Zygnematales

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Michael Melkonian - One of the best experts on this subject based on the ideXlab platform.

  • Molecular phylogeny of conjugating green algae (Zygnemophyceae, Streptophyta) inferred from SSU rDNA sequence comparisons.
    Journal of Molecular Evolution, 2020
    Co-Authors: Andrey A. Gontcharov, Birger Marin, Michael Melkonian
    Abstract:

    Nuclear-encoded SSU rDNA sequences have been obtained from 64 strains of conjugating green algae (Zygnemophyceae, Streptophyta, Viridiplantae). Molecular phylogenetic analyses of 90 SSU rDNA sequences of Viridiplantae (inciuding 78 from the Zygnemophyceae) were performed using complex evolutionary models and maximum likelihood, distance, and maximum parsimony methods. The significance of the results was tested by bootstrap analyses, deletion of long-branch taxa, relative rate tests, and Kishino–Hasegawa tests with user-defined trees. All results support the monophyly of the class Zygnemophyceae and of the order Desmidiales. The second order, Zygnematales, forms a series of early-branching clades in paraphyletic succession, with the two traditional families Mesotaeniaceae and Zygnemataceae not recovered as lineages. Instead, a long-branch Spirogyra/Sirogonium clade and the later-diverging Netrium and Roya clades represent independent clades. Within the order Desmidiales, the families Gonatozygaceae and Closteriaceae are monophyletic, whereas the Peniaceae (represented only by Penium margaritaceum) and the Desmidiaceae represent a single weakly supported lineage. Within the Desmidiaceae short internal branches and varying rates of sequence evolution among taxa reduce the phylogenetic resolution significantly. The SSU rDNA-based phylogeny is largely congruent with a published analysis of the rbcL phylogeny of the Zygnemophyceae (McCourt et al. 2000) and is also in general agreement with classification schemes based on cell wall ultrastructure. The extended taxon sampling at the subgenus level provides solid evidence that many genera in the Zygnemophyceae are not monophyletic and that the genus concept in the group needs to be revised.

  • Origin of land plants: Do conjugating green algae hold the key?
    BMC Evolutionary Biology, 2011
    Co-Authors: Sabina Wodniok, Henner Brinkmann, Gernot Glöckner, Andrew J. Heidel, Hervé Philippe, Michael Melkonian, Burkhard Becker
    Abstract:

    The terrestrial habitat was colonized by the ancestors of modern land plants about 500 to 470 million years ago. Today it is widely accepted that land plants (embryophytes) evolved from streptophyte algae, also referred to as charophycean algae. The streptophyte algae are a paraphyletic group of green algae, ranging from unicellular flagellates to morphologically complex forms such as the stoneworts (Charales). For a better understanding of the evolution of land plants, it is of prime importance to identify the streptophyte algae that are the sister-group to the embryophytes. The Charales, the Coleochaetales or more recently the Zygnematales have been considered to be the sister group of the embryophytes However, despite many years of phylogenetic studies, this question has not been resolved and remains controversial. Here, we use a large data set of nuclear-encoded genes (129 proteins) from 40 green plant taxa (Viridiplantae) including 21 embryophytes and six streptophyte algae, representing all major streptophyte algal lineages, to investigate the phylogenetic relationships of streptophyte algae and embryophytes. Our phylogenetic analyses indicate that either the Zygnematales or a clade consisting of the Zygnematales and the Coleochaetales are the sister group to embryophytes. Our analyses support the notion that the Charales are not the closest living relatives of embryophytes. Instead, the Zygnematales or a clade consisting of Zygnematales and Coleochaetales are most likely the sister group of embryophytes. Although this result is in agreement with a previously published phylogenetic study of chloroplast genomes, additional data are needed to confirm this conclusion. A Zygnematales/embryophyte sister group relationship has important implications for early land plant evolution. If substantiated, it should allow us to address important questions regarding the primary adaptations of viridiplants during the conquest of land. Clearly, the biology of the Zygnematales will receive renewed interest in the future.

  • MOLECULAR PHYLOGENY AND REVISION OF THE GENUS NETRIUM (ZYGNEMATOPHYCEAE, STREPTOPHYTA): NUCLEOTAENIUM GEN. NOV.1
    Journal of Phycology, 2010
    Co-Authors: Andrey A. Gontcharov, Michael Melkonian
    Abstract:

    Nuclear-encoded SSU rDNA, chloroplast LSU rDNA, and rbcL genes were sequenced from 53 strains of conjugating green algae (Zygnematophyceae, Streptophyta) and used to analyze phylogenetic relationships in the traditional order Zygnematales. Analyses of a concatenated data set (5,220 nt) established 12 well-supported clades in the order; seven of these constituted a superclade, termed “Zygnemataceae.” Together with genera (Zygnema, Mougeotia) traditionally placed in the family Zygnemataceae, the “Zygnemataceae” also included representatives of the genera Cylindrocystis and Mesotaenium, traditionally placed in the family Mesotaeniaceae. A synapomorphic amino acid replacement (codon 192, cysteine replaced by valine) in the LSU of RUBISCO characterized this superclade. The traditional genera Netrium, Cylindrocystis, and Mesotaenium were shown to be para- or polyphyletic, highlighting the inadequacy of phenotypic traits used to define these genera. Species of the traditional genus Netrium were resolved as three well-supported clades each distinct in the number of chloroplasts per cell, their surface morphology (structure and arrangement of lamellae) and the position of the nucleus or nuclear behavior during cell division. Based on molecular phylogenetic analyses and synapomorphic phenotypic traits, the genus Netrium has been revised, and a new genus, Nucleotaenium gen. nov., was established. The genus Planotaenium, also formerly a part of Netrium, was identified as the sister group of the derived Roya/Desmidiales clade and thus occupies a key position in the evolutionary radiation leading to the most species-rich group of streptophyte green algae.

  • EST analysis of the scaly green flagellate Mesostigma viride (Streptophyta): Implications for the evolution of green plants (Viridiplantae)
    BMC Plant Biology, 2006
    Co-Authors: Andreas Simon, Gernot Glöckner, Michael Melkonian, Marius Felder, Burkhard Becker
    Abstract:

    Background The Viridiplantae (land plants and green algae) consist of two monophyletic lineages, the Chlorophyta and the Streptophyta. The Streptophyta include all embryophytes and a small but diverse group of freshwater algae traditionally known as the Charophyceae (e.g. Charales, Coleochaete and the Zygnematales). The only flagellate currently included in the Streptophyta is Mesostigma viride Lauterborn. To gain insight into the genome evolution in streptophytes, we have sequenced 10,395 ESTs from Mesostigma representing 3,300 independent contigs and compared the ESTs of Mesostigma with available plant genomes (Arabidopsis, Oryza, Chlamydomonas), with ESTs from the bryophyte Physcomitrella, the genome of the rhodophyte Cyanidioschyzon, the ESTs from the rhodophyte Porphyra, and the genome of the diatom Thalassiosira.

  • primary and secondary structure analyses of the rdna group i introns of the Zygnematales charophyta
    Current Genetics, 1996
    Co-Authors: Debashish Bhattacharya, Simon H Damberger, Barbara Surek, Michael Melkonian
    Abstract:

    The Zygnematales (Charophyta) contain a group-I intron (subgroup ICl) within their nuclear-encoded small subunit ribosomal DNA (SSU rDNA) coding region. This intron, which is inserted after position 1506 (relative to the SSU rDNA ofEscherichia coli), is proposed to have been vertically inherited since the origin of the Zygnematales approximately 350–400 million years ago. Primary and secondary structure analyses were carried out to model group-I intron evolution in the Zygnematales. Secondary structure analyses support genetic data regarding sequence conservation within regions known to be functionally important for in vitro self-splicing of group-I introns. Comparisons of zygnematalean group-I intron secondary structures also provided some new insights into sequences that may have important roles in in vivo RNA splicing. Sequence analyses showed that sequence divergence rates and the nucleotide compositions of introns and coding regions within any one taxon varied widely, suggesting that the “1506” group-I introns and rDNA coding regions in the Zygnematales evolve independently.

Debashish Bhattacharya - One of the best experts on this subject based on the ideXlab platform.

  • evolutionary analyses of small subunit rdna coding regions and the 1506 group i introns of the Zygnematales charophyceae streptophyta
    Journal of Phycology, 1999
    Co-Authors: Anja Besendahl, Debashish Bhattacharya
    Abstract:

    We sequenced the small-subunit (SSU) rDNA coding region and 1506 group I intron (that interrupts this gene) in Closterium ehrenbergii Menegh. ex Ralfs, Closterium littorale Gay, Cylindrocystis brebissonii (Menegh.) de Bary, Penium margaritaceum (Ehr.) de Breb. ex Ralfs, and Staurastrum punctulatum de Breb. and the 1506 intron in Sirogonium sticticum (J.E. Smith) Kutz. (Zygnematales). Reverse transcriptase (RT)/PCR analyses demonstrated that the 1506 introns are not present in vivo in mature rRNA. Splicing analyses in vitro showed, however, that these introns do not catalyze their own excision from the rRNA coding region. Mutation of the conserved G (ωG) to an A at the 3′ terminus of the 1506 intron of Gonatozygon aculeatum Hastings (Zygnematales) restored self-splicing activity. This mutant intron utilized a new 3′ splice site to facilitate autoexcision. We speculate that the 3′ terminus of the wild-type 1506 intron may be a target for a “helper” factor that facilitates the second step of splicing (exon ligation) in vivo in the Zygnematales. Phylogenetic analyses showed congruence of rDNA and intron trees confirming an ancient origin of the 1506 intron in the common ancestor of the Zygnematales. The rDNA trees were compared to those inferred from rbcL sequence analyses. These trees were in general agreement and showed polyphyly of the Mesotaeniaceae and the Zygnemataceae. The 1506 introns contain significant evolutionary signal and provided strong phylogenetic support for groups within the Zygnematales when analyzed alone or in combination with the SSU rDNA coding regions. The secondary structure of 1506 group I introns was studied to identify RNA elements that may be useful as systematic markers. This analysis showed an optional helix found in RNA domain P2 that was lost in a monophyletic group of Desmidiaceae. This helix is found in all other 1506 group I introns, including those interrupting red algal and fungal SSU rDNAs.

  • EVOLUTIONARY ANALYSES OF SMALL‐SUBUNIT rDNA CODING REGIONS AND THE 1506 GROUP I INTRONS OF THE Zygnematales (CHAROPHYCEAE, STREPTOPHYTA)
    Journal of Phycology, 1999
    Co-Authors: Anja Besendahl, Debashish Bhattacharya
    Abstract:

    We sequenced the small-subunit (SSU) rDNA coding region and 1506 group I intron (that interrupts this gene) in Closterium ehrenbergii Menegh. ex Ralfs, Closterium littorale Gay, Cylindrocystis brebissonii (Menegh.) de Bary, Penium margaritaceum (Ehr.) de Breb. ex Ralfs, and Staurastrum punctulatum de Breb. and the 1506 intron in Sirogonium sticticum (J.E. Smith) Kutz. (Zygnematales). Reverse transcriptase (RT)/PCR analyses demonstrated that the 1506 introns are not present in vivo in mature rRNA. Splicing analyses in vitro showed, however, that these introns do not catalyze their own excision from the rRNA coding region. Mutation of the conserved G (ωG) to an A at the 3′ terminus of the 1506 intron of Gonatozygon aculeatum Hastings (Zygnematales) restored self-splicing activity. This mutant intron utilized a new 3′ splice site to facilitate autoexcision. We speculate that the 3′ terminus of the wild-type 1506 intron may be a target for a “helper” factor that facilitates the second step of splicing (exon ligation) in vivo in the Zygnematales. Phylogenetic analyses showed congruence of rDNA and intron trees confirming an ancient origin of the 1506 intron in the common ancestor of the Zygnematales. The rDNA trees were compared to those inferred from rbcL sequence analyses. These trees were in general agreement and showed polyphyly of the Mesotaeniaceae and the Zygnemataceae. The 1506 introns contain significant evolutionary signal and provided strong phylogenetic support for groups within the Zygnematales when analyzed alone or in combination with the SSU rDNA coding regions. The secondary structure of 1506 group I introns was studied to identify RNA elements that may be useful as systematic markers. This analysis showed an optional helix found in RNA domain P2 that was lost in a monophyletic group of Desmidiaceae. This helix is found in all other 1506 group I introns, including those interrupting red algal and fungal SSU rDNAs.

  • primary and secondary structure analyses of the rdna group i introns of the Zygnematales charophyta
    Current Genetics, 1996
    Co-Authors: Debashish Bhattacharya, Simon H Damberger, Barbara Surek, Michael Melkonian
    Abstract:

    The Zygnematales (Charophyta) contain a group-I intron (subgroup ICl) within their nuclear-encoded small subunit ribosomal DNA (SSU rDNA) coding region. This intron, which is inserted after position 1506 (relative to the SSU rDNA ofEscherichia coli), is proposed to have been vertically inherited since the origin of the Zygnematales approximately 350–400 million years ago. Primary and secondary structure analyses were carried out to model group-I intron evolution in the Zygnematales. Secondary structure analyses support genetic data regarding sequence conservation within regions known to be functionally important for in vitro self-splicing of group-I introns. Comparisons of zygnematalean group-I intron secondary structures also provided some new insights into sequences that may have important roles in in vivo RNA splicing. Sequence analyses showed that sequence divergence rates and the nucleotide compositions of introns and coding regions within any one taxon varied widely, suggesting that the “1506” group-I introns and rDNA coding regions in the Zygnematales evolve independently.

  • group i introns are inherited through common ancestry in the nuclear encoded rrna of Zygnematales charophyceae
    Proceedings of the National Academy of Sciences of the United States of America, 1994
    Co-Authors: Debashish Bhattacharya, Barbara Surek, M Rusing, S Damberger, Michael Melkonian
    Abstract:

    Abstract Group I introns are found in organellar genomes, in the genomes of eubacteria and phages, and in nuclear-encoded rRNAs. The origin and distribution of nuclear-encoded rRNA group I introns are not understood. To elucidate their evolutionary relationships, we analyzed diverse nuclear-encoded small-subunit rRNA group I introns including nine sequences from the green-algal order Zygnematales (Charophyceae). Phylogenetic analyses of group I introns and rRNA coding regions suggest that lateral transfers have occurred in the evolutionary history of group I introns and that, after transfer, some of these elements may form stable components of the host-cell nuclear genomes. The Zygnematales introns, which share a common insertion site (position 1506 relative to the Escherichia coli small-subunit rRNA), form one subfamily of group I introns that has, after its origin, been inherited through common ancestry. Since the first Zygnematales appear in the middle Devonian within the fossil record, the "1506" group I intron presumably has been a stable component of the Zygnematales small-subunit rRNA coding region for 350-400 million years.

Hiroyuki Sekimoto - One of the best experts on this subject based on the ideXlab platform.

  • Stable Nuclear Transformation of the Closterium peracerosum-strigosum-littorale Complex
    Plant and Cell Physiology, 2011
    Co-Authors: Sachie Hori, Yuki Tsuchikane, Naoko Kitao, Misako Kato, Hiroyuki Sekimoto
    Abstract:

    Although charophycean algae form a relevant monophyly with embryophytes and hence occupy a fundamental place in the development of Streptophyta, no tools for genetic transformation in these organisms have been developed. Here we present the first stable nuclear transformation system for the unicellular Zygnematales, the Closterium peracerosum–strigosum–littorale complex (C. psl complex), which is one of the most useful organisms for experimental research on charophycean algae. When a vector, pSA106, containing the dominant selectable marker ble (phleomycinresistant) gene and a reporter cgfp (Chlamydomonas-adapted green fluorescent protein) gene was introduced into cells via particle bombardment, a total of 19 phleomycin-resistant cells were obtained in the presence of a low concentration of phleomycin. Six isogenic strains isolated using conditioned medium showed consecutive cgfp expression and long-term stability for phleomycin resistance. DNA analyses verified single or tandem/redundant integration of � 10 copies of pSA106 into the C. psl complex genome. We also constructed an overexpression vector, pSA1102, and then integrated a CpPI gene encoding minus-specific sex pheromone into pSA1102. Ectopic overexpression of CpPI and the pheromonal function were confirmed when the vector pSA1102_CpPI was introduced into mt + cells. The present efficient transformation system for theC. psl complex should provide not only a basis for molecular investigation of Closterium but also an insight into important processes in early development and evolution of Streptophyta.

  • Stable Nuclear Transformation of the Closterium peracerosum–strigosum–littorale Complex
    Plant and Cell Physiology, 2011
    Co-Authors: Sachie Hori, Yuki Tsuchikane, Naoko Kitao, Misako Kato, Hiroyuki Sekimoto
    Abstract:

    Although charophycean algae form a relevant monophyly with embryophytes and hence occupy a fundamental place in the development of Streptophyta, no tools for genetic transformation in these organisms have been developed. Here we present the first stable nuclear transformation system for the unicellular Zygnematales, the Closterium peracerosum–strigosum–littorale complex (C. psl complex), which is one of the most useful organisms for experimental research on charophycean algae. When a vector, pSA106, containing the dominant selectable marker ble (phleomycinresistant) gene and a reporter cgfp (Chlamydomonas-adapted green fluorescent protein) gene was introduced into cells via particle bombardment, a total of 19 phleomycin-resistant cells were obtained in the presence of a low concentration of phleomycin. Six isogenic strains isolated using conditioned medium showed consecutive cgfp expression and long-term stability for phleomycin resistance. DNA analyses verified single or tandem/redundant integration of � 10 copies of pSA106 into the C. psl complex genome. We also constructed an overexpression vector, pSA1102, and then integrated a CpPI gene encoding minus-specific sex pheromone into pSA1102. Ectopic overexpression of CpPI and the pheromonal function were confirmed when the vector pSA1102_CpPI was introduced into mt + cells. The present efficient transformation system for theC. psl complex should provide not only a basis for molecular investigation of Closterium but also an insight into important processes in early development and evolution of Streptophyta.

  • reproductive isolation by sex pheromones in the closterium peracerosum strigosum littorale complex Zygnematales charophyceae 1
    Journal of Phycology, 2008
    Co-Authors: Yuki Tsuchikane, Hiroyuki Sekimoto
    Abstract:

    : The Closterium peracerosum-strigosum-littorale (C. psl.) complex consists of unicellular algae and is known to be composed of several reproductively isolated mating groups of heterothallic strains. Group I-E is completely isolated from mating groups II-A and II-B, groups II-A and II-B are partially isolated from each other, and only mating-type plus (mt(+) ) cells of group II-A and mating-type minus (mt(-) ) cells of group II-B form zygotes. Based on the alignment of 1506 group I introns, significant phylogenetic relationships were observed among mating groups II-A and II-B, while mating group I-E was distant from groups II-A and II-B. Sexual cell division in both mating-type cells of group II-A was stimulated in conditioned media in which cells of group II-B had been cultured. When mt(-) cells of group II-B were stimulated in conditioned medium derived from group II-A, mt(+) cells of group II-B did not respond to the conditioned medium. Conditioned media derived from group I-E did not exhibit sexual cell division (SCD)-inducing activity against any strain except those within its own group. From the alignment of deduced amino acid sequences from orthologous protoplast-release-inducing protein (PR-IP) Inducer genes, we detected a significant similarity among groups II-A and II-B, and mating group I-E had low similarity to other mating groups. The existing degree of reproductive isolation can be partially explained by differences in molecular structures and physiological activities of sex pheromones of these heterothallic mating groups.

  • REPRODUCTIVE ISOLATION BY SEX PHEROMONES IN THE CLOSTERIUM PERACEROSUM–STRIGOSUM–LITTORALE COMPLEX (Zygnematales, CHAROPHYCEAE)1
    Journal of Phycology, 2008
    Co-Authors: Yuki Tsuchikane, Hiroyuki Sekimoto
    Abstract:

    : The Closterium peracerosum-strigosum-littorale (C. psl.) complex consists of unicellular algae and is known to be composed of several reproductively isolated mating groups of heterothallic strains. Group I-E is completely isolated from mating groups II-A and II-B, groups II-A and II-B are partially isolated from each other, and only mating-type plus (mt(+) ) cells of group II-A and mating-type minus (mt(-) ) cells of group II-B form zygotes. Based on the alignment of 1506 group I introns, significant phylogenetic relationships were observed among mating groups II-A and II-B, while mating group I-E was distant from groups II-A and II-B. Sexual cell division in both mating-type cells of group II-A was stimulated in conditioned media in which cells of group II-B had been cultured. When mt(-) cells of group II-B were stimulated in conditioned medium derived from group II-A, mt(+) cells of group II-B did not respond to the conditioned medium. Conditioned media derived from group I-E did not exhibit sexual cell division (SCD)-inducing activity against any strain except those within its own group. From the alignment of deduced amino acid sequences from orthologous protoplast-release-inducing protein (PR-IP) Inducer genes, we detected a significant similarity among groups II-A and II-B, and mating group I-E had low similarity to other mating groups. The existing degree of reproductive isolation can be partially explained by differences in molecular structures and physiological activities of sex pheromones of these heterothallic mating groups.

Minchul Yoon - One of the best experts on this subject based on the ideXlab platform.

  • effect of gamma irradiation on physiological and proteomic changes of arctic zygnema sp chlorophyta Zygnematales
    Phycologia, 2015
    Co-Authors: Jongil Choi, Minchul Yoon, Hyun Jin Park
    Abstract:

    Abstract: In this study, the effect of ionizing radiation on an Arctic alga was examined by assessing photosynthetic efficiency, antioxidant capacity, and proteomic changes. Arctic Zygnema sp. was gamma-irradiated at doses of 1, 3, and 5 kGy and showed serious cell damage after irradiation with the 5 kGy dose. The photosynthetic efficiency markedly decreased in gamma-irradiated Zygnema sp.; whereas, antioxidant capacity significantly increased. To investigate changes in protein expression levels, two-dimensional electrophoresis was performed. Thirty-nine protein spots were differently expressed. Several proteins, both upregulated and downregulated, were identified as photosynthesis-related proteins, confirming an important effect of gamma irradiation on the photosynthetic process. On the one hand, proteins similar to those involved in energy metabolism, isoprene biosynthesis, and protein biosynthesis were significantly downregulated. On the other hand, proteins related to DNA repair, quinone oxireductase,...

  • 179 conjugation process of a freshwater green alga spirogyra varians Zygnematales charophyceae examined by fitc lectins
    Journal of Phycology, 2003
    Co-Authors: Minchul Yoon
    Abstract:

    The conjugation processes of filamentous freshwater green alga Spirogyra varians were examined by the use of FITC-lectins. Conjugation comprised of five steps: 1) array with adjacent filaments, 2) formation of conjugation protrusion (papilla), 3) fusion of the protrusions, 4) formation of conjugation tube, and 5) formation of zygotes. Three lectins, ConA, RCA and UEA, showed considerable labeling during the progression of conjugation. FITC-ConA labeled the surfaces of filaments throughout the whole conjugation processes. No labeling of FITC-RCA was detected on the surface of vegetative filaments. FITC-RCA labeling was observed at the conjugation protrusions only after the papilla formation. Strong labeling continued until formation of zygotes even in hollow area between the conjugation tube. The labeling decreased gradually over time and disappeared when zygotes were formed. FITC-UEA showed similar labeling pattern with FITC-RCA except that the labeling did not disappear even after zygote formation. Inhibition experiments using D-galactose, L-fucose and D-mannose, which are complementary carbohydrates for the above lectins, showed considerable decrease of conjugation (<50% vs. 83% in control). Hamagglutination experiment using crude extract of Spyrogyra varians revealed existence of lectins specific for the above carbohydrates. These results suggested that the lectin-carbohydrate recognition system might be involved in the conjugation of Spirogyra varians.

  • 179 Conjugation Process of a Freshwater Green Alga, Spirogyra Varians (Zygnematales, Charophyceae Examined by Fitc‐Lectins)
    Journal of Phycology, 2003
    Co-Authors: Minchul Yoon
    Abstract:

    The conjugation processes of filamentous freshwater green alga Spirogyra varians were examined by the use of FITC-lectins. Conjugation comprised of five steps: 1) array with adjacent filaments, 2) formation of conjugation protrusion (papilla), 3) fusion of the protrusions, 4) formation of conjugation tube, and 5) formation of zygotes. Three lectins, ConA, RCA and UEA, showed considerable labeling during the progression of conjugation. FITC-ConA labeled the surfaces of filaments throughout the whole conjugation processes. No labeling of FITC-RCA was detected on the surface of vegetative filaments. FITC-RCA labeling was observed at the conjugation protrusions only after the papilla formation. Strong labeling continued until formation of zygotes even in hollow area between the conjugation tube. The labeling decreased gradually over time and disappeared when zygotes were formed. FITC-UEA showed similar labeling pattern with FITC-RCA except that the labeling did not disappear even after zygote formation. Inhibition experiments using D-galactose, L-fucose and D-mannose, which are complementary carbohydrates for the above lectins, showed considerable decrease of conjugation (

Yuki Tsuchikane - One of the best experts on this subject based on the ideXlab platform.

  • Stable Nuclear Transformation of the Closterium peracerosum-strigosum-littorale Complex
    Plant and Cell Physiology, 2011
    Co-Authors: Sachie Hori, Yuki Tsuchikane, Naoko Kitao, Misako Kato, Hiroyuki Sekimoto
    Abstract:

    Although charophycean algae form a relevant monophyly with embryophytes and hence occupy a fundamental place in the development of Streptophyta, no tools for genetic transformation in these organisms have been developed. Here we present the first stable nuclear transformation system for the unicellular Zygnematales, the Closterium peracerosum–strigosum–littorale complex (C. psl complex), which is one of the most useful organisms for experimental research on charophycean algae. When a vector, pSA106, containing the dominant selectable marker ble (phleomycinresistant) gene and a reporter cgfp (Chlamydomonas-adapted green fluorescent protein) gene was introduced into cells via particle bombardment, a total of 19 phleomycin-resistant cells were obtained in the presence of a low concentration of phleomycin. Six isogenic strains isolated using conditioned medium showed consecutive cgfp expression and long-term stability for phleomycin resistance. DNA analyses verified single or tandem/redundant integration of � 10 copies of pSA106 into the C. psl complex genome. We also constructed an overexpression vector, pSA1102, and then integrated a CpPI gene encoding minus-specific sex pheromone into pSA1102. Ectopic overexpression of CpPI and the pheromonal function were confirmed when the vector pSA1102_CpPI was introduced into mt + cells. The present efficient transformation system for theC. psl complex should provide not only a basis for molecular investigation of Closterium but also an insight into important processes in early development and evolution of Streptophyta.

  • Stable Nuclear Transformation of the Closterium peracerosum–strigosum–littorale Complex
    Plant and Cell Physiology, 2011
    Co-Authors: Sachie Hori, Yuki Tsuchikane, Naoko Kitao, Misako Kato, Hiroyuki Sekimoto
    Abstract:

    Although charophycean algae form a relevant monophyly with embryophytes and hence occupy a fundamental place in the development of Streptophyta, no tools for genetic transformation in these organisms have been developed. Here we present the first stable nuclear transformation system for the unicellular Zygnematales, the Closterium peracerosum–strigosum–littorale complex (C. psl complex), which is one of the most useful organisms for experimental research on charophycean algae. When a vector, pSA106, containing the dominant selectable marker ble (phleomycinresistant) gene and a reporter cgfp (Chlamydomonas-adapted green fluorescent protein) gene was introduced into cells via particle bombardment, a total of 19 phleomycin-resistant cells were obtained in the presence of a low concentration of phleomycin. Six isogenic strains isolated using conditioned medium showed consecutive cgfp expression and long-term stability for phleomycin resistance. DNA analyses verified single or tandem/redundant integration of � 10 copies of pSA106 into the C. psl complex genome. We also constructed an overexpression vector, pSA1102, and then integrated a CpPI gene encoding minus-specific sex pheromone into pSA1102. Ectopic overexpression of CpPI and the pheromonal function were confirmed when the vector pSA1102_CpPI was introduced into mt + cells. The present efficient transformation system for theC. psl complex should provide not only a basis for molecular investigation of Closterium but also an insight into important processes in early development and evolution of Streptophyta.

  • reproductive isolation by sex pheromones in the closterium peracerosum strigosum littorale complex Zygnematales charophyceae 1
    Journal of Phycology, 2008
    Co-Authors: Yuki Tsuchikane, Hiroyuki Sekimoto
    Abstract:

    : The Closterium peracerosum-strigosum-littorale (C. psl.) complex consists of unicellular algae and is known to be composed of several reproductively isolated mating groups of heterothallic strains. Group I-E is completely isolated from mating groups II-A and II-B, groups II-A and II-B are partially isolated from each other, and only mating-type plus (mt(+) ) cells of group II-A and mating-type minus (mt(-) ) cells of group II-B form zygotes. Based on the alignment of 1506 group I introns, significant phylogenetic relationships were observed among mating groups II-A and II-B, while mating group I-E was distant from groups II-A and II-B. Sexual cell division in both mating-type cells of group II-A was stimulated in conditioned media in which cells of group II-B had been cultured. When mt(-) cells of group II-B were stimulated in conditioned medium derived from group II-A, mt(+) cells of group II-B did not respond to the conditioned medium. Conditioned media derived from group I-E did not exhibit sexual cell division (SCD)-inducing activity against any strain except those within its own group. From the alignment of deduced amino acid sequences from orthologous protoplast-release-inducing protein (PR-IP) Inducer genes, we detected a significant similarity among groups II-A and II-B, and mating group I-E had low similarity to other mating groups. The existing degree of reproductive isolation can be partially explained by differences in molecular structures and physiological activities of sex pheromones of these heterothallic mating groups.

  • REPRODUCTIVE ISOLATION BY SEX PHEROMONES IN THE CLOSTERIUM PERACEROSUM–STRIGOSUM–LITTORALE COMPLEX (Zygnematales, CHAROPHYCEAE)1
    Journal of Phycology, 2008
    Co-Authors: Yuki Tsuchikane, Hiroyuki Sekimoto
    Abstract:

    : The Closterium peracerosum-strigosum-littorale (C. psl.) complex consists of unicellular algae and is known to be composed of several reproductively isolated mating groups of heterothallic strains. Group I-E is completely isolated from mating groups II-A and II-B, groups II-A and II-B are partially isolated from each other, and only mating-type plus (mt(+) ) cells of group II-A and mating-type minus (mt(-) ) cells of group II-B form zygotes. Based on the alignment of 1506 group I introns, significant phylogenetic relationships were observed among mating groups II-A and II-B, while mating group I-E was distant from groups II-A and II-B. Sexual cell division in both mating-type cells of group II-A was stimulated in conditioned media in which cells of group II-B had been cultured. When mt(-) cells of group II-B were stimulated in conditioned medium derived from group II-A, mt(+) cells of group II-B did not respond to the conditioned medium. Conditioned media derived from group I-E did not exhibit sexual cell division (SCD)-inducing activity against any strain except those within its own group. From the alignment of deduced amino acid sequences from orthologous protoplast-release-inducing protein (PR-IP) Inducer genes, we detected a significant similarity among groups II-A and II-B, and mating group I-E had low similarity to other mating groups. The existing degree of reproductive isolation can be partially explained by differences in molecular structures and physiological activities of sex pheromones of these heterothallic mating groups.

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