENSCHAFTEN 70 (11): 571-572 1983

 

 

HOFFMAN JL

 

EFFECTS OF MONENSIN TREATMENT ON SEXUAL DEVELOPMENT IN VOLVOX

J CELL BIOL 97 (5): A63-A63 1983

 

 

MATTSON DM, GREEN KJ

 

BASAL BODY ABNORMALITIES IN A MORPHOGENETIC MUTANT OF VOLVOX

J CELL BIOL 97 (5): A206-A206 1983

 

 

HARPER JF, KIRK DL

 

LINKAGE ANALYSIS OF VOLVOX MORPHOGENETIC MUTANTS, USING A MAP BASED ON RESTRICTION POLYMORPHISMS

J CELL BIOL 97 (5): A327-A327 1983

 

 

VASILETS V, COTTRELL SF

 

AGE-DEPENDENT ALTERATIONS IN THE SOMATIC-CELLS OF VOLVOX-CARTERI

J CELL BIOL 97 (5): A345-A345 1983

 

GANF GG, SHIEL RJ, MERRICK CJ

 

PARASITISM - THE POSSIBLE CAUSE OF THE COLLAPSE OF A VOLVOX POPULATION IN MOUNT BOLD RESERVOIR, SOUTH-AUSTRALIA

AUST J MAR FRESH RES 34 (3): 489-494 1983

 

 

WEINHEIMER T

 

CELLULAR-DEVELOPMENT IN THE GREEN-ALGA VOLVOX-CARTERI

CYTOBIOS 36 (143-): 161-173 1983

 

KIRK DL, KIRK MM

 

PROTEIN SYNTHETIC PATTERNS DURING THE ASEXUAL LIFE-CYCLE OF VOLVOX-CARTERI

DEV BIOL 96 (2): 493-506 1983

 

 

BAUSE E, MULLER T, JAENICKE L

 

SYNTHESIS AND CHARACTERIZATION OF LIPID-LINKED MANNOSYL OLIGOSACCHARIDES IN VOLVOX-CARTERI F-NAGARIENSIS

ARCH BIOCHEM BIOPHYS 220 (1): 200-207 1983

 

1982

 

COLEMAN AW, MAGUIRE MJ

 

A MICROSPECTROFLUOROMETRIC ANALYSIS OF NUCLEAR AND CHLOROPLAST DNA IN VOLVOX

DEV BIOL 94 (2): 441-450 1982

 

 

GILLES R, JAENICKE L

 

DIFFERENTIATION IN VOLVOX-CARTERI - STUDY OF PATTERN VARIATION OF REPRODUCTIVE CELLS

Z NATURFORSCH C 37 (10): 1023-1030 1982

 

BARAN GJ, HUSKEY RJ

 

GENE-EXPRESSION DURING RE-DIFFERENTIATION OF SOMATIC-CELLS IN VOLVOX

J CELL BIOL 95 (2): A48-A48 1982

 

 

PANNAMAN L, ELMANN E, BLAMIRE J, et al.

 

AGE-DEPENDENT RELEASE OF DAUGHTER SPHEROIDS IN VOLVOX CARTERI-F-NAGARIENSIS

J CELL BIOL 95 (2): A117-A117 1982

 

MATTSON DM, BRYANT JL, GREEN KJ, et al.

 

GENETIC LESIONS OF CYTOSKELETON-MEDIATED MORPHOGENESIS IN VOLVOX

J CELL BIOL 95 (2): A353-A353 1982

 

HARPER JF

 

TUBULIN GENES OF VOLVOX-CARTERI

J CELL BIOL 95 (2): A353-A353 1982

 

 

MULLER T, BAUSE E, JAENICKE L

 

FORMATION OF LIPID-LINKED MANNOSYL OLIGOSACCHARIDES IN VOLVOX-CARTERI

H-S Z PHYSIOL CHEM 363 (9): 1035-1035 1982

 

 

GREEN KJ, KIRK DL

 

A REVISION OF THE CELL LINEAGES RECENTLY REPORTED FOR VOLVOX-CARTERI EMBRYOS

J CELL BIOL 94 (3): 741-742 1982

 

POMMERVILLE J, KOCHERT G

 

EFFECTS OF SENESCENCE ON SOMATIC-CELL PHYSIOLOGY IN THE GREEN-ALGA VOLVOX-CARTERI

EXP CELL RES 140 (1): 39-45 1982

 

KURN N, DUKSIN D

 

EXTRACELLULAR-MATRIX GLYCOPROTEINS OF VOLVOX-CARTERI

ISRAEL J MED SCI 18 (6): 12-12 1982

 

KURN N

 

INHIBITION OF PHOSPHATE-UPTAKE BY FLUPHENAZINE, A CALMODULIN INHIBITOR - ANALYSIS OF VOLVOX WILD-TYPE AND FLUPHENAZINE-RESISTANT MUTANT STRAINS

FEBS LETT 144 (1): 68-72 1982

 

 

KURN N, DUKSIN D

 

EFFECTS OF TUNICAMYCIN ON PROTEIN GLYCOSYLATION AND DEVELOPMENT IN VOLVOX-CARTERI

ROUX ARCH DEV BIOL 191 (3): 169-175 1982

 

 

WENZL S, SUMPER M

 

THE OCCURRENCE OF DIFFERENT SULFATED CELL-SURFACE GLYCOPROTEINS CORRELATES WITH DEFINED DEVELOPMENTAL EVENTS IN VOLVOX

FEBS LETT 143 (2): 311-315 1982

 

 

WILLADSEN P, SUMPER M

 

SULFATION OF A CELL-SURFACE GLYCOPROTEIN FROM VOLVOX-CARTERI - EVIDENCE FOR A MEMBRANE-BOUND SULFOKINASE WORKING WITH PAPS

FEBS LETT 139 (1): 113-116 1982

 

 

J CELL BIOL 91 (2): A21-A21 1981 JAENICKE L

 

VOLVOX BIOCHEMISTRY COMES OF AGE

TRENDS BIOCHEM SCI 7 (2): 61-64 1982

 

1981

 

POMMERVILLE J, KOCHERT G

 

SOMATIC-CELL SENESCENCE IN THE GREEN-ALGA VOLVOX

J CELL BIOL 91 (2): A17-A17 1981

 

HOFFMAN JL

 

SPECIFIC POLYPEPTIDE-SYNTHESIS DURING SEXUAL DEVELOPMENT IN VOLVOX

J CELL BIOL 91 (2): A21-A21 1981

 

 

BARAN GJ, HUSKEY RJ

 

MOLECULAR ANALYSIS OF CYTODIFFERENTIATION IN VOLVOX CARTERI

J CELL BIOL 91 (2): A33-A33 1981

 

TEMPLEMAN MN, MCGOWAN RE, BLAMIRE J, et al.

 

CHARACTERIZATION AND COMPARISON OF THE EXTRACELLULAR-MATRIX IN HETEROGENOUS POPULATIONS OF 2 STRAINS OF VOLVOX-CARTERI

J CELL BIOL 91 (2): A159-A159 1981

 

 

GREEN KJ, KIRK DL

 

THE MECHANISM OF CYTOKINESIS DURING CLEAVAGE IN VOLVOX

J CELL BIOL 91 (2): A166-A166 1981

 

 

MCCRACKEN MD, BARCELLONA WJ

 

ULTRASTRUCTURE OF SHEATH SYNTHESIS IN VOLVOX-ROUSSELETII

CYTOBIOS 32 (127-): 179-187 1981

 

KURN N, SELA BA

 

ALTERED CALMODULIN ACTIVITY IN FLUPHENAZINE-RESISTANT MUTANT STRAINS - PLEIOTROPIC EFFECT ON DEVELOPMENT AND CELLULAR-ORGANIZATION IN VOLVOX-CARTERI

EUR J BIOCHEM 121 (1): 53-57 1981

 

 

MILLER CE, STARR RC

 

THE CONTROL OF SEXUAL MORPHOGENESIS IN VOLVOX-CAPENSIS

BER DEUT BOT GES 94 (3): 357-372 1981

 

JAENICKE L, WAFFENSCHMIDT S

 

LIBERATION OF REPRODUCTIVE UNITS IN VOLVOX AND CHLAMYDOMONAS - PROTEOLYTIC PROCESSES

BER DEUT BOT GES 94 (3): 375-386 1981

 

SENFT WH, HUNCHBERGER RA, ROBERTS KE

 

TEMPERATURE-DEPENDENCE OF GROWTH AND PHOSPHORUS UPTAKE IN 2 SPECIES OF VOLVOX (VOLVOCALES, CHLOROPHYTA)

J PHYCOL 17 (4): 323-329 1981

 

 

GREEN KJ, KIRK DL

 

CLEAVAGE PATTERNS, CELL LINEAGES, AND DEVELOPMENT OF A CYTOPLASMIC BRIDGE SYSTEM IN VOLVOX EMBRYOS

J CELL BIOL 91 (3): 743-755 1981

 

 

GREEN KJ, VIAMONTES GI, KIRK DL

 

MECHANISM OF FORMATION, ULTRASTRUCTURE, AND FUNCTION OF THE CYTOPLASMIC BRIDGE SYSTEM DURING MORPHOGENESIS IN VOLVOX

J CELL BIOL 91 (3): 756-769 1981

 

KURN N

 

ALTERED DEVELOPMENT OF THE MULTICELLULAR ALGA VOLVOX-CARTERI CAUSED BY LECTIN BINDING

CELL BIOL INT REP 5 (9): 867-875 1981

 

 

KURN N, SELA B

 

ALTERED CALMODULIN ACTIVITY AND ABERRANT DEVELOPMENT IN FLUPHENAZINE RESISTANT VOLVOX MUTANT STRAINS

ISRAEL J MED SCI 17 (6): 484-484 1981

 

 

POMMERVILLE JC, KOCHERT GD

 

CHANGES IN SOMATIC-CELL STRUCTURE DURING SENESCENCE OF VOLVOX CARTERI

EUR J CELL BIOL 24 (2): 236-243 1981

 

WENZL S, SUMPER M

 

SULFATION OF A CELL-SURFACE GLYCOPROTEIN CORRELATES WITH THE DEVELOPMENTAL PROGRAM DURING EMBRYOGENESIS OF VOLVOX-CARTERI

P NATL ACAD SCI-BIOL 78 (6): 3716-3720 1981

 

 

MULLER T, BAUSE E, JAENICKE L

 

GLYCOLIPID FORMATION IN VOLVOX-CARTERI-F-NAGARIENSIS - EFFECTS OF TUNICAMYCIN AND SHOWDOMYCIN

FEBS LETT 128 (2): 208-212 1981

 

IRELAND GW, HAWKINS SE

 

INVERSION IN VOLVOX-TERTIUS - THE EFFECTS OF CON-A

J CELL SCI 48 (APR): 355-366 1981

 

GILLES R, BITTNER C, JAENICKE L

 

SITE AND TIME OF FORMATION OF THE SEX-INDUCING GLYCOPROTEIN IN VOLVOX-CARTERI

FEBS LETT 124 (1): 57-60 1981

 

 

1980

 

 

ZEIKUS JA, DARDEN WH, BROOKS D

 

SEXUAL SPHEROID FORMATION IN VOLVOX-CARTERI F NAGARIENSIS LYENGAR INDUCED BY PHENOLIC EXTRACTS

MICROBIOS 28 (113-): 173-184 1980

 

IRELAND GW, HAWKINS SE

 

A METHOD FOR STUDYING THE EFFECT OF INHIBITORS ON THE DEVELOPMENT OF THE ISOLATED GONIDIA OF VOLVOX-TERTIUS

MICROBIOS 28 (113-): 185-201 1980

 

 

CAPLEN HS, BLAMIRE J

 

POLYADENYLATED RNA OF VOLVOX - ISOLATION AND PARTIAL CHARACTERIZATION

CYTOBIOS 29 (114): 115-128 1980

 

DARDEN WH

 

SOME PROPERTIES OF MALE-INDUCING PHERMONES FROM VOLVOX-AUREUS M5

MICROBIOS 28 (111): 27-39 1980

 

TASHIMOVICH A, COTTRELL SF, BLAMIRE J

 

AGING IN VOLVOX - THE EFFECT OF ENVIRONMENTAL-CONDITIONS

AGE 3 (4): 117-117 1980

 

 

CALLAHAN AM, HUSKEY RJ

 

GENETIC-CONTROL OF SEXUAL DEVELOPMENT IN VOLVOX

DEV BIOL 80 (2): 419-435 1980

 

ZAGRIS N, KIRK DL

 

SELECTIVE, HIGH-EFFICIENCY MUTAGENESIS OF A GENE CONTROLLING CYTODIFFERENTIATION IN VOLVOX CARTERI

J CELL BIOL 87 (2): A15-A15 1980

 

 

COTTRELL SF

 

THE ISOLATION AND CHARACTERIZATION OF SUBCELLULAR ORGANELLES IN BOTH SOMATIC AND REPRODUCTIVE CELLS OF VOLVOX-CARTERI

J CELL BIOL 87 (2): A17-A17 1980

 

 

COGGIN S, KOCHERT G

 

FLAGELLAR GROWTH AND REGENERATION IN THE LIFE-CYCLE OF VOLVOX-CARTERI

J CELL BIOL 87 (2): A39-A39 1980

 

 

BARCELLONA WJ, MCCRACKEN MD

 

ULTRASTRUCTURAL ASPECTS OF SHEATH SYNTHESIS IN VOLVOX

J CELL BIOL 87 (2): A92-A92 1980

 

 

TEMPLEMAN MN, MCGOWAN RE, BLAMIRE J, et al.

 

BIOCHEMICAL-CHANGES IN THE EXTRA CELLULAR MATRIX OF VOLVOX-CARTERII DURING DEVELOPMENT

J CELL BIOL 87 (2): A122-A122 1980

 

 

BRYANT JL, GREEN KJ, KIRK DL

 

TIME-LAPSE CINEMICROGRAPHIC ANALYSIS OF MORPHOGENESIS IN WILD-TYPE AND MUTANT VOLVOX EMBRYOS

J CELL BIOL 87 (2): A133-A133 1980

 

 

BLAMIRE J, COTTRELL SF, TASHIMOVICH A

 

ANALYSIS OF REPRODUCTIVE CELL VULNERABILITY FOLLOWING FORMALDEHYDE EXPOSURE IN VOLVOX-CARTERI

J CELL BIOL 87 (2): A320-A320 1980

 

 

GREEN KJ

 

DEVELOPMENT OF CYTOPLASMIC BRIDGES DURING CLEAVAGE IN VOLVOX

EUR J CELL BIOL 22 (1): 298-298 1980

 

 

VIAMONTES GI

 

INVERSION IN VOLVOX - ROLES OF THE CYTOSKELETON AND THE CYTOPLASMIC BRIDGES

EUR J CELL BIOL 22 (1): 299-299 1980

 

GILLES R, BITTNER C, CRAMER M, et al.

 

RADIOIMMUNOASSAY FOR THE SEX INDUCER OF VOLVOX-CARTERIF, NAGARIENSIS

FEBS LETT 116 (1): 102-106 1980

 

KURN N, DUKSIN D

 

GLYCOPROTEIN INVOLVEMENT IN THE REGULATION OF VOLVOX DEVELOPMENT - THE EFFECT OF TUNICAMYCIN

ISRAEL J MED SCI 16 (6): 475-476 1980

 

SUMPER M, WENZL S

 

SULFATION-DESULFATION OF A MEMBRANE COMPONENT PROPOSED TO BE INVOLVED IN CONTROL OF DIFFERENTIATION IN VOLVOX-CARTERI

FEBS LETT 114 (2): 307-312 1980

 

DAUWALDER M, WHALEY WG, STARR RC

 

DIFFERENTIATION AND SECRETION IN VOLVOX

J ULTRA MOL STRUCT R 70 (3): 318-335 1980

 

ZEIKUS JA, STARR RC

 

THE GENETICS AND PHYSIOLOGY OF NON-INDUCIBILITY IN VOLVOX-CARTERI F-NAGARIENSIS IYGENGAR

ARCH PROTISTENKD 123 (2): 127-161 1980

 

STARR RC, ONEIL RM, MILLER CE

 

L-GLUTAMIC ACID AS A MEDIATOR OF SEXUAL MORPHOGENESIS IN VOLVOX-CAPENSIS

P NATL ACAD SCI-BIOL 77 (2): 1025-1028 1980

 

MOSELEY KR, THOMPSON GA

 

LIPID-COMPOSITION AND METABOLISM OF VOLVOX-CARTERI

PLANT PHYSIOL 65 (2): 260-265 1980

 

1979

 

MARGOLISKAZAN H, BLAMIRE J

 

EFFECT OF TETRAHYDROCANNABINOL AND ETHIDIUM-BROMIDE ON DNA METABOLISM AND EMBRYOGENESIS IN VOLVOX

CYTOBIOS 26 (102): 75-95 1979

 

 

MARGOLISKAZAN H, BLAMIRE J

 

EFFECT OF DELTA-9-TETRAHYDROCANNABINOL ON CYTOPLASMIC DNA METABOLISM IN A SOMATIC-CELL REGENERATOR MUTANT OF VOLVOX

MICROBIOS LETT 11 (41): 7-13 1979

 

SAKAGUCHI H

 

EFFECT OF EXTERNAL IONIC ENVIRONMENT ON PHOTOTAXIS OF VOLVOX-CARTERI

PLANT CELL PHYSIOL 20 (8): 1643-1651 1979

 

 

COTTRELL SF, BLAMIRE J, MCGOWAN RE

 

BIOCHEMICAL AND ULTRASTRUCTURAL ANALYSIS OF VOLVOX-CARTERI SOMATIC-CELLS DURING SENESCENCE

AGE 2 (4): 134-134 1979

 

 

BIRCHEM R, KOCHERT G

 

DEVELOPMENT OF SPERM CELLS OF VOLVOX-CARTERI F WEISMANNIA (CHLOROPHYCEAE)

PHYCOLOGIA 18 (4): 409-419 1979

 

SUMPER M

 

CONTROL OF DIFFERENTIATION IN VOLVOX-CARTERI - MODEL EXPLAINING PATTERN FORMATION DURING EMBRYOGENESIS

FEBS LETT 107 (1): 241-246 1979

 

WENZL S, SUMPER M

 

EVIDENCE FOR MEMBRANE-MEDIATED CONTROL OF DIFFERENTIATION DURING EMBRYOGENESIS OF VOLVOX-CARTERI

FEBS LETT 107 (1): 247-249 1979

 

JAENICKE L, WAFFENSCHMIDT S

 

MATRIX-LYSIS AND RELEASE OF DAUGHTER SPHEROIDS IN VOLVOX-CARTERI - PROTEOLYTIC PROCESS

FEBS LETT 107 (1): 250-253 1979

 

KOCHERT G, CRUMP WJ

 

REVERSAL OF SEXUAL INDUCTION IN VOLVOX CARTERI BY ULTRAVIOLET-IRRADIATION AND REMOVAL OF SEXUAL PHEROMONE

GAMETE RES 2 (3): 259-264 1979

 

 

BAUSE E, JAENICKE L

 

FORMATION OF LIPID-LINKED SUGAR COMPOUNDS IN VOLVOX-CARTERI F NAGARIENSIS IYENGAR

FEBS LETT 106 (2): 321-324 1979

 

KURN N, SELA B

 

CHARACTERIZATION OF CELL-SURFACE COMPONENTS IN THE MULTICELLULAR ALGA VOLVOX-CARTERI

ISRAEL J MED SCI 15 (9): 800-800 1979

 

HUSKEY RJ, GRIFFIN BE

 

GENETIC-CONTROL OF SOMATIC-CELL DIFFERENTIATION IN VOLVOX - ANALYSIS OF SOMATIC REGENERATOR MUTANTS

DEV BIOL 72 (2): 226-235 1979

 

HUSKEY RJ

 

MUTANTS AFFECTING VEGETATIVE CELL ORIENTATION IN VOLVOX-CARTERI

DEV BIOL 72 (2): 236-243 1979

 

COGGIN SJ, HUTT W, KOCHERT G

 

SPERM BUNDLE FEMALE SOMATIC-CELL INTERACTION IN THE FERTILIZATION PROCESS OF VOLVOX-CARTERI F-WEISMANNIA (CHLOROPHYTA)

J PHYCOL 15 (3): 247-251 1979

 

 

SAKAGUCHI H, IWASA K

 

2 PHOTOPHOBIC RESPONSES IN VOLVOX-CARTERI

PLANT CELL PHYSIOL 20 (5): 909-916 1979

 

KURN N, SELA BA

 

SURFACE GLYCOPROTEINS OF THE MULTICELLULAR ALGA VOLVOX-CARTERI - DEVELOPMENTAL REGULATION, EXCLUSIVE CON-A BINDING AND INDUCED REDISTRIBUTION

FEBS LETT 104 (2): 249-252 1979

 

 

BIRCHEM R, KOCHERT G

 

MITOSIS AND CYTOKINESIS IN ANDROGONIDIA OF VOLVOX-CARTERI F WEISMANNIA

PROTOPLASMA 100 (1): 1-12 1979

 

 

VIAMONTES GI, FOCHTMANN LJ, KIRK DL

 

MORPHOGENESIS IN VOLVOX - ANALYSIS OF CRITICAL VARIABLES

CELL 17 (3): 537-550 1979

 

 

HILL J

 

CHARACTERIZATION OF THE SEXUAL PHEROMONE OF VOLVOX-ROUSSELETII (CHLOROPHYCEAE)

J PHYCOL 15: 15-15 Suppl. S 1979

 

 

KOCHERT G

 

GLYCOPROTEIN SEXUAL PHEROMONES IN VOLVOX

J PHYCOL 15: 24-24 Suppl. S 1979

 

 

HUSKEY RJ

 

GENETIC-ANALYSIS OF VOLVOX-CARTERI (CHLOROPHYCEAE)

J PHYCOL 15: 24-24 Suppl. S 1979

 

 

KIRK DL

 

CONTROL OF MORPHOGENESIS IN VOLVOX

J PHYCOL 15: 24-24 Suppl. S 1979

 

STARR RC

 

PEPTIDE-HORMONE IN VOLVOX-CAPENSIS K-37

J PHYCOL 15: 24-24 Suppl. S 1979

 

 

HUSKEY RJ, GRIFFIN BE, CECIL PO, et al.

 

PRELIMINARY GENETIC INVESTIGATION OF VOLVOX-CARTERI

GENETICS 91 (2): 229-244 1979

 

HUSKEY RJ, SEMENKOVICH CF, GRIFFIN BE, et al.

 

MUTANTS OF VOLVOX-CARTERI AFFECTING NITROGEN ASSIMILATION

MOL GEN GENET 169 (2): 157-161 1979

 

 

KAMIYA H, NAKA K, HASHIMOTO K

 

ICHTHYO-TOXICITY OF A FLAGELLATE UROGLENA-VOLVOX

B JPN SOC SCI FISH 45 (1): 129-129 1979

 

1978

 

KIRK DL, KIRK MM

 

CELL AND STAGE SPECIFIC PROTEIN-SYNTHESIS IN VOLVOX

J CELL BIOL 79 (2): A27-A27 1978

 

 

KURN N, COLB M, SHAPIRO L

 

SPONTANEOUS FREQUENCY OF A DEVELOPMENTAL MUTANT IN VOLVOX

DEV BIOL 66 (1): 266-269 1978

 

BIRCHEM R

 

ULTRASTRUCTURE OF EGG CELLS OF VOLVOX-CARTERI F WEISMANNIA

J PHYCOL 14: 30-30 Suppl. S 1978

 

 

HAGEN G, KOCHERT G

 

SENESCENCE IN VOLVOX

J PHYCOL 14: 40-40 Suppl. S 1978

 

HILL JE, KOCHERT G

 

DEVELOPMENT OF A RADIOIMMUNOASSAY FOR SEXUAL HORMONE OF VOLVOX-CARTERI F WEISMANNIA (CHLOROPHYCEAE)

J PHYCOL 14: 40-40 Suppl. S 1978

 

 

COGGIN SJ, HUTT W, KOCHERT G

 

SPERM BUNDLE-SOMATIC CELL-INTERACTION IN VOLVOX FERTILIZATION PROCESS

J PHYCOL 14: 40-40 Suppl. S 1978

 

 

NOLAND T, YATES I, KOCHERT G

 

BINDING PROPERTIES OF RADIOIODINATED SEXUAL PHEROMONE IN VOLVOX-CARTERI F WEISMANNIA

J PHYCOL 14: 40-40 Suppl. S 1978

 

KIRK MM, KIRK DL

 

CARRIER-MEDIATED UPTAKE OF ARGININE AND UREA BY VOLVOX-CARTERI-F-NAGARIENSIS

PLANT PHYSIOL 61 (4): 549-555 1978

 

1977

 

KELLAND JL

 

INVERSION IN VOLVOX (CHLOROPHYCEAE)

J PHYCOL 13 (4): 373-378 1977

 

VIAMONTES GI, KIRK DL

 

CELL-SHAPE CHANGES AND MECHANISM OF INVERSION IN VOLVOX

J CELL BIOL 75 (3): 719-730 1977

 

 

VIAMONTES GI, KIRK DL

 

CELL-SHAPE CHANGES CAUSE INVERSION IN VOLVOX

J CELL BIOL 75 (2): A274-A274 1977

 

SAKAGUCHI H, TAWADA K

 

TEMPERATURE EFFECT ON PHOTO-ACCUMULATION AND PHOBIC RESPONSE OF VOLVOX-AUREUS

J PROTOZOOL 24 (2): 284-288 1977

 

ESSER SC, VANVALKENBURG SD

 

FINE-STRUCTURE OF VEGETATIVE AND STATOSPORE-FORMING CELLS OF UROGLENA-VOLVOX EHRENBERG

J PHYCOL 13: 20-20 Suppl. S 1977

 

NOLAND T, YATES I, KOCHERT G

 

BINDING CHARACTERISTICS OF I-125-LABELED SEXUAL INDUCER TO VOLVOX-CARTERI F WEISMANNIA

J PHYCOL 13: 49-49 Suppl. S 1977

 

SAKAGUCHI H, SAITO S, IWASA K

 

MECHANISM OF PHOTOTACTIC RESPONSE IN VOLVOX-CARTERI

J PHYCOL 13: 59-59 Suppl. S 1977

 

TIMPANO P, THOMPSON R

 

GONIDIAL DIFFERENTIATION OF VOLVOX-CARTERI AUREUS

J PHYCOL 13: 68-68 Suppl. S 1977

 

1976

 

MARGOLISKAZAN H, BLAMIRE J

 

DNA OF VOLVOX-CARTERI - BIOPHYSICAL AND BIOSYNTHETIC CHARACTERIZATION

CYTOBIOS 15 (60): 201-216 1976

 

YATES I, KOCHERT G

 

NUCLEIC-ACID AND PROTEIN DIFFERENCES IN VOLVOX-CARTERI CELL-TYPES

CYTOBIOS 15 (57): 7-21 1976

 

LEE WSB, KOCHERT G

 

BACTERIAL ENDOSYMBIONTS IN VOLVOX-CARTERI (CHLOROPHYCEAE)

J PHYCOL 12 (2): 194-197 1976

 

KIRK DL, KIRK MM

 

PROTEIN-SYNTHESIS IN VOLVOX-CARTERI-F-NAGARIENSIS

DEV BIOL 50 (2): 413-427 1976

 

 

MCCRACKEN MD, BARCELLONA WJ

 

ELECTRON HISTOCHEMISTRY AND ULTRASTRUCTURAL LOCALIZATION OF CARBOHYDRATE-CONTAINING SUBSTANCES IN SHEATH OF VOLVOX

J HISTOCHEM CYTOCHEM 24 (5): 668-673 1976

 

1975

 

YATES I, DARLEY M, KOCHERT G

 

SEPARATION OF CELL-TYPES IN SYNCHRONIZED CULTURES OF VOLVOX-CARTERI

CYTOBIOS 12 (47-4): 211-223 1975

 

 

MEREDITH RF, STARR RC

 

GENETIC BASIS OF MALE POTENCY IN VOLVOX-CARTERI F-NAGARIENSIS (CHLOROPHYCEAE)

J PHYCOL 11 (3): 265-272 1975

 

BRADLEY DM, CLAYBROOK JR

 

INTERCELLULAR AND LIFE-CYCLE VARIATIONS IN HISTONES OF VOLVOX-CARTERI

GENETICS 80 (3): S16-S16 1975

 

HUSKEY RJ, CECIL PO

 

GENETIC-CONTROL OF SEXUAL-RESPONSE IN VOLVOX-CARTERI F NAGARIENSIS

GENETICS 80 (3): S44-S44 1975

 

ZEIKUS JA

 

MUTANT LOCUS EFFECTING NON-INDUCIBILITY IN VOLVOX-CARTERI F NAGARIENSIS

J PHYCOL 11: 16-16 Suppl. S 1975

 

EWART B

 

SEX AND SINGLE VOLVOX

NAT HIST 84 (4): 50-& 1975

 

 

1974

 

 

KOCHERT G, YATES I

 

CHARACTERIZATION OF A GLYCOPROTEIN SEXUAL INDUCER FROM VOLVOX

J PHYCOL 10: 6-6 Suppl. S 1974

 

 

MEREDITH R

 

GENETIC BASIS OF MALE POTENCY IN VOLVOX-CARTERI VOLVOX-NAGARIENSIS

J PHYCOL 10: 6-6 Suppl. S 1974

 

 

BRADLEY DM, CLAYBROO.JR, GOLDIN HH

 

ANALYSIS OF HISTONES IN VOLVOX-CARTERI

GENETICS 77: S6-S6 Suppl. 1 1974

 

 

GRIFFIN BE, HUSKEY RJ

 

GENETIC-CONTROL OF DIFFERENTIATION IN VOLVOX

GENETICS 77: S27-S27 Suppl. 1 1974

 

 

MEREDITH R

 

INHERITANCE OF MALE POTENCY IN VOLVOX-CARTERI VOLVOX-NAGARIENSIS

GENETICS 77: S44-S44 Suppl. 1 1974

 

BRADLEY DM, GOLDIN HH, CLAYBROO.JR

 

HISTONE ANALYSIS IN VOLVOX

FEBS LETT 41 (2): 219-222 1974

 

 

STARR RC, JAENICKE L

 

PURIFICATION AND CHARACTERIZATION OF HORMONE INITIATING SEXUAL MORPHOGENESIS IN VOLVOX-CARTERI-F-NAGARIENSIS IYENGAR

P NATL ACAD SCI USA 71 (4): 1050-1054 1974

 

 

KOCHERT G, YATES I

 

PURIFICATION AND PARTIAL CHARACTERIZATION OF A GLYCOPROTEIN SEXUAL INDUCER FROM VOLVOX-CARTERI

P NATL ACAD SCI USA 71 (4): 1211-1214 1974

 

WIRT NS

 

GALVANIC STIMULATION OF VOLVOX-GLOBATOR .1. ELECTROOSMOTIC PATTERNS ASSOCIATED WITH ION-EXCHANGE PROPERTIES

J PROTOZOOL 21 (1): 121-125 1974

 

WIRT NS

 

GALVANIC STIMULATION OF VOLVOX-GLOBATOR .2. MECHANISM OF GALVANIC RESPONSE, AN EFFECT OF CALCIUM DISPLACEMENT

J PROTOZOOL 21 (1): 126-128 1974

 

PALL ML

 

EVIDENCE FOR GLYCOPROTEIN NATURE OF INDUCER OF SEXUALITY IN VOLVOX

BIOCHEM BIOPH RES CO 57 (3): 683-688 1974

 

1973

 

DARDEN WH

 

FORMATION AND ASSAY OF A VOLVOX-FACTOR-HISTONE COMPLEX

MICROBIOS 8 (31-3): 167-174 1973