Catherine Boyen
University of Paris
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Featured researches published by Catherine Boyen.
Nature | 2010
J. Mark Cock; Lieven Sterck; Pierre Rouzé; Delphine Scornet; Andrew E. Allen; Grigoris D. Amoutzias; Véronique Anthouard; François Artiguenave; Jean-Marc Aury; Jonathan H. Badger; Bank Beszteri; Kenny Billiau; Eric Bonnet; John H. Bothwell; Chris Bowler; Catherine Boyen; Colin Brownlee; Carl J. Carrano; Bénédicte Charrier; Ga Youn Cho; Susana M. Coelho; Jonas Collén; Erwan Corre; Corinne Da Silva; Ludovic Delage; Nicolas Delaroque; Simon M. Dittami; Sylvie Doulbeau; Marek Eliáš; Garry Farnham
Brown algae (Phaeophyceae) are complex photosynthetic organisms with a very different evolutionary history to green plants, to which they are only distantly related. These seaweeds are the dominant species in rocky coastal ecosystems and they exhibit many interesting adaptations to these, often harsh, environments. Brown algae are also one of only a small number of eukaryotic lineages that have evolved complex multicellularity (Fig. 1). We report the 214 million base pair (Mbp) genome sequence of the filamentous seaweed Ectocarpus siliculosus (Dillwyn) Lyngbye, a model organism for brown algae, closely related to the kelps (Fig. 1). Genome features such as the presence of an extended set of light-harvesting and pigment biosynthesis genes and new metabolic processes such as halide metabolism help explain the ability of this organism to cope with the highly variable tidal environment. The evolution of multicellularity in this lineage is correlated with the presence of a rich array of signal transduction genes. Of particular interest is the presence of a family of receptor kinases, as the independent evolution of related molecules has been linked with the emergence of multicellularity in both the animal and green plant lineages. The Ectocarpus genome sequence represents an important step towards developing this organism as a model species, providing the possibility to combine genomic and genetic approaches to explore these and other aspects of brown algal biology further.
Proceedings of the National Academy of Sciences of the United States of America | 2013
Jonas Collén; Betina M. Porcel; Wilfrid Carré; Steven G. Ball; Cristian Chaparro; Thierry Tonon; Tristan Barbeyron; Gurvan Michel; Benjamin Noel; Klaus Valentin; Marek Eliáš; François Artiguenave; Alok Arun; Jean-Marc Aury; Jose Fernandes Barbosa-Neto; John H. Bothwell; François-Yves Bouget; Loraine Brillet; Francisco Cabello-Hurtado; Salvador Capella-Gutiérrez; Bénédicte Charrier; Lionel Cladière; J. Mark Cock; Susana M. Coelho; Christophe Colleoni; Mirjam Czjzek; Corinne Da Silva; Ludovic Delage; Philippe Deschamps; Simon M. Dittami
Red seaweeds are key components of coastal ecosystems and are economically important as food and as a source of gelling agents, but their genes and genomes have received little attention. Here we report the sequencing of the 105-Mbp genome of the florideophyte Chondrus crispus (Irish moss) and the annotation of the 9,606 genes. The genome features an unusual structure characterized by gene-dense regions surrounded by repeat-rich regions dominated by transposable elements. Despite its fairly large size, this genome shows features typical of compact genomes, e.g., on average only 0.3 introns per gene, short introns, low median distance between genes, small gene families, and no indication of large-scale genome duplication. The genome also gives insights into the metabolism of marine red algae and adaptations to the marine environment, including genes related to halogen metabolism, oxylipins, and multicellularity (microRNA processing and transcription factors). Particularly interesting are features related to carbohydrate metabolism, which include a minimalistic gene set for starch biosynthesis, the presence of cellulose synthases acquired before the primary endosymbiosis showing the polyphyly of cellulose synthesis in Archaeplastida, and cellulases absent in terrestrial plants as well as the occurrence of a mannosylglycerate synthase potentially originating from a marine bacterium. To explain the observations on genome structure and gene content, we propose an evolutionary scenario involving an ancestral red alga that was driven by early ecological forces to lose genes, introns, and intergenetic DNA; this loss was followed by an expansion of genome size as a consequence of activity of transposable elements.
Genome Biology | 2009
Simon M. Dittami; Delphine Scornet; Jean-Louis Petit; Béatrice Segurens; Corinne Da Silva; Erwan Corre; Michael Dondrup; Karl-Heinz Glatting; Rainer König; Lieven Sterck; Pierre Rouzé; Yves Van de Peer; J. Mark Cock; Catherine Boyen; Thierry Tonon
BackgroundBrown algae (Phaeophyceae) are phylogenetically distant from red and green algae and an important component of the coastal ecosystem. They have developed unique mechanisms that allow them to inhabit the intertidal zone, an environment with high levels of abiotic stress. Ectocarpus siliculosus is being established as a genetic and genomic model for the brown algal lineage, but little is known about its response to abiotic stress.ResultsHere we examine the transcriptomic changes that occur during the short-term acclimation of E. siliculosus to three different abiotic stress conditions (hyposaline, hypersaline and oxidative stress). Our results show that almost 70% of the expressed genes are regulated in response to at least one of these stressors. Although there are several common elements with terrestrial plants, such as repression of growth-related genes, switching from primary production to protein and nutrient recycling processes, and induction of genes involved in vesicular trafficking, many of the stress-regulated genes are either not known to respond to stress in other organisms or are have been found exclusively in E. siliculosus.ConclusionsThis first large-scale transcriptomic study of a brown alga demonstrates that, unlike terrestrial plants, E. siliculosus undergoes extensive reprogramming of its transcriptome during the acclimation to mild abiotic stress. We identify several new genes and pathways with a putative function in the stress response and thus pave the way for more detailed investigations of the mechanisms underlying the stress tolerance ofbrown algae.
New Phytologist | 2007
Bénédicte Charrier; Susana M. Coelho; Aude Le Bail; Thierry Tonon; Gurvan Michel; Philippe Potin; Bernard Kloareg; Catherine Boyen; Akira F. Peters; J. Mark Cock
Brown algae share several important features with land plants, such as their photoautotrophic nature and their cellulose-containing wall, but the two groups are distantly related from an evolutionary point of view. The heterokont phylum, to which the brown algae belong, is a eukaryotic crown group that is phylogenetically distinct not only from the green lineage, but also from the red algae and the opisthokont phylum (fungi and animals). As a result of this independent evolutionary history, the brown algae exhibit many novel features and, moreover, have evolved complex multicellular development independently of the other major groups already mentioned. In 2004, a consortium of laboratories, including the Station Biologique in Roscoff and Genoscope, initiated a project to sequence the genome of Ectocarpus siliculosus, a small filamentous brown alga that is found in temperate, coastal environments throughout the globe. The E. siliculosus genome, which is currently being annotated, is expected to be the first completely characterized genome of a multicellular alga. In this review we look back over two centuries of work on this brown alga and highlight the advances that have led to the choice of E. siliculosus as a genomic and genetic model organism for the brown algae.
Journal of Phycology | 2005
Vincent Roeder; Jonas Collén; Sylvie Rousvoal; Erwan Corre; Catherine Leblanc; Catherine Boyen
To characterize stress and defense‐induced genes in the brown alga Laminaria digitata (Hudson) J.V. Lamouroux, 1985 expressed sequence tags (ESTs) were generated from L. digitata protoplasts. Comparison of the ESTs with public databases allowed putative functions to be assigned to 45% of the sequences. Comparison with ESTs from L. digitata sporophytes showed that protoplasts expressed more stress genes than intact thalli. Several transcripts in the stress gene class coded for proteins involved in cell protection against oxygen radicals, including thioredoxins (six ESTs), thioredoxin peroxidases (two ESTs), and glutathione‐S‐transferase (GST) (41 ESTs). The GSTs appear to be part of the sigma class, making them the first GST sigma identified in a photosynthetic organism. Other stress genes included a new type of vanadium‐dependent bromoperoxidases (vBPO) showing 71% similarity with vBPOs previously identified in the sporophytic‐thalli phase of L. digitata. The ESTs coding for 22 different mannuronan‐C5‐epimerases were identified among the cell wall biosynthesis genes, and several ESTs showed similarity with the genome of the Ectocarpus siliculosus virus.
Plant Cell and Environment | 2011
Simon M. Dittami; Antoine Gravot; David Renault; Sophie Goulitquer; Anja Eggert; Alain Bouchereau; Catherine Boyen; Thierry Tonon
The model brown alga Ectocarpus siliculosus undergoes extensive transcriptomic changes in response to abiotic stress, many of them related to primary metabolism and particularly to amino acid biosynthesis and degradation. In this study we seek to improve our knowledge of the mechanisms underlying the stress tolerance of this alga, in particular with regard to compatible osmolytes, by examining the effects of these changes on metabolite concentrations. We performed extensive metabolic profiling (urea, amino acids, sugars, polyols, organic acids, fatty acids) of Ectocarpus samples subjected to short-term hyposaline, hypersaline and oxidative stress, and integrated the results with previously published transcriptomic data. The most pronounced changes in metabolite concentrations occurred under hypersaline stress: both mannitol and proline were accumulated, but their low final concentrations indicate that, in this stress condition, both compounds are not likely to significantly contribute to osmoregulation at the level of the entire cell. Urea and trehalose were not detected in any of our samples. We also observed a shift in fatty acid composition from n-3 to n-6 fatty acids under high salinities, and demonstrated the salt stress-induced accumulation of small amounts of γ-aminobutyric acid (GABA). GABA could be synthesized in E. siliculosus through a salt stress-induced putrescine-degradation pathway.
BMC Evolutionary Biology | 2010
Simon M. Dittami; Gurvan Michel; Jonas Collén; Catherine Boyen; Thierry Tonon
BackgroundChlorophyll-binding proteins (CBPs) constitute a large family of proteins with diverse functions in both light-harvesting and photoprotection. The evolution of CBPs has been debated, especially with respect to the origin of the LI818 subfamily, members of which function in non-photochemical quenching and have been found in chlorophyll a/c-containing algae and several organisms of the green lineage, but not in red algae so far. The recent publication of the Ectocarpus siliculosus genome represents an opportunity to expand on previous work carried out on the origin and function of CBPs.ResultsThe Ectocarpus genome codes for 53 CBPs falling into all major families except the exclusively green family of chlorophyll a/b binding proteins. Most stress-induced CBPs belong to the LI818 family. However, we highlight a few stress-induced CBPs from Phaeodactylum tricornutum and Chondrus crispus that belong to different sub-families and are promising targets for future functional studies. Three-dimensional modeling of two LI818 proteins revealed features common to all LI818 proteins that are likely to interfere with their capacity to bind chlorophyll b and lutein, but may enable binding of chlorophyll c and fucoxanthin. In the light of this finding, we examined the possibility that LI818 proteins may have originated in a chlorophyll c/fucoxanthin containing organism and compared this scenario to three alternatives: an independent evolution of LI818 proteins in different lineages, an ancient origin together with the first CBPs, before the separation of the red and the green lineage, or an origin in the green lineage and a transfer to an ancestor of haptophytes and heterokonts during a cryptic endosymbiosis event.ConclusionsOur findings reinforce the idea that the LI818 family of CBPs has a role in stress response. In addition, statistical analyses of phylogenetic trees show an independent origin in different eukaryotic lineages or a green algal origin of LI818 proteins to be highly unlikely. Instead, our data favor an origin in an ancestral chlorophyll a/c-containing organism and a subsequent lateral transfer to some green algae, although an origin of LI818 proteins in a common ancestor of red and green algae cannot be ruled out.
Plant Physiology | 2003
Pi Nyvall; Erwan Corre; Claire Boisset; Tristan Barbeyron; Sylvie Rousvoal; Delphine Scornet; Bernard Kloareg; Catherine Boyen
Alginate is an industrially important polysaccharide obtained commercially by harvesting brown algae. The final step in alginate biosynthesis, the epimerization of β-1,4-d-mannuronic acid to α-1,4-l-guluronic acid, a structural change that controls the physicochemical properties of the alginate, is catalyzed by the enzyme mannuronan C-5-epimerase. Six different cDNAs with homology to bacterial mannuronan C-5-epimerases were isolated from the brown alga Laminaria digitata (Phaeophyceae). Hydrophobic cluster analysis indicated that the proteins encoded by the L. digitata sequences have important structural similarities to the bacterial mannuronan C-5-epimerases, including conservation of the catalytic site. The expression of the C-5-epimerase genes was examined by northern-blot analysis and reverse transcriptase-polymerase chain reaction in L. digitata throughout a year. Expression was also monitored in protoplast cultures by northern and western blot, reverse transcriptase-polymerase chain reaction, and activity measurements. From both the structural comparisons and the expression pattern, it appears that the cDNAs isolated from L. digitata encode functional mannuronan C-5-epimerases. The phylogenetic relationships of the bacterial and brown algal enzymes and the inferences on the origin of alginate biosynthetic machinery are discussed.
Current Genetics | 2006
Cécile Hervé; Thierry Tonon; Jonas Collén; Erwan Corre; Catherine Boyen
The red macro-alga Chondrus crispus is known to produce superoxide radicals in response to cell-free extracts of its green algal pathogenic endophyte Acrochaete operculata. So far, no enzymes involved in this metabolism have been isolated from red algae. We report here the isolation of a gene encoding a homologue of the respiratory burst oxidase gp91phox in C. crispus, named Ccrboh. This single copy gene encodes a polypeptide of 825 amino acids. Search performed in available genome and EST algal databases identified sequences showing common features of NADPH oxidases in other algae such as the red unicellular Cyanidioschyzon merolae, the economically valuable red macro-alga Porphyra yezoensis and the two diatoms Phaeodactylum tricornutum and Thalassiosira pseudonana. Domain organization and phylogenetic relationships with plant, animal, fungal and algal NADPH oxidase homologues were analyzed. Transcription analysis of the C. crispus gene revealed that it was over-transcribed during infection of C. crispus gametophyte by the endophyte A. operculata, and after incubation in presence of atrazine, methyl jasmonate and hydroxyperoxides derived from C20 polyunsaturated fatty acids (PUFAs). These results also illustrate the interest of exploring the red algal lineage for gaining insight into the deep evolution of NADPH oxidases in Eukaryotes.
Journal of Phycology | 2006
Jonas Collén; Vincent Roeder; Sylvie Rousvoal; Olivier Collin; Bernard Kloareg; Catherine Boyen
In order to identify genes involved in cell wall regeneration and stress responses in red algae, expressed sequence tags (ESTs) from protoplasts (2002 ESTs) and thalli (2052 ESTs) from the seaweed Chondrus crispus (Stackh.) were studied. Clustering gave 2291 non‐redundant sequences; 50% of the ESTs showed similarity (e<10−4) to known sequences. The fraction of stress‐related ESTs was five‐times higher in the protoplast library than in the thallus library. The ESTs that were statistically over‐represented in protoplasts included: glutathione S‐transferases, heat shock proteins, vanadium bromoperoxidase, and several genes of unknown function; in all 32 transcripts. Over‐represented genes in thallus included: NADH dehydrogenase, a peroxidase, and several genes of unknown function; in all 12 transcripts. In general, the ESTs from the two libraries were very different; for example, only 38% of contigs had members of both catalogues. The approach allowed the identification of numerous stress genes; including 23 different heat shock proteins and molecular chaperones, antioxidative enzymes, and several genes potentially involved in detoxification. Genes potentially involved in the construction of the cell wall or the extracellular matrix included α‐galactosidase, pullulanase, sulfohydrolase, and several sequences with von Willebrand factor type A domains with similarities to cochlin, integrin, and vitrin.