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Hisayoshi Nozaki - One of the best experts on this subject based on the ideXlab platform.
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Delineation of six species of the primitive algal genus Glaucocystis based on in situ ultrastructural characteristics.
Scientific Reports, 2016Co-Authors: Toshiyuki Takahashi, Mayuko Sato, Kiminori Toyooka, Ryo Matsuzaki, Tomoki Nishida, Akihiro Tuji, Chieko Saito, Hidehiro Yasuda, Hisayoshi NozakiAbstract:The field of microbiology was established in the 17th century upon the discovery of microorganisms by Antonie van Leeuwenhoek using a single-lens microscope. Now, the detailed ultrastructures of microorganisms can be elucidated in situ using three-dimensional electron microscopy. Since the availability of electron microscopy, the taxonomy of microscopic organisms has entered a new era. Here, we established a new taxonomic system of the primitive algal genus Glaucocystis (Glaucophyta) using a new-generation electron microscopic methodology: ultra-high-voltage electron microscopy (UHVEM) and field-emission scanning electron microscopy (FE-SEM). Various globally distributed Glaucocystis strains were delineated into six species, based on differences in in situ ultrastructural features of the protoplast periphery under UHVEM tomography and in the mother cell wall by FE-SEM, as well as differences in the light microscopic characteristics and molecular phylogenetic results. The present work on Glaucocystis provides a model case of new-generation taxonomy.
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a new type of 3 d peripheral ultrastructure in glaucocystis glaucocystales Glaucophyta as revealed by ultra high voltage electron microscopy
Journal of Phycology, 2016Co-Authors: Toshiyuki Takahashi, Tomoki Nishida, Chieko Saito, Hidehiro Yasuda, Hisayoshi NozakiAbstract:: The coccoid glaucophyte genus Glaucocystis is characterized by having a thick cell wall, which has to date prohibited examination of the native ultrastructural features of the protoplast periphery. Recently, however, the three-dimensional (3-D) ultrastructure of the protoplast periphery was revealed in two divergent Glaucocystis species, with the world's most powerful ultra-high voltage electron microscope (UHVEM). The two species exhibit morphological diversity in terms of their 3-D ultrastructural features. However, these two types do not seem to encompass actual ultrastructural diversity in the genetically diverse genus Glaucocystis. Here, we report a new type of peripheral 3-D ultrastructure resolved in "G. incrassata" SAG 229-2 cells by 3-D modeling based on UHVEM tomography using high-pressure freezing and freeze-substitution fixation. The plasma membrane and underlying flattened vesicles in "G. incrassata" SAG 229-2 exhibited grooves at intervals of 200-600 nm, and the flattened vesicles often overlapped one another at the protoplast periphery. This 3-D ultrastructure differs from those of the two types previously reported in other species of Glaucocystis. The possibility of classification of Glaucocystis species based on the 3-D ultrastructure of the protoplast periphery is discussed.
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five cyanophora cyanophorales Glaucophyta species delineated based on morphological and molecular data
Journal of Phycology, 2014Co-Authors: Toshiyuki Takahashi, Mayuko Sato, Kiminori Toyooka, Ryo Matsuzaki, Kaoru Kawafune, Mai Kawamura, Kazuo Okuda, Hisayoshi NozakiAbstract:: Cyanophora is an important glaucophyte genus of unicellular biflagellates that may have retained ancestral features of photosynthetic eukaryotes. The nuclear genome of Cyanophora was recently sequenced, but taxonomic studies of more than two strains are lacking for this genus. Furthermore, no study has used molecular methods to taxonomically delineate Cyanophora species. Here, we delimited the species of Cyanophora using light and electron microscopy, combined with molecular data from several globally distributed strains, including one newly established. Using a light microscope, we identified two distinct morphological groups: one with ovoid to ellipsoidal vegetative cells and another with dorsoventrally flattened or broad, bean-shaped vegetative cells containing duplicated plastids. Our light and scanning electron microscopy clearly distinguished three species with ovoid to ellipsoidal cells (C. paradoxa Korshikov, C. cuspidata Tos.Takah. & Nozaki sp. nov., and C. kugrensii Tos.Takah. & Nozaki sp. nov.) and two species with broad, bean-shaped cells (C. biloba Kugrens, B.L.Clay, C.J.Mey. & R.E.Lee and C. sudae Tos.Takah. & Nozaki sp. nov.) based on differences in cell shape and surface ornamentations of the vegetative cells under the field-emission scanning electron microscope. Molecular phylogenetic analyses of P700 chl a apoprotein A2 (psaB) genes and internal transcribed spacer (ITS) regions of nuclear ribosomal DNA (rDNA), as well as a comparison of secondary structures of nuclear rDNA ITS-2 and genetic distances of psaB genes, supported the delineation of five morphological species of Cyanophora.
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phylogenetic positions of Glaucophyta green plants archaeplastida and haptophyta chromalveolata as deduced from slowly evolving nuclear genes
Molecular Phylogenetics and Evolution, 2009Co-Authors: Hisayoshi Nozaki, Motomichi Matsuzaki, Shinichiro Maruyama, Takashi Nakada, Syou Kato, Kazuharu MisawaAbstract:The phylogenetic positions of the primary photosynthetic eukaryotes, or Archaeplastida (green plants, red algae, and glaucophytes) and the secondary photosynthetic chromalveolates, Haptophyta, vary depending on the data matrices used in the previous nuclear multigene phylogenetic studies. Here, we deduced the phylogeny of three groups of Archaeplastida and Haptophyta on the basis of sequences of the multiple slowly evolving nuclear genes and reduced the gaps or missing data, especially in glaucophyte operational taxonomic units (OTUs). The present multigene phylogenetic analyses resolved that Haptophyta and two other groups of Chromalveolata, stramenopiles and Alveolata, form a monophyletic group that is sister to the green plants and that the glaucophytes and red algae are basal to the clade composed of green plants and Chromalveolata. The bootstrap values supporting these phylogenetic relationships increased with the exclusion of long-branched OTUs. The close relationship between green plants and Chromalveolata is further supported by the common replacement in two plastid-targeted genes.
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Origins of a cyanobacterial 6-phosphogluconate dehydrogenase in plastid-lacking eukaryotes
BMC Evolutionary Biology, 2008Co-Authors: Shinichiro Maruyama, Kazuharu Misawa, Mineo Iseki, Masakatsu Watanabe, Hisayoshi NozakiAbstract:Background Plastids have inherited their own genomes from a single cyanobacterial ancestor, but the majority of cyanobacterial genes, once retained in the ancestral plastid genome, have been lost or transferred into the eukaryotic host nuclear genome via endosymbiotic gene transfer. Although previous studies showed that cyanobacterial gnd genes, which encode 6-phosphogluconate dehydrogenase, are present in several plastid-lacking protists as well as primary and secondary plastid-containing phototrophic eukaryotes, the evolutionary paths of these genes remain elusive. Results Here we show an extended phylogenetic analysis including novel gnd gene sequences from Excavata and Glaucophyta. Our analysis demonstrated the patchy distribution of the excavate genes in the gnd gene phylogeny. The Diplonema gene was related to cytosol-type genes in red algae and Opisthokonta, while heterolobosean genes occupied basal phylogenetic positions with plastid-type red algal genes within the monophyletic eukaryotic group that is sister to cyanobacterial genes. Statistical tests based on exhaustive maximum likelihood analyses strongly rejected that heterolobosean gnd genes were derived from a secondary plastid of green lineage. In addition, the cyanobacterial gnd genes from phototrophic and phagotrophic species in Euglenida were robustly monophyletic with Stramenopiles, and this monophyletic clade was moderately separated from those of red algae. These data suggest that these secondary phototrophic groups might have acquired the cyanobacterial genes independently of secondary endosymbioses. Conclusion We propose an evolutionary scenario in which plastid-lacking Excavata acquired cyanobacterial gnd genes via eukaryote-to-eukaryote lateral gene transfer or primary endosymbiotic gene transfer early in eukaryotic evolution, and then lost either their pre-existing or cyanobacterial gene.
Catherine Tirtiaux - One of the best experts on this subject based on the ideXlab platform.
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The evolution of glycogen and starch metabolism in eukaryotes gives molecular clues to understand the establishment of plastid endosymbiosis.
Journal of Experimental Botany, 2011Co-Authors: Steven Ball, Ugo Cenci, Jenifer Nirmal Raj, Christophe Colleoni, Catherine TirtiauxAbstract:Solid semi-crystalline starch and hydrosoluble glycogen define two distinct physical states of the same type of storage polysaccharide. Appearance of semi-crystalline storage polysaccharides appears linked to the requirement of unicellular diazotrophic cyanobacteria to fuel nitrogenase and protect it from oxygen through respiration of vast amounts of stored carbon. Starch metabolism itself resulted from the merging of the bacterial and eukaryote pathways of storage polysaccharide metabolism after endosymbiosis of the plastid. This generated the three Archaeplastida lineages: the green algae and land plants (Chloroplastida), the red algae (Rhodophyceae), and the glaucophytes (Glaucophyta). Reconstruction of starch metabolism in the common ancestor of Archaeplastida suggests that polysaccharide synthesis was ancestrally cytosolic. In addition, the synthesis of cytosolic starch from the ADP-glucose exported from the cyanobacterial symbiont possibly defined the original metabolic flux by which the cyanobiont provided photosynthate to its host. Additional evidence supporting this scenario include the monophyletic origin of the major carbon translocators of the inner membrane of eukaryote plastids which are sisters to nucleotide-sugar transporters of the eukaryote endomembrane system. It also includes the extent of enzyme subfunctionalization that came as a consequence of the rewiring of this pathway to the chloroplasts in the green algae. Recent evidence suggests that, at the time of endosymbiosis, obligate intracellular energy parasites related to extant Chlamydia have donated important genes to the ancestral starch metabolism network.
Eberhard Schnepf - One of the best experts on this subject based on the ideXlab platform.
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Infection of Glaucocystis nostochinearum (Glaucophyta) by Lagenidium sp. (Oomycota) and its hyperparasite Pythiella sp. (Oomycota)
Hydrobiologia, 2002Co-Authors: Stefanie F. Kühn, Eberhard SchnepfAbstract:The glaucophyte Glaucocystis nostochinearum has to our knowledge been observed to be infected by a parasite for the first time. It was found in samples taken from the northernmost freshwater pond in Germany (on the island of Sylt). The fungal parasite was identified as the oomycete Lagenidium sp. which itself was parasitised by another oomycete, Pythiella sp.
Toshiyuki Takahashi - One of the best experts on this subject based on the ideXlab platform.
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Delineation of six species of the primitive algal genus Glaucocystis based on in situ ultrastructural characteristics.
Scientific Reports, 2016Co-Authors: Toshiyuki Takahashi, Mayuko Sato, Kiminori Toyooka, Ryo Matsuzaki, Tomoki Nishida, Akihiro Tuji, Chieko Saito, Hidehiro Yasuda, Hisayoshi NozakiAbstract:The field of microbiology was established in the 17th century upon the discovery of microorganisms by Antonie van Leeuwenhoek using a single-lens microscope. Now, the detailed ultrastructures of microorganisms can be elucidated in situ using three-dimensional electron microscopy. Since the availability of electron microscopy, the taxonomy of microscopic organisms has entered a new era. Here, we established a new taxonomic system of the primitive algal genus Glaucocystis (Glaucophyta) using a new-generation electron microscopic methodology: ultra-high-voltage electron microscopy (UHVEM) and field-emission scanning electron microscopy (FE-SEM). Various globally distributed Glaucocystis strains were delineated into six species, based on differences in in situ ultrastructural features of the protoplast periphery under UHVEM tomography and in the mother cell wall by FE-SEM, as well as differences in the light microscopic characteristics and molecular phylogenetic results. The present work on Glaucocystis provides a model case of new-generation taxonomy.
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a new type of 3 d peripheral ultrastructure in glaucocystis glaucocystales Glaucophyta as revealed by ultra high voltage electron microscopy
Journal of Phycology, 2016Co-Authors: Toshiyuki Takahashi, Tomoki Nishida, Chieko Saito, Hidehiro Yasuda, Hisayoshi NozakiAbstract:: The coccoid glaucophyte genus Glaucocystis is characterized by having a thick cell wall, which has to date prohibited examination of the native ultrastructural features of the protoplast periphery. Recently, however, the three-dimensional (3-D) ultrastructure of the protoplast periphery was revealed in two divergent Glaucocystis species, with the world's most powerful ultra-high voltage electron microscope (UHVEM). The two species exhibit morphological diversity in terms of their 3-D ultrastructural features. However, these two types do not seem to encompass actual ultrastructural diversity in the genetically diverse genus Glaucocystis. Here, we report a new type of peripheral 3-D ultrastructure resolved in "G. incrassata" SAG 229-2 cells by 3-D modeling based on UHVEM tomography using high-pressure freezing and freeze-substitution fixation. The plasma membrane and underlying flattened vesicles in "G. incrassata" SAG 229-2 exhibited grooves at intervals of 200-600 nm, and the flattened vesicles often overlapped one another at the protoplast periphery. This 3-D ultrastructure differs from those of the two types previously reported in other species of Glaucocystis. The possibility of classification of Glaucocystis species based on the 3-D ultrastructure of the protoplast periphery is discussed.
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five cyanophora cyanophorales Glaucophyta species delineated based on morphological and molecular data
Journal of Phycology, 2014Co-Authors: Toshiyuki Takahashi, Mayuko Sato, Kiminori Toyooka, Ryo Matsuzaki, Kaoru Kawafune, Mai Kawamura, Kazuo Okuda, Hisayoshi NozakiAbstract:: Cyanophora is an important glaucophyte genus of unicellular biflagellates that may have retained ancestral features of photosynthetic eukaryotes. The nuclear genome of Cyanophora was recently sequenced, but taxonomic studies of more than two strains are lacking for this genus. Furthermore, no study has used molecular methods to taxonomically delineate Cyanophora species. Here, we delimited the species of Cyanophora using light and electron microscopy, combined with molecular data from several globally distributed strains, including one newly established. Using a light microscope, we identified two distinct morphological groups: one with ovoid to ellipsoidal vegetative cells and another with dorsoventrally flattened or broad, bean-shaped vegetative cells containing duplicated plastids. Our light and scanning electron microscopy clearly distinguished three species with ovoid to ellipsoidal cells (C. paradoxa Korshikov, C. cuspidata Tos.Takah. & Nozaki sp. nov., and C. kugrensii Tos.Takah. & Nozaki sp. nov.) and two species with broad, bean-shaped cells (C. biloba Kugrens, B.L.Clay, C.J.Mey. & R.E.Lee and C. sudae Tos.Takah. & Nozaki sp. nov.) based on differences in cell shape and surface ornamentations of the vegetative cells under the field-emission scanning electron microscope. Molecular phylogenetic analyses of P700 chl a apoprotein A2 (psaB) genes and internal transcribed spacer (ITS) regions of nuclear ribosomal DNA (rDNA), as well as a comparison of secondary structures of nuclear rDNA ITS-2 and genetic distances of psaB genes, supported the delineation of five morphological species of Cyanophora.
Ugo Cenci - One of the best experts on this subject based on the ideXlab platform.
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Analysis of an improved Cyanophora paradoxa genome assembly.
DNA Research, 2019Co-Authors: Dana C. Price, Steven G. Ball, Ursula Goodenough, Robyn Roth, Thamali Kariyawasam, Marek Mutwil, Camilla Ferrari, Fabio Facchinelli, Ugo CenciAbstract:Glaucophyta are members of the Archaeplastida, the founding group of photosynthetic eukaryotes that also includes red algae (Rhodophyta), green algae, and plants (Viridiplantae). Here we present a high-quality assembly, built using long-read sequences, of the ca. 100 Mb nuclear genome of the model glaucophyte Cyanophora paradoxa. We also conducted a quick-freeze deep-etch electron microscopy (QFDEEM) analysis of C. paradoxa cells to investigate glaucophyte morphology in comparison to other organisms. Using the genome data, we generated a resolved 115-taxon eukaryotic tree of life that includes a well-supported, monophyletic Archaeplastida. Analysis of muroplast peptidoglycan (PG) ultrastructure using QFDEEM shows that PG is most dense at the cleavage-furrow. Analysis of the chlamydial contribution to glaucophytes and other Archaeplastida shows that these foreign sequences likely played a key role in anaerobic glycolysis in primordial algae to alleviate ATP starvation under night-time hypoxia. The robust genome assembly of C. paradoxa significantly advances knowledge about this model species and provides a reference for exploring the panoply of traits associated with the anciently diverged glaucophyte lineage.
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Convergent Evolution of Starch Metabolism in Cyanobacteria and Archaeplastida
Evolutionary Biology, 2016Co-Authors: Christophe Colleoni, Ugo CenciAbstract:It is widely accepted that Archaeplastida phylum comprising Glaucophyta, Rhodophyta, and Chloroplastida originates from a unique endosymbiosis event, called primary plastid endosymbiosis, between a cyanobacterium and a eukaryotic cell. In addition to acquiring oxygenic photosynthesis, the three sister lineages gained the ability to synthesize a novel semi-crystalline storage polysaccharide: starch. In Archaeplastida, several lines of evidence reveal that the transition from glycogen synthesis to starch accumulation results in the recruitment of an isoamylase (ISA)-type debranching enzyme. The latter removes short-branched glucan chains, which prevent amylopectin crystallization. Recently, a small group of unicellular diazotrophic cyanobacteria, possibly the closest relative of the ancestral plastid, have been reported accumulating starch-like granules composed of both amylose and amylopectin fractions instead of glycogen particles. In order to understand starch metabolism in this particular group of cyanobacteria, a random mutagenesis was carried out on the unicellular starch-accumulating Cyanobacterium sp. CLg1. Throughout iodine crystal vapors screening, fourteen mutant strains have substituted starch granules by that of glycogen particles. Interestingly, such as in plants, all mutant strains were impaired in an isoamylase-type debranching enzyme activity. However, phylogenetic analyses point out that the critical step for starch crystallization in Archaeplastida did not evolve from the cyanobacterial isoamylase/glgX gene, but from another pathogenic bacteria. Based on this work, it appears that the transition from glycogen to starch has evolved independently in both cyanobacteria and Archaeplastida by following a common glucan trimming mechanism.
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The evolution of glycogen and starch metabolism in eukaryotes gives molecular clues to understand the establishment of plastid endosymbiosis.
Journal of Experimental Botany, 2011Co-Authors: Steven Ball, Ugo Cenci, Jenifer Nirmal Raj, Christophe Colleoni, Catherine TirtiauxAbstract:Solid semi-crystalline starch and hydrosoluble glycogen define two distinct physical states of the same type of storage polysaccharide. Appearance of semi-crystalline storage polysaccharides appears linked to the requirement of unicellular diazotrophic cyanobacteria to fuel nitrogenase and protect it from oxygen through respiration of vast amounts of stored carbon. Starch metabolism itself resulted from the merging of the bacterial and eukaryote pathways of storage polysaccharide metabolism after endosymbiosis of the plastid. This generated the three Archaeplastida lineages: the green algae and land plants (Chloroplastida), the red algae (Rhodophyceae), and the glaucophytes (Glaucophyta). Reconstruction of starch metabolism in the common ancestor of Archaeplastida suggests that polysaccharide synthesis was ancestrally cytosolic. In addition, the synthesis of cytosolic starch from the ADP-glucose exported from the cyanobacterial symbiont possibly defined the original metabolic flux by which the cyanobiont provided photosynthate to its host. Additional evidence supporting this scenario include the monophyletic origin of the major carbon translocators of the inner membrane of eukaryote plastids which are sisters to nucleotide-sugar transporters of the eukaryote endomembrane system. It also includes the extent of enzyme subfunctionalization that came as a consequence of the rewiring of this pathway to the chloroplasts in the green algae. Recent evidence suggests that, at the time of endosymbiosis, obligate intracellular energy parasites related to extant Chlamydia have donated important genes to the ancestral starch metabolism network.