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Monique Turmel - One of the best experts on this subject based on the ideXlab platform.

  • complete mitogenomes of the chlorophycean green algae bulbochaete rectangularis var hiloensis oedogoniales and stigeoclonium helveticum Chaetophorales provide insight into the sequence of events that led to the acquisition of a reduced derived patter
    Mitochondrial DNA Part B, 2020
    Co-Authors: Monique Turmel, Christian Otis, Anne-sophie Bélanger, Claude Lemieux
    Abstract:

    AbstractMitogenome evolution in the Chlorophyceae is characterized by the acquisition of a reduced-derived pattern by the Chlamydomonadales + Sphaeropleales clade. Because no mitogenomes are availa...

  • Proliferation of group II introns in the chloroplast genome of the green alga Oedocladium carolinianum (Chlorophyceae)
    PeerJ, 2016
    Co-Authors: Jean-simon Brouard, Monique Turmel, Christian Otis, Claude Lemieux
    Abstract:

    The chloroplast genome sustained extensive changes in architecture during the evolution of the Chlorophyceae, a morphologically and ecologically diverse class of green algae belonging to the Chlorophyta; however, the forces driving these changes are poorly understood. The five orders recognized in the Chlorophyceae form two major clades: the CS clade consisting of the Chlamydomonadales and Sphaeropleales, and the OCC clade consisting of the Oedogoniales, Chaetophorales, and Chaetopeltidales. In the OCC clade, considerable variations in chloroplast DNA (cpDNA) structure, size, gene order, and intron content have been observed. The large inverted repeat (IR), an ancestral feature characteristic of most green plants, is present in Oedogonium cardiacum (Oedogoniales) but is lacking in the examined members of the Chaetophorales and Chaetopeltidales. Remarkably, the Oedogonium 35.5-kb IR houses genes that were putatively acquired through horizontal DNA transfer. To better understand the dynamics of chloroplast genome evolution in the Oedogoniales, we analyzed the cpDNA of a second representative of this order, Oedocladium carolinianum.The Oedocladium cpDNA was sequenced and annotated. The evolutionary distances separating Oedocladium and Oedogonium cpDNAs and two other pairs of chlorophycean cpDNAs were estimated using a 61-gene data set. Phylogenetic analysis of an alignment of group IIA introns from members of the OCC clade was performed. Secondary structures and insertion sites of oedogonialean group IIA introns were analyzed.The 204,438-bp Oedocladium genome is 7.9 kb larger than the Oedogonium genome, but its repertoire of conserved genes is remarkably similar and gene order differs by only one reversal. Although the 23.7-kb IR is missing the putative foreign genes found in Oedogonium, it contains sequences coding for a putative phage or bacterial DNA primase and a hypothetical protein. Intergenic sequences are 1.5-fold longer and dispersed repeats are more abundant, but a smaller fraction of the Oedocladium genome is occupied by introns. Six additional group II introns are present, five of which lack ORFs and carry highly similar sequences to that of the ORF-less IIA intron shared with Oedogonium. Secondary structure analysis of the group IIA introns disclosed marked differences in the exon-binding sites; however, each intron showed perfect or nearly perfect base pairing interactions with its target site.Our results suggest that chloroplast genes rearrange more slowly in the Oedogoniales than in the Chaetophorales and raise questions as to what was the nature of the foreign coding sequences in the IR of the common ancestor of the Oedogoniales. They provide the first evidence for intragenomic proliferation of group IIA introns in the Viridiplantae, revealing that intron spread in the Oedocladium lineage likely occurred by retrohoming after sequence divergence of the exon-binding sites.

  • the chloroplast genome of the green alga schizomeris leibleinii chlorophyceae provides evidence for bidirectional dna replication from a single origin in the Chaetophorales
    Genome Biology and Evolution, 2011
    Co-Authors: Jean-simon Brouard, Christian Otis, Claude Lemieux, Monique Turmel
    Abstract:

    In the Chlorophyceae, the chloroplast genome is extraordinarily fluid in architecture and displays unique features relative to other groups of green algae. For the Chaetophorales, 1 of the 5 major lineages of the Chlorophyceae, it has been shown that the distinctive architecture of the 223,902-bp genome of Stigeoclonium helveticum is consistent with bidirectional DNA replication from a single origin. Here, we report the 182,759-bp chloroplast genome sequence of Schizomeris leibleinii, a member of the earliest diverging lineage of the Chaetophorales. Like its Stigeoclonium homolog, the Schizomeris genome lacks a large inverted repeat encoding the rRNA operon and displays a striking bias in coding regions that is associated with a bias in base composition along each strand. Our results support the notion that these two chaetophoralean genomes replicate bidirectionally from a putative origin located in the vicinity of the small subunit ribosomal RNA gene. Their shared structural characteristics were most probably inherited from the common ancestor of all chaetophoralean algae. Short dispersed repeats account for most of the 41-kb size variation between the Schizomeris and Stigeoclonium genomes, and there is no indication that homologous recombination between these repeated elements led to the observed gene rearrangements. A comparison of the extent of variation sustained by the Stigeoclonium and Schizomeris chloroplast DNAs (cpDNAs) with that observed for the cpDNAs of the chlamydomonadalean Chlamydomonas and Volvox suggests that gene rearrangements as well as changes in the abundance of intergenic and intron sequences occurred at a slower pace in the Chaetophorales than in the Chlamydomonadales.

  • The Exceptionally Large Chloroplast Genome of the Green Alga Floydiella terrestris Illuminates the Evolutionary History of the Chlorophyceae
    Genome Biology and Evolution, 2010
    Co-Authors: Jean-simon Brouard, Christian Otis, Claude Lemieux, Monique Turmel
    Abstract:

    The Chlorophyceae, an advanced class of chlorophyte green algae, comprises five lineages that form two major clades (Chlamydomonadales + Sphaeropleales and Oedogoniales + Chaetopeltidales + Chaetophorales). The four complete chloroplast DNA (cpDNA) sequences currently available for chlorophyceans uncovered an extraordinarily fluid genome architecture as well as many structural features distinguishing this group from other green algae. We report here the 521,168-bp cpDNA sequence from a member of the Chaetopeltidales (Floydiella terrestris), the sole chlorophycean lineage not previously sampled for chloroplast genome analysis. This genome, which contains 97 conserved genes and 26 introns (19 group I and 7 group II introns), is the largest chloroplast genome ever sequenced. Intergenic regions account for 77.8% of the genome size and are populated by short repeats. Numerous genomic features are shared with the cpDNA of the chaetophoralean Stigeoclonium helveticum, notably the absence of a large inverted repeat and the presence of unique gene clusters and trans-spliced group II introns. Although only one of the Floydiella group I introns encodes a homing endonuclease gene, our finding of five free-standing reading frames having similarity with such genes suggests that chloroplast group I introns endowed with mobility were once more abundant in the Floydiella lineage. Parsimony analysis of structural genomic features and phylogenetic analysis of chloroplast sequence data unambiguously resolved the Oedogoniales as sister to the Chaetopeltidales and Chaetophorales. An evolutionary scenario of the molecular events that shaped the chloroplast genome in the Chlorophyceae is presented.

  • chloroplast dna sequence of the green alga oedogonium cardiacum chlorophyceae unique genome architecture derived characters shared with the Chaetophorales and novel genes acquired through horizontal transfer
    BMC Genomics, 2008
    Co-Authors: Jean-simon Brouard, Christian Otis, Claude Lemieux, Monique Turmel
    Abstract:

    Background To gain insight into the branching order of the five main lineages currently recognized in the green algal class Chlorophyceae and to expand our understanding of chloroplast genome evolution, we have undertaken the sequencing of chloroplast DNA (cpDNA) from representative taxa. The complete cpDNA sequences previously reported for Chlamydomonas (Chlamydomonadales), Scenedesmus (Sphaeropleales), and Stigeoclonium (Chaetophorales) revealed tremendous variability in their architecture, the retention of only few ancestral gene clusters, and derived clusters shared by Chlamydomonas and Scenedesmus. Unexpectedly, our recent phylogenies inferred from these cpDNAs and the partial sequences of three other chlorophycean cpDNAs disclosed two major clades, one uniting the Chlamydomonadales and Sphaeropleales (CS clade) and the other uniting the Oedogoniales, Chaetophorales and Chaetopeltidales (OCC clade). Although molecular signatures provided strong support for this dichotomy and for the branching of the Oedogoniales as the earliest-diverging lineage of the OCC clade, more data are required to validate these phylogenies. We describe here the complete cpDNA sequence of Oedogonium cardiacum (Oedogoniales).

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

  • the Chaetophorales chlorophyceae a taxonomic revision at family level
    European Journal of Phycology, 2018
    Co-Authors: Lenka Caisova, Michael Melkonian
    Abstract:

    ABSTRACTThe Chaetophorales (Chlorophyceae) consist of filamentous green algae that were mostly described directly from natural samples by light microscopy. However, the descriptions were often based on morphological characters that are either homoplasious or sensitive to environmental factors. This clearly prevents proper identification of several chaetophoralean taxa and highlights the need for taxonomic revision at different taxonomic levels. In the present study, we focused on revision of the Chaetophorales at the family level. We used a well-resolved molecular phylogeny to re-evaluate morphological characters in the Chaetophorales under clearly defined laboratory conditions. We identified five morphological characters that permitted unambiguous identification of most chaetophoralean families, and used these characters to establish a new family, the Fritschiellaceae (fam. nov.), and emend the Chaetophoraceae Greville 1824. Knowledge gained from this study lends additional weight to the current classifi...

  • The Chaetophorales (Chlorophyceae) – a taxonomic revision at family level
    European Journal of Phycology, 2018
    Co-Authors: Lenka Caisova, Michael Melkonian
    Abstract:

    ABSTRACTThe Chaetophorales (Chlorophyceae) consist of filamentous green algae that were mostly described directly from natural samples by light microscopy. However, the descriptions were often based on morphological characters that are either homoplasious or sensitive to environmental factors. This clearly prevents proper identification of several chaetophoralean taxa and highlights the need for taxonomic revision at different taxonomic levels. In the present study, we focused on revision of the Chaetophorales at the family level. We used a well-resolved molecular phylogeny to re-evaluate morphological characters in the Chaetophorales under clearly defined laboratory conditions. We identified five morphological characters that permitted unambiguous identification of most chaetophoralean families, and used these characters to establish a new family, the Fritschiellaceae (fam. nov.), and emend the Chaetophoraceae Greville 1824. Knowledge gained from this study lends additional weight to the current classifi...

  • Barrancaceae: A new green algal lineage with structural and behavioral adaptations to a fluctuating environment
    American Journal of Botany, 2015
    Co-Authors: Lenka Caisova, Carolina Pérez Reyes, Virginia Cruz Álamo, Antera Martel Quintana, Barbara Surek, Michael Melkonian
    Abstract:

    To enhance our knowledge of the diversity of microalgae, a phycological survey of the Canary Islands (Spain) was undertaken. Here we report the discovery of a (semi)terrestrial green filamentous alga isolated from a steep volcanic canyon on La Palma. This alga is continually exposed to changing weather conditions (floods vs. droughts) and thus provides a good opportunity to investigate possible adaptations to a semiterrestrial habitat with large fluctuations of environmental parameters.We used axenic cultures, simulated flood and drought stresses and studied their effect on the life history of the alga using light, confocal laser scanning and scanning electron microscopy including fluorescent staining. Furthermore, phylogenetic analyses using rDNA sequence comparisons were performed.Three specific life-history traits that likely represent adaptations to the fluctuating environment of the canyon were observed: (1) fragmentation through "filament splitting", a unique branching mechanism not reported before in algae and initiated by formation of oblique cross walls, (2) aplanospore formation, and (3) reproduction by multiflagellate zoospores with 4-24 flagella arranged in groups of four. Phylogenetic analyses identified the alga as Barranca multiflagellata gen. et sp. nov. (Barrancaceae fam. nov., Chaetophorales, Chlorophyceae). Moreover, the Chaetophoraceae Greville, 1824 was emended and a new family, Uronemataceae (fam. nov.) erected.The discovery of Barrancaceae fam. nov. highlights the importance of investigating nonconventional habitats to explore microalgal diversity. The reproductive versatility demonstrated by Barranca suggests adaptation to a semiterrestrial habitat with large fluctuations in water availability.

  • A Consensus Secondary Structure of ITS2 in the Chlorophyta Identified by Phylogenetic Reconstruction
    Protist, 2013
    Co-Authors: Lenka Caisova, Birger Marin, Michael Melkonian
    Abstract:

    The definition of species plays a pivotal role in biology. It has been proposed that Compensatory Base Changes (CBCs) in the fast-evolving Internal Transcribed Spacer 2 (ITS2) correlate with speciation and thus can be used to distinguish species. The applicability of CBC - based species concepts using ITS2, however, rests on the homology of the investigated ITS2 positions. We studied the ITS2 molecule of 147 strains of Chlorophyceae (Chlorophyta, Viridiplantae) including 26 new sequences in the order Chaetophorales, and compared their secondary structures to ITS2 in the sister class Ulvophyceae, represented by the order Ulvales. Using a phylogenetic/comparative approach, it was possible to identify 1) the first consensus structure model of the ITS2 molecule that can be applied to two classes of green algae [Ulvophyceae (Ulvales), Chlorophyceae] and 2) landmarks (the spacer regions separating the ITS2 Helices) for more robust prediction of the secondary structures in green algae. Moreover, we found that CBCs in homologous positions in these 147 strains (representing 115 validly described species) are either completely absent or mostly associated with internal branches representing higher order taxonomic levels (genera, families, orders). As reported for the Ulvales, CBCs are not diagnostic at the species level in the dataset used.

  • polyphyly of chaetophora and stigeoclonium within the Chaetophorales chlorophyceae revealed by sequence comparisons of nuclear encoded ssu rrna genes
    Journal of Phycology, 2011
    Co-Authors: Lenka Caisova, Birger Marin, Nicole Sausen, Thomas Proschold, Michael Melkonian
    Abstract:

    : Previously published molecular phylogenetic analyses of the Chaetophorales (Chlorophyceae) suffered from limited taxon sampling (six genera with only a single species per genus). To test the monophyly of species-rich genera, and to analyze the phylogenetic relationships among families and genera in the Chaetophorales, we determined nuclear-encoded SSU rDNA sequences from 30 strains of Chaetophorales, performed phylogenetic analyses using various methods, and screened clades for support by unique molecular synapomorphies in the SSU rRNA secondary structure. The Schizomeridaceae and the weakly supported Aphanochaetaceae were recovered as basal lineages. The derived family Chaetophoraceae diverged into two clades: the "Uronema clade" containing unbranched filaments, and a sister clade designated as "branched Chaetophoraceae" comprising Chaetophora, Stigeoclonium, Draparnaldia, Caespitella, and Fritschiella. Although some terminal clades corresponded to genera described (e.g., Caespitella and Draparnaldia), other clades were in conflict with traditional taxonomic designations. Especially, the genera Stigeoclonium and Chaetophora were shown to be polyphyletic. The globose species Chaetophora elegans was unrelated to lobate Chaetophora spp. (e.g., Chaetophora lobata). Since the original description of Chaetophora referred to a lobate thallus organization, the latter clade represented Chaetophora sensu stricto. In consequence, C. lobata was designated as lectotype of Chaetophora. Two Stigeoclonium species, Stigeoclonium farctum Berthold and Stigeoclonium'Longipilus', diverged independently from the type species of Stigeoclonium, Stigeoclonium tenue (C. Agardh) Kutz. These results indicated that some commonly used taxonomic characters are either homoplasious or plesiomorphic and call for a reevaluation of the systematics of the Chaetophorales using novel morphological and molecular approaches.

Lenka Caisova - One of the best experts on this subject based on the ideXlab platform.

  • Molecular phylogeny and taxonomic revision of chaetophoralean algae (Chlorophyta)
    2020
    Co-Authors: Lenka Caisova
    Abstract:

    Since the human inclination to estimate and trace natural diversity, usable species definitions as well as taxonomical systems are required. As a consequence, the first proposed classification schemes assigned the filamentous and parenchymatous taxa to the green algal order Chaetophorales sensu Wille. The introduction of ultrastructural and molecular methods provided novel insight into algal evolution and generated taxonomic revisions based on phylogenetic inference. However, until now, the number of molecular phylogenetic studies focusing on the Chaetophorales s.s. is surprisingly low. To enhance knowledge about phylogenetic relationships among taxa within the order, the nuclear?encoded SSU rDNA sequences from 30 strains covering all three chaetophoralean families have been investigated. All revealed monophyletic groupings were further screened for molecular non-homoplasious synapomorphies within the Viridiplantae. To address the question of the correspondence between morphological characters traditionally used for taxonomical delimitation of the Chaetophorales and the tree topology favored by molecular data, the list of morphological/ ultrastructural/ecological characters was elaborated and further analyzed. In addition, to obtain a close-up view into the evolution of Compensatory Base Changes (CBCs) of the second internal transcribed spacer (ITS2) which is currently often used to delimit putative biological species, 86 newly obtained/published sequences of ITS2 for five families of the order Ulvales were analyzed. Furthermore, a detailed comparative study of all ITS2 substitutions has been done. Subsequently all revealed CBCs and hemi- CBCs have been mapped upon the ITS2 phylogenetic tree topology. Finally, CBCs/hCBCs taxonomic inference in the Ulvales has been discussed.

  • Draparnaldia, a chlorophyte model for comparative analyses of plant terrestrialization.
    Journal of Experimental Botany, 2020
    Co-Authors: Lenka Caisova
    Abstract:

    It is generally accepted that land plants evolved from streptophyte algae. However, there are also many chlorophytes (a sister group of streptophyte algae and land plants) that moved to terrestrial habitats and even resemble mosses. Why have no land plants evolved from chlorophytes? If we want to better understand what enabled streptophyte algae to conquer the land, we need to study the chlorophytes as well. In this review, I will introduce the freshwater filamentous chlorophyte alga Draparnaldia sp. (Chaetophorales, Chlorophyceae) as a model for comparative analyses between these two lineages. I will also focus on current knowledge about chlorophyte versus streptophyte evolution of morphological complexity and their respective morphological/behavioural adaptations to semi-terrestrial habitats, and show why Draparnaldia, as a new model system is needed.

  • Regeneration and transient gene expression in protoplasts of Draparnaldia (chlorophytes), an emerging model for comparative analyses with basal streptophytes
    Plant Methods, 2019
    Co-Authors: Lenka Caisova, Timothy O. Jobe
    Abstract:

    Green plants comprise two lineages: (1) the streptophytes that colonised land and (2) the chlorophytes that have adaptations to land but remained mostly aquatic. To better understand what made streptophytes so successful, we are currently establishing the chlorophyte alga Draparnaldia sp. (Chaetophorales, Chlorophyceae) as a model for comparative analyses between these two lineages. However, establishing Draparnaldia as a valuable model requires that it can be transformed. Thus, our goal is to develop a transformation protocol for this alga. We have established the first transformation protocol for Draparnaldia. This protocol is based on protoplast transformation by electroporation. It includes instructions on protoplast isolation, regeneration and transient transfection. It also provides a list of the effective selective agents for future Draparnaldia transformations. Our protocol opens a way for Draparnaldia functional genomics analyses. Moreover, it also provides an important base for establishment of stable transformation.

  • the Chaetophorales chlorophyceae a taxonomic revision at family level
    European Journal of Phycology, 2018
    Co-Authors: Lenka Caisova, Michael Melkonian
    Abstract:

    ABSTRACTThe Chaetophorales (Chlorophyceae) consist of filamentous green algae that were mostly described directly from natural samples by light microscopy. However, the descriptions were often based on morphological characters that are either homoplasious or sensitive to environmental factors. This clearly prevents proper identification of several chaetophoralean taxa and highlights the need for taxonomic revision at different taxonomic levels. In the present study, we focused on revision of the Chaetophorales at the family level. We used a well-resolved molecular phylogeny to re-evaluate morphological characters in the Chaetophorales under clearly defined laboratory conditions. We identified five morphological characters that permitted unambiguous identification of most chaetophoralean families, and used these characters to establish a new family, the Fritschiellaceae (fam. nov.), and emend the Chaetophoraceae Greville 1824. Knowledge gained from this study lends additional weight to the current classifi...

  • The Chaetophorales (Chlorophyceae) – a taxonomic revision at family level
    European Journal of Phycology, 2018
    Co-Authors: Lenka Caisova, Michael Melkonian
    Abstract:

    ABSTRACTThe Chaetophorales (Chlorophyceae) consist of filamentous green algae that were mostly described directly from natural samples by light microscopy. However, the descriptions were often based on morphological characters that are either homoplasious or sensitive to environmental factors. This clearly prevents proper identification of several chaetophoralean taxa and highlights the need for taxonomic revision at different taxonomic levels. In the present study, we focused on revision of the Chaetophorales at the family level. We used a well-resolved molecular phylogeny to re-evaluate morphological characters in the Chaetophorales under clearly defined laboratory conditions. We identified five morphological characters that permitted unambiguous identification of most chaetophoralean families, and used these characters to establish a new family, the Fritschiellaceae (fam. nov.), and emend the Chaetophoraceae Greville 1824. Knowledge gained from this study lends additional weight to the current classifi...

Eduardo J Caceres - One of the best experts on this subject based on the ideXlab platform.

  • a comprehensive study of the life cycle of a south american population of stigeoclonium tenue Chaetophorales chlorophyta 1
    Journal of Phycology, 2010
    Co-Authors: Karina M Michetti, Patricia I Leonardi, Eduardo J Caceres
    Abstract:

    The diplobiontic–haplodiplontic life cycle with alternating isomorphic generations in Stigeoclonium tenue (C. Agardh) Kutz. is described for the first time. Sporophytes (2n = 10) arise from tetraflagellate zoospores that are produced by meiosis. Sporic meiosis might be inferred from the cruciform divisions formed during zoosporogenesis and is confirmed through observations of prophase I substages. Zoospores do not germinate directly but produce a haploid cyst that germinates to give rise to a gametophyte (n = 5). Gametophytes produce biflagellate isogametes, which fuse to produce zygotes that germinate by mitosis into the sporophytic stage. Gametophytes and sporophytes reproduce asexually both via mitotic tetraflagellate zoospores and by thallus fragmentation. Results from this study indicate that both the cosmopolitan distribution and dominance of S. tenue in many periphytic communities might be due to its multiple reproductive strategies.

  • morphology cytology and taxonomic remarks of four species of stigeoclonium Chaetophorales chlorophyceae from argentina
    Phycological Research, 2010
    Co-Authors: Karina M Michetti, Patricia I Leonardi, Eduardo J Caceres
    Abstract:

    SUMMARY Four species of Stigeoclonium from Argentina were studied by means of transmission electron microscopy and light microscopy. For species identification, we collected data related to the prostrate system and zoospore germination. We also determined the chromosome number for each species. Stigeoclonium aestivale showed a more developed erect system than the prostrate one, zoospore germination was predominantly of erect type and the chromosome number was 8. Stigeoclonium tenue presented well developed, erect and prostrate systems, zoospore germination was initially of the prostrate type and the chromosome number was 5. In Stigeoclonium variabile the prostrate system predominated over the erect one, zoospore germination was strictly of the prostrate type and the chromosome number was 3. Stigeoclonium farctum presented a more developed prostrate system than the erect one, zoospore germination was strictly of the prostrate type and the chromosome number was 8. The ontogeny of the zoospore germination was related to the final relative development of the prostrate and erect portions of adult thalli.

  • cytochemical localization of acid phosphatase in stigeoclonium tenue Chaetophorales chlorophyceae
    Biocell, 2006
    Co-Authors: Karina M Michetti, Patricia I Leonardi, Eduardo J Caceres
    Abstract:

    : Nonspecific acid phosphatases are a group of enzymes whose activity increases the availability of exogenous and endogenous orthophosphate either through extra- or intracellular hydrolysis of phosphate compounds. Our study demonstrates the activity of acid phosphatases in the filamentous freshwater alga Stigeoclonium tenue. These enzymes were detected following a cerium-based method in which cerium was used as an orthophosphate-capture reagent. In thalli from S. tenue from the natural environment, acid phosphatases were found in the longitudinal cell wall, plasmalemma, and vacuole. In thalli from Bold's Basal Medium culture, these enzymes were found mainly in the plasmalemma; they were scarce in the cell wall. In the thalli grown in phosphate-enriched culture medium, enzymes were found only in the plasmalemma. The low availability of orthophosphate in the medium seems to induce the transport of these enzymes to the cell wall. Its abundance, on the contrary, seems to attenuate this response without affecting the localization of acid phosphatases in the plasmalemma.

  • precisiones sobre la morfologia y ultraestructura del talo de chaetophora elegans Chaetophorales chlorophyta
    Darwiniana, 2003
    Co-Authors: Karina M Michetti, Patricia I Leonardi, Eduardo J Caceres
    Abstract:

    Se describe el talo de Chaetophora elegans precisando la morfologia de los sistemas postrado y erguido, se realiza el primer estudio detallado de la ultraestructura vegetativa en el genero y se amplia la distribucion de la especie en la Republica Argentina.

  • a light and electron microscopy study on the formation structure and germination of akinetes of stigeoclonium tenue Chaetophorales chlorophyceae
    Algological Studies Archiv für Hydrobiologie Supplement Volumes, 2002
    Co-Authors: Karina M Michetti, Patricia I Leonardi, Eduardo J Caceres
    Abstract:

    Akinete formation in Stigeoclonium tenue (AG) KUTZ began under unfavourable conditions (exhaustion of nutrients and/or evaporation of the culture medium). Cells from both prostrate and erect portions produced akinetes. A gradual change in the shape of vegetative cells was observed. They lost their typical straight edges and acquired an oval contour with constrictions at the level of the transverse cell walls. At the ultrastructural level, the changes were: 1) accumulation of starch and lipids as reserve substances; 2) disorganization of the chloroplast; 3) reduction of the vacuole until it disappeared in mature akinetes; 4) thickening of the wall resulting from the synthesis of both an additional new own wall next to the parental wall and a mucilage external layer; 5) disorganization of the plasmodesmata in the transverse walls of vegetative cells. All of these drastic cytological changes are essential to the development of akinetes which provide S. tenue with an effective survival mechanism under unfavourable conditions.

Zheng Yu Hu - One of the best experts on this subject based on the ideXlab platform.

  • Taxonomic scheme of the order Chaetophorales (Chlorophyceae, Chlorophyta) based on Chloroplast genomes
    2020
    Co-Authors: Benwen Liu(former Corresponding Author), Yu Xin Hu, Zheng Yu Hu, Huan Zhu(new Corresponding Author)
    Abstract:

    Abstract Background: Order Chaetophorales currently includes six families, namely Schizomeridaceae, Aphanochaetaceae, Barrancaceae, Uronemataceae, Fritschiellaceae, and Chaetophoraceae. The phylogenetic relationships of Chaetophorales have been inferred primarily through phylogenetic analysis based on rDNA sequences. Most studies have primarily focused on intergeneric phylogenetic relationships within this order and the phylogenetic relationships with four other Chlorophycean orders (Chaetophorales, Chaetopeltidales and Oedogoniales, and Volvocales). The phylogenetic relationships among families in order Chaetophorales remain unclear. This study aimed to phylogenetically reconstruct order Chaetophorales and determine the taxonomic scheme and to further the current understanding of the evolution of order Chaetophorales . Results: In the present study, seven complete and five fragmentary chloroplast genomes were harvested. Phylogenomic and comparative genomic analysis were performed to determine the taxonomic scheme within Chaetophorales. Consequently, Oedogoniales was found to be a sister to a clade linking Chaetophorales and Chaetopeltidales. Schizomeriaceae, and Aphanochaetaceae clustered into a well-resolved basal clade in Chaetophorales, inconsistent with the results of phylogenetic analysis based on rDNA sequences. Comparative genomic analyses revealed that the chloroplast genomes of Schizomeriaceae and Aphanochaetaceae were highly conserved and homologous, highlighting the closest relationship in this order. Germination types of zoospores precisely correlated with the phylogenetic relationships. Conclusions: chloroplast genome structure analyses, synteny analyses, and zoospore germination analyses were concurrent with phylogenetic analyses based on the chloroplast genome, and all of them robustly determined the unique taxonomic scheme of Chaetophorales and the relationships of Oedogoniales, Chaetophorales, and Chaetopeltidales.

  • Taxonomic scheme of the order Chaetophorales (Chlorophyceae, Chlorophyta) based on Chloroplast genomes
    2020
    Co-Authors: Yu Xin Hu, Zheng Yu Hu
    Abstract:

    Abstract Background Order Chaetophorales currently includes six families, namely Schizomeridaceae, Aphanochaetaceae, Barrancaceae, Uronemataceae, Fritschiellaceae, and Chaetophoraceae. Most studies have primarily focused on intergeneric phylogenetic relationships within this order and the phylogenetic relationships with four other Chlorophycean orders (Chaetophorales, Chaetopeltidales and Oedogoniales, and Volvocales). This study aimed to phylogenetically reconstruct order Chaetophorales and determine the taxonomic scheme and to further the current understanding of the evolution of order Chaetophorales. The taxonomic scheme of Chaetophorales has been inferred primarily through phylogenetic analysis based on rDNA sequences and phylogenetic relationships among families in order Chaetophorales remain unclear. Results In present study, seven complete and five fragmentary chloroplast genomes were harvested. Phylogenomic and comparative genomic analysis were performed to determine the taxonomic scheme within Chaetophorales. Consequently, Oedogoniales was found to be a sister to a clade linking Chaetophorales and Chaetopeltidales, Schizomeriaceae, and Aphanochaetaceae clustered into a well-resolved basal clade in Chaetophorales, inconsistent with the results of phylogenetic analysis based on rDNA sequences. Comparative genomic analyses revealed that the chloroplast genomes of Schizomeriaceae and Aphanochaetaceae were highly conserved and homologous, highlighting the closest relationship in this order. Germination types of zoospores precisely correlated with the phylogenetic relationships. Conclusions In conclusion, chloroplast genome structure analyses, synteny analyses, and zoospore germination analyses were concurrent with phylogenetic analyses based on the chloroplast genome, and all of them robustly determined the unique taxonomic scheme of Chaetophorales and the relationships of Oedogoniales, Chaetophorales, and Chaetopeltidales.

  • taxonomic transfer of gongrosira fluminensis fritsch Chaetophorales chlorophyceae to lithotrichon darienko et proschold ulvales ulvophyceae based on morphological observation and phylogenetic analyses
    Fottea, 2019
    Co-Authors: Qinghua Wang, Shuyin Li, Jiao Fang, Zheng Yu Hu
    Abstract:

    One green algal specimen from China was identified as Gongrosira fluminensis Fritsch, due to its unique morphology that pseudoparenchymal basal stratum with rounded or polygonal cells grew into dense little-branched upright threads that reached approximately the same height with specific akinete formation and germination and formed strong cushions without calcification. Examination of the ultrastructural characteristics of plasmodesmata and pyrenoid confirmed that Gongrosira fluminensis Fritsch should be excluded from the order Chaetophorales. The phylogenetic evidence based on DNA sequence data from the nucleus (18S rDNA, ITS rDNA) and chloroplast (tufA) sequences clearly revealed that the Gongrosira fluminensis Fritsch should be classified in the Ulvales (Ulvophyceae) as the new combination species of the genus Lithotrichon Darienko et Proschold, instead of the Chaetophorales (Chlorophyceae). More specimens in conjunction with natural morphological investigation and molecular analyses are required to reevaluate the microfilamentous genus Gongrosira Kutzing and reveal hidden diversities among the Ulvophyceae.

  • reassessment of the species stigeoclonium polyrhizum chaetophoraceae Chaetophorales based on morphological and molecular data
    Phytotaxa, 2018
    Co-Authors: Qinghua Wang, Zheng Yu Hu
    Abstract:

    Four specimens of Stigeoclonium spp., sampled in China between 2015 and 2016, were identified as the species Stigeoclonium polyrhizum (Chaetophoraceae, Chaetophorales) due to their unique morphology. A large part of the main filament and branches was tightly enclosed by numerous rhizoidal branches, which extended downward to the base of the plant to form an expanded holdfast. S. polyrhizum has previously been regarded as a synonym of S. longipilum or other related species by most phycologists. Therefore, a reassessment of S. polyrhizum based on morphological and molecular data was conducted. Rhizoidal branch development of S. polyrhizum was also described, showing the abundant rhizoidal branches present from the juvenile stage to the mature stage under controlled culture conditions. Phylogenetic evidence, using nuclear - encoded SSU rDNA data, clearly revealed that the Chaetophoraceae diverged into two well - supported sister clades: the Chaetophora- clade and the Fritschiella- clade. S. polyrhizum was included in the Fritschiella- clade instead of the Chaetophora- clade where Chaetophora draparnaldioides ( S. longipilum ) was found. The morphological and molecular data unambiguously show that S. polyrhizum is a valid species rather than a synonym of S. longipilum or other related species. Thylakoid bands appressed to the periphery of the pyrenoid matrix of S. polyrhizum was also described.