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Hisayoshi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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cell size for commitment to cell division and number of successive cell divisions in multicellular volvocine green algae tetrabaena socialis and Gonium pectorale
Proceedings of the Japan Academy. Series B Physical and biological sciences, 2017Co-Authors: Hisayoshi Nozaki, Shinya Miyagishima, Takayuki Fujiwara, Lin Wei JongAbstract:Volvocine algae constitute a green algal lineage comprising unicellular Chlamydomonas, four-celled Tetrabaena, eight to 32-celled Gonium, and others up to Volvox spp., which consist of up to 50,000 cells. These algae proliferate by multiple fissions with cellular growth up to several fold in size and subsequent successive cell divisions. Chlamydomonas reinhardtii cells produce two to 32 daughter cells by one to five divisions, depending on cellular growth in the G1 phase. By contrast, in this study, we found that Tetrabaena socialis and Gonium pectorale cells mostly produced four and eight daughter cells by two and three successive divisions, respectively. In contrast to C. reinhardtii, which is committed to cell division when the cell has grown two-fold, T. socialis and G. pectorale are committed only when the cells have grown four- and eight-fold, respectively. Thus, our results suggest that evolutionary changes in cellular size for commitment largely contributes to the emergence and evolution of multicellularity in volvocine algae.
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Additional file 2 of Evolution of cytokinesis-related protein localization during the emergence of multicellularity in volvocine green algae
2017Co-Authors: Yoko Arakaki, Shinya Miyagishima, Takayuki Fujiwara, Hiroko Kawai-toyooka, Kaoru Kawafune, Jonathan Featherston, Pierre Durand, Hisayoshi NozakiAbstract:Figure S1. Alignment of DRP1A from Arabidopsis thaliana (At) and DRP1 from Chlamydomonas reinhardtii (Cr), Tetrabaena socialis (Ts), Gonium pectorale (Gp) and Volvox carteri (Vc). Black and gray background indicates identical or similar amino acid, respectively. GTPase domain, dynamin middle domain, and GTPase effector domain are indicated by pink, green, and yellow background color, respectively. The region corresponding to the antigen for an anti-TsDRP1 antibody is showed under the alignment (gray bar). Figure S2. Specificity of the affinity-purified anti-TsDRP1 antibody. The specificity of the anti-TsDRP1 antibody was validated in three volvocine algae by western blotting. A single band was detected in each lane (~75 kDa) with the antibody that was incubated with acetone powder of E. coli with the empty vector (left) while no signal was detected with the antibody that was incubated with acetone powder of E. coli expressing TsDRP1 (middle). For details of the methods, see Information S1 (Additional file 2). Figure S3. Western blot analyses of DRP1 proteins of Chlamydomonas reinhardtii (CrDRP1), Tetrabaena socialis (TsDRP1), and Gonium pectorale (GpDRP1) using anti-TsDRP1 antibody. Time-course of synchronous culture and western blot (WB) of C. reinhardtii, T. socialis, and G. pectorale are shown in a, b, and c, respectively. Time-course samples were obtained from five points (arrows in each line graph): the greatest number of dividing cells (0), three (−3) and six (−6) hours before 0 point, and three (+3) and six (+6) hours after 0 point. Coomassie brilliant blue (CBB) staining of a duplicate gel shows the equal protein loading in each lane. Information S1. Methods for specificity of the affinity-purified anti-TsDRP1 antibody (Additional file 2: Figure S2). (PDF 1785 kb
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Synonymous (dS) and nonsynonymous (dN) substitutions of MID genes in the Volvocaceae of volvocine algae (Fig 2).
2017Co-Authors: Kayoko Yamamoto, Takashi Hamaji, Patrick J. Ferris, Hiroko Kawai-toyooka, Yuki Tsuchikane, Toshiyuki Mori, Fumio Takahashi, Hiroyuki Sekimoto, Hisayoshi NozakiAbstract:Analyses were conducted with the outgroup Gonium pectorale MID gene (AB353340) using the modified Nei-Gojobori (assumed transition/transversion bias = 1.55) model ([23,24] by MEGA6[21]. All positions containing gaps and missing data were eliminated. There were a total of 162 positions in the final dataset. Filled circles (●) indicate the homothallic strain.
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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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Additional file 5: Figure S1. of Alternative evolution of a spheroidal colony in volvocine algae: developmental analysis of embryogenesis in Astrephomene (Volvocales, Chlorophyta)
2016Co-Authors: Shota Yamashita, Yoko Arakaki, Hiroko Kawai-toyooka, Akira Noga, Masafumi Hirono, Hisayoshi NozakiAbstract:Morphological observation of vegetative colonies in Astrephomene gubernaculifera strain 2014-1002-YkAs8. Figure S2. Maximum-likelihood tree of Astrephomene and Gonium based on rbcL genes. Figure S3. Diagram of making preparations for light microscopy time-lapse imaging of Astrephomene embryogenesis. Figure S4. Western blot of two species with anti-CrSAS-6 antibody. (PDF 688Â kb
Takashi Hamaji - One of the best experts on this subject based on the ideXlab platform.
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Synonymous (dS) and nonsynonymous (dN) substitutions of MID genes in the Volvocaceae of volvocine algae (Fig 2).
2017Co-Authors: Kayoko Yamamoto, Takashi Hamaji, Patrick J. Ferris, Hiroko Kawai-toyooka, Yuki Tsuchikane, Toshiyuki Mori, Fumio Takahashi, Hiroyuki Sekimoto, Hisayoshi NozakiAbstract:Analyses were conducted with the outgroup Gonium pectorale MID gene (AB353340) using the modified Nei-Gojobori (assumed transition/transversion bias = 1.55) model ([23,24] by MEGA6[21]. All positions containing gaps and missing data were eliminated. There were a total of 162 positions in the final dataset. Filled circles (●) indicate the homothallic strain.
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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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the Gonium pectorale genome demonstrates co option of cell cycle regulation during the evolution of multicellularity
Nature Communications, 2016Co-Authors: Erik R Hanschen, Takashi Hamaji, Patrick J. Ferris, Tara N Marriage, Atsushi Toyoda, Asao Fujiyama, Rafik Neme, Hideki Noguchi, Yohei Minakuchi, Masahiro SuzukiAbstract:The transition to multicellularity has occurred numerous times in all domains of life, yet its initial steps are poorly understood. The volvocine green algae are a tractable system for understanding the genetic basis of multicellularity including the initial formation of cooperative cell groups. Here we report the genome sequence of the undifferentiated colonial alga, Gonium pectorale, where group formation evolved by co-option of the retinoblastoma cell cycle regulatory pathway. Significantly, expression of the Gonium retinoblastoma cell cycle regulator in unicellular Chlamydomonas causes it to become colonial. The presence of these changes in undifferentiated Gonium indicates extensive group-level adaptation during the initial step in the evolution of multicellularity. These results emphasize an early and formative step in the evolution of multicellularity, the evolution of cell cycle regulation, one that may shed light on the evolutionary history of other multicellular innovations and evolutionary transitions.
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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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morphology molecular phylogeny and taxonomy of Gonium maiaprilis sp nov goniaceae chlorophyta from japan
Phycologia, 2010Co-Authors: Mahoko Hayama, Takashi Hamaji, Takashi Nakada, Hisayoshi NozakiAbstract:Abstract Hayama M., Nakada T., Hamaji T. and Nozaki H. 2010. Morphology, molecular phylogeny and taxonomy of Gonium maiaprilis sp. nov. (Goniaceae, Chlorophyta) from Japan. Phycologia 49: 221–234. DOI: 10.2216/09-56.1 The morphology, molecular phylogeny and taxonomy of Gonium maiaprilis Hayama et al. sp. nov. (Goniaceae, Chlorophyta) were studied using clonal cultured material originating from Fukuoka Prefecture, Japan. This species is similar to G. pectorale O. F. Muller and G. viridistellatum M. Watanabe in having one to three stable pyrenoids in the chloroplasts of eight- or 16-celled vegetative colonies. However, it is distinguished from G. pectorale and G. viridistellatum by the cell arrangement of the eight-celled colonies and from G. pectorale by aplanozygote morphology. Sexual reproduction of G. maiaprilis is heterothallic and isogamous, and the germinating zygote gives rise to a four-cell germ colony. Phylogenetic analyses based on the plastid large subunit of Rubisco genes and sequences for the ...
Shinya Miyagishima - One of the best experts on this subject based on the ideXlab platform.
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cell size for commitment to cell division and number of successive cell divisions in multicellular volvocine green algae tetrabaena socialis and Gonium pectorale
Proceedings of the Japan Academy. Series B Physical and biological sciences, 2017Co-Authors: Hisayoshi Nozaki, Shinya Miyagishima, Takayuki Fujiwara, Lin Wei JongAbstract:Volvocine algae constitute a green algal lineage comprising unicellular Chlamydomonas, four-celled Tetrabaena, eight to 32-celled Gonium, and others up to Volvox spp., which consist of up to 50,000 cells. These algae proliferate by multiple fissions with cellular growth up to several fold in size and subsequent successive cell divisions. Chlamydomonas reinhardtii cells produce two to 32 daughter cells by one to five divisions, depending on cellular growth in the G1 phase. By contrast, in this study, we found that Tetrabaena socialis and Gonium pectorale cells mostly produced four and eight daughter cells by two and three successive divisions, respectively. In contrast to C. reinhardtii, which is committed to cell division when the cell has grown two-fold, T. socialis and G. pectorale are committed only when the cells have grown four- and eight-fold, respectively. Thus, our results suggest that evolutionary changes in cellular size for commitment largely contributes to the emergence and evolution of multicellularity in volvocine algae.
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Additional file 2 of Evolution of cytokinesis-related protein localization during the emergence of multicellularity in volvocine green algae
2017Co-Authors: Yoko Arakaki, Shinya Miyagishima, Takayuki Fujiwara, Hiroko Kawai-toyooka, Kaoru Kawafune, Jonathan Featherston, Pierre Durand, Hisayoshi NozakiAbstract:Figure S1. Alignment of DRP1A from Arabidopsis thaliana (At) and DRP1 from Chlamydomonas reinhardtii (Cr), Tetrabaena socialis (Ts), Gonium pectorale (Gp) and Volvox carteri (Vc). Black and gray background indicates identical or similar amino acid, respectively. GTPase domain, dynamin middle domain, and GTPase effector domain are indicated by pink, green, and yellow background color, respectively. The region corresponding to the antigen for an anti-TsDRP1 antibody is showed under the alignment (gray bar). Figure S2. Specificity of the affinity-purified anti-TsDRP1 antibody. The specificity of the anti-TsDRP1 antibody was validated in three volvocine algae by western blotting. A single band was detected in each lane (~75 kDa) with the antibody that was incubated with acetone powder of E. coli with the empty vector (left) while no signal was detected with the antibody that was incubated with acetone powder of E. coli expressing TsDRP1 (middle). For details of the methods, see Information S1 (Additional file 2). Figure S3. Western blot analyses of DRP1 proteins of Chlamydomonas reinhardtii (CrDRP1), Tetrabaena socialis (TsDRP1), and Gonium pectorale (GpDRP1) using anti-TsDRP1 antibody. Time-course of synchronous culture and western blot (WB) of C. reinhardtii, T. socialis, and G. pectorale are shown in a, b, and c, respectively. Time-course samples were obtained from five points (arrows in each line graph): the greatest number of dividing cells (0), three (−3) and six (−6) hours before 0 point, and three (+3) and six (+6) hours after 0 point. Coomassie brilliant blue (CBB) staining of a duplicate gel shows the equal protein loading in each lane. Information S1. Methods for specificity of the affinity-purified anti-TsDRP1 antibody (Additional file 2: Figure S2). (PDF 1785 kb
Patrick J. Ferris - One of the best experts on this subject based on the ideXlab platform.
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Synonymous (dS) and nonsynonymous (dN) substitutions of MID genes in the Volvocaceae of volvocine algae (Fig 2).
2017Co-Authors: Kayoko Yamamoto, Takashi Hamaji, Patrick J. Ferris, Hiroko Kawai-toyooka, Yuki Tsuchikane, Toshiyuki Mori, Fumio Takahashi, Hiroyuki Sekimoto, Hisayoshi NozakiAbstract:Analyses were conducted with the outgroup Gonium pectorale MID gene (AB353340) using the modified Nei-Gojobori (assumed transition/transversion bias = 1.55) model ([23,24] by MEGA6[21]. All positions containing gaps and missing data were eliminated. There were a total of 162 positions in the final dataset. Filled circles (●) indicate the homothallic strain.
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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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the Gonium pectorale genome demonstrates co option of cell cycle regulation during the evolution of multicellularity
Nature Communications, 2016Co-Authors: Erik R Hanschen, Takashi Hamaji, Patrick J. Ferris, Tara N Marriage, Atsushi Toyoda, Asao Fujiyama, Rafik Neme, Hideki Noguchi, Yohei Minakuchi, Masahiro SuzukiAbstract:The transition to multicellularity has occurred numerous times in all domains of life, yet its initial steps are poorly understood. The volvocine green algae are a tractable system for understanding the genetic basis of multicellularity including the initial formation of cooperative cell groups. Here we report the genome sequence of the undifferentiated colonial alga, Gonium pectorale, where group formation evolved by co-option of the retinoblastoma cell cycle regulatory pathway. Significantly, expression of the Gonium retinoblastoma cell cycle regulator in unicellular Chlamydomonas causes it to become colonial. The presence of these changes in undifferentiated Gonium indicates extensive group-level adaptation during the initial step in the evolution of multicellularity. These results emphasize an early and formative step in the evolution of multicellularity, the evolution of cell cycle regulation, one that may shed light on the evolutionary history of other multicellular innovations and evolutionary transitions.
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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), 2026Co-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
Yusuf Yagci - One of the best experts on this subject based on the ideXlab platform.
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visible light initiated free radical promoted cationic polymerization using acylgermane based photoinitiator in the presence of onium salts
Macromolecules, 2008Co-Authors: Yasemin Yuksel Durmaz, Norbe Moszne, Yusuf YagciAbstract:The cationic polymerization of cyclohexene oxide (CHO) was achieved by UV irradiation (λ = 350−420 nm) of methylene chloride solutions containing benzoyltrimethylgermane (BTG) and onium salts, such as diphenyliodonium hexafluorophosphate (Ph2I+PF6−) or N-ethoxy-2-methylpyridinium hexafluorophosphate (EMP+PF6−). A feasible initiation mechanism involves the photogeneration of germyl radicals and benzoyl radicals in the first step. Subsequent oxidation of germyl radicals by onium salts yields germanium ions capable of initiating the polymerization of CHO. In agreement with the proposed mechanism, the polymerization was completely inhibited by a radical scavanger such as 2,2,6,6-tetramethylpiperidinyl-1-oxy, and polymerization efficiency was directly related to the reduction potential of the onium salts, i.e. Ph2I+PF6− (Ered1/2 = −0.2 V) was found to be more efficient than EMP+PF6− (Ered1/2 = −0.7 V). The results were compared to the other photoinitiators generally used in free radical promoted cationic polym...
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visible light initiated free radical promoted cationic polymerization using acylgermane based photoinitiator in the presence of onium salts
Macromolecules, 2008Co-Authors: Yasemin Yuksel Durmaz, Norbert Moszner, Yusuf YagciAbstract:The cationic polymerization of cyclohexene oxide (CHO) was achieved by UV irradiation (λ = 350−420 nm) of methylene chloride solutions containing benzoyltrimethylgermane (BTG) and onium salts, such...
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free radical promoted cationic polymerization by using bisacylphosphine oxide photoinitiators substituent effect on the reactivity of phosphinoyl radicals
Polymer, 2003Co-Authors: Canan Dursun, Yusuf Yagci, Mustafa Degirmenci, Steffen Jockusch, Nicholas J TurroAbstract:The cationic polymerization of cyclohexene oxide (CHO) was achieved upon UV irradiation ðl ¼ 380 nmÞ of methylene chloride solutions containing a series of bisacylphosphine oxides and onium salts, such as diphenyliodonium hexafluorophosphate (Ph2I þ PF6 )o rNethoxy-2-methylpyridinium hexafluorophosphate (EMP þ PF6 ). A feasible initiation mechanism involves the photogeneration of phosphinoyl radicals and benzoyl radicals in the first step. Subsequent oxidation of phosphinoyl radicals by onium salts yields phosphonium ions capable of initiating the polymerization of CHO. In agreement with the proposed mechanism, the polymerization efficiency was directly related to the reduction potential of the onium salts, i.e. Ph2I þ PF6 (E 1/2 ¼ 2 0.2 V) was found to be more efficient than EMP þ PF6 (E 1/2 ¼ 20.7 V). The variation in reactivity of the different phosphorous radicals was correlated with p-character of the phosphinoyl radical as reflected by the 31 P hyperfine coupling constant. The results were compared to a monoacylphosphine oxide, (2,4,6-trimethylbenzoyl) diphenylphosphine oxide, which showed only a low efficiency in promoting cationic polymerization. In addition to CHO monomer, butyl vinyl ether and N-vinyl carbazole were polymerized in the presence of bisacylphosphine oxides and onium salts with high efficiency. q 2003 Elsevier Ltd. All rights reserved.