The Experts below are selected from a list of 87 Experts worldwide ranked by ideXlab platform
Hisayoshi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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Maximum-likelihood (ML) tree (based on LG model) of 16 full-length MID proteins from colonial volvocine species and two species of Chlamydomonas.
2017Co-Authors: Kayoko Yamamoto, Takashi Hamaji, Patrick J. Ferris, Yuki Tsuchikane, Hiroyuki Sekimoto, Hiroko Kawai-toyooka, Toshiyuki Mori, Fumio Takahashi, Hisayoshi NozakiAbstract:Branch lengths are proportional to the estimated amino acid substitutions, which are indicated by the scale bar above the tree. Numbers above and below branch points indicate bootstrap values (50% or more) of the ML and neighbor-joining (based on the JTT model), analyses, respectively. The sequences of MID orthologs with asterisks (*) were determined in this study; filled circles (●) indicate Homothallic Strains.
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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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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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Zygospore formation between Homothallic and heterothallic Strains of Closterium
Sexual Plant Reproduction, 2012Co-Authors: Yuki Tsuchikane, Hisayoshi Nozaki, Miki Tsuchiya, František Hindák, Hiroyuki SekimotoAbstract:Zygospore formation in different Strains of the Closterium peracerosum - strigosum - littorale complex was examined in this unicellular isogamous charophycean alga to shed light on gametic mating Strains in this taxon, which is believed to share a close phylogenetic relationship with land plants. Zygospores typically form as a result of conjugation between mating-type plus (mt^+) and mating-type minus (mt^−) cells during sexual reproduction in the heterothallic strain, similar to Chlamydomonas . However, within clonal cells, zygospores are formed within Homothallic Strains, and the majority of these zygospores originate as a result of conjugation of two recently divided sister gametangial cells derived from one vegetative cell. In this study, we analyzed conjugation of Homothallic cells in the presence of phylogenetically closely related heterothallic cells to characterize the reproductive function of Homothallic sister gametangial cells. The relative ratio of non-sister zygospores to sister zygospores increased in the presence of heterothallic mt^+ cells, compared with that in the Homothallic strain alone and in a coculture with mt^− cells. Heterothallic cells were surface labeled with calcofluor white, permitting fusions with Homothallic cells to be identified and confirming the formation of hybrid zygospores between the Homothallic cells and heterothallic mt^+ cells. These results show that at least some of the Homothallic gametangial cells possess heterothallic mt^−-like characters. This finding supports speculation that division of one vegetative cell into two sister gametangial cells is a segregative process capable of producing complementary mating types.
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Distribution of the sex-determining gene MID and molecular correspondence of mating types within the isogamous genus Gonium (Volvocales, Chlorophyta).
Public Library of Science (PLoS), 1Co-Authors: Takashi Hamaji, Patrick J. Ferris, Ichiro Nishii, Yoshiki Nishimura, Hisayoshi NozakiAbstract: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.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.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
James R. Broach - One of the best experts on this subject based on the ideXlab platform.
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α2p controls donor preference during mating type interconversion in yeast by inactivating a recombinational enhancer of chromosome III
Genes & development, 1997Co-Authors: Lisa Szeto, Maria K. Fafalios, Hualin Zhong, Andrew K. Vershon, James R. BroachAbstract:Homothallic Strains of Saccharomyces cerevisiae can change mating type as often as every generation by replacing the allele at the MAT locus with a copy of mating type information present at one of two storage loci, HML and HMR, located on either end of chromosome III. Selection of the appropriate donor locus is dictated by a mating type-specific repressor protein, alpha2p: Cells containing alpha2p select HMR, whereas those lacking alpha2p select HML. As a repressor protein, alpha2p binds to DNA cooperatively with the transcriptional activator Mcm1p. Here we show that two alpha2p/Mcm1p-binding sites, DPS1 and DPS2, control donor selection. DPS1 and DPS2 are located approximately 30 kb from the left arm of chromosome III, well removed from HML, HMR, and MAT. Precise deletion of only DPS1 and DPS2 results in random selection of donor loci and in a cells without affecting selection in alpha cells. Reciprocally, deletion of only the alpha2p binding segments in each of these two sites results in selection of the wrong donor loci in alpha cells without affecting preference in a cells. These results suggest that Mcm1p, bound to these two sites in the absence of alpha2p, activates HML as donor. Binding of alpha2p blocks the ability of Mcm1p bound to DPS1 and DPS2 to activate HML, resulting in default selection of HMR as donor. DPS1 and DPS2 also regulate expression of several noncoding RNAs, although deletion of at least one of these RNA loci does not affect donor preference. This suggests that transcriptional activation, rather than transcription of a specific product, is the initiating event in activating the left arm of chromosome III for donor selection.
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Mutations affecting donor preference during mating type interconversion in Saccharomyces cerevisiae.
Genetics, 1995Co-Authors: K S Weiler, L Szeto, James R. BroachAbstract:Homothallic Strains of Saccharomyces cerevisiae can convert mating type from a to alpha or alpha to a as often as every generation, by replacing genetic information specifying one mating type at the expressor locus, MAT, with information specifying the opposite mating type. The cryptic mating type information that is copied and inserted at MAT is contained in either of two loci, HML or HMR. The particular locus selected as donor during mating type interconversion is regulated by the allele expressed at MAT. MATa cells usually select HML, and MAT alpha cells usually select HMR, a process referred to as donor preference. To identify factors required for donor preference, we isolated and characterized a number of mutants that frequently selected the nonpreferred donor locus during mating type interconversion. Many of these mutants were found to harbor chromosome rearrangements or mutations at MAT or HML that interfered with the switching process. However, one mutant carried a recessive allele of CHL1, a gene previously shown to be required for efficient chromosome segregation during mitosis. Homothallic Strains of yeast containing a null allele of CHL1 exhibited almost random selection of the donor locus in a MATa background but were normal in their ability to select HMR in a MAT alpha background. Our results indicate that Chl1p participates in the process of donor selection and are consistent with a model in which Chl1p helps establish an intrinsic bias in donor preference.
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Donor locus selection during Saccharomyces cerevisiae mating type interconversion responds to distant regulatory signals.
Genetics, 1992Co-Authors: K S Weiler, James R. BroachAbstract:Mating type interconversion in Homothallic Strains of the yeast Saccharomyces cerevisiae results from directed transposition of a mating type allele from one of the two silent donor loci, HML and HMR, to the expressing locus, MAT. Cell type regulates the selection of the particular donor locus to be utilized during mating type interconversion: MATa cells preferentially select HML alpha and MAT alpha cells preferentially select HMRa. Such preferential selection indicates that the cell is able to distinguish between HML and HMR during mating type interconversion. Accordingly, we designed experiments to identify those features perceived by the cell to discriminate HML and HMR. We demonstrate that discrimination does not derive from the different structures of the HML and HMR loci, from the unique sequences flanking each donor locus nor from any of the DNA distal to the HM loci on chromosome III. Moreover, we find that the sequences flanking the MAT locus do not function in the preferential selection of one donor locus over the other. We propose that the positions of the donor loci on the left and right arms of chromosome III is the characteristic utilized by the cell to distinguish HML and HMR. This positional information is not generated by either CEN3 or the MAT locus, but probably derives from differences in the chromatin structure, chromosome folding or intranuclear localization of the two ends of chromosome III.
Hiroyuki Sekimoto - One of the best experts on this subject based on the ideXlab platform.
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The genus Closterium, a new model organism to study sexual reproduction in streptophytes
The New phytologist, 2018Co-Authors: Yuki Tsuchikane, Hiroyuki SekimotoAbstract:Contents Summary 99 I. Introduction 99 II. Life cycle of Closterium 100 III. Sexual reproductive processes in the heterothallic Closterium peracerosum-strigosum-littorale complex 101 IV. Homothallism in the C. psl. complex 102 V. Sexual reproduction and inheritance of mating types in Closterium ehrenbergii 102 VI. mt-determining gene of the C. psl. complex 103 VII. Future perspectives 103 Acknowledgements 103 References 103 SUMMARY: Closterium occupies a key phylogenetic position as an ancestor of land plants and is the best-characterized Charophycean alga in terms of the process of sexual reproduction. Zygospores form as a result of sexual reproduction between genetically determined mating type plus (mt+ ) and mating type minus (mt- ) cells in heterothallic Strains, or between clonal cells in Homothallic Strains. Here we review knowledge on the intercellular communication and mating type determination for successful sexual reproduction in Closterium. Using genomic information and transgenic techniques, the genus could be a model organism to study the mechanisms and evolution of sexual reproduction in streptophytes.
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Maximum-likelihood (ML) tree (based on LG model) of 16 full-length MID proteins from colonial volvocine species and two species of Chlamydomonas.
2017Co-Authors: Kayoko Yamamoto, Takashi Hamaji, Patrick J. Ferris, Yuki Tsuchikane, Hiroyuki Sekimoto, Hiroko Kawai-toyooka, Toshiyuki Mori, Fumio Takahashi, Hisayoshi NozakiAbstract:Branch lengths are proportional to the estimated amino acid substitutions, which are indicated by the scale bar above the tree. Numbers above and below branch points indicate bootstrap values (50% or more) of the ML and neighbor-joining (based on the JTT model), analyses, respectively. The sequences of MID orthologs with asterisks (*) were determined in this study; filled circles (●) indicate Homothallic Strains.
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Zygospore formation between Homothallic and heterothallic Strains of Closterium
Sexual Plant Reproduction, 2012Co-Authors: Yuki Tsuchikane, Hisayoshi Nozaki, Miki Tsuchiya, František Hindák, Hiroyuki SekimotoAbstract:Zygospore formation in different Strains of the Closterium peracerosum - strigosum - littorale complex was examined in this unicellular isogamous charophycean alga to shed light on gametic mating Strains in this taxon, which is believed to share a close phylogenetic relationship with land plants. Zygospores typically form as a result of conjugation between mating-type plus (mt^+) and mating-type minus (mt^−) cells during sexual reproduction in the heterothallic strain, similar to Chlamydomonas . However, within clonal cells, zygospores are formed within Homothallic Strains, and the majority of these zygospores originate as a result of conjugation of two recently divided sister gametangial cells derived from one vegetative cell. In this study, we analyzed conjugation of Homothallic cells in the presence of phylogenetically closely related heterothallic cells to characterize the reproductive function of Homothallic sister gametangial cells. The relative ratio of non-sister zygospores to sister zygospores increased in the presence of heterothallic mt^+ cells, compared with that in the Homothallic strain alone and in a coculture with mt^− cells. Heterothallic cells were surface labeled with calcofluor white, permitting fusions with Homothallic cells to be identified and confirming the formation of hybrid zygospores between the Homothallic cells and heterothallic mt^+ cells. These results show that at least some of the Homothallic gametangial cells possess heterothallic mt^−-like characters. This finding supports speculation that division of one vegetative cell into two sister gametangial cells is a segregative process capable of producing complementary mating types.
Takashi Hamaji - One of the best experts on this subject based on the ideXlab platform.
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Maximum-likelihood (ML) tree (based on LG model) of 16 full-length MID proteins from colonial volvocine species and two species of Chlamydomonas.
2017Co-Authors: Kayoko Yamamoto, Takashi Hamaji, Patrick J. Ferris, Yuki Tsuchikane, Hiroyuki Sekimoto, Hiroko Kawai-toyooka, Toshiyuki Mori, Fumio Takahashi, Hisayoshi NozakiAbstract:Branch lengths are proportional to the estimated amino acid substitutions, which are indicated by the scale bar above the tree. Numbers above and below branch points indicate bootstrap values (50% or more) of the ML and neighbor-joining (based on the JTT model), analyses, respectively. The sequences of MID orthologs with asterisks (*) were determined in this study; filled circles (●) indicate Homothallic Strains.
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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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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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Distribution of the sex-determining gene MID and molecular correspondence of mating types within the isogamous genus Gonium (Volvocales, Chlorophyta).
Public Library of Science (PLoS), 1Co-Authors: Takashi Hamaji, Patrick J. Ferris, Ichiro Nishii, Yoshiki Nishimura, Hisayoshi NozakiAbstract: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.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.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
K S Weiler - One of the best experts on this subject based on the ideXlab platform.
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Mutations affecting donor preference during mating type interconversion in Saccharomyces cerevisiae.
Genetics, 1995Co-Authors: K S Weiler, L Szeto, James R. BroachAbstract:Homothallic Strains of Saccharomyces cerevisiae can convert mating type from a to alpha or alpha to a as often as every generation, by replacing genetic information specifying one mating type at the expressor locus, MAT, with information specifying the opposite mating type. The cryptic mating type information that is copied and inserted at MAT is contained in either of two loci, HML or HMR. The particular locus selected as donor during mating type interconversion is regulated by the allele expressed at MAT. MATa cells usually select HML, and MAT alpha cells usually select HMR, a process referred to as donor preference. To identify factors required for donor preference, we isolated and characterized a number of mutants that frequently selected the nonpreferred donor locus during mating type interconversion. Many of these mutants were found to harbor chromosome rearrangements or mutations at MAT or HML that interfered with the switching process. However, one mutant carried a recessive allele of CHL1, a gene previously shown to be required for efficient chromosome segregation during mitosis. Homothallic Strains of yeast containing a null allele of CHL1 exhibited almost random selection of the donor locus in a MATa background but were normal in their ability to select HMR in a MAT alpha background. Our results indicate that Chl1p participates in the process of donor selection and are consistent with a model in which Chl1p helps establish an intrinsic bias in donor preference.
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Donor locus selection during Saccharomyces cerevisiae mating type interconversion responds to distant regulatory signals.
Genetics, 1992Co-Authors: K S Weiler, James R. BroachAbstract:Mating type interconversion in Homothallic Strains of the yeast Saccharomyces cerevisiae results from directed transposition of a mating type allele from one of the two silent donor loci, HML and HMR, to the expressing locus, MAT. Cell type regulates the selection of the particular donor locus to be utilized during mating type interconversion: MATa cells preferentially select HML alpha and MAT alpha cells preferentially select HMRa. Such preferential selection indicates that the cell is able to distinguish between HML and HMR during mating type interconversion. Accordingly, we designed experiments to identify those features perceived by the cell to discriminate HML and HMR. We demonstrate that discrimination does not derive from the different structures of the HML and HMR loci, from the unique sequences flanking each donor locus nor from any of the DNA distal to the HM loci on chromosome III. Moreover, we find that the sequences flanking the MAT locus do not function in the preferential selection of one donor locus over the other. We propose that the positions of the donor loci on the left and right arms of chromosome III is the characteristic utilized by the cell to distinguish HML and HMR. This positional information is not generated by either CEN3 or the MAT locus, but probably derives from differences in the chromatin structure, chromosome folding or intranuclear localization of the two ends of chromosome III.