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Simon M Dittami - One of the best experts on this subject based on the ideXlab platform.
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Revisiting Australian Ectocarpus subulatus (Phaeophyceae) from the Hopkins River: distribution, abiotic environment, and associated microbiota
Journal of Phycology, 2020Co-Authors: Simon M Dittami, Akira Peters, Thierry Cariou, Hetty Kleinjan, Aurelie Prechoux, Suhelen Egan, Bezhin Rosko, John West, Bertille Burgunter-delamare, Catherine BoyenAbstract:In 1995 a strain of Ectocarpus was isolated from Hopkins River Falls, Victoria, Australia, constituting one of few available freshwater or nearly freshwater brown algae, and the only one belonging to the genus Ectocarpus. It has since been used as a model to study acclimation and adaptation to low salinities and the role of its microbiota in these processes. To provide more background information on this model, we assessed if Ectocarpus was still present in the Hopkins river twenty-two years after the original finding, estimated its present distribution, described its abiotic environment, and determined its in situ microbial composition. We sampled for Ectocarpus at 15 sites along the Hopkins River as well as 10 neighboring sites and found individuals with ITS and cox1 sequences identical to the original isolate at three sites upstream of Hopkins River Falls. The salinity of the water at these sites ranged from 3.1-6.9 psu, and it was rich in sulfate (1-5 mM). The diversity of bacteria associated with the algae in situ (1312 operational taxonomic units) was one order of magnitude higher than in previous studies of the original laboratory culture, and 95 alga-associated bacterial strains were isolated from algal filaments on site. In particular, species of Planctomycetes were abundant in situ but rare in laboratory-cultures. Our results confirmed that Ectocarpus was still present in the Hopkins River, and the newly isolated algal and bacterial strains offer new possibilities to study the adaptation of Ectocarpus to low salinity and its interactions with its microbiome.
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revisiting australian Ectocarpus subulatus phaeophyceae from the hopkins river distribution abiotic environment and associated microbiota
Journal of Phycology, 2020Co-Authors: Simon M Dittami, Akira F. Peters, John A West, Thierry Cariou, Hetty Kleinjan, Bertille Burgunterdelamare, Aurelie Prechoux, Suhelen Egan, Catherine BoyenAbstract:: In 1995 a strain of Ectocarpus was isolated from Hopkins River Falls, Victoria, Australia, constituting one of few available freshwater or nearly freshwater brown algae, and the only one belonging to the genus Ectocarpus. It has since been used as a model to study acclimation and adaptation to low salinities and the role of its microbiota in these processes. To provide more background information on this model, we assessed if Ectocarpus was still present in the Hopkins river 22 years after the original finding, estimated its present distribution, described its abiotic environment, and determined its in situ microbial composition. We sampled for Ectocarpus at 15 sites along the Hopkins River as well as 10 neighboring sites and found individuals with ITS and cox1 sequences identical to the original isolate at three sites upstream of Hopkins River Falls. The salinity of the water at these sites ranged from 3.1 to 6.9, and it was rich in sulfate (1-5 mM). The diversity of bacteria associated with the algae in situ (1312 operational taxonomic units) was one order of magnitude higher than in previous studies of the original laboratory culture, and 95 alga-associated bacterial strains were isolated from algal filaments on site. In particular, species of Planctomycetes were abundant in situ but rare in laboratory cultures. Our results confirmed that Ectocarpus was still present in the Hopkins River, and the newly isolated algal and bacterial strains offer new possibilities to study the adaptation of Ectocarpus to low salinity and its interactions with its microbiome.
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The genome of Ectocarpus subulatus - A highly stress-tolerant brown alga.
Marine Genomics, 2020Co-Authors: Simon M Dittami, Erwan Corre, Komlan Avia, Agnieszka Lipinska, Loraine Brillet-guéguen, Noe Pontoizeau, Meziane Aite, Christophe Caron, Chung Hyun Cho, Jonas CollénAbstract:Brown algae are multicellular photosynthetic stramenopiles that colonize marine rocky shores worldwide. Ectocarpus sp. Ec32 has been established as a genomic model for brown algae. Here we present the genome and metabolic network of the closely related species, Ectocarpus subulatus Kutzing, which is characterized by high abiotic stress tolerance. Since their separation, both strains show new traces of viral sequences and the activity of large retrotransposons, which may also be related to the expansion of a family of chlorophyll-binding proteins. Further features suspected to contribute to stress tolerance include an expanded family of heat shock proteins, the reduction of genes involved in the production of halogenated defence compounds, and the presence of fewer cell wall polysaccharide-modifying enzymes. Overall, E. subulatus has mainly lost members of gene families down-regulated in low salinities, and conserved those that were up-regulated in the same condition. However, 96% of genes that differed between the two examined Ectocarpus species, as well as all genes under positive selection, were found to encode proteins of unknown function. This underlines the uniqueness of brown algal stress tolerance mechanisms as well as the significance of establishing E. subulatus as a comparative model for future functional studies.
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The genome of Ectocarpus subulatus – A highly stress-tolerant brown alga
Marine Genomics, 2020Co-Authors: Simon M Dittami, Erwan Corre, Komlan Avia, Agnieszka Lipinska, Loraine Brillet-guéguen, Noe Pontoizeau, Meziane Aite, Christophe Caron, Chung Hyun Cho, Jonas CollénAbstract:Brown algae are multicellular photosynthetic stramenopiles that colonize marine rocky shores worldwide. Ectocarpus sp. Ec32 has been established as a genomic model for brown algae. Here we present the genome and metabolic network of the closely related species, Ectocarpus subulatus Kützing, which is characterized by high abiotic stress tolerance. Since their separation, both strains show new traces of viral sequences and the activity of large retrotransposons, which may also be related to the expansion of a family of chlorophyll-binding proteins. Further features suspected to contribute to stress tolerance include an expanded family of heat shock proteins, the reduction of genes involved in the production of halogenated defence compounds, and the presence of fewer cell wall polysaccharide-modifying enzymes. Overall, E. subulatus has mainly lost members of gene families down-regulated in low salinities, and conserved those that were up-regulated in the same condition. However, 96% of genes that differed between the two examined Ectocarpus species, as well as all genes under positive selection, were found to encode proteins of unknown function. This underlines the uniqueness of brown algal stress tolerance mechanisms as well as the significance of establishing E. subulatus as a comparative model for future functional studies.
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Genome Sequences of 72 Bacterial Strains Isolated from Ectocarpus subulatus: A Resource for Algal Microbiology.
Genome Biology and Evolution, 2019Co-Authors: Elham Karimi, Erwan Corre, Hetty Kleinjan, Enora Geslain, Gwenn Tanguy, Erwan Legeay, Simon M DittamiAbstract:Brown algae are important primary producers and ecosystem engineers in the ocean, and Ectocarpus has been established as a laboratory model for this lineage. Like most multicellular organisms, Ectocarpus is associated with a community of microorganisms, a partnership frequently referred to as holobiont due to the tight interconnections between the components. Although genomic resources for the algal host are well established, its associated microbiome is poorly characterized from a genomic point of view, limiting the possibilities of using these types of data to study host-microbe interactions. To address this gap in knowledge, we present the annotated draft genome sequences of seventy-two cultivable Ectocarpus-associated bacteria. A screening of gene clusters related to the production of secondary metabolites revealed terpene, bacteriocin, NRPS, PKS-t3, siderophore, PKS-t1, and homo-serine lactone clusters to be abundant among the sequenced genomes. These compounds may be used by the bacteria to communicate with the host and other microbes. Moreover, detoxification and provision of vitamin B pathways have been observed in most sequenced genomes, highlighting potential contributions of the bacterial metabolism toward host fitness and survival. The genomes sequenced in this study form a valuable resource for comparative genomic analyses and evolutionary surveys of alga-associated bacteria. They help establish Ectocarpus as a model for brown algal holobionts and will enable the research community to produce testable hypotheses about the molecular interactions within this complex system.
Akira F. Peters - One of the best experts on this subject based on the ideXlab platform.
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revisiting australian Ectocarpus subulatus phaeophyceae from the hopkins river distribution abiotic environment and associated microbiota
Journal of Phycology, 2020Co-Authors: Simon M Dittami, Akira F. Peters, John A West, Thierry Cariou, Hetty Kleinjan, Bertille Burgunterdelamare, Aurelie Prechoux, Suhelen Egan, Catherine BoyenAbstract:: In 1995 a strain of Ectocarpus was isolated from Hopkins River Falls, Victoria, Australia, constituting one of few available freshwater or nearly freshwater brown algae, and the only one belonging to the genus Ectocarpus. It has since been used as a model to study acclimation and adaptation to low salinities and the role of its microbiota in these processes. To provide more background information on this model, we assessed if Ectocarpus was still present in the Hopkins river 22 years after the original finding, estimated its present distribution, described its abiotic environment, and determined its in situ microbial composition. We sampled for Ectocarpus at 15 sites along the Hopkins River as well as 10 neighboring sites and found individuals with ITS and cox1 sequences identical to the original isolate at three sites upstream of Hopkins River Falls. The salinity of the water at these sites ranged from 3.1 to 6.9, and it was rich in sulfate (1-5 mM). The diversity of bacteria associated with the algae in situ (1312 operational taxonomic units) was one order of magnitude higher than in previous studies of the original laboratory culture, and 95 alga-associated bacterial strains were isolated from algal filaments on site. In particular, species of Planctomycetes were abundant in situ but rare in laboratory cultures. Our results confirmed that Ectocarpus was still present in the Hopkins River, and the newly isolated algal and bacterial strains offer new possibilities to study the adaptation of Ectocarpus to low salinity and its interactions with its microbiome.
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revisiting australian Ectocarpus subulatus phaeophyceae from the hopkins river distribution abiotic environment and associated microbiota
bioRxiv, 2019Co-Authors: Simon M Dittami, Akira F. Peters, John A West, Thierry Cariou, Hetty Kleinjan, Bertille Burgunterdelamare, Aurelie Prechoux, Suhelen Egan, Catherine BoyenAbstract:Ectocarpus is a genus of common marine brown algae. In 1995 a strain of Ectocarpus was isolated from Hopkins River Falls, Victoria, Australia, constituting one of few available freshwater or nearly freshwater brown algae, and the only one belonging to Ectocarpus. It has since been used as a model to study acclimation and adaptation to low salinities and the role of its microbiota in these processes. However, little is known about the distribution of this strain or whether it represents a stable population. Furthermore, its microbiota may have been impacted by the long period of cultivation. Twenty-two years after the original finding we searched for Ectocarpus in the Hopkins River and surrounding areas. We found individuals with ITS and cox1 sequences identical to the original isolate at three sites upstream of Hopkins River Falls, but none at the original isolation site. The osmolarity of the water at these sites ranged from 74-170 mOsmol, and it was rich in sulfate. The diversity of bacteria associated with the algae in situ was approximately one order of magnitude higher than in previous studies of the original laboratory culture, and 95 alga-associated bacterial strains were isolated from E. subulatus filaments on site. In particular, Planctomycetes were abundant in situ but rare in the laboratory-cultured strain. Our results confirm that E. subulatus has stably colonized the Hopkins River, and the newly isolated algal and bacterial strains offer new possibilities to study the adaptation of Ectocarpus to low salinity and its interactions with its microbiome.
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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.
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The Ectocarpus IMMEDIATE UPRIGHT gene encodes a member of a novel family of cysteine-rich proteins with an unusual distribution across the eukaryotes
Development, 2017Co-Authors: Nicolas Macaisne, Delphine Scornet, Martina Strittmatter, Akira F. Peters, Marie-mathilde Perrineau, Agnieszka Lipinska, Fuli Liu, Antoine Henry, Susana M. CoelhoAbstract:The sporophyte generation of the brown alga Ectocarpus sp. exhibits an unusual pattern of development compared to the majority of brown algae. The first cell division is symmetrical and the apical/basal axis is established late in development. In the IMMEDIATE UPRIGHT mutant the initial cell undergoes an asymmetric division to immediately establish the apical/basal axis. We provide evidence which suggests that this phenotype corresponds to the ancestral state of the sporophyte. The IMM gene encodes a protein of unknown function, containing a repeated motif also found in the EsV-1-7 gene of the Ectocarpus virus. Brown algae possess large families of EsV-1-7 domain genes but these genes are rare in other stramenopiles suggesting that the expansion of this family may have been linked with the emergence of multicellular complexity. EsV-1-7 domain genes have a patchy distribution across eukaryotic supergroups and occur in several viral genomes, suggesting possible horizontal transfer during eukaryote evolution.
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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).
Catherine Boyen - One of the best experts on this subject based on the ideXlab platform.
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Revisiting Australian Ectocarpus subulatus (Phaeophyceae) from the Hopkins River: distribution, abiotic environment, and associated microbiota
Journal of Phycology, 2020Co-Authors: Simon M Dittami, Akira Peters, Thierry Cariou, Hetty Kleinjan, Aurelie Prechoux, Suhelen Egan, Bezhin Rosko, John West, Bertille Burgunter-delamare, Catherine BoyenAbstract:In 1995 a strain of Ectocarpus was isolated from Hopkins River Falls, Victoria, Australia, constituting one of few available freshwater or nearly freshwater brown algae, and the only one belonging to the genus Ectocarpus. It has since been used as a model to study acclimation and adaptation to low salinities and the role of its microbiota in these processes. To provide more background information on this model, we assessed if Ectocarpus was still present in the Hopkins river twenty-two years after the original finding, estimated its present distribution, described its abiotic environment, and determined its in situ microbial composition. We sampled for Ectocarpus at 15 sites along the Hopkins River as well as 10 neighboring sites and found individuals with ITS and cox1 sequences identical to the original isolate at three sites upstream of Hopkins River Falls. The salinity of the water at these sites ranged from 3.1-6.9 psu, and it was rich in sulfate (1-5 mM). The diversity of bacteria associated with the algae in situ (1312 operational taxonomic units) was one order of magnitude higher than in previous studies of the original laboratory culture, and 95 alga-associated bacterial strains were isolated from algal filaments on site. In particular, species of Planctomycetes were abundant in situ but rare in laboratory-cultures. Our results confirmed that Ectocarpus was still present in the Hopkins River, and the newly isolated algal and bacterial strains offer new possibilities to study the adaptation of Ectocarpus to low salinity and its interactions with its microbiome.
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revisiting australian Ectocarpus subulatus phaeophyceae from the hopkins river distribution abiotic environment and associated microbiota
Journal of Phycology, 2020Co-Authors: Simon M Dittami, Akira F. Peters, John A West, Thierry Cariou, Hetty Kleinjan, Bertille Burgunterdelamare, Aurelie Prechoux, Suhelen Egan, Catherine BoyenAbstract:: In 1995 a strain of Ectocarpus was isolated from Hopkins River Falls, Victoria, Australia, constituting one of few available freshwater or nearly freshwater brown algae, and the only one belonging to the genus Ectocarpus. It has since been used as a model to study acclimation and adaptation to low salinities and the role of its microbiota in these processes. To provide more background information on this model, we assessed if Ectocarpus was still present in the Hopkins river 22 years after the original finding, estimated its present distribution, described its abiotic environment, and determined its in situ microbial composition. We sampled for Ectocarpus at 15 sites along the Hopkins River as well as 10 neighboring sites and found individuals with ITS and cox1 sequences identical to the original isolate at three sites upstream of Hopkins River Falls. The salinity of the water at these sites ranged from 3.1 to 6.9, and it was rich in sulfate (1-5 mM). The diversity of bacteria associated with the algae in situ (1312 operational taxonomic units) was one order of magnitude higher than in previous studies of the original laboratory culture, and 95 alga-associated bacterial strains were isolated from algal filaments on site. In particular, species of Planctomycetes were abundant in situ but rare in laboratory cultures. Our results confirmed that Ectocarpus was still present in the Hopkins River, and the newly isolated algal and bacterial strains offer new possibilities to study the adaptation of Ectocarpus to low salinity and its interactions with its microbiome.
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revisiting australian Ectocarpus subulatus phaeophyceae from the hopkins river distribution abiotic environment and associated microbiota
bioRxiv, 2019Co-Authors: Simon M Dittami, Akira F. Peters, John A West, Thierry Cariou, Hetty Kleinjan, Bertille Burgunterdelamare, Aurelie Prechoux, Suhelen Egan, Catherine BoyenAbstract:Ectocarpus is a genus of common marine brown algae. In 1995 a strain of Ectocarpus was isolated from Hopkins River Falls, Victoria, Australia, constituting one of few available freshwater or nearly freshwater brown algae, and the only one belonging to Ectocarpus. It has since been used as a model to study acclimation and adaptation to low salinities and the role of its microbiota in these processes. However, little is known about the distribution of this strain or whether it represents a stable population. Furthermore, its microbiota may have been impacted by the long period of cultivation. Twenty-two years after the original finding we searched for Ectocarpus in the Hopkins River and surrounding areas. We found individuals with ITS and cox1 sequences identical to the original isolate at three sites upstream of Hopkins River Falls, but none at the original isolation site. The osmolarity of the water at these sites ranged from 74-170 mOsmol, and it was rich in sulfate. The diversity of bacteria associated with the algae in situ was approximately one order of magnitude higher than in previous studies of the original laboratory culture, and 95 alga-associated bacterial strains were isolated from E. subulatus filaments on site. In particular, Planctomycetes were abundant in situ but rare in the laboratory-cultured strain. Our results confirm that E. subulatus has stably colonized the Hopkins River, and the newly isolated algal and bacterial strains offer new possibilities to study the adaptation of Ectocarpus to low salinity and its interactions with its microbiome.
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Exploring the Cultivable Ectocarpus Microbiome.
Frontiers in Microbiology, 2017Co-Authors: Hetty Kleinjan, Catherine Boyen, Christian Jeanthon, Simon M DittamiAbstract:Coastal areas form the major habitat of brown macroalgae, photosynthetic multicellular eukaryotes that have great ecological value and industrial potential. Macroalgal growth, development, and physiology are influenced by the microbial community they accommodate. Studying the algal microbiome should thus increase our fundamental understanding of algal biology and may help to improve culturing efforts. Currently, a freshwater strain of the brown macroalga Ectocarpus subulatus is being developed as a model organism for brown macroalgal physiology and algal microbiome studies. It can grow in high and low salinities depending on which microbes it hosts. However, the molecular mechanisms involved in this process are still unclear. Cultivation of Ectocarpus-associated bacteria is the first step towards the development of a model system for in vitro functional studies of brown macroalgal-bacterial interactions during abiotic stress. The main aim of the present study is thus to provide an extensive collection of cultivable E. subulatus-associated bacteria. To meet the variety of metabolic demands of Ectocarpus-associated bacteria, several isolation techniques were applied, i.e. direct plating and dilution-to-extinction cultivation techniques, each with chemically defined and undefined bacterial growth media. Algal tissue and algal growth media were directly used as inoculum, or they were pretreated with antibiotics, by filtration, or by digestion of algal cell walls. In total, 388 isolates were identified falling into 33 genera (46 distinct strains), of which Halomonas (Gammaproteobacteria), Bosea (Alphaproteobacteria), and Limnobacter (Betaproteobacteria) were the most abundant. Comparisons with 16S rRNA gene metabarcoding data showed that culturability in this study was remarkably high (~50%), although several cultivable strains were not detected or only present in extremely low abundance in the libraries. These undetected bacteria could be considered as part of the rare biosphere and they may form the basis for the temporal changes in the Ectocarpus microbiome.
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Molecular and biochemical characterization of mannitol-1-phosphate dehydrogenase from the model brown alga Ectocarpus sp.
Phytochemistry, 2015Co-Authors: Patricia Bonin, Agnès Groisillier, Alice Raimbault, Anaïs Guibert, Catherine Boyen, Thierry TononAbstract:The sugar alcohol mannitol is important in the food, pharmaceutical, medical and chemical industries. It is one of the most commonly occurring polyols in nature, with the exception of Archaea and animals. It has a range of physiological roles, including as carbon storage, compatible solute, and osmolyte. Mannitol is present in large amounts in brown algae, where its synthesis involved two steps: a mannitol-1-phosphate dehydrogenase (M1PDH) catalyzes a reversible reaction between fructose-6-phosphate (F6P) and mannitol-1-phosphate (M1P) (EC 1.1.1.17), and a mannitol-1-phosphatase hydrolyzes M1P to mannitol (EC 3.1.3.22). Analysis of the model brown alga Ectocarpus sp. genome provided three candidate genes for M1PDH activities. We report here the sequence analysis of Ectocarpus M1PDHs (EsM1PDHs), and the biochemical characterization of the recombinant catalytic domain of EsM1PDH1 (EsM1PDH1cat). Ectocarpus M1PDHs are representatives of a new type of modular M1PDHs among the polyol-specific long-chain dehydrogenases/reductases (PSLDRs). The N-terminal domain of EsM1PDH1 was not necessary for enzymatic activity. Determination of kinetic parameters indicated that EsM1PDH1cat displayed higher catalytic efficiency for F6P reduction compared to M1P oxidation. Both activities were influenced by NaCl concentration and inhibited by the thioreactive compound pHMB. These observations were completed by measurement of endogenous M1PDH activity and of EsM1PDH gene expression during one diurnal cycle. No significant changes in enzyme activity were monitored between day and night, although transcription of two out of three genes was altered, suggesting different levels of regulation for this key metabolic pathway in brown algal physiology.
Susana M. Coelho - One of the best experts on this subject based on the ideXlab platform.
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targeted crispr cas9 based gene knockouts in the model brown alga Ectocarpus
New Phytologist, 2021Co-Authors: Yacine Badis, Delphine Scornet, Susana M. Coelho, Taizo Motomura, Olivier Godfroy, Claire M. M. Gachon, Minori Harada, Celine Caillard, Morgane Raphalen, Chikako NagasatoAbstract:Brown algae are an important group of multicellular eukaryotes, phylogenetically distinct from both the animal and land plant lineages. Ectocarpus has emerged as a model organism to study diverse aspects of brown algal biology, but this system currently lacks an effective reverse genetics methodology to analyse the functions of selected target genes. Here, we report that mutations at specific target sites are generated following the introduction of CRISPR-Cas9 ribonucleoproteins into Ectocarpus cells, using either biolistics or microinjection as the delivery method. Individuals with mutations affecting the ADENINE PHOSPHORIBOSYL TRANSFERASE (APT) gene were isolated following treatment with 2-fluoroadenine, and this selection system was used to isolate individuals in which mutations had been introduced simultaneously at APT and at a second gene. This double mutation approach could potentially be used to isolate mutants affecting any Ectocarpus gene, providing an effective reverse genetics tool for this model organism. The availability of this tool will significantly enhance the utility of Ectocarpus as a model organism for this ecologically and economically important group of marine organisms. Moreover, the methodology described here should be readily transferable to other brown algal species.
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Unusual Patterns of Mitochondrial Inheritance in the Brown Alga Ectocarpus
'Oxford University Press (OUP)', 2019Co-Authors: Mignero Laure, Nagasato Chikako, Peters Akira, Perrineau Marie-mathilde, Scorne Delphine, Pontheau Floria, Djema Walid, Adis Yacine, Motomura Taizo, Susana M. CoelhoAbstract:International audienceMost eukaryotes inherit their mitochondria from only one of their parents. When there are different sexes, it is almost always the maternal mitochondria that are transmitted. Indeed, maternal uniparental inheritance has been reported for the brown alga Ectocarpus but we show in this study that different strains of Ectocarpus can exhibit different patterns of inheritance: Ectocarpus siliculosus strains showed maternal uniparental inheritance, as expected, but crosses using different Ectocarpus species 7 strains exhibited either paternal uniparental inheritance or an unusual pattern of transmission where progeny inherited either maternal or paternal mitochondria, but not both. A possible correlation between the pattern of mitochondrial inheritance and male gamete parthenogenesis was investigated. Moreover, in contrast to observations in the green lineage, we did not detect any change in the pattern of mitochondrial inheritance in mutant strains affected in life cycle progression. Finally, an analysis of field-isolated strains provided evidence of mitochondrial genome recombination in both Ectocarpus species
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High-density genetic map and identification of QTLs for responses to temperature and salinity stresses in the model brown alga Ectocarpus.
Scientific Reports, 2017Co-Authors: Komlan Avia, Susana M. Coelho, Alexandre Cormier, Myriam Valero, Stéphane Mauger, Sylvain Faugeron, Gabriel J Montecinos, Fiona Lerck, Pierre BoudryAbstract:Deciphering the genetic architecture of adaptation of brown algae to environmental stresses such as temperature and salinity is of evolutionary as well as of practical interest. The filamentous brown alga Ectocarpus sp. is a model for the brown algae and its genome has been sequenced. As sessile organisms, brown algae need to be capable of resisting the various abiotic stressors that act in the intertidal zone (e.g. osmotic pressure, temperature, salinity, UV radiation) and previous studies have shown that an important proportion of the expressed genes is regulated in response to hyposaline, hypersaline or oxidative stress conditions. Using the double digest RAD sequencing method, we constructed a dense genetic map with 3,588 SNP markers and identified 39 QTLs for growth-related traits and their plasticity under different temperature and salinity conditions (tolerance to high temperature and low salinity). GO enrichment tests within QTL intervals highlighted membrane transport processes such as ion transporters. Our study represents a significant step towards deciphering the genetic basis of adaptation of Ectocarpus sp. to stress conditions and provides a substantial resource to the increasing list of tools generated for the species.
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The Ectocarpus IMMEDIATE UPRIGHT gene encodes a member of a novel family of cysteine-rich proteins with an unusual distribution across the eukaryotes
Development, 2017Co-Authors: Nicolas Macaisne, Delphine Scornet, Martina Strittmatter, Akira F. Peters, Marie-mathilde Perrineau, Agnieszka Lipinska, Fuli Liu, Antoine Henry, Susana M. CoelhoAbstract:The sporophyte generation of the brown alga Ectocarpus sp. exhibits an unusual pattern of development compared to the majority of brown algae. The first cell division is symmetrical and the apical/basal axis is established late in development. In the IMMEDIATE UPRIGHT mutant the initial cell undergoes an asymmetric division to immediately establish the apical/basal axis. We provide evidence which suggests that this phenotype corresponds to the ancestral state of the sporophyte. The IMM gene encodes a protein of unknown function, containing a repeated motif also found in the EsV-1-7 gene of the Ectocarpus virus. Brown algae possess large families of EsV-1-7 domain genes but these genes are rare in other stramenopiles suggesting that the expansion of this family may have been linked with the emergence of multicellular complexity. EsV-1-7 domain genes have a patchy distribution across eukaryotic supergroups and occur in several viral genomes, suggesting possible horizontal transfer during eukaryote evolution.
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Sexual Dimorphism and the Evolution of Sex-Biased Gene Expression in the Brown Alga Ectocarpus
Molecular Biology and Evolution, 2015Co-Authors: Agnieszka Lipinska, Rémy Luthringer, Erwan Corre, Alexandre Cormier, Akira F. Peters, Claire M. M. Gachon, Susana M. CoelhoAbstract:Males and females often have marked phenotypic differences, and the expression of these dissimilarities invariably involves sex differences in gene expression. Sex-biased gene expression has been well characterized in animal species, where a high proportion of the genome may be differentially regulated in males and females during development. Male-biased genes tend to evolve more rapidly than female-biased genes, implying differences in the strength of the selective forces acting on the two sexes. Analyses of sex-biased gene expression have focused on organisms that exhibit separate sexes during the diploid phase of the life cycle (diploid sexual systems), but the genetic nature of the sexual system is expected to influence the evolutionary trajectories of sex-biased genes. We analyze here the patterns of sex-biased gene expression in Ectocarpus, a brown alga with haploid sex determination (dioicy) and a low level of phenotypic sexual dimorphism. In Ectocarpus, female-biased genes were found to be evolving as rapidly as male-biased genes. Moreover, genes expressed at fertility showed faster rates of evolution than genes expressed in immature gametophytes. Both male-and female-biased genes had a greater proportion of sites experiencing positive selection, suggesting that their accelerated evolution is at least partly driven by adaptive evolution. Gene duplication appears to have played a significant role in the generation of sex-biased genes in Ectocarpus, expanding previous models that propose this mechanism for the resolution of sexual antagonism in diploid systems. The patterns of sex-biased gene expression in Ectocarpus are consistent both with predicted characteristics of UV (haploid) sexual systems and with the distinctive aspects of this organism's reproductive biology.
Dieter G. Müller - One of the best experts on this subject based on the ideXlab platform.
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pathogens of brown algae culture studies of anisolpidium ectocarpii and a rosenvingei reveal that the anisolpidiales are uniflagellated oomycetes
European Journal of Phycology, 2017Co-Authors: Claire M. M. Gachon, Martina Strittmatter, Yacine Badis, Kyle I Fletcher, Pieter Van West, Dieter G. MüllerAbstract:Using laboratory cultures, we have documented the life cycle of Anisolpidium ectocarpii, a pathogen of Ectocarpus and other filamentous brown algae, and presented preliminary observations on Anisol...
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Cryopreservation of the model alga Ectocarpus (Phaeophyceae).
Cryo letters, 2012Co-Authors: Heesch H, Hiroshi Kawai, John G. Day, Takahiro Yamagishi, Dieter G. MüllerAbstract:The brown alga Ectocarpus has recently become the first fully sequenced multicellular alga and is an important biological model. Due to the large and growing number of Ectocarpus strains isolated and maintained by the research community, including increasing numbers of mutants, there is an urgent need for developing reliable, cost-effective long-term maintenance techniques. We report here that cryopreservation constitutes an attractive option in this respect, using a simple two-step protocol employing combined DMSO 10 percent (v/v) and sorbitol 9 percent (w/v) as cryoprotectants. This model organism appears to be remarkably robust and post-cryo recovery has been observed in all strains tested in this study. Cultures can be regenerated by the germination of cryopreserved zooids (spores), or the recovery of vegetative cells. In the latter case, dividing surviving cells may grow into the cell lumen of a neighbouring dead cell, eventually regenerating a phenotypically normal thalloidal structure.
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characterization and immunolocalization of major structural proteins in the brown algal virus esv 1
Virology, 2000Co-Authors: Nicolas Delaroque, Dieter G. Müller, Susanne Wolf, Rolf KnippersAbstract:The Ectocarpus siliculosus virus (EsV-1) is endemic in all populations of the cosmopolitan filamentous brown alga Ectocarpus siliculosus. EsV-1 has a large circular double-stranded DNA genome of about 320 kilobase pairs, and a complex virion structure with a central nucleoprotein core surrounded by several proteinaceous layers. To investigate the protein composition of the virion, we screened an expression library of EsV-1 with antibodies raised against purified detergent-disrupted viral particles. We isolated several clones encoding novel structural proteins and investigated two of them in detail. These clones encode viral proteins vp55 and vp74. Electron microscopy reveals that vp55 is most likely a component of the surface of the viral core, whereas vp74 may be part of an inner core structure. To initiate a genetic analysis, we sequenced regions of the EsV-1 genome encoding vp55 and vp74 and found several adjacent open reading frames with the potential to code for several interesting viral proteins including a putative calcium-binding protein, a collagen-like protein, and a RING finger protein.
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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.
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Detection of virus DNA in Ectocarpus siliculosus and E. fasciculatus (Phaeophyceae) from various geographic areas
European Journal of Phycology, 1996Co-Authors: M.r. Sengco, M. Bräutigam, M. Kapp, Dieter G. MüllerAbstract:The filamentous marine brown algae Ectocarpus siliculosus and E. fasciculatus are frequently infected by DNA viruses. We used polymerase chain reaction amplification (PCR) of a virus-specific nucleotide sequence to detect the presence of viral DNA in extracts of Ectocarpus plants, and applied this technique to a collection of 97 unialgal Ectocarpus cultures from coasts of all oceans and continents. We found that 42 isolates contained viral DNA. Among these were four sporophytes, which produced gametophytes free of virus DNA. This observation supports previous studies showing that the viral genome segregates like a Mendelian trait during meiosis. The pandemy and epidemiology of the host-virus relationship in Ectocarpus is discussed.
