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Charles F. Delwiche - One of the best experts on this subject based on the ideXlab platform.
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uncovering the evolutionary origin of plant molecular processes comparison of Coleochaete coleochaetales and spirogyra zygnematales transcriptomes
BMC Plant Biology, 2010Co-Authors: Ruth E. Timme, Charles F. DelwicheAbstract:Background The large and diverse land plant lineage is nested within a clade of fresh water green algae, the charophytes. Collection of genome-scale data for land plants and other organisms over the past decade has invigorated the field of evolutionary biology. One of the core questions in the field asks: how did a colonization event by a green algae over 450 mya lead to one of the most successful lineages on the tree of life? This question can best be answered using the comparative method, the first step of which is to gather genome-scale data across closely related lineages to land plants. Before sequencing an entire genome it is useful to first gather transcriptome data: it is less expensive, it targets the protein coding regions of the genome, and provides support for gene models for future genome sequencing. We built Expressed Sequence Tag (EST) libraries for two charophyte species, Coleochaete orbicularis (Coleochaetales) and Spirogyra pratensis (Zygnematales). We used both Sanger sequencing and next generation 454 sequencing to cover as much of the transcriptome as possible.
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uncovering the evolutionary origin of plant molecular processes comparison of Coleochaete coleochaetales and spirogyra zygnematales transcriptomes
BMC Plant Biology, 2010Co-Authors: Ruth E. Timme, Charles F. DelwicheAbstract:Background The large and diverse land plant lineage is nested within a clade of fresh water green algae, the charophytes. Collection of genome-scale data for land plants and other organisms over the past decade has invigorated the field of evolutionary biology. One of the core questions in the field asks: how did a colonization event by a green algae over 450 mya lead to one of the most successful lineages on the tree of life? This question can best be answered using the comparative method, the first step of which is to gather genome-scale data across closely related lineages to land plants. Before sequencing an entire genome it is useful to first gather transcriptome data: it is less expensive, it targets the protein coding regions of the genome, and provides support for gene models for future genome sequencing. We built Expressed Sequence Tag (EST) libraries for two charophyte species, Coleochaete orbicularis (Coleochaetales) and Spirogyra pratensis (Zygnematales). We used both Sanger sequencing and next generation 454 sequencing to cover as much of the transcriptome as possible.
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(1569-1570) Proposals to conserve the name Coleochaete soluta against C. prostrata and the name C. orbicularis against Phyllactidium pulchellum with a note on the name C. nitellarum (Coleochaetaceae, Chlorophyceae)
TAXON, 2003Co-Authors: Matthew T. Cimino, James L. Reveal, Charles F. DelwicheAbstract:The genus Coleochaete Breb. (in Ann. Sci. Nat., ser. 3, 1: 29. 1844), nom. cons., comprising roughly 15 species, is found in clean freshwater lakes and ponds worldwide. The genus is becoming the subject of many studies, particularly because this and other members of the Coleochaetales and Charales are considered key elements in the evolution of early land plants (Karol & al. in Science 294: 2351-2353. 2001). Members of both orders have been investigated by a number of researchers, all of whom have used a consistent nomenclature based to a significant degree on their exchange of cultures and genetic material. Though effort has been made to clarify the nomenclature of many of the earliest names in Coleochaete (Szymanska in Taxon 39: 572-575. 1990; Szymanska & Spalik in Arch. Hydrobiol. 98 (Suppl.): 29-37. 1993), the names applied to two widely studied species remain particularly at risk while that of a third has been questioned. Given the body of literature containing the names Coleochaete soluta (Rabenhorst, Fl. Eur. Alg. 3(2): 389. 1868; Wolle, Fresh-water Alg.: 64. 1887; Wildeman, Fl. Alg.: 22. 1896; G. S. West, Algae: 315. 1916; Graham in Amer. J. Bot. 69: 447-454. 1982; Graham & Wilcox in Amer. J. Bot. 70: 113-120. 1983; Graham & Wilcox, Algae: 525. 2000), C. orbicularis (e.g., Rabenhorst, I.c.: 390. 1868; Wolle, l.c.: 64. 1887; Wildeman, l.c.: 20. 1896; G. S. West, l.c.: 315. 1916; Islam in Bangladesh J. Bot. 3: 35-43. 1974; Graham in Amer. J. Bot. 69: 447-454. 1982; Graham & Wilcox in Amer. J. Bot. 70: 113-120. 1983; Delwiche, Graham, & Thompson in Science 245: 399-401. 1989; Graham, Delwiche & Mishler in Adv. Bryol. 4: 213-244. 1991; Kenrick & Crane, Origin Diversif. Land PI.: 30. 1997; Graham & Wilcox, Algae: 535. 2000), and C. nitellarum (G. M. Smith, Fresh-waterAlg. U.S.: 410. 1933; Chapman & al., Molec. Syst. P1. 2: 530. 1998; Nishiyama & Kato in Molec. Biol. Evol. 16: 1027-1036. 1999; Graham & Wilcox, Algae: 535. 2000; Cimino & Delwiche in J. Phycol. 38: 1213-1221. 2002), changes in the application of these names would only result in unnecessary nomenclatural confusion. Therefore, our effort here is to ensure the maintenance of these three names in current
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MOLECULAR AND MORPHOLOGICAL DATA IDENTIFY A CRYPTIC SPECIES COMPLEX IN ENDOPHYTIC MEMBERS OF THE GENUS Coleochaete BRÉB. (CHAROPHYTA: COLEOCHAETACEAE) 1
Journal of Phycology, 2002Co-Authors: Matthew T. Cimino, Charles F. DelwicheAbstract:The genus Coleochaete Breb. is a relatively small group of freshwater microscopic green algae with about 15 recognized species. Although Coleochaete has long been considered to be a close relative of embryophytes, a comprehensive study of the genus has not been published since Pringsheim's 1860 monograph. As part of a systematic study of Coleochaete, we investigated four accessions of the genus that are morphologically similar to the endophytic species C. nitellarum Jost. Each of the four cultures was determined to be capable of endophytic growth in Nitella C. A. Agardh, a member of the closely related order Charales. Maximum likelihood and maximum parsimony analyses were performed on nucleotide data from the chloroplast genes atpB and rbcL that were sequenced from 16 members of the Coleochaetales and from other members of the Charophyceae, embryophytes, and outgroup taxa. These analyses indicate that the Coleochaetales are monophyletic and that the endophytic accessions are members of the scutata group of species. In addition, cell size and nucleotide data suggest that at least three different endophytic species may be represented. Herbivory, nutritional benefits, and substrate competition are three hypotheses that could explain the evolution and maintenance of the endophytic habit in Coleochaete. These data also imply that diversity in the genus may be markedly underestimated.
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PHYLOGENY OF THE GENUS Coleochaete (COLEOCHAETALES, CHAROPHYTA) AND RELATED TAXA INFERRED BY ANALYSIS OF THE CHLOROPLAST GENE rbcL 1
Journal of Phycology, 2002Co-Authors: Charles F. Delwiche, Matthew T. Cimino, Kenneth G. Karol, Kenneth J. SytsmaAbstract:The genus Coleochaete Breb. is considered to be a key taxon in the evolution of green algae and embryophytes (land plants), but only a few of the approximately 15 species have been studied with molecular phylogenetic methods. We report here the sequences of the gene rbcL from six new cultures of Coleochaete and two of Chaetosphaeridium Klebahn. These sequences were combined with 32 additional sequences, and phylogenetic analyses were performed with maximum likelihood, distance optimality, and parsimony methods. Important subgroups within Coleochaete include two primary lineages, one marked by fully corticated zygotes and the other by naked or weakly corticated zygotes. In the first lineage there is a subclade with tightly joined filaments and distinctive (“T-shaped”) cell division, an assemblage of strains that resembles the endophytic species Coleochaete nitellarum Jost, and a clade with loosely joined filaments and “Y-shaped” cell divisions. Consistent with recent multigene phylogenies, these analyses support the monophyly of the Coleochaetales, place the Charales as the sister taxon to land plants, and indicate that Chaetosphaeridium is far more closely related to Coleochaete than to Mesostigma Lauterborn.
David Haig - One of the best experts on this subject based on the ideXlab platform.
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Coleochaete and the origin of sporophytes
American journal of botany, 2015Co-Authors: David HaigAbstract:UNLABELLED • PREMISE OF THE STUDY Zygotes of Coleochaete are provisioned by the maternal thallus before undergoing 3-5 rounds of division to produce 8-32 zoospores. An understanding of the selective forces favoring postzygotic divisions would be relevant not only to the interpretation of Coleochaete life history but also to the origin of a multicellular diploid phase in embryophytes.• METHODS Simple optimization models are developed of the number of zygotes per maternal thallus and number of zoospores per zygote.• KEY RESULTS Zygotic mitosis is favored once zygotic size exceeds a threshold, but natural selection usually promotes investment in additional zygotes before zygotes reach this threshold. Factors that favor production of fewer, larger zygotes include multiple paternity, low fecundity, and accessory costs of zygote production. Such factors can result in zygotes exceeding the size at which zygotic mitosis becomes profitable.• CONCLUSIONS Coleochaete may possess large zygotes that undergo multiple fission because of accessory costs associated with matrotrophy, including costs of cortical cells and unfertilized oogonia. The unpredictability of fertilization on land is proposed to have increased accessory costs from unfertilized ova and, as a consequence, to have favored the production of larger zygotes that underwent postzygotic division to produce diploid sporophytes.
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what do we know about charophyte streptophyta life cycles
Journal of Phycology, 2010Co-Authors: David HaigAbstract:The charophyte algae are the closest living relatives of land plants. Their life cycles are usually characterized as haploid with zygotic meiosis. This conclusion, however, is based on a small number of observations and on theoretical assumptions about what kinds of life cycle are possible. Little is known about the life cycles of most charophytes, but unusual phenomena have been reported in comparatively well-studied taxa: Spirogyra and Sirogonium are reported to produce diploid gametes with synapsis of homologous chromosomes before fusion of gametic nuclei; Closterium ehrenbergii is reported to undergo chromosome reduction both before and after syngamy; and zygotes of Coleochaete scutata are reported to replicate their DNA to high levels before a series of reduction divisions. All of these phenomena require confirmation, as does the conventional account.
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Homologous Versus Antithetic Alternation of Generations and the Origin of Sporophytes
The Botanical Review, 2008Co-Authors: David HaigAbstract:The late-nineteenth/early-twentieth century debate over homologous versus antithetic alternation of generations is reviewed. Supporters of both theories, at first, used Coleochaete as a model for the origin of land-plant life cycles. The early debate focused on the morphological interpretation of the sporophyte and on whether vascular cryptogams had bryophyte-like ancestors. The terms of the debate shifted after the discovery that the alternation of morphological generations was accompanied by an alternation of chromosome number. Supporters of homologous alternation now promoted a model in which land plants had been derived from an algal ancestor with an isomorphic alternation of haploid and diploid generations whereas supporters of antithetic alternation favored a model in which land plants were derived from a haploid algal ancestor with zygotic meiosis. Modern evidence that embryophytes are derived from charophycean green algae is more compatible with an updated version of the antithetic theory.
Linda E. Graham - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary Roots of Plant Microbiomes and Biogeochemical Impacts of Nonvascular Autotroph-Microbiome Systems over Deep Time
International Journal of Plant Sciences, 2018Co-Authors: Linda E. Graham, James M. Graham, Lee W. Wilcox, Martha E. Cook, Patricia Arancibia-avila, Jennifer J. KnackAbstract:Since rooted vascular plants rose to dominance, associated microbiota have powerfully influenced global biogeochemistry by mobilizing N and P and otherwise aiding plant health, thereby fostering sequestration of CO2 into coal and soil organics. Less well understood are evolutionary history and biogeochemical roles of microbiomes of ecologically significant nonvascular plants and related algae, whose lineages penetrate more deeply into time. Because analyses of diverse host-microbiome systems indicate that evolutionary history commonly influences microbiome composition and function, we mapped onto a geological time frame biogeochemical features inferred in our previous metagenomic studies of a phylogenetic spectrum of multicellular, freshwater-terrestrial, nonvascular autotroph-microbiome systems: Nostoc commune, representing microbialite-forming cyanobacteria; the Nostoc lichen Peltigera ponojensis; chlorophyte Cladophora glomerata; streptophyte alga Coleochaete pulvinata; moss Sphagnum fimbriatum; and li...
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Direction of illumination controls gametophyte orientation in seedless plants and related algae.
Plant signaling & behavior, 2015Co-Authors: Christopher Cardona-correa, Alice Ecker, Linda E. GrahamAbstract:The environmental influences that determine dorsiventral or axial gametophyte orientation are unknown for most modern seedless plants. To fill this gap, an experimental laboratory system was employed to evaluate the relative effects of light direction and gravity on body orientation of the dorsiventral green alga Coleochaete orbicularis, and gametophytes of liverworts Blasia pusilla and Marchantia polymorpha, early-diverging moss Sphagnum compactum, and fern Ceratopteris richardii, the latter functioning as experimental control. Replicate clonal cultures were experimentally illuminated only from above, only from below, or from multiple directions, with the same near-saturation PAR level for periods brief enough to minimize nutrient limitation effects, and orientation of new growth was evaluated. For all species tested, direction of illumination exerted stronger control over gametophyte body orientation than gravity. When illuminated only from below: 1) axial Sphagnum gametophores that had initially grown into an overlying air space inverted growth by 180°, burrowing into the substrate; 2) new growth of dorsiventral Blasia, Marchantia, and Ceratopteris gametophytes-whose ventral rhizoids initially penetrated agar substrate and dorsal surfaces initially faced overlying airspace-twisted 180° so that ventral surfaces bearing rhizoids faced overlying air space and rhizoids extended into the air; and 3) Coleochaete lost typical dorsiventral organization and diagnostic dorsal hairs. Direction of illumination also exerted stronger control over orientation of liverwort new growth than surface contact did. These results indicate that early land plants likely inherited light-directed gametophyte body orientation from ancestral streptophyte algae and suggest a mechanism for reorientation of gametophyte-dominant land plants after spatial disturbance.
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Microbiomes of Streptophyte Algae and Bryophytes Suggest That a Functional Suite of Microbiota Fostered Plant Colonization of Land
International Journal of Plant Sciences, 2015Co-Authors: Jennifer J. Knack, James M. Graham, Lee W. Wilcox, Martha E. Cook, Pierre-marc Delaux, Jean-michel Ané, Michael J. Piotrowski, Linda E. GrahamAbstract:Premise of research. The origin of land plants catalyzed key changes in Earth’s atmosphere and biota. Microbial associations likely nurtured earliest plants and influenced their biogeochemical roles. Because angiosperm and animal microbiomes—bacteria, archaea, microbial eukaryotes, and genes that promote host survival—are known to display lineage effects, we hypothesized that microbiomes of early-diverging modern bryophytes and phylogenetically closely related green algae might likewise reveal commonalities reflecting ancestral traits.Methodology. New metagenomic sequence data were obtained for the late-diverging streptophyte algae Chaetosphaeridium globosum and Coleochaete pulvinata and the liverwort Conocephalum conicum, representing early-diverging land plants. New 16S rDNA amplicon sequences were acquired for the charalean Nitella tenuissima. Sequence data were used to infer bacterial genera and fungi for comparisons among streptophyte microbiota and with our published microbiome data for the outgroup...
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Aeroterrestrial Coleochaete (Streptophyta, Coleochaetales) models early plant adaptation to land
American journal of botany, 2011Co-Authors: Linda E. Graham, Patricia Arancibia-avila, Wilson A. Taylor, Paul K. Strother, Martha E. CookAbstract: Premise of the study: The streptophyte water-to-land transition was a pivotal, but poorly understood event in Earth history. While some early-diverging modern streptophyte algae are aeroterrestrial (living in subaerial habitats), aeroterrestrial survival had not been tested for Coleochaete , widely regarded as obligately aquatic and one of the extant green algal genera most closely related to embryophytes. This relationship motivated a comparison of aeroterrestrial Coleochaete to lower Paleozoic microfossils whose relationships have been uncertain. Methods: We tested the ability of two species of the experimentally tractable, complex streptophyte algal genus Coleochaete Br e b. to (1) grow and reproduce when cultivated under conditions that mimic humid subaerial habitats, (2) survive desiccation for some period of time, and (3) produce degradation-resistant remains comparable to enigmatic Cambrian microfossils. Key results: When grown on mineral agar media or on quartz sand, both species displayed bodies structurally distinct from those expressed in aquatic habitats. Aeroterrestrial Coleochaete occurred as hairless, multistratose, hemispherical bodies having unistratose lobes or irregular clusters of cells with thick, layered, and chemically resistant walls that resemble certain enigmatic lower Paleozoic microfossils. Whether grown under humid conditions or air-dried for a week, then exposed to liquid water, aeroterrestrial Coleochaete produced typical asexual zoospores and germlings. Cells that had been air-dried for periods up to several months maintained their integrity and green pigmentation. Conclusions: Features of modern aeroterrestrial Coleochaete suggest that ancient complex streptophyte algae could grow and reproduce in moist subaerial habitats, persist through periods of desiccation, and leave behind distinctive microfossil remains.
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Phylogenetic Position of the Green Flagellate Mesostigma viride Based on α‐Tubulin and β‐Tubulin Gene Sequences
International Journal of Plant Sciences, 2006Co-Authors: Lee W. Wilcox, Marvin W. Fawley, Linda E. GrahamAbstract:The green alga Mesostigma viride has attracted considerable recent attention as a model system useful for understanding the evolutionary origin of the Viridiplantae (all green algae plus embryophytes) or the Streptophyta (charophycean algae plus embryophytes). Mesostigma’s utility for such studies depends on its phylogenetic position, which has been controversial. Phylogenetic analyses based on organellar genes have given conflicting results; some support a hypothesis that Mesostigma represents the first branch of the Viridiplantae, whereas others support an alternative hypothesis that it occupies a basal position within Streptophyta. Nuclear‐encoded actin and small subunit ribosomal gene sequences also mark Mesostigma as a basal lineage in Streptophyta. We tested these two alternative hypotheses by analyses of nuclear‐encoded α‐ and β‐tubulin sequences. We obtained new α‐ and β‐tubulin gene sequences from M. viride as well as from the charophycean Coleochaete scutata and the green flagellates Pterosperma...
Martha E. Cook - One of the best experts on this subject based on the ideXlab platform.
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Evolutionary Roots of Plant Microbiomes and Biogeochemical Impacts of Nonvascular Autotroph-Microbiome Systems over Deep Time
International Journal of Plant Sciences, 2018Co-Authors: Linda E. Graham, James M. Graham, Lee W. Wilcox, Martha E. Cook, Patricia Arancibia-avila, Jennifer J. KnackAbstract:Since rooted vascular plants rose to dominance, associated microbiota have powerfully influenced global biogeochemistry by mobilizing N and P and otherwise aiding plant health, thereby fostering sequestration of CO2 into coal and soil organics. Less well understood are evolutionary history and biogeochemical roles of microbiomes of ecologically significant nonvascular plants and related algae, whose lineages penetrate more deeply into time. Because analyses of diverse host-microbiome systems indicate that evolutionary history commonly influences microbiome composition and function, we mapped onto a geological time frame biogeochemical features inferred in our previous metagenomic studies of a phylogenetic spectrum of multicellular, freshwater-terrestrial, nonvascular autotroph-microbiome systems: Nostoc commune, representing microbialite-forming cyanobacteria; the Nostoc lichen Peltigera ponojensis; chlorophyte Cladophora glomerata; streptophyte alga Coleochaete pulvinata; moss Sphagnum fimbriatum; and li...
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Microbiomes of Streptophyte Algae and Bryophytes Suggest That a Functional Suite of Microbiota Fostered Plant Colonization of Land
International Journal of Plant Sciences, 2015Co-Authors: Jennifer J. Knack, James M. Graham, Lee W. Wilcox, Martha E. Cook, Pierre-marc Delaux, Jean-michel Ané, Michael J. Piotrowski, Linda E. GrahamAbstract:Premise of research. The origin of land plants catalyzed key changes in Earth’s atmosphere and biota. Microbial associations likely nurtured earliest plants and influenced their biogeochemical roles. Because angiosperm and animal microbiomes—bacteria, archaea, microbial eukaryotes, and genes that promote host survival—are known to display lineage effects, we hypothesized that microbiomes of early-diverging modern bryophytes and phylogenetically closely related green algae might likewise reveal commonalities reflecting ancestral traits.Methodology. New metagenomic sequence data were obtained for the late-diverging streptophyte algae Chaetosphaeridium globosum and Coleochaete pulvinata and the liverwort Conocephalum conicum, representing early-diverging land plants. New 16S rDNA amplicon sequences were acquired for the charalean Nitella tenuissima. Sequence data were used to infer bacterial genera and fungi for comparisons among streptophyte microbiota and with our published microbiome data for the outgroup...
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Immunofluorescence localization of the tubulin cytoskeleton during cell division and cell growth in members of the Coleochaetales (Streptophyta)
Journal of Phycology, 2014Co-Authors: Karen F Doty, Amy M. Betzelberger, Kevin M. Kocot, Martha E. CookAbstract:Study of charophycean green algae, including the Coleochaetales, may shed light on the evolutionary history of characters they share with their land plant relatives. We examined the tubulin cytoskeleton during mitosis, cytokinesis, and growth in members of the Coleochaetales with diverse morphologies to determine if phragmoplasts occurred throughout this order and to identify microtubular patterns associated with cell growth. Species representing three subgroups of Coleochaete and its sister genus Chaetosphaeridium were studied. Cytokinesis involving a phragmoplast was found in the four taxa examined. Differential interference contrast microscopy of living cells confirmed that polar cytokinesis like that described in the model flowering plant Arabidopsis occurred in all species when the forming cell plate traversed a vacuole. Calcofluor labeling of cell walls demonstrated directed growth from particular cell regions of all taxa. Electron microscopy confirmed directed growth in the unusual growth pattern of Chaetosphaeridium. All four species exhibited unordered microtubule patterns associated with diffuse growth in early cell expansion. In subsequent elongating cells, Coleochaete irregularis Pringsheim and Chaetosphaeridium globosum (Nordstedt) Klebahn exhibited tubulin cytoskeleton arrays corresponding to growth patterns associated with tip growth in plants, fungi, and other charophycean algae. Hoop-shaped microtubules frequently associated with diffuse growth of elongating cells in plants were not observed in any of these species. Presence of phragmoplasts in the diverse species studied supports the hypothesis that cytokinesis involving a phragmoplast originated in a common ancestor of the Coleochaetales, and possibly in a common ancestor of Charales, Coleochaetales, Zygnematales, and plants.
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Aeroterrestrial Coleochaete (Streptophyta, Coleochaetales) models early plant adaptation to land
American journal of botany, 2011Co-Authors: Linda E. Graham, Patricia Arancibia-avila, Wilson A. Taylor, Paul K. Strother, Martha E. CookAbstract: Premise of the study: The streptophyte water-to-land transition was a pivotal, but poorly understood event in Earth history. While some early-diverging modern streptophyte algae are aeroterrestrial (living in subaerial habitats), aeroterrestrial survival had not been tested for Coleochaete , widely regarded as obligately aquatic and one of the extant green algal genera most closely related to embryophytes. This relationship motivated a comparison of aeroterrestrial Coleochaete to lower Paleozoic microfossils whose relationships have been uncertain. Methods: We tested the ability of two species of the experimentally tractable, complex streptophyte algal genus Coleochaete Br e b. to (1) grow and reproduce when cultivated under conditions that mimic humid subaerial habitats, (2) survive desiccation for some period of time, and (3) produce degradation-resistant remains comparable to enigmatic Cambrian microfossils. Key results: When grown on mineral agar media or on quartz sand, both species displayed bodies structurally distinct from those expressed in aquatic habitats. Aeroterrestrial Coleochaete occurred as hairless, multistratose, hemispherical bodies having unistratose lobes or irregular clusters of cells with thick, layered, and chemically resistant walls that resemble certain enigmatic lower Paleozoic microfossils. Whether grown under humid conditions or air-dried for a week, then exposed to liquid water, aeroterrestrial Coleochaete produced typical asexual zoospores and germlings. Cells that had been air-dried for periods up to several months maintained their integrity and green pigmentation. Conclusions: Features of modern aeroterrestrial Coleochaete suggest that ancient complex streptophyte algae could grow and reproduce in moist subaerial habitats, persist through periods of desiccation, and leave behind distinctive microfossil remains.
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Cytokinesis in Coleochaete orbicularis (Charophyceae): an ancestral mechanism inherited by plants
American journal of botany, 2004Co-Authors: Martha E. CookAbstract:Recently, highly vacuolate cells of Arabidopsis were shown to exhibit "polarized" cytokinesis, in which the phragmoplast and cell plate contact the mother cell wall and then progress from one side of the cell to the other, rather than forming uniformly outward from the cell center (Cutler and Ehrhardt, 2002, Proceedings of the National Academy of Sciences, USA 99: 2812-2817). It was not known if such a mechanism was unique to flowering plants or whether it occurred more broadly in the plant clade. To determine if a polar mechanism of cell division might have been characteristic of the first plants, differential interference contrast optics were used to examine living cells of the charophycean green alga Coleochaete orbicularis, a close relative of plants, with cytokinesis involving a phragmoplast. By recording images in different focal planes over time, such "polarized" cytokinesis was found in cells dividing either parallel or perpendicular to the edge of this radially symmetrical organism. Previously reported differences between these two types of division in Coleochaete were clarified. Polarized cytokinesis appears to be an ancestral mechanism of plant cell division inherited from the highly vacuolate cells of the charophycean algal ancestors of plants.
Ruth E. Timme - One of the best experts on this subject based on the ideXlab platform.
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uncovering the evolutionary origin of plant molecular processes comparison of Coleochaete coleochaetales and spirogyra zygnematales transcriptomes
BMC Plant Biology, 2010Co-Authors: Ruth E. Timme, Charles F. DelwicheAbstract:Background The large and diverse land plant lineage is nested within a clade of fresh water green algae, the charophytes. Collection of genome-scale data for land plants and other organisms over the past decade has invigorated the field of evolutionary biology. One of the core questions in the field asks: how did a colonization event by a green algae over 450 mya lead to one of the most successful lineages on the tree of life? This question can best be answered using the comparative method, the first step of which is to gather genome-scale data across closely related lineages to land plants. Before sequencing an entire genome it is useful to first gather transcriptome data: it is less expensive, it targets the protein coding regions of the genome, and provides support for gene models for future genome sequencing. We built Expressed Sequence Tag (EST) libraries for two charophyte species, Coleochaete orbicularis (Coleochaetales) and Spirogyra pratensis (Zygnematales). We used both Sanger sequencing and next generation 454 sequencing to cover as much of the transcriptome as possible.
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uncovering the evolutionary origin of plant molecular processes comparison of Coleochaete coleochaetales and spirogyra zygnematales transcriptomes
BMC Plant Biology, 2010Co-Authors: Ruth E. Timme, Charles F. DelwicheAbstract:Background The large and diverse land plant lineage is nested within a clade of fresh water green algae, the charophytes. Collection of genome-scale data for land plants and other organisms over the past decade has invigorated the field of evolutionary biology. One of the core questions in the field asks: how did a colonization event by a green algae over 450 mya lead to one of the most successful lineages on the tree of life? This question can best be answered using the comparative method, the first step of which is to gather genome-scale data across closely related lineages to land plants. Before sequencing an entire genome it is useful to first gather transcriptome data: it is less expensive, it targets the protein coding regions of the genome, and provides support for gene models for future genome sequencing. We built Expressed Sequence Tag (EST) libraries for two charophyte species, Coleochaete orbicularis (Coleochaetales) and Spirogyra pratensis (Zygnematales). We used both Sanger sequencing and next generation 454 sequencing to cover as much of the transcriptome as possible.