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Hisayoshi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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Distribution of the Sex-Determining Gene MID and Molecular Correspondence of Mating Types within the Isogamous Genus Gonium (Volvocales, Chlorophyta)
2016Co-Authors: Takashi Hamaji, Patrick J. Ferris, Ichiro Nishii, Yoshiki Nishimura, Hisayoshi NozakiAbstract:Background: Isogamous organisms lack obvious cytological differences in the gametes of the two complementary mating types. Consequently, it is difficult to ascertain which of the two mating types are homologous when comparing related but sexual isolated strains or species. The colonial volvocalean algal genus Gonium consists of such isogamous organisms with heterothallic mating types designated arbitrarily as plus or minus in addition to homothallic strains. Homologous molecular markers among lineages may provide an ‘‘objective’ ’ framework to assign heterothallic mating types. Methodology/Principal Findings: Using degenerate primers designed based on previously reported MID orthologs, the ‘‘master regulator’ ’ of mating types/sexes in the colonial Volvocales, MID homologs were identified and their presence/ absence was examined in nine strains of four species of Gonium. Only one of the two complementary mating types in each of the four heterothallic species has a MID homolog. In addition to heterothallic strains, a homothallic strain of G. multicoccum has MID. Molecular evolutionary analysis suggests that MID of this homothallic strain retains functional constraint comparable to that of the heterothallic strains. Conclusion/Significance: We coordinated mating genotypes based on presence or absence of a MID homolog, respectively, in heterothallic species. This scheme should be applicable to heterothallic species of other isogamous colonial Volvocales including Pandorina and Yamagishiella. Homothallism emerged polyphyletically in the colonial Volvocales, although it
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Origin of Female/Male Gender as Deduced by the Mating-Type Loci of the Colonial Volvocalean Greens
Sexual Reproduction in Animals and Plants, 2014Co-Authors: Hisayoshi NozakiAbstract:Colonial Volvocales (green algae) are a model lineage for the study of the evolution of sexual reproduction because isogamy, anisogamy, and oogamy are recognized within the closely related group, and several mating type (sex)-specific genes were identified in the closely related unicellular Chlamydomonas reinhardtii during the past century. In 2006, we first identified a sex-specific gene within the colonial Volvocales using the anisogamous colonial volvocalean alga Pleodorina starrii, namely, a male-specific gene called “OTOKOGI,” which is a homologue of the minus mating type-determining gene MID of the isogamous C. reinhardtii. Thus, it was speculated that the derived or minus mating type of C. reinhardtii is homologous to the male in the anisogamous/oogamous members of the colonial Volvocales. The discovery of the male-specific gene facilitated comparative studies of the mating-type locus (MT) (primitive sex chromosomal region) because it must be localized in MT. Recently, our international research group determined the genome sequence of MT in the oogamous Volvox carteri. V. carteri MT shows remarkable expansion and divergence relative to that from C. reinhardtii. Five new female-limited “HIBOTAN” genes and ten male-limited genes (including “OTOKOGI”) were identified in V. carteri MT. These observations suggest that the origins of femaleness and maleness are principally affected by the evolution of MT, which has undergone a remarkable expansion and gain of new male- and female-limited genes. Our recent results regarding the evolution of the volvocalean MT gene MAT3/RB are also discussed in relationship to the evolution of male–female sexual dimorphism.
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Distribution of the Sex-Determining Gene MID and Molecular Correspondence of Mating Types within the Isogamous Genus Gonium (Volvocales, Chlorophyta)
PLoS ONE, 2013Co-Authors: Takashi Hamaji, Patrick J. Ferris, Ichiro Nishii, Yoshiki Nishimura, Hisayoshi NozakiAbstract:Background: Isogamous organisms lack obvious cytological differences in the gametes of the two complementary mating types. Consequently, it is difficult to ascertain which of the two mating types are homologous when comparing related but sexual isolated strains or species. The colonial volvocalean algal genus Gonium consists of such isogamous organisms with heterothallic mating types designated arbitrarily as plus or minus in addition to homothallic strains. Homologous molecular markers among lineages may provide an ‘‘objective’’ framework to assign heterothallic mating types. Methodology/Principal Findings: Using degenerate primers designed based on previously reported MID orthologs, the ‘‘master regulator’’ of mating types/sexes in the colonial Volvocales, MID homologs were identified and their presence/ absence was examined in nine strains of four species of Gonium. Only one of the two complementary mating types in each of the four heterothallic species has a MID homolog. In addition to heterothallic strains, a homothallic strain of G. multicoccum has MID. Molecular evolutionary analysis suggests that MID of this homothallic strain retains functional constraint comparable to that of the heterothallic strains. Conclusion/Significance: We coordinated mating genotypes based on presence or absence of a MID homolog, respectively, in heterothallic species. This scheme should be applicable to heterothallic species of other isogamous colonial Volvocales including Pandorina and Yamagishiella. Homothallism emerged polyphyletically in the colonial Volvocales, although its mechanism remains unknown. Our identification of a MID homolog for a homothallic strain of G. multicoccum suggests a MID-dependent mechanism is involved in the sexual developmental program of this homothallic species.
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Description of Chloromonas kasaiae sp. nov. (Volvocales, Chlorophyceae), based on comparative electron microscopy and molecular data
Phycologia, 2013Co-Authors: Ryo Matsuzaki, Takashi Nakada, Yoshiaki Hara, Hisayoshi NozakiAbstract:Chloromonas kasaiae sp. nov. (Volvocales, Chlorophyceae) was described based on a new culture strain originating from Japan. Based on light microscopy, vegetative cells of this new species were very similar to those of C. reticulata and C. serbinowii. However, C. kasaiae differed from these two species in the ultrastructure of eyespots (number of globule layers). Our phylogenetic analyses, based on a combined data set from nuclear-encoded 18S ribosomal (r) RNA, the ATP synthase beta subunit and P700 chlorophyll a apoprotein A2 genes, robustly resolved that C. kasaiae was separate from C. reticulata. Although these analyses did not resolve the phylogenetic relationship between C. kasaiae and C. serbinowii, separation of the two was supported based on a comparison of the secondary structure of nuclear rDNA internal transcribed spacer 2.
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IDENTIFICATION OF THE MINUS MATING-TYPE SPECIFIC GENE MTD1 FROM GONIUM PECTORALE (Volvocales, CHLOROPHYTA)(1).
Journal of Phycology, 2009Co-Authors: Takashi Hamaji, Patrick J. Ferris, Ichiro Nishii, Hisayoshi NozakiAbstract:Gonium pectorale O. F. Mull. (Volvocales, Chlorophyta), a colonial 8- or 16-cellular alga, is phylogenetically important as an intermediate form between isogametic unicellular Chlamydomonas and oogamous Volvox. We identified the mating-type specific gene GpMTD1, from G. pectorale, the first homologue of Chlamydomonas reinhardtii MTD1 (CrMTD1). The GpMTD1 gene was found to be present only in the minus mating-type locus and was expressed specifically in the gametic phase as is the case for CrMTD1, suggested to participate in development of the minus gametes. This gene is useful as a probe in analyzing the bacterial artificial chromosome (BAC) library for resolving genomic structures of the mating-type loci in isogamous and oogamous colonial volvocaleans.
Takashi Nakada - One of the best experts on this subject based on the ideXlab platform.
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Taxonomic revision of oil-producing green algae, Chlorococcum oleofaciens (Volvocales, Chlorophyceae), and its relatives
Journal of Phycology, 2015Co-Authors: Yuriko Kawasaki, Takashi Nakada, Masaru TomitaAbstract:Historically, species in Volvocales were classified based primarily on morphology. Although the taxonomy of Chlamydomonas has been re-examined using a polyphasic approach including molecular phylogeny, that of Chlorococcum (Cc.), the largest coccoid genus in Volvocales, has yet to be reexamined. Six species thought to be synonymous with the oil-producing alga Cc. oleofaciens were previously not confirmed by molecular phylogeny. In this study, seven authentic strains of Cc. oleofaciens and its putative synonyms, along with 11 relatives, were examined based on the phylogeny of the 18S ribosomal RNA (rRNA) gene, comparisons of secondary structures of internal transcribed spacer 1 (ITS1) and ITS2 rDNA, and morphological observations by light microscopy. Seven 18S rRNA types were recognized among these strains and three were distantly related to Cc. oleofaciens. Comparisons of ITS rDNA structures suggested possible separation of the remaining four types into different species. Shapes of vegetative cells, thickness of the cell walls in old cultures, the size of cells in old cultures, and stigma morphology of zoospores also supported the 18S rRNA grouping. Based on these results, the 18 strains examined were reclassified into seven species. Among the putative synonyms, synonymy of Cc. oleofaciens, Cc. croceum, and Cc. granulosum was confirmed, and Cc. microstigmatum, Cc. rugosum, Cc. aquaticum, and Cc. nivale were distinguished from Cc. oleofaciens. Furthermore, another related strain is described as a new species, Macrochloris rubrioleum sp. nov.
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Description of Chloromonas kasaiae sp. nov. (Volvocales, Chlorophyceae), based on comparative electron microscopy and molecular data
Phycologia, 2013Co-Authors: Ryo Matsuzaki, Takashi Nakada, Yoshiaki Hara, Hisayoshi NozakiAbstract:Chloromonas kasaiae sp. nov. (Volvocales, Chlorophyceae) was described based on a new culture strain originating from Japan. Based on light microscopy, vegetative cells of this new species were very similar to those of C. reticulata and C. serbinowii. However, C. kasaiae differed from these two species in the ultrastructure of eyespots (number of globule layers). Our phylogenetic analyses, based on a combined data set from nuclear-encoded 18S ribosomal (r) RNA, the ATP synthase beta subunit and P700 chlorophyll a apoprotein A2 genes, robustly resolved that C. kasaiae was separate from C. reticulata. Although these analyses did not resolve the phylogenetic relationship between C. kasaiae and C. serbinowii, separation of the two was supported based on a comparison of the secondary structure of nuclear rDNA internal transcribed spacer 2.
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Phylogenetic position of a rare loricated green alga, Cephalomonas granulata N. L. Higinb. (Volvocales, Chlorophyceae)
Phycological Research, 2010Co-Authors: Takashi Nakada, Tomoyoshi Soga, Masaru TomitaAbstract:SUMMARY Cephalomonas (Cp.) granulata N. L. Higinb. (Volvocales, Chlorophyceae), a rare volvocalean phytoflagellate, has recently been isolated from a paddy field in Japan and examined by light and fluorescence microscopy. The vegetative cells of Cp. granulata have granulate loricae and a characteristic mushroom-like shape with a hemispherical to spherical anterior part and narrower posterior part. Cp. granulata has been classified among the Phacotaceae along with other loricated genera. However, its phylogenetic position has not been investigated using molecular phylogeny. To evaluate the phylogenetic position of Cephalomonas, the 18S rRNA gene sequence of the Japanese strain was determined. The phylogenetic analyses revealed that Cp. granulata was not closely related to other loricated taxa with known phylogenetic affinities, such as Phacotaceae sensu stricto (Phacotus, Pteromonas, and Wislouchiella) and Dysmorphococcus globosus. This indicates at least three independent origins of loricae within the Volvocales.
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molecular systematics of Volvocales chlorophyceae chlorophyta based on exhaustive 18s rrna phylogenetic analyses
Molecular Phylogenetics and Evolution, 2008Co-Authors: Takashi Nakada, Kazuharu Misawa, Hisayoshi NozakiAbstract:Abstract The taxonomy of Volvocales (Chlorophyceae, Chlorophyta) was traditionally based solely on morphological characteristics. However, because recent molecular phylogeny largely contradicts the traditional subordinal and familial classifications, no classification system has yet been established that describes the subdivision of Volvocales in a manner consistent with the phylogenetic relationships. Towards development of a natural classification system at and above the generic level, identification and sorting of hundreds of sequences based on subjective phylogenetic definitions is a significant step. We constructed an 18S rRNA gene phylogeny based on 449 volvocalean sequences collected using exhaustive BLAST searches of the GenBank database. Many chimeric sequences, which can cause fallacious phylogenetic trees, were detected and excluded during data collection. The results revealed 21 strongly supported primary clades within phylogenetically redefined Volvocales. Phylogenetic classification following PhyloCode was proposed based on the presented 18S rRNA gene phylogeny along with the results of previous combined 18S and 26S rRNA and chloroplast multigene analyses.
Hallmann Armin - One of the best experts on this subject based on the ideXlab platform.
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The pherophorins: common, versatile building blocks in the evolution of extracellular matrix architecture in Volvocales
'Wiley', 2006Co-Authors: Hallmann ArminAbstract:Hallmann A. The pherophorins: common, versatile building blocks in the evolution of extracellular matrix architecture in Volvocales. Plant J. 2006;45(2):292-307.Green algae of the order Volvocales provide an unrivalled opportunity for exploring the transition from unicellularity to multicellularity. They range from unicells, like Chlamydomonas, through homocytic colonial forms with increasing cooperation of individual cells, like Gonium or Pandorina, to heterocytic multicellular forms with different cell types and a complete division of labour, like Volvox. A fundamental requirement for the evolution of multicellularity is the development of a complex, multifunctional extracellular matrix (ECM). The ECM has many functions, which can change under developmental control or as a result of environmental factors. Here molecular data from 15 novel proteins are presented. These proteins have been identified in Chlamydomonas reinhardtii, Gonium pectorale, Pandorina morum and Volvox carteri, and all belong to a single protein family, the pherophorins. Pherophorin-V1 is shown to be a glycoprotein localized to the 'cellular zone' of the V. carteri ECM. Pherophorin-V1 and -V2 mRNAs are strongly induced not only by the sex inducer, which triggers sexual development at extremely low concentrations, but also by mechanical wounding. Like the extensins of higher plants, which are also developmentally controlled or sometimes inducible by wounding, the pherophorins contain a (hydroxy-)proline-rich (HR) rod-like domain and are abundant within the extracellular compartment. In contrast to most extensins, pherophorins have additional globular A and B domains on both ends of the HR domains. Therefore pherophorins most closely resemble a particular class of higher plant extensin, the solanaceous lectins (e.g. potato lectin), suggesting multivalent carbohydrate-binding functions are present within the A and B domains and are responsible for cross-linking. Our results suggest that pherophorins are used as the building blocks for the extracellular scaffold throughout the Volvocales, with the characteristic mesh sizes in different ECM structures being a result of the highly diverse extensions of the HR domains. Pherophorins have therefore been a versatile element during the evolution of ECM architecture in these green algae
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Experienced developers of multicellularity - the Volvocales
GBI-Genios Deutsche Wirtschaftsdatenbank GmbH, 2003Co-Authors: Hallmann ArminAbstract:Hallmann A. Experienced developers of multicellularity - the Volvocales. Bioforum Europe. 2003;6:326-328
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Evolution zur Vielzelligkeit. Wiederholungstäter unter den Volvocales
2003Co-Authors: Hallmann ArminAbstract:Hallmann A. Evolution zur Vielzelligkeit. Wiederholungstäter unter den Volvocales. Bioforum. 2003;(Sonderausgabe Zellbiologie 1):30-32
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Die Extrazelluläre Matrix und die Entwicklung zur Vielzelligkeit
'Springer Fachmedien Wiesbaden GmbH', 2001Co-Authors: Hallmann ArminAbstract:Hallmann A. Die Extrazelluläre Matrix und die Entwicklung zur Vielzelligkeit. Biospektrum. 2001;7(5):440-441.Bei den Grünalgen der Ordnung Volvocales ist es möglich den Übergang vom Einzeller zum Vielzeller innerhalb einer phylogenetisch eng verwandten Gruppe zu untersuchen. Die Komplexität der Morphologie nimmt dort vom Einzeller Chlamydomonas über die Mehrzeller Gonium, Pandorina, Eudorina und Pleodorina bis hin zu Volvox ständig zu. Volvox ist ein echter Vielzeller mit einer vollständigen Arbeitsteilung zwischen zwei Zelltypen, somatischen und reproduktiven Zellen (umfangreiche Datensammlung über Volvox in [1]). Volvox ist somit einer der einfachsten, wenn nicht der einfachste Vielzeller überhaupt, und trotzdem teilt sich Volvox eine Vielzahl von Eigenschaften mit viel komplexeren Organismen. Der Übergang von der Einzelligkeit zur Vielzelligkeit fand in der Ordnung der Volvocales vor etwa 50-75 Millionen Jahre statt und stellt damit ein recht junges Ereignis in der Evolution dar. Eine der wichtigsten Grundvoraussetzungen für die Realisation des Übergangs zur Vielzelligkeit war die Entwicklung einer komplexen Extrazellulären Matrix (ECM), ausgehend von einer einfachen Zellwand. Die ECM eines Vielzellers ist ein komplexes Organell, das strukturelle und enzymatische Aufgaben besitzt, viele Entwicklungsantworten einschließlich der Regulation von Wachstum, Differenzierung, Wundheilung und Pathogenabwehr vermittelt und auch eine wichtige Rolle bei der Antwort auf Stresssituationen und bei der Anpassung auf Veränderungen in der Umgebung des Organismus spielt. Es stellt sich die Frage, welche Veränderungen auf molekularer Ebene nötig waren um eine derartige Entwicklung hin zu einer komplexen ECM zu ermöglichen
Tsuneyoshi Kuroiwa - One of the best experts on this subject based on the ideXlab platform.
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Phylogeny of the quadriflagellate Volvocales (Chlorophyceae) based on chloroplast multigene sequences.
Molecular Phylogenetics and Evolution, 2003Co-Authors: Hisayoshi Nozaki, Osami Misumi, Tsuneyoshi KuroiwaAbstract:Since the phylogenetic relationships of the green plants (green algae and land plants) have been extensively studied using 18S ribosomal RNA sequences, change in the arrangement of basal bodies in flagellate cells is considered to be one of the major evolutionary events in the green plants. However, the phylogenetic relationships between biflagellate and quadriflagellate species within the Volvocales remain uncertain. This study examined the phylogeny of three genera of quadriflagellate Volvocales (Carteria, Pseudocarteria, and Hafniomonas) using concatenated sequences from three chloroplast genes. Using these multigene sequences, all three quadriflagellate genera were basal to other members (biflagellates) of the CW (clockwise) group (the Volvocales and their relatives, the Chlorophyceae) and formed three robust clades. Since the flagellar apparatuses of these three quadriflagellate lineages are diverse, including counter clockwise (CCW) and CW orientation of the basal bodies, the CW orientation of the basal bodies might have evolved from the CCW orientation in the ancestral quadriflagellate volvocalean algae, giving rise to the biflagellates, major members of the CW group.
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Ultrastructure of the vegetative colonies and systematic position of Basichlamys (Volvocales, Chlorophyta)
European Journal of Phycology, 1996Co-Authors: Hisayoshi Nozaki, Makoto M. Watanabe, Motomi Itoh, Tsuneyoshi KuroiwaAbstract:Vegetative ultrastructure of the colonial green flagellate Basichlamys sacculifera was examined, with particular regard to the extracellular matrix. Each cell of the colonies was surrounded by a tripartite layer of matrix, the “cellular boundary”. This situation, essentially different from that in the Volvocaceae, is similar to that found in the Goniaceae and the Tetrabaenaceae. Cladistic analysis based on morphological data from B. sacculifera and 25 species of the colonial Volvocales suggested that Basichlamys and Tetrabaena constitute a monophyletic group which is sister to the large monophyletic group composed of the Volvocaceae and Goniaceae. The Tetrabaenaceae thus contains these two genera and has a synapomorphy “reticulate zygote walls”.
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PHYLOGENETIC RELATIONSHIPS WITHIN THE COLONIAL Volvocales (CHLOROPHYTA) INFERRED FROM rbcL GENE SEQUENCE DATA
Journal of Phycology, 1995Co-Authors: Hisayoshi Nozaki, Makoto M. Watanabe, Motomi Itoh, Ryosuke Sano, Hidenobu Uchida, Tsuneyoshi KuroiwaAbstract: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.
D Santikul - One of the best experts on this subject based on the ideXlab platform.
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the ph tolerance of chlamydomonas applanata Volvocales chlorophyta
Archives of Environmental Contamination and Toxicology, 2000Co-Authors: I Visviki, D SantikulAbstract:The effects of hydrogen ions on the growth and ultrastructure of Chlamydomonas applanata Pringsheim were examined. This species exhibits wide tolerance growing at pH values ranging from 3.4 to 8.4, with optimum growth obtained at 7.4. Growth is noticeably depressed at pH 4.4 and 3.4. At the ultrastructural level, exposure to pH 4.4 results in a 10% decrease in cell volume of single vegetative cells, an increase in pyrenoidal volume, and reduction of starch reserves. Palmelloid colonies also appear. pH 3.4 induces excessive production of mucilage and leads to the preponderance of palmelloid colonies. Cell death of both colony and single cells is seen, as well as loss of motility and abnormal cell division. Surviving single cells are significantly larger than controls, with thicker cell walls, smaller chloroplasts, and larger vacuome. Such cells entering dormancy ensure the survival of the species in times of stress.
