Exploration fonctionnelle de gènes différentiellement exprimés entre les souches d'huîtres creuses Crassostrea gigas résistantes et sensibles à la mortalité estivale

This work contributed to the development of specific genomic tools for the Pacific oyster Crassostrea gigas, aiming to identify molecular markers associated with summer survival of this species. To do so, 29745 ESTs obtained from different sequencing programs were grouped in a unique database. 9058 unigenes have been used to produce a cDNA microarray, to compare lines selected to be Resistant (R) or Sensitive (S) to summer mortality. 34 genes were observed as differentially expressed before the mortality event. Most of these genes are associated with reproduction and oxidative stress. This underlines the implication of the cost of reproduction and the importance of oxidative stress defenses in development of an immune weakness before the mortality event. The gene oyster-gonadal-TGFbeta-like, specifically expressed in the somatic cells of the gonad, could be involved in the differential reproductive investment observed between R and S lines. This hypothesis gives additional clue to study the implication of reproductive cost in the summer mortality phenomena. Genes will be studied by functional analyses and will also be mapped, in order to unravel their function and to identify their role in the mortality event.