@article {4235, title = {Additive transcriptomic variation associated with reproductive traits suggest local adaptation in a recently settled population of the Pacific oyster, Crassostrea gigas.}, journal = {BMC Genomics}, volume = {16}, year = {2015}, month = {2015}, pages = {808}, abstract = {

BACKGROUND: Originating from Northeast Asia, the Pacific oyster Crassostrea gigas has been introduced into a large number of countries for aquaculture purpose. Following introduction, the Pacific oyster has turned into an invasive species in an increasing number of coastal areas, notably recently in Northern Europe.

METHODS: To explore potential adaptation of reproductive traits in populations with different histories, we set up a common garden experiment based on the comparison of progenies from two populations of Pacific oyster sampled in France and Denmark and their hybrids. Sex ratio, condition index and microarray gene expression in gonads, were analyzed in each progeny (n = 60).

RESULTS: A female-biased sex-ratio and a higher condition index were observed in the Danish progeny, possibly reflecting an evolutionary reproductive strategy to increase the potential success of natural recruitment in recently settled population. Using multifarious statistical approaches and accounting for sex differences we identified several transcripts differentially expressed between the Danish and French progenies, for which additive genetic basis is suspected (showing intermediate expression levels in hybrids, and therefore additivity). Candidate transcripts included mRNA coding for sperm quality and insulin metabolism, known to be implicated in coordinated control and success of reproduction.

CONCLUSIONS: Observed differences suggest that adaptation of invasive populations might have occurred during expansion acting on reproductive traits, and in particular on a female-biased sex-ratio, gamete quality and fertility.

}, issn = {1471-2164}, doi = {10.1186/s12864-015-1972-8}, author = {Sussarellu, Rossana and Huvet, Arnaud and Lap{\`e}gue, Sylvie and Virgile Quillien and Christophe Lelong and Cornette, Florence and Jensen, Lasse Fast and Bierne, Nicolas and Boudry, Pierre} } @article {4419, title = {GigaTON: an extensive publicly searchable database providing a new reference transcriptome in the pacific oyster Crassostrea gigas.}, journal = {BMC Bioinformatics}, volume = {16}, year = {2015}, month = {2015}, pages = {401}, abstract = {

BACKGROUND: The Pacific oyster, Crassostrea gigas, is one of the most important aquaculture shellfish resources worldwide. Important efforts have been undertaken towards a better knowledge of its genome and transcriptome, which makes now C. gigas becoming a model organism among lophotrochozoans, the under-described sister clade of ecdysozoans within protostomes. These massive sequencing efforts offer the opportunity to assemble gene expression data and make such resource accessible and exploitable for the scientific community. Therefore, we undertook this assembly into an up-to-date publicly available transcriptome database: the GigaTON (Gigas TranscriptOme pipeliNe) database.

DESCRIPTION: We assembled 2204 million sequences obtained from 114 publicly available RNA-seq libraries that were realized using all embryo-larval development stages, adult organs, different environmental stressors including heavy metals, temperature, salinity and exposure to air, which were mostly performed as part of the Crassostrea gigas genome project. This data was analyzed in silico and resulted into 56621 newly assembled contigs that were deposited into a publicly available database, the GigaTON database. This database also provides powerful and user-friendly request tools to browse and retrieve information about annotation, expression level, UTRs, splice and polymorphism, and gene ontology associated to all the contigs into each, and between all libraries.

CONCLUSIONS: The GigaTON database provides a convenient, potent and versatile interface to browse, retrieve, confront and compare massive transcriptomic information in an extensive range of conditions, tissues and developmental stages in Crassostrea gigas. To our knowledge, the GigaTON database constitutes the most extensive transcriptomic database to date in marine invertebrates, thereby a new reference transcriptome in the oyster, a highly valuable resource to physiologists and evolutionary biologists.

}, keywords = {Animals, Base Sequence, Computational Biology, Crassostrea, Databases, Genetic, Gene Library, Gene Ontology, Genome, High-Throughput Nucleotide Sequencing, Molecular Sequence Data, Sequence Analysis, RNA, Software, Transcriptome}, issn = {1471-2105}, doi = {10.1186/s12859-015-0833-4}, author = {Guillaume Rivi{\`e}re and Klopp, Christophe and Ibouniyamine, Nabihoudine and Huvet, Arnaud and Boudry, Pierre and Pascal Favrel} } @article {3395, title = {Functional characterization of a short neuropeptide F-related receptor in a lophotrochozoan, the mollusk Crassostrea gigas.}, journal = {J Exp Biol}, volume = {217}, year = {2014}, month = {2014 Aug 15}, pages = {2974-82}, abstract = {

Members of the short neuropeptide F (sNPF) family of peptides and their cognate receptors play key roles in a variety of physiological processes in arthropods. In silico screening of GigasDatabase, a specific expressed sequence tag database from the Pacific oyster Crassostrea gigas, resulted in the identification of a receptor (Cg-sNPFR-like) phylogenetically closely related to sNPF receptors (sNPFRs) of insects. A reverse endocrinology approach was undertaken to identify the peptide ligand(s) of this orphan receptor. Though structurally distinct from insect sNPFs, three RFamide peptides derived from the same precursor, i.e. GSLFRFamide, SSLFRFamide and GALFRFamide, specifically activate the receptor in a dose-dependent manner, with respective EC50 values (half-maximal effective concentrations) of 1.1, 2.1 and 4.1 μmol l(-1). We found that both Cg-sNPFR-like receptor and LFRFamide encoding transcripts are expressed in the oyster central nervous system and in other tissues as well, albeit at lower levels. Mass spectrometry analysis confirmed the wide distribution of LFRFamide mature peptides in several central and peripheral tissues. The Cg-sNPFR-like receptor was more abundantly expressed in ganglia of females than of males, and upregulated in starved oysters. In the gonad area, highest receptor gene expression occurred at the start of gametogenesis, when storage activity is maximal. Our results suggest that signaling of LFRFamide peptides through the Cg-sNPFR-like receptor might play a role in the coordination of nutrition, energy storage and metabolism in C. gigas, possibly by promoting storage at the expense of reproduction.

}, issn = {1477-9145}, doi = {10.1242/jeb.104067}, author = {Bigot, Laetitia and Beets, Isabel and Marie-Pierre Dubos and Boudry, Pierre and Schoofs, Liliane and Pascal Favrel} } @article {3398, title = {Transcriptomic profiling of gametogenesis in triploid Pacific Oysters Crassostrea gigas: towards an understanding of partial sterility associated with triploidy.}, journal = {PLoS One}, volume = {9}, year = {2014}, month = {2014}, pages = {e112094}, abstract = {

BACKGROUND: Triploidy can occur in many animal species but is often lethal. Among invertebrates, amphibians and fishes, triploids are viable although often sterile or infertile. Most triploids of the Pacific oyster Crassostrea gigas are almost sterile (named "3nβ") yet a low but significant proportion show an advanced gametogenesis (named "3nα"). These oysters thus constitute an interesting model to study the effect of triploidy on germ cell development. We used microarrays to compare the gonad transcriptomes of diploid 2n and the abovementioned triploid 3nβ and 3nα male and female oysters throughout gametogenesis.

RESULTS: All triploids displayed an upregulation of genes related to DNA repair and apoptosis and a downregulation of genes associated with cell division. The comparison of 3nα and 3nβ transcriptomes with 2n revealed the likely involvement of a cell cycle checkpoint during mitosis in the successful but delayed development of gonads in 3nα individuals. In contrast, a disruption of sex differentiation mechanisms may explain the sterility of 3nβ individuals with 3nβ females expressing male-specific genes and 3nβ males expressing female-specific genes.

CONCLUSIONS: The disruption of sex differentiation and mitosis may be responsible for the impaired gametogenesis of triploid Pacific oysters. The function of the numerous candidate genes identified in our study should now be studied in detail in order to elucidate their role in sex determination, mitosis/meiosis control, pachytene cell cycle checkpoint, and the control of DNA repair/apoptosis.

}, issn = {1932-6203}, doi = {10.1371/journal.pone.0112094}, author = {Dheilly, Nolwenn M and Jouaux, Aude and Boudry, Pierre and Pascal Favrel and Christophe Lelong} }