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Santec, France

Peters A.F.,University Pierre and Marie Curie | Peters A.F.,Marine Biological Association of The United Kingdom | van Wijk S.J.,University Pierre and Marie Curie | van Wijk S.J.,Bangor University | And 8 more authors.
Phycological Research | Year: 2010

Based on morphological characters, cross-fertility and molecular systematics, two species are currently recognized in the ubiquitous temperate brown algal genus Ectocarpus: the type species E. siliculosus (Dillwyn) Lyngbye and E. fasciculatus Harvey. We studied diversity, cross-fertility and ecology of Ectocarpus in megatidal areas in northwest France (Western Europe) and propose to reinstate a third species, E. crouaniorum Thuret in Le Jolis. Genotyping of 67 individuals from five localities, including the type locality of E. crouaniorum, using internal transcribed spacer 1 (ITS1) length as a marker, showed that the three species co-occurred whenever the habitat was suitable. Our survey also revealed a single putative field hybrid between E. crouaniorum and E. siliculosus, and a single individual of a further Ectocarpus genotype. In laboratory experiments, E. crouaniorum was crossed with E. siliculosus and E. fasciculatus. In 12 of 13 crosses, the zygotes did not develop (postzygotic sterility); in one experiment a viable hybrid was produced after crossing a female E. crouaniorum with a male E. siliculosus, but this hybrid was unable to form meiospores. Phylogenetic analysis of five molecular markers from the nuclear, mitochondrial and plastid genomes (in total 1818 bp) confirmed genetic separation of the three species. Ecologically, E. crouaniorum was confined to high intertidal pools and run-offs, where the gametophyte was common from spring to summer. Another characteristic was that it usually occurred as an epiphyte of up to 12 cm in length on erect thalli of Scytosiphon lomentaria. Sporophytes of E. crouaniorum were found all year long; they were <3 cm in size or microscopic and were epilithic in the same habitat. The presence of a third species of Ectocarpus in Western Europe suggests that species diversity in this genus is larger than recognized during the last 40 years. © 2010 Japanese Society of Phycology. Source

Tsiamis K.,Hellenic Center for Marine Research | Peters A.F.,BEZHIN ROSKO | Shewring D.M.,University of Aberdeen | Asensi A.O.,15 rue Lamblardie | And 2 more authors.
Journal of the Marine Biological Association of the United Kingdom | Year: 2014

This paper provides a comprehensive checklist of the marine benthic macroalgal flora of Ascension Island (tropical South Atlantic Ocean), based on both new collections and previous literature. 82 marine macroalgae were identified from our work, including 18 green algae (Ulvophyceae), 15 brown algae (Phaeophyceae) and 49 red algae (Rhodophyta). Among our collections, 38 species and infraspecific taxa are reported for the first time from Ascension Island, including seven green, three brown and 28 red macroalgae, raising the total number of seaweeds recorded in Ascension so far to 112 taxa in species and infraspecific level. No seagrasses have been recorded at Ascension Island. Copyright © Marine Biological Association of the United Kingdom 2014. Source

Dittami S.M.,CNRS Integrative Biology of Marine Models | Dittami S.M.,University of Oslo | Gravot A.,University of Rennes 1 | Gravot A.,European University of Brittany | And 8 more authors.
Plant Journal | Year: 2012

Colonizations of freshwater by marine species are rare events, and little information is known about the underlying mechanisms. Brown algae are an independent lineage of photosynthetic and multicellular organisms from which few species inhabit freshwater. As a marine alga that is also found in freshwater, Ectocarpus is of particular interest for studying the transition between these habitats. To gain insights into mechanisms of the transition, we examined salinity tolerance and adaptations to low salinities in a freshwater strain of Ectocarpus on physiological and molecular levels. We show that this isolate belongs to a widely distributed and highly stress-resistant clade, and differed from the genome-sequenced marine strain in its tolerance of low salinities. It also exhibited profound, but reversible, morphological, physiological, and transcriptomic changes when transferred to seawater. Although gene expression profiles were similar in both strains under identical conditions, metabolite and ion profiles differed strongly, the freshwater strain exhibiting e.g. higher cellular contents of amino acids and nitrate, higher contents of n-3 fatty acids, and lower intracellular mannitol and sodium concentrations. Moreover, several stress markers were noted in the freshwater isolate in seawater. This finding suggests that, while high stress tolerance and plasticity may be prerequisites for the colonization of freshwater, genomic alterations have occurred that produced permanent changes in the metabolite profiles to stabilize the transition. © 2012 The Authors. Source

Dittami S.M.,CNRS Integrative Biology of Marine Models | Dittami S.M.,University of Oslo | Proux C.,Institute Pasteur Paris | Rousvoal S.,CNRS Integrative Biology of Marine Models | And 6 more authors.
BMC Molecular Biology | Year: 2011

Background: Brown algae of the genus Ectocarpus exhibit high levels of genetic diversity and variability in morphological and physiological characteristics. With the establishment of E. siliculosus as a model and the availability of a complete genome sequence, it is now of interest to analyze variability among different species, ecotypes, and strains of the genus Ectocarpus both at the genome and the transcriptome level.Results: We used an E. siliculosus gene expression microarray based on EST sequences from the genome-sequenced strain (reference strain) to carry out comparative genome hybridizations for five Ectocarpus strains: four E. siliculosus isolates (the male genome strain, a female strain used for outcrosses with the genome strain, a strain isolated from freshwater, and a highly copper-tolerant strain), as well as one strain of the sister species E. fasciculatus. Our results revealed significant genomic differences between ecotypes of the same species, and enable the selection of conserved probes for future microarray experiments with these strains. In the two closely related strains (a male and a female strain used for crosses), genomic differences were also detected, but concentrated in two smaller genomic regions, one of which corresponds to a viral insertion site.Conclusion: The high variability between strains supports the concept of E. siliculosus as a complex of cryptic species. Moreover, our data suggest that several parts of the Ectocarpus genome may have evolved at different rates: high variability was detected particularly in transposable elements and fucoxanthin chlorophyll a/c binding proteins. © 2011 Dittami et al; licensee BioMed Central Ltd. Source

Heesch S.,CNRS Integrative Biology of Marine Models | Cho G.Y.,CNRS Integrative Biology of Marine Models | Peters A.F.,BEZHIN ROSKO | Le Corguille G.,Computer and Genomics Resource Center | And 8 more authors.
New Phytologist | Year: 2010

•Ectocarpus siliculosus has been proposed as a genetic and genomic model for the brown algae and the 214 Mbp genome of this organism has been sequenced. The aim of this project was to obtain a chromosome-scale view of the genome by constructing a genetic map using microsatellite markers that were designed based on the sequence supercontigs.•To map genetic markers, a segregating F2 population was generated from a cross between the sequenced strain (Ec 32) and a compatible strain from northern Chile. Amplified fragment length polymorphism (AFLP) analysis indicated a significant degree of polymorphism (41%) between the genomes of these two parental strains. Of 1,152 microsatellite markers that were selected for analysis based on their location on long supercontigs, their potential as markers and their predicted ability to amplify a single genomic locus, 407 were found to be polymorphic.•A genetic map was constructed using 406 markers, resulting in 34 linkage groups. The 406 markers anchor 325 of the longest supercontigs on to the map, representing 70.1% of the genome sequence.•The Ectocarpus genetic map described here not only provides a large-scale assembly of the genome sequence, but also represents an important tool for future genetic analysis using this organism. © The Authors (2010). Journal compilation © New Phytologist Trust (2010). Source

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