The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Akira F. Peters - One of the best experts on this subject based on the ideXlab platform.
-
organelle inheritance and genome architecture variation in isogamous brown algae
Scientific Reports, 2020Co-Authors: Ji Won Choi, Mark J Cock, Akira F. Peters, Louis Graf, Koki Nishitsuji, Asuka Arimoto, Eiichi Shoguchi, Chikako Nagasato, Chang Geun ChoiAbstract:Among the brown algal lineages, Ectocarpales species have isogamous fertilization in which male and female gametes are morphologically similar. In contrast, female gametes are much larger than male gametes in the oogamous species found in many other brown algal lineages. It has been reported that the plastids of isogamous species are biparentally inherited whereas the plastids of oogamous species are maternally inherited. In contrast, in both isogamous and oogamous species, the mitochondria are usually inherited maternally. To investigate whether there is any relationship between the modes of inheritance and organellar genome architecture, we sequenced six plastid genomes (ptDNA) and two mitochondrial genomes (mtDNA) of isogamous species from the Ectocarpales and compared them with previously sequenced organellar genomes. We found that the biparentally inherited ptDNAs of isogamous species presented distinctive structural rearrangements whereas maternally inherited ptDNAs of oogamous species showed no rearrangements. Our analysis permits the hypothesis that structural rearrangements in ptDNAs may be a consequence of the mode of inheritance.
-
taxonomic revision of eudesme Ectocarpales s l phaeophyceae proposing a new species e borealis sp nov
Phycologia, 2019Co-Authors: Hiroshi Kawai, Takeaki Hanyuda, Ignacio Barbara, Akira F. PetersAbstract:ABSTRACTMolecular phylogeny of Eudesme specimens collected from various localities in the Northern Hemisphere using mitochondrial cox1 and cox3 and chloroplast atpB, psaA, psbA and rbcL gene sequen...
-
Phaeoviral Infections Are Present in Macrocystis, Ecklonia and Undaria (Laminariales) and Are Influenced by Wave Exposure in Ectocarpales.
Viruses, 2018Co-Authors: Dean A Mckeown, Akira F. Peters, Kim Stevens, Murray T. Brown, Joanna L. Schroeder, Claudio A. Sáez, Jihae Park, Mark D. Rothman, John J. Bolton, Declan C. SchroederAbstract:Two sister orders of the brown macroalgae (class Phaeophyceae), the morphologically complex Laminariales (commonly referred to as kelp) and the morphologically simple Ectocarpales are natural hosts for the dsDNA phaeoviruses (family Phycodnaviridae) that persist as proviruses in the genomes of their hosts. We have previously shown that the major capsid protein (MCP) and DNA polymerase concatenated gene phylogeny splits phaeoviruses into two subgroups, A and B (both infecting Ectocarpales), while MCP-based phylogeny suggests that the kelp phaeoviruses form a distinct third subgroup C. Here we used MCP to better understand the host range of phaeoviruses by screening a further 96 and 909 samples representing 11 and 3 species of kelp and Ectocarpales, respectively. Sporophyte kelp samples were collected from their various natural coastal habitats spanning five continents: Africa, Asia, Australia, Europe, and South America. Our phylogenetic analyses showed that while most of the kelp phaeoviruses, including one from Macrocystispyrifera, belonged to the previously designated subgroup C, new lineages of Phaeovirus in 3 kelp species, Ecklonia maxima, Ecklonia radiata, Undaria pinnatifida, grouped instead with subgroup A. In addition, we observed a prevalence of 26% and 63% in kelp and Ectocarpales, respectively. Although not common, multiple phaeoviral infections per individual were observed, with the Ectocarpales having both intra- and inter-subgroup phaeoviral infections. Only intra-subgroup phaeoviral infections were observed in kelp. Furthermore, prevalence of phaeoviral infections within the Ectocarpales is also linked to their exposure to waves. We conclude that phaeoviral infection is a widely occurring phenomenon in both lineages, and that phaeoviruses have diversified with their hosts at least since the divergence of the Laminariales and Ectocarpales.
-
Phaeoviruses discovered in kelp (Laminariales)
The ISME journal, 2017Co-Authors: Dean A Mckeown, Akira F. Peters, Kim Stevens, Peter Bond, Glenn M. Harper, Colin Brownlee, Murray T. Brown, Declan C. SchroederAbstract:Phaeoviruses are latent double-stranded DNA viruses that insert their genomes into those of their brown algal (Phaeophyceae) hosts. So far these viruses are known only from members of the Ectocarpales, which are small and short-lived macroalgae. Here we report molecular and morphological evidence for a new Phaeovirus cluster, referred to as sub-group C, infecting kelps (Laminariales) of the genera Laminaria and Saccharina, which are ecologically and commercially important seaweeds. Epifluorescence and TEM observations indicate that the Laminaria digitata Virus (LdigV), the type species of sub-group C, targets the host nucleus for its genome replication, followed by gradual degradation of the chloroplast and assembly of virions in the cytoplasm of both vegetative and reproductive cells. This study is the first to describe phaeoviruses in kelp. In the field, these viruses infected two thirds of their host populations; however, their biological impact remains unknown.
-
species delimitation and phylogeographic analyses in the ectocarpus subgroup siliculosi Ectocarpales phaeophyceae
Journal of Phycology, 2017Co-Authors: Akira F. Peters, Alejandro E. Montecinos, Lucía Couceiro, Antoine Desrut, Myriam Valero, Marie-laure GuilleminAbstract:The genus Ectocarpus (Ectocarpales, Phaeophyceae) contains filamentous algae widely distributed in marine and estuarine habitats of temperate regions in both hemispheres. While E. siliculosus has become a model organism for genomics and genetics of the brown macroalgae, accurate species delineation, distribution patterns and diversity for the genus Ectocarpus remain problematic. In this study, we used three independent species delimitation approaches to generate a robust species hypothesis for 729 Ectocarpus specimens collected mainly along the European and Chilean coasts. These approaches comprised phylogenetic reconstructions and two bioinformatics tools developed to objectively define species boundaries (GMYC; General Mixed Yule Coalescence Method and ABGD; Automatic Barcode Gap Discovery). Our analyses were based on DNA sequences of two loci: the mitochondrial cytochrome oxidase subunit 1 (COI-5P) and the nuclear internal transcribed spacer 1 of the ribosomal DNA (ITS1). Our analyses showed the presence of at least 15 cryptic species and suggest the existence of incomplete lineage sorting or introgression between five of them. These results suggested the possible existence of different levels of reproductive barriers within this species complex. We also detected differences among species in their phylogeographic patterns, range and depth distributions which may suggest different biogeographic histories (e.g., endemic species or recent introductions). This article is protected by copyright. All rights reserved.
Kazuhiro Kogame - One of the best experts on this subject based on the ideXlab platform.
-
Systematics, distribution, and sexual compatibility of six Scytosiphon species (Scytosiphonaceae, Phaeophyceae) from Japan and the description of four new species.
Journal of phycology, 2020Co-Authors: Masakazu Hoshino, Masanori Hiraoka, Atsuko Tanaka, Mitsunobu Kamiya, Shinya Uwai, Kazuhiro KogameAbstract:The brown alga Scytosiphon lomentaria (Scytosiphonaceae, Ectocarpales) has been reported from cold and warm waters worldwide. Although previous molecular phylogenetic studies and crossing experiments have shown that it is a complex of multiple distinct species, the taxonomic position and accurate distribution of each species have remained largely unclear. For the S. lomentaria complex from Japan, our cox1 and rbcL phylogenetic analyses detected six species. In addition to five previously detected species (species Ia-Va), one species (species VI) was newly found in the subtropical area, Okinawa Island. Species VI was recovered as a sister to species Ia-Va in rbcL. Based on the morphological and phylogenetic data, we concluded that species Ia is S. lomentaria, species IIIa is S. promiscuus, and the other four species are newly described: S. shibazakiorum for species IIa, S. tosaensis for species IVa, S. arcanus for species Va, and S. subtropicus for species VI. The cox1-based analysis also showed that S. lomentaria, S. shibazakiorum, and S. promiscuus have worldwide distributions, while the other three species were not found outside of Japan. In Japan, except for S. subtropicus, distributions of these species overlapped. Our crossing experiments showed that gametic incompatibility (pre-zygotic barrier) was less developed between the allopatric species (i.e., S. subtropicus and others) compared with the sympatric species. It may suggest that pre-zygotic barriers have evolved among the sympatric species due to reinforcement.
-
parthenogenesis is rare in the reproduction of a sexual field population of the isogamous brown alga scytosiphon scytosiphonaceae Ectocarpales
Journal of Phycology, 2019Co-Authors: Masakazu Hoshino, Kazuhiro KogameAbstract:Parthenogenetic development of unfused gametes is commonly observed in laboratory cultures among various brown algal taxa. There is, however, little information on the contribution of parthenogenesis to the reproduction of field populations. In this study, we investigated whether parthenogenesis is present in a sexual population of the isogamous brown alga Scytosiphon with a 1:1 sex ratio. In culture, both female and male gametes showed higher mortality and slower development compared to zygotes. More than 90% of surviving partheno-germlings formed parthenosporophytes irrespective of the culture conditions tested. Therefore, if parthenogenesis occurs in the field, most unfused gametes are expected to form parthenosporophytes. Contrary to this expectation, parthenosporophytes were rare in the field population. We collected 126 sporophytic thalli and isolated and cultured a unilocular sporangium from each of them. We confirmed that cultures of 120 unilocular sporangia produced both female and male gametophytes by the observation of zygotes or amplification of PCR-based sex markers indicating that these sporangia originated from zygotic sporophytes. Only females were detected in cultures from two sporangia and only males from four sporangia suggesting that these sporangia originated from parthenosporophytes. In the Scytosiphon population, although parthenogenesis is observable in culture, our results demonstrate that the contribution of parthenogenesis to reproduction is small (≤4.8%) compared to sexual reproduction. Unfused gametes may not survive to form mature parthenosporophytes in significant numbers in the field partly due to their higher mortality and slower development compared from zygotes.
-
Parthenogenetic female populations in the brown alga Scytosiphon lomentaria (Scytosiphonaceae, Ectocarpales): decay of a sexual trait and acquisition of asexual traits.
Journal of phycology, 2018Co-Authors: Masakazu Hoshino, Tatsufumi Okino, Kazuhiro KogameAbstract:In isogamous brown algae, the sexuality of populations needs to be tested by laboratory crossing experiments, as the sexes of gametophytes are morphologically indistinguishable. In some cases, gamete fusion is not observed and the precise reproductive mode of the populations is unknown. In the isogamous brown alga Scytosiphon lomentaria in Japan, both asexual (gamete fusion is unobservable) and sexual populations (gamete fusion is observable) have been reported. In order to elucidate the reproductive mode of asexual populations in this species, we used PCR-based sex markers to investigate the sex ratio of three asexual and two sexual field populations. The markers indicated that the asexual populations consisted only of female individuals, whereas sexual populations are composed of both males and females. In culture, female gametes of most strains from asexual populations were able to fuse with male gametes; however, they had little to no detectable sexual pheromones, significantly larger cell sizes, and more rapid parthenogenetic development compared to female/male gametes from sexual populations. Investigations of sporophytic stages in the field indicated that alternation of gametophytic and parthenosporophytic stages occur in an asexual population. These results indicate that the S. lomentaria asexual populations are female populations that lack sexual reproduction and reproduce parthenogenetically. It is likely that females in the asexual populations have reduced a sexual trait (pheromone production) and have acquired asexual traits (larger gamete sizes and rapid parthenogenetic development).
-
Concordance between DNA-based species boundaries and reproductive isolating barriers in the Scytosiphon lomentaria species complex (Ectocarpales, Phaeophyceae)
Phycologia, 2018Co-Authors: Masakazu Hoshino, Shozo Ishikawa, Kazuhiro KogameAbstract:Abstract: DNA-based species delimitation methods often predict many putative cryptic species. Interpretation of these putative species (i.e. do they represent distinct species, or is this an erroneous estimate based on DNA variability?) is challenging because estimates of DNA-based delimitation are often difficult to verify using nongenetic data such as morphology or geographical distribution. In the present study, estimates of DNA-based delimitation methods were verified based on the biological species concept in Japanese populations of Scytosiphon lomentaria. Three DNA-based species delimitation methods (Generalised Mixed Yule Coalescent, Poisson Tree Processes and Automatic Barcode Gap Discovery) were conducted using mitochondrial (cox1) and nuclear (second intron of centrin gene) DNA sequence datasets. In the S. lomentaria species complex, five putative cryptic species (Ia–Va) were well-supported by DNA-based species delimitation, and these putative species were often found in the same locality. To ve...
-
Delimitation of cryptic species of the Scytosiphon lomentaria complex (Scytosiphonaceae, Phaeophyceae) in Japan, based on mitochondrial and nuclear molecular markers
Phycological Research, 2015Co-Authors: Kazuhiro Kogame, Shinya Uwai, Shozo Ishikawa, Kei Yamauchi, Akira Kurihara, Michio MasudaAbstract:Scytosiphon lomentaria (Scytosiphonaceae, Ectocarpales) is believed to include some cryptic species, particularly in the Pacific. We attempted to delimit these species in Japan using mitochondrial cox1 and cox3 and nuclear ITS2 and the second intron of the centrin gene ( cetn-int2). Fifty-three cox1+cox3 mitotypes, 26 ITS2 ribotypes and 45 cetn-int2 haplotypes were found in 107 samples collected from 33 localities in Japan. Based on phylogenetic analyses, similar sequence types were grouped into ten mitogroups, eight ribogroups and six cetn-int2 haplogroups (sequence-type groups). From the molecular trees and combinations of the mito-, ribo- and haplogroups, three cryptic species were apparent (Groups I–III). Group I, widely distributed on Pacific coasts, was highly supported by all molecular trees, whereas Groups II (North Pacific) and III (Northwestern Pacific and Australasia) were more closely related to each other. However, sequence-type-group combinations that would be characteris- tic of hybrids between Groups II and III were not detected, suggesting no gene flow between the two Groups. Further investigations of an additional 127 sympatrically growing plants supported the absence of gene flow between Groups II and III. Four samples did not belong to any of the Groups I–III and possibly represent additional species
Marie-laure Guillemin - One of the best experts on this subject based on the ideXlab platform.
-
species delimitation and phylogeographic analyses in the ectocarpus subgroup siliculosi Ectocarpales phaeophyceae
Journal of Phycology, 2017Co-Authors: Akira F. Peters, Alejandro E. Montecinos, Lucía Couceiro, Antoine Desrut, Myriam Valero, Marie-laure GuilleminAbstract:The genus Ectocarpus (Ectocarpales, Phaeophyceae) contains filamentous algae widely distributed in marine and estuarine habitats of temperate regions in both hemispheres. While E. siliculosus has become a model organism for genomics and genetics of the brown macroalgae, accurate species delineation, distribution patterns and diversity for the genus Ectocarpus remain problematic. In this study, we used three independent species delimitation approaches to generate a robust species hypothesis for 729 Ectocarpus specimens collected mainly along the European and Chilean coasts. These approaches comprised phylogenetic reconstructions and two bioinformatics tools developed to objectively define species boundaries (GMYC; General Mixed Yule Coalescence Method and ABGD; Automatic Barcode Gap Discovery). Our analyses were based on DNA sequences of two loci: the mitochondrial cytochrome oxidase subunit 1 (COI-5P) and the nuclear internal transcribed spacer 1 of the ribosomal DNA (ITS1). Our analyses showed the presence of at least 15 cryptic species and suggest the existence of incomplete lineage sorting or introgression between five of them. These results suggested the possible existence of different levels of reproductive barriers within this species complex. We also detected differences among species in their phylogeographic patterns, range and depth distributions which may suggest different biogeographic histories (e.g., endemic species or recent introductions). This article is protected by copyright. All rights reserved.
-
Species delimitation and phylogeographic analyses in the Ectocarpus subgroup siliculosi (Ectocarpales, Phaeophyceae).
Journal of Phycology, 2016Co-Authors: Alejandro E. Montecinos, Akira F. Peters, Lucía Couceiro, Antoine Desrut, Myriam Valero, Marie-laure GuilleminAbstract:The genus Ectocarpus (Ectocarpales, Phaeophyceae) contains filamentous algae widely distributed in marine and estuarine habitats of temperate regions in both hemispheres. While E. siliculosus has become a model organism for genomics and genetics of the brown macroalgae, accurate species delineation, distribution patterns and diversity for the genus Ectocarpus remain problematic. In this study, we used three independent species delimitation approaches to generate a robust species hypothesis for 729 Ectocarpus specimens collected mainly along the European and Chilean coasts. These approaches comprised phylogenetic reconstructions and two bioinformatics tools developed to objectively define species boundaries (General Mixed Yule Coalescence Method and Automatic Barcode Gap Discovery). Our analyses were based on DNA sequences of two loci: the mitochondrial cytochrome oxidase subunit 1 and the nuclear internal transcribed spacer 1 of the ribosomal DNA. Our analyses showed the presence of at least 15 cryptic species and suggest the existence of incomplete lineage sorting or introgression between five of them. These results suggested the possible existence of different levels of reproductive barriers within this species complex. We also detected differences among species in their phylogeographic patterns, range and depth distributions, which may suggest different biogeographic histories (e.g., endemic species or recent introductions).
Dieter G. Müller - One of the best experts on this subject based on the ideXlab platform.
-
Maullinia ectocarpii gen. et sp. nov. (Plasmodiophorea), an Intracellular Parasite in Ectocarpus siliculosus (Ectocarpales, Phaeophyceae) and other Filamentous Brown Algae
Protist, 2000Co-Authors: Ingo Maier, Elisa Rosalia Parodi, Renato Westermeier, Dieter G. MüllerAbstract:An obligate intracellular parasite infecting Ectocarpus spp. and other filamentous marine brown algae is described. The pathogen forms an unwalled multinucleate syncytium (plasmodium) within the host cell cytoplasm and causes hypertrophy. Cruciform nuclear divisions occur during early development. Mature plasmodia become transformed into single sporangia, filling the host cell completely, and then cleave into several hundred spores. The spores are motile with two unequal, whiplash-type flagella inserted subapically and also show amoeboid movement. Upon settlement, cysts with chitinous walls are formed. Infection of host cells is accomplished by means of an adhesorium and a stachel apparatus penetrating the host cell wall, and injection of the cyst content into the host cell cytoplasm. The parasite is characterized by features specific for the plasmodiophorids and is described as a new genus and species, Maullinia ectocarpii.
-
Molecular systematics of Ectocarpus and Kuckuckia (Ectocarpales, Phaeophyceae) inferred from phylogenetic analysis of nuclear and plastid-encoded DNA sequences
Journal of Phycology, 1997Co-Authors: Birgit Stache‐crain, Dieter G. Müller, Lynda J. GoffAbstract:The phylogeny of Ectocarpus and Kuckuckia strains representing widely separated populations from both hemispheres was inferred from sequence analysis of the internal transcribed spacers of the nuclear ribosomal DNA (ITS 1—5.8S-ITS 2) and the spacer region in the plastid-encoded ribulose-bis-phosphate-carboxylase (RUBISCO) cistron (partial rbc L-spacer-partial rbc S). Both sequences resulted in matching phylogenies, with the RUBISCO spacer region being most informative at the level of genera and species and the internal transcribed spacer sequences at the level of species and populations. Three major clades were formed by strains previously described by morphology and physiology as Kuckuckia, E. fasciculatus, and E. siliculosus, confirming the validity of these taxa. Ectocarpus and Kuckuckia are regarded as sibling taxa with respect to the outgroup species Feldmannia simplex, Hincksia mitchelliae, and Pilayella littoralis. The clade formed by sexual E. siliculosus strains and most asexual Ectocarpus strains was subdivided into several clades that are consistent with geographical races within E. siliculosus. The inferred phylogeny of Ectocarpus corresponds generally with results from cross-fertilization experiments, morphology, and lipid analysis. A hypothesis on the origin and dispersal of E. siliculosus suggests several natural dispersal events during periods of global cooling as well as recent and possibly anthropogenic dispersal events.
-
PASSAGE OF A MARINE BROWN ALGAL DNA VIRUS FROM ECTOCARPUS FASCICULATUS (Ectocarpales, PHAEOPHYCEAE) TO MYRIOTRICHIA CLAVAEFORMIS (DICTYOSIPHONALES, PHAEOPHYCEAE): INFECTION SYMPTOMS AND RECOVERY1
Journal of Phycology, 1997Co-Authors: Ingo Maier, Dieter G. Müller, Elke Rometsch, Susanne Wolf, Markus Kapp, Hiroshi KawaiAbstract:A dsDNA virus (EfasV-1) isolated from Ectocarpus fasciculatus Harvey infected Myriotrichia clavaeformis Harvey, a species belonging to a different brown algal order. The virus did not complete its infection cycle in the foreign host but caused infertility due to malformed reproductive structures. After some time in culture, the host's reproductive capacity was sometimes restored with concomitant loss of at least part of the viral genome. This incidence of interordinal virus transfer is discussed in relation to possibilities for virus-mediated horizontal gene transfer in brown algae.
-
CROSSING EXPERIMENTS, LIPID COMPOSITION, AND THE SPECIES CONCEPT IN ECTOCARPUS SILICULOSUS AND E. FASCICULATUS (PHAEOPHYCEAE, Ectocarpales)1
Journal of Phycology, 1995Co-Authors: Dieter G. Müller, Waldemar EichenbergerAbstract:Sporophytes of Ectocarpus siliculosus (Dillwyn) Lyngbye and E. fasciculatus Harvey were collected in the vicinity of Roscoff Brittany, France. Gametophytes derived from meiospores were used for intra- and interspecific crosses. Intraspecific gamete combinations gave viable zygotes, which developed into fertile sporophytes. Interspecific crosses were unsuccessful. Gamete fusions did not occur between female gametes of E. fasciculatus and male gametes of E. siliculosus. Hybrid zygotes were formed in the reciprocal combination but died soon after germination. We conclude that the two species of Ectocarpus at Roscoff represent distinct taxonomic entities, which are separated by pre- and postzygotic compatibility barriers. These biological findings are confirmed by the differential occurrence of the chemotaxonomic marker betaine-lipid diacetylglycerylhydroxymethyltrimethyl-β-alanine, which is present in our cultures of E. fasciculatus but absent in E. siliculosus.
-
Field and culture studies on virus infections in Hincksia hincksiae and Ectocarpus fasciculatus (Ectocarpales, Phaeophyceae)
European Journal of Phycology, 1994Co-Authors: Elisa R. Parodi, Dieter G. MüllerAbstract:Dense populations of Hincksia hincksiae and Ectocarpus fasciculatus were found on blades of Laminaria hyperborea and Saccorhiza polyschides in Brittany, France. Clonal cultures of healthy and infected plants were established, and infectivity of the virus particles was demonstrated. Size and morphology of the virions are similar to those previously found in Ectocarpus siliculosus and in the genus Feldmannia.
Claire Jubin - One of the best experts on this subject based on the ideXlab platform.
-
plastid genomes of two brown algae ectocarpus siliculosus and fucus vesiculosus further insights on the evolution of red algal derived plastids
BMC Evolutionary Biology, 2009Co-Authors: Gildas Le Corguille, Akira F. Peters, Marta Valente, Carla Viegas, Bernhard Gschloessl, Erwan Corre, Xavier Bailly, Claire Jubin, Gareth A PearsonAbstract:Heterokont algae, together with cryptophytes, haptophytes and some alveolates, possess red-algal derived plastids. The chromalveolate hypothesis proposes that the red-algal derived plastids of all four groups have a monophyletic origin resulting from a single secondary endosymbiotic event. However, due to incongruence between nuclear and plastid phylogenies, this controversial hypothesis remains under debate. Large-scale genomic analyses have shown to be a powerful tool for phylogenetic reconstruction but insufficient sequence data have been available for red-algal derived plastid genomes. The chloroplast genomes of two brown algae, Ectocarpus siliculosus and Fucus vesiculosus, have been fully sequenced. These species represent two distinct orders of the Phaeophyceae, which is a major group within the heterokont lineage. The sizes of the circular plastid genomes are 139,954 and 124,986 base pairs, respectively, the size difference being due principally to the presence of longer inverted repeat and intergenic regions in E. siliculosus. Gene contents of the two plastids are similar with 139-148 protein-coding genes, 28-31 tRNA genes, and 3 ribosomal RNA genes. The two genomes also exhibit very similar rearrangements compared to other sequenced plastid genomes. The tRNA-Leu gene of E. siliculosus lacks an intron, in contrast to the F. vesiculosus and other heterokont plastid homologues, suggesting its recent loss in the Ectocarpales. Most of the brown algal plastid genes are shared with other red-algal derived plastid genomes, but a few are absent from raphidophyte or diatom plastid genomes. One of these regions is most similar to an apicomplexan nuclear sequence. The phylogenetic relationship between heterokonts, cryptophytes and haptophytes (collectively referred to as chromists) plastids was investigated using several datasets of concatenated proteins from two cyanobacterial genomes and 18 plastid genomes, including most of the available red algal and chromist plastid genomes. The phylogenetic studies using concatenated plastid proteins still do not resolve the question of the monophyly of all chromist plastids. However, these results support both the monophyly of heterokont plastids and that of cryptophyte and haptophyte plastids, in agreement with nuclear phylogenies.
-
Plastid genomes of two brown algae, Ectocarpus siliculosus and Fucus vesiculosus: further insights on the evolution of red-algal derived plastids
BMC Evolutionary Biology, 2009Co-Authors: Gildas Le Corguillé, Akira F. Peters, Gareth Pearson, Marta Valente, Carla Viegas, Bernhard Gschloessl, Erwan Corre, Xavier Bailly, Claire Jubin, Benoit VacherieAbstract:Background: Heterokont algae, together with cryptophytes, haptophytes and some alveolates, possess red-algal derived plastids. The chromalveolate hypothesis proposes that the red-algal derived plastids of all four groups have a monophyletic origin resulting from a single secondary endosymbiotic event. However, due to incongruence between nuclear and plastid phylogenies, this controversial hypothesis remains under debate. Large-scale genomic analyses have shown to be a powerful tool for phylogenetic reconstruction but insufficient sequence data have been available for red-algal derived plastid genomes. Results: The chloroplast genomes of two brown algae, Ectocarpus siliculosus and Fucus vesiculosus, have been fully sequenced. These species represent two distinct orders of the Phaeophyceae, which is a major group within the heterokont lineage. The sizes of the circular plastid genomes are 139,954 and 124,986 base pairs, respectively, the size difference being due principally to the presence of longer inverted repeat and intergenic regions in E. siliculosus. Gene contents of the two plastids are similar with 139-148 protein-coding genes, 28-31 tRNA genes, and 3 ribosomal RNA genes. The two genomes also exhibit very similar rearrangements compared to other sequenced plastid genomes. The tRNA-Leu gene of E. siliculosus lacks an intron, in contrast to the F. vesiculosus and other heterokont plastid homologues, suggesting its recent loss in the Ectocarpales. Most of the brown algal plastid genes are shared with other red-algal derived plastid genomes, but a few are absent from raphidophyte or diatom plastid genomes. One of these regions is most similar to an apicomplexan nuclear sequence. The phylogenetic relationship between heterokonts, cryptophytes and haptophytes (collectively referred to as chromists) plastids was investigated using several datasets of concatenated proteins from two cyanobacterial genomes and 18 plastid genomes, including most of the available red algal and chromist plastid genomes. Conclusion: The phylogenetic studies using concatenated plastid proteins still do not resolve the question of the monophyly of all chromist plastids. However, these results support both the monophyly of heterokont plastids and that of cryptophyte and haptophyte plastids, in agreement with nuclear phylogenies.
