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Kenneth G. Karol - One of the best experts on this subject based on the ideXlab platform.
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first discovery of the charophycean green alga lychnothamnus barbatus Charophyceae extant in the new world
American Journal of Botany, 2017Co-Authors: Kenneth G. Karol, Richard M. Mccourt, Paul M Skawinski, Michelle E Nault, Reesa Evans, Martha Barton, Matthew S Berg, Donna Perleberg, John D. HallAbstract:Premise of the study Although some species of Characeae, known as stoneworts, can be found on every continent except Antarctica, many species and some genera have limited geographic distributions. The genus Lychnothamnus, represented by a single extant species L. barbatus, was known only from scattered localities in Europe and Australasia until it was recently discovered in North America. Methods Morphological identifications were made from specimens collected in Minnesota and Wisconsin, USA. DNA sequences were obtained for three plastid-encoded genes (atpB, psbC, rbcL) from seven putative Lychnothamnus samples from two states in the USA Distribution and abundance were estimated in each lake using point intercept surveys where surveyors sampled aquatic vegetation. Key results Fourteen lakes in Wisconsin and two lakes in Minnesota, USA, were found to harbor Lychnothamnus barbatus. These represent the first report of this rare charophycean extant in the New World. The North American specimens matched the morphological description for L. barbatus and were compared directly with the neotype. Phylogenetic results using three plastid-encoded genes confirmed the identification placing New World samples with those from Europe and Australasia. Our phylogenetic analyses also confirmed the sister relationship between L. barbatus and Nitellopsis obtusa. Conclusions Because this taxon is not known for aggressive invasiveness in its native range, it may have existed in heretofore-undiscovered native populations, although the possibility that it is a recent introduction cannot be eliminated. The potential for discovery of novel lineages of green algae in even well-studied regions is apparently far from exhausted.
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Phylogenetic congruence of ribosomal operon and plastid gene sequences for the Characeae with an emphasis on Tolypella (Characeae, Charophyceae)
Phycologia, 2017Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Michele T. Casanova, Kenneth G. KarolAbstract:Abstract: To clarify species diversity of Tolypella (Characeae, Charophyceae) and the relationship between Tolypella and other genera in Characeae, sequence data from the nuclear ribosomal operon were assembled for 18 individuals of Tolypella. These represented nine named species and two potentially new species from Australia, as well as 13 other taxa of Characeae. Phylogenetic analyses were performed on ribosomal gene sequences (18S, 5.8S and 28S) for Characeae and on ribosomal gene and internal transcribed spacer (ITS) sequences (ribosomal genes + ITS1 + ITS2) for Tolypella. Analyses were also performed on the ribosomal gene and ITS sequences combined with plastid gene sequences (atpB, psbC and rbcL). Ribosomal gene sequences alone were conservative and their phylogenetic analyses resulted in topologies similar to a previously published plastid gene-based study but with less support and resolution. In contrast, ITS sequences showed greater variability and their addition resulted in greater resolution am...
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Oospore dimensions and morphology in North American Tolypella (Charophyceae, Charophyta).
Journal of phycology, 2015Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Kenneth G. KarolAbstract:Characteristics of the oospores have been used to delimit sections and, in some cases, species in the genus Tolypella A. Braun. To test the utility of oospore characters for identifying North American species of Tolypella, we investigated oospores from field-collected and herbarium specimens. Oospore dimensions (length, width, and length to width ratio) and morphology (color, ridge number and shape, wall ornamentation, and basal impression number) were measured. Oospore dimensions were statistically analyzed and oospore morphology was studied with light and scanning electron microscopy. Statistical analyses showed significant differences in length, width, and length to width ratios among most Tolypella species and populations but there was considerable overlap, which suggested that species identification based on oospore measurements alone is not wholly reliable. In addition, oospore morphology was not unique for every species.
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Phylogeny of North American Tolypella (Charophyceae, Charophyta) based on plastid DNA sequences with a description of Tolypella ramosissima sp. nov.
Journal of phycology, 2014Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Kenneth G. KarolAbstract:Characeae (Charophyceae, Charophyta) contains two tribes with six genera: tribe Chareae with four genera and tribe Nitelleae, which includes Tolypella and Nitella. This paper uses molecular and morphological data to elucidate the phylogeny of Tolypella species in North America. In the most comprehensive taxonomic treatment of Characeae, 16 Tolypella species worldwide were subsumed into two species, T. intricata and T. nidifica, in two sections, Rothia and Tolypella respectively. It was further suggested that Tolypella might be a derived group within Nitella. In this investigation into species diversity and relationships in North American Tolypella, sequence data from the plastid genes atpB, psbC, and rbcL were assembled for a broad range of charophycean and land plant taxa. Molecular data were used in conjunction with morphology to test monophyly of the genus and species within it. Phylogenetic analyses of the sequence data showed that Characeae is monophyletic but that Nitelleae is paraphyletic with Tolypella sister to a monophyletic Nitella + Chareae. The results also supported the monophyly of Tolypella and the sections Rothia and Tolypella. Morphologically defined species were supported as clades with little or no DNA sequence differences. In addition, molecular data revealed several lineages and a new species (T. ramosissima sp. nov.), which suggests greater species diversity in Tolypella than previously recognized.
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A revision of Chara sect. Protochara, comb. et stat. nov. (Characeae: Charophyceae)
Australian Systematic Botany, 2014Co-Authors: Michelle T Casanova, Kenneth G. KarolAbstract:A revision of a group of ecorticate species of Chara is presented, on the basis of fresh, pressed and spirit-preserved material. The following seven species are recognised, characterised by a very simple morphology, with few or inconspicuous accessory cells (cortication, stipulodes, bract cells, bracteoles) and large gametangia: Chara australis R.Br., C. lucida (A.Braun) Casanova & Karol comb et. stat. nov., C. porteri Casanova, sp. nov., C. protocharoides Casanova & Karol, nom. nov. (=Protochara australis Womersley & Ophel) and C. stuartiana (Kutz.) Casanova & Karol comb. et. stat. nov. from Australia, and C. corallina Klein ex Willd. and C. wallichii A.Braun from Asia. A new section, Chara subg. Charopsis sect. Protochara (Womersley & Ophel) Casanova & Karol, comb. et stat. nov., is erected to accommodate these taxa, formerly placed in sect. Charopsis.
Richard M. Mccourt - One of the best experts on this subject based on the ideXlab platform.
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first discovery of the charophycean green alga lychnothamnus barbatus Charophyceae extant in the new world
American Journal of Botany, 2017Co-Authors: Kenneth G. Karol, Richard M. Mccourt, Paul M Skawinski, Michelle E Nault, Reesa Evans, Martha Barton, Matthew S Berg, Donna Perleberg, John D. HallAbstract:Premise of the study Although some species of Characeae, known as stoneworts, can be found on every continent except Antarctica, many species and some genera have limited geographic distributions. The genus Lychnothamnus, represented by a single extant species L. barbatus, was known only from scattered localities in Europe and Australasia until it was recently discovered in North America. Methods Morphological identifications were made from specimens collected in Minnesota and Wisconsin, USA. DNA sequences were obtained for three plastid-encoded genes (atpB, psbC, rbcL) from seven putative Lychnothamnus samples from two states in the USA Distribution and abundance were estimated in each lake using point intercept surveys where surveyors sampled aquatic vegetation. Key results Fourteen lakes in Wisconsin and two lakes in Minnesota, USA, were found to harbor Lychnothamnus barbatus. These represent the first report of this rare charophycean extant in the New World. The North American specimens matched the morphological description for L. barbatus and were compared directly with the neotype. Phylogenetic results using three plastid-encoded genes confirmed the identification placing New World samples with those from Europe and Australasia. Our phylogenetic analyses also confirmed the sister relationship between L. barbatus and Nitellopsis obtusa. Conclusions Because this taxon is not known for aggressive invasiveness in its native range, it may have existed in heretofore-undiscovered native populations, although the possibility that it is a recent introduction cannot be eliminated. The potential for discovery of novel lineages of green algae in even well-studied regions is apparently far from exhausted.
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Phylogenetic congruence of ribosomal operon and plastid gene sequences for the Characeae with an emphasis on Tolypella (Characeae, Charophyceae)
Phycologia, 2017Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Michele T. Casanova, Kenneth G. KarolAbstract:Abstract: To clarify species diversity of Tolypella (Characeae, Charophyceae) and the relationship between Tolypella and other genera in Characeae, sequence data from the nuclear ribosomal operon were assembled for 18 individuals of Tolypella. These represented nine named species and two potentially new species from Australia, as well as 13 other taxa of Characeae. Phylogenetic analyses were performed on ribosomal gene sequences (18S, 5.8S and 28S) for Characeae and on ribosomal gene and internal transcribed spacer (ITS) sequences (ribosomal genes + ITS1 + ITS2) for Tolypella. Analyses were also performed on the ribosomal gene and ITS sequences combined with plastid gene sequences (atpB, psbC and rbcL). Ribosomal gene sequences alone were conservative and their phylogenetic analyses resulted in topologies similar to a previously published plastid gene-based study but with less support and resolution. In contrast, ITS sequences showed greater variability and their addition resulted in greater resolution am...
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Oospore dimensions and morphology in North American Tolypella (Charophyceae, Charophyta).
Journal of phycology, 2015Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Kenneth G. KarolAbstract:Characteristics of the oospores have been used to delimit sections and, in some cases, species in the genus Tolypella A. Braun. To test the utility of oospore characters for identifying North American species of Tolypella, we investigated oospores from field-collected and herbarium specimens. Oospore dimensions (length, width, and length to width ratio) and morphology (color, ridge number and shape, wall ornamentation, and basal impression number) were measured. Oospore dimensions were statistically analyzed and oospore morphology was studied with light and scanning electron microscopy. Statistical analyses showed significant differences in length, width, and length to width ratios among most Tolypella species and populations but there was considerable overlap, which suggested that species identification based on oospore measurements alone is not wholly reliable. In addition, oospore morphology was not unique for every species.
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Phylogeny of North American Tolypella (Charophyceae, Charophyta) based on plastid DNA sequences with a description of Tolypella ramosissima sp. nov.
Journal of phycology, 2014Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Kenneth G. KarolAbstract:Characeae (Charophyceae, Charophyta) contains two tribes with six genera: tribe Chareae with four genera and tribe Nitelleae, which includes Tolypella and Nitella. This paper uses molecular and morphological data to elucidate the phylogeny of Tolypella species in North America. In the most comprehensive taxonomic treatment of Characeae, 16 Tolypella species worldwide were subsumed into two species, T. intricata and T. nidifica, in two sections, Rothia and Tolypella respectively. It was further suggested that Tolypella might be a derived group within Nitella. In this investigation into species diversity and relationships in North American Tolypella, sequence data from the plastid genes atpB, psbC, and rbcL were assembled for a broad range of charophycean and land plant taxa. Molecular data were used in conjunction with morphology to test monophyly of the genus and species within it. Phylogenetic analyses of the sequence data showed that Characeae is monophyletic but that Nitelleae is paraphyletic with Tolypella sister to a monophyletic Nitella + Chareae. The results also supported the monophyly of Tolypella and the sections Rothia and Tolypella. Morphologically defined species were supported as clades with little or no DNA sequence differences. In addition, molecular data revealed several lineages and a new species (T. ramosissima sp. nov.), which suggests greater species diversity in Tolypella than previously recognized.
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PHYLOGENY OF THE BASAL LINEAGES OF STREPTOPHYTA BASED ON RBCL AND ATPB GENE SEQUENCE DATA
Journal of Phycology, 2000Co-Authors: Kenneth G. Karol, Charles F. Delwiche, Richard M. MccourtAbstract:The streptophytes comprise the Charophyceae sensu Mattox and Stewart (a morphologically diverse group of fresh-water green algae) and the embryophytes (land plants). Several charophycean groups are currently recognized. These include the Charales, Coleochaetales, Chlorokybales, Klebsormidiales and Zygnemophyceae (Desmidiales and Zygnematales). Recently, SSU rRNA gene sequence data allied Mesostigma viride (Prasinophyceae) with the Streptophyta. Complete chloroplast sequence data, however, placed Mesostigma sister to all green algae, not with the streptophytes. Several morphological, ultrastructural and biochemical features unite these lineages into a monophyletic group including embryophytes, but evolutionary relationships among the basal streptophytes remain ambiguous. To date, numerous studies using SSU rRNA gene sequences have yielded differing phylogenies with varying degrees of support dependent upon taxon sampling and choice of phylogenetic method. Like SSU data, chloroplast DNA sequence data have been used to examine relationships within the Charales, Coleochaetales, Zygnemophyceae and embryophytes. Representatives of all basal streptophyte lineages have not been examined using chloroplast data in a single analysis. Phylogenetic analyses were performed using DNA sequences of rbcL (the genes encoding the large subunit of rubisco) and atpB (the beta-subunit of ATPase) to examine relationships of basal streptophyte lineages. Preliminary analyses placed the branch leading to Mesostigma as the basal lineage in the Streptophyta with Chlorokybus, the sole representative of the Chlorokybales, branching next. Klebsormidiales and the enigmatic genus Entransia were sister taxa. Sister to these, the Charales, Coleochaetales, embryophytes and Zygnemophyceae formed a monophyletic group with Charales and Coleochaetales sister to each other and this clade sister to the embryophytes.
John D. Hall - One of the best experts on this subject based on the ideXlab platform.
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first discovery of the charophycean green alga lychnothamnus barbatus Charophyceae extant in the new world
American Journal of Botany, 2017Co-Authors: Kenneth G. Karol, Richard M. Mccourt, Paul M Skawinski, Michelle E Nault, Reesa Evans, Martha Barton, Matthew S Berg, Donna Perleberg, John D. HallAbstract:Premise of the study Although some species of Characeae, known as stoneworts, can be found on every continent except Antarctica, many species and some genera have limited geographic distributions. The genus Lychnothamnus, represented by a single extant species L. barbatus, was known only from scattered localities in Europe and Australasia until it was recently discovered in North America. Methods Morphological identifications were made from specimens collected in Minnesota and Wisconsin, USA. DNA sequences were obtained for three plastid-encoded genes (atpB, psbC, rbcL) from seven putative Lychnothamnus samples from two states in the USA Distribution and abundance were estimated in each lake using point intercept surveys where surveyors sampled aquatic vegetation. Key results Fourteen lakes in Wisconsin and two lakes in Minnesota, USA, were found to harbor Lychnothamnus barbatus. These represent the first report of this rare charophycean extant in the New World. The North American specimens matched the morphological description for L. barbatus and were compared directly with the neotype. Phylogenetic results using three plastid-encoded genes confirmed the identification placing New World samples with those from Europe and Australasia. Our phylogenetic analyses also confirmed the sister relationship between L. barbatus and Nitellopsis obtusa. Conclusions Because this taxon is not known for aggressive invasiveness in its native range, it may have existed in heretofore-undiscovered native populations, although the possibility that it is a recent introduction cannot be eliminated. The potential for discovery of novel lineages of green algae in even well-studied regions is apparently far from exhausted.
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Phylogenetic congruence of ribosomal operon and plastid gene sequences for the Characeae with an emphasis on Tolypella (Characeae, Charophyceae)
Phycologia, 2017Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Michele T. Casanova, Kenneth G. KarolAbstract:Abstract: To clarify species diversity of Tolypella (Characeae, Charophyceae) and the relationship between Tolypella and other genera in Characeae, sequence data from the nuclear ribosomal operon were assembled for 18 individuals of Tolypella. These represented nine named species and two potentially new species from Australia, as well as 13 other taxa of Characeae. Phylogenetic analyses were performed on ribosomal gene sequences (18S, 5.8S and 28S) for Characeae and on ribosomal gene and internal transcribed spacer (ITS) sequences (ribosomal genes + ITS1 + ITS2) for Tolypella. Analyses were also performed on the ribosomal gene and ITS sequences combined with plastid gene sequences (atpB, psbC and rbcL). Ribosomal gene sequences alone were conservative and their phylogenetic analyses resulted in topologies similar to a previously published plastid gene-based study but with less support and resolution. In contrast, ITS sequences showed greater variability and their addition resulted in greater resolution am...
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Oospore dimensions and morphology in North American Tolypella (Charophyceae, Charophyta).
Journal of phycology, 2015Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Kenneth G. KarolAbstract:Characteristics of the oospores have been used to delimit sections and, in some cases, species in the genus Tolypella A. Braun. To test the utility of oospore characters for identifying North American species of Tolypella, we investigated oospores from field-collected and herbarium specimens. Oospore dimensions (length, width, and length to width ratio) and morphology (color, ridge number and shape, wall ornamentation, and basal impression number) were measured. Oospore dimensions were statistically analyzed and oospore morphology was studied with light and scanning electron microscopy. Statistical analyses showed significant differences in length, width, and length to width ratios among most Tolypella species and populations but there was considerable overlap, which suggested that species identification based on oospore measurements alone is not wholly reliable. In addition, oospore morphology was not unique for every species.
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Phylogeny of North American Tolypella (Charophyceae, Charophyta) based on plastid DNA sequences with a description of Tolypella ramosissima sp. nov.
Journal of phycology, 2014Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Kenneth G. KarolAbstract:Characeae (Charophyceae, Charophyta) contains two tribes with six genera: tribe Chareae with four genera and tribe Nitelleae, which includes Tolypella and Nitella. This paper uses molecular and morphological data to elucidate the phylogeny of Tolypella species in North America. In the most comprehensive taxonomic treatment of Characeae, 16 Tolypella species worldwide were subsumed into two species, T. intricata and T. nidifica, in two sections, Rothia and Tolypella respectively. It was further suggested that Tolypella might be a derived group within Nitella. In this investigation into species diversity and relationships in North American Tolypella, sequence data from the plastid genes atpB, psbC, and rbcL were assembled for a broad range of charophycean and land plant taxa. Molecular data were used in conjunction with morphology to test monophyly of the genus and species within it. Phylogenetic analyses of the sequence data showed that Characeae is monophyletic but that Nitelleae is paraphyletic with Tolypella sister to a monophyletic Nitella + Chareae. The results also supported the monophyly of Tolypella and the sections Rothia and Tolypella. Morphologically defined species were supported as clades with little or no DNA sequence differences. In addition, molecular data revealed several lineages and a new species (T. ramosissima sp. nov.), which suggests greater species diversity in Tolypella than previously recognized.
William Pérez - One of the best experts on this subject based on the ideXlab platform.
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Phylogenetic congruence of ribosomal operon and plastid gene sequences for the Characeae with an emphasis on Tolypella (Characeae, Charophyceae)
Phycologia, 2017Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Michele T. Casanova, Kenneth G. KarolAbstract:Abstract: To clarify species diversity of Tolypella (Characeae, Charophyceae) and the relationship between Tolypella and other genera in Characeae, sequence data from the nuclear ribosomal operon were assembled for 18 individuals of Tolypella. These represented nine named species and two potentially new species from Australia, as well as 13 other taxa of Characeae. Phylogenetic analyses were performed on ribosomal gene sequences (18S, 5.8S and 28S) for Characeae and on ribosomal gene and internal transcribed spacer (ITS) sequences (ribosomal genes + ITS1 + ITS2) for Tolypella. Analyses were also performed on the ribosomal gene and ITS sequences combined with plastid gene sequences (atpB, psbC and rbcL). Ribosomal gene sequences alone were conservative and their phylogenetic analyses resulted in topologies similar to a previously published plastid gene-based study but with less support and resolution. In contrast, ITS sequences showed greater variability and their addition resulted in greater resolution am...
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Oospore dimensions and morphology in North American Tolypella (Charophyceae, Charophyta).
Journal of phycology, 2015Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Kenneth G. KarolAbstract:Characteristics of the oospores have been used to delimit sections and, in some cases, species in the genus Tolypella A. Braun. To test the utility of oospore characters for identifying North American species of Tolypella, we investigated oospores from field-collected and herbarium specimens. Oospore dimensions (length, width, and length to width ratio) and morphology (color, ridge number and shape, wall ornamentation, and basal impression number) were measured. Oospore dimensions were statistically analyzed and oospore morphology was studied with light and scanning electron microscopy. Statistical analyses showed significant differences in length, width, and length to width ratios among most Tolypella species and populations but there was considerable overlap, which suggested that species identification based on oospore measurements alone is not wholly reliable. In addition, oospore morphology was not unique for every species.
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Phylogeny of North American Tolypella (Charophyceae, Charophyta) based on plastid DNA sequences with a description of Tolypella ramosissima sp. nov.
Journal of phycology, 2014Co-Authors: William Pérez, Richard M. Mccourt, John D. Hall, Kenneth G. KarolAbstract:Characeae (Charophyceae, Charophyta) contains two tribes with six genera: tribe Chareae with four genera and tribe Nitelleae, which includes Tolypella and Nitella. This paper uses molecular and morphological data to elucidate the phylogeny of Tolypella species in North America. In the most comprehensive taxonomic treatment of Characeae, 16 Tolypella species worldwide were subsumed into two species, T. intricata and T. nidifica, in two sections, Rothia and Tolypella respectively. It was further suggested that Tolypella might be a derived group within Nitella. In this investigation into species diversity and relationships in North American Tolypella, sequence data from the plastid genes atpB, psbC, and rbcL were assembled for a broad range of charophycean and land plant taxa. Molecular data were used in conjunction with morphology to test monophyly of the genus and species within it. Phylogenetic analyses of the sequence data showed that Characeae is monophyletic but that Nitelleae is paraphyletic with Tolypella sister to a monophyletic Nitella + Chareae. The results also supported the monophyly of Tolypella and the sections Rothia and Tolypella. Morphologically defined species were supported as clades with little or no DNA sequence differences. In addition, molecular data revealed several lineages and a new species (T. ramosissima sp. nov.), which suggests greater species diversity in Tolypella than previously recognized.
Claude Lemieux - One of the best experts on this subject based on the ideXlab platform.
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2014Co-Authors: Chara Vulgaris, Monique Turmel, Christian Otis, Of Green Algae, Claude LemieuxAbstract:Mitochondrial DNA (mtDNA) has undergone radical changes during the evolution of green plants, yet little is known about the dynamics of mtDNA evolution in this phylum. Land plant mtDNAs differ from the few green algal mtDNAs that have been analyzed to date by their expanded size, long spacers, and diversity of introns. We have determined the mtDNA sequence of Chara vulgaris (Charophyceae), a green alga belonging to the charophycean order (Charales) that is thought to be the most closely related alga to land plants. This 67,737-bp mtDNA sequence, displaying 68 conserved genes and 27 introns, was compared with those of three angiosperms, the bryophyt
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The Chloroplast Genome Sequence of Chara vulgaris Sheds New Light into the Closest Green Algal Relatives of Land Plants
Molecular Biology and Evolution, 2006Co-Authors: Monique Turmel, Christian Otis, Claude LemieuxAbstract:: The phylum Streptophyta comprises all land plants and six monophyletic groups of charophycean green algae (Mesostigmatales, Chlorokybales, Klebsormidiales, Zygnematales, Coleochaetales, and Charales). Phylogenetic analyses of four genes encoded in three cellular compartments suggest that the Charales are sister to land plants and that charophycean green algae evolved progressively toward an increasing cellular complexity. To validate this phylogenetic hypothesis and to understand how and when the highly conservative pattern displayed by land plant chloroplast DNAs (cpDNAs) originated in the Streptophyta, we have determined the complete chloroplast genome sequence (184,933 bp) of a representative of the Charales, Chara vulgaris, and compared this genome to those of Mesostigma (Mesostigmatales), Chlorokybus (Chlorokybales), Staurastrum and Zygnema (Zygnematales), Chaetosphaeridium (Coleochaetales), and selected land plants. The phylogenies we inferred from 76 cpDNA-encoded proteins and genes using various methods favor the hypothesis that the Charales diverged before the Coleochaetales and Zygnematales. The Zygnematales were identified as sister to land plants in the best tree topology (T1), whereas Chaetosphaeridium (T2) or a clade uniting the Zygnematales and Chaetosphaeridium (T3) occupied this position in alternative topologies. Chara remained at the same basal position in trees including more land plant taxa and inferred from 56 proteins/genes. Phylogenetic inference from gene order data yielded two most parsimonious trees displaying the T1 and T3 topologies. Analyses of additional structural cpDNA features (gene order, gene content, intron content, and indels in coding regions) provided better support for T1 than for the topology of the above-mentioned four-gene tree. Our structural analyses also revealed that many of the features conserved in land plant cpDNAs were inherited from their green algal ancestors. The intron content data predicted that at least 15 of the 21 land plant group II introns were gained early during the evolution of streptophytes and that a single intron was acquired during the transition from charophycean green algae to land plants. Analyses of genome rearrangements based on inversions predicted no alteration in gene order during the transition from charophycean green algae to land plants.
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the complete chloroplast dna sequences of the charophycean green algae staurastrum and zygnema reveal that the chloroplast genome underwent extensive changes during the evolution of the zygnematales
BMC Biology, 2005Co-Authors: Monique Turmel, Christian Otis, Claude LemieuxAbstract:Background The Streptophyta comprise all land plants and six monophyletic groups of charophycean green algae. Phylogenetic analyses of four genes from three cellular compartments support the following branching order for these algal lineages: Mesostigmatales, Chlorokybales, Klebsormidiales, Zygnematales, Coleochaetales and Charales, with the last lineage being sister to land plants. Comparative analyses of the Mesostigma viride (Mesostigmatales) and land plant chloroplast genome sequences revealed that this genome experienced many gene losses, intron insertions and gene rearrangements during the evolution of charophyceans. On the other hand, the chloroplast genome of Chaetosphaeridium globosum (Coleochaetales) is highly similar to its land plant counterparts in terms of gene content, intron composition and gene order, indicating that most of the features characteristic of land plant chloroplast DNA (cpDNA) were acquired from charophycean green algae. To gain further insight into when the highly conservative pattern displayed by land plant cpDNAs originated in the Streptophyta, we have determined the cpDNA sequences of the distantly related zygnematalean algae Staurastrum punctulatum and Zygnema circumcarinatum.
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the complete chloroplast dna sequences of the charophycean green algae staurastrum and zygnema reveal that the chloroplast genome underwent extensive changes during the evolution of the zygnematales
BMC Biology, 2005Co-Authors: Monique Turmel, Christian Otis, Claude LemieuxAbstract:The Streptophyta comprise all land plants and six monophyletic groups of charophycean green algae. Phylogenetic analyses of four genes from three cellular compartments support the following branching order for these algal lineages: Mesostigmatales, Chlorokybales, Klebsormidiales, Zygnematales, Coleochaetales and Charales, with the last lineage being sister to land plants. Comparative analyses of the Mesostigma viride (Mesostigmatales) and land plant chloroplast genome sequences revealed that this genome experienced many gene losses, intron insertions and gene rearrangements during the evolution of charophyceans. On the other hand, the chloroplast genome of Chaetosphaeridium globosum (Coleochaetales) is highly similar to its land plant counterparts in terms of gene content, intron composition and gene order, indicating that most of the features characteristic of land plant chloroplast DNA (cpDNA) were acquired from charophycean green algae. To gain further insight into when the highly conservative pattern displayed by land plant cpDNAs originated in the Streptophyta, we have determined the cpDNA sequences of the distantly related zygnematalean algae Staurastrum punctulatum and Zygnema circumcarinatum. The 157,089 bp Staurastrum and 165,372 bp Zygnema cpDNAs encode 121 and 125 genes, respectively. Although both cpDNAs lack an rRNA-encoding inverted repeat (IR), they are substantially larger than Chaetosphaeridium and land plant cpDNAs. This increased size is explained by the expansion of intergenic spacers and introns. The Staurastrum and Zygnema genomes differ extensively from one another and from their streptophyte counterparts at the level of gene order, with the Staurastrum genome more closely resembling its land plant counterparts than does Zygnema cpDNA. Many intergenic regions in Zygnema cpDNA harbor tandem repeats. The introns in both Staurastrum (8 introns) and Zygnema (13 introns) cpDNAs represent subsets of those found in land plant cpDNAs. They represent 16 distinct insertion sites, only five of which are shared by the two zygnematalean genomes. Three of these insertions sites have not been identified in Chaetosphaeridium cpDNA. The chloroplast genome experienced substantial changes in overall structure, gene order, and intron content during the evolution of the Zygnematales. Most of the features considered earlier as typical of land plant cpDNAs probably originated before the emergence of the Zygnematales and Coleochaetales.
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The Mitochondrial Genome of Chara vulgaris: Insights into the Mitochondrial DNA Architecture of the Last Common Ancestor of Green Algae and Land Plants
The Plant Cell, 2003Co-Authors: Monique Turmel, Christian Otis, Claude LemieuxAbstract:Mitochondrial DNA (mtDNA) has undergone radical changes during the evolution of green plants, yet little is known about the dynamics of mtDNA evolution in this phylum. Land plant mtDNAs differ from the few green algal mtDNAs that have been analyzed to date by their expanded size, long spacers, and diversity of introns. We have determined the mtDNA sequence of Chara vulgaris (Charophyceae), a green alga belonging to the charophycean order (Charales) that is thought to be the most closely related alga to land plants. This 67,737-bp mtDNA sequence, displaying 68 conserved genes and 27 introns, was compared with those of three angiosperms, the bryophyte Marchantia polymorpha, the charophycean alga Chaetosphaeridium globosum (Coleochaetales), and the green alga Mesostigma viride. Despite important differences in size and intron composition, Chara mtDNA strikingly resembles Marchantia mtDNA; for instance, all except 9 of 68 conserved genes lie within blocks of colinear sequences. Overall, our genome comparisons and phylogenetic analyses provide unequivocal support for a sister-group relationship between the Charales and the land plants. Only four introns in land plant mtDNAs appear to have been inherited vertically from a charalean algar ancestor. We infer that the common ancestor of green algae and land plants harbored a tightly packed, gene-rich, and relatively intron-poor mitochondrial genome. The group II introns in this ancestral genome appear to have spread to new mtDNA sites during the evolution of bryophytes and charalean green algae, accounting for part of the intron diversity found in Chara and land plant mitochondria.