Differential expression of immune response genes in Pacific oyster, Crassostrea gigas spat, fed with dinoflagellates Gymnodinium catenatum and Prorocentrum lima

The effects of Gymnodynium catenatum and Prorocentrum lima, dinoflagellate species present in the Gulf of California, on marine bivalves, have demonstrated physiological alterations and changes in gene expression patterns; however, modification effects of the genes involved in immune defense are still poorly understood. This study analyzed the mRNA levels of five genes encoding for the immune defense of oyster Crassostrea gigas spat fed with a control diet (Isochrysis galbana alone) and a combination of the two toxic dinoflagellates. Expression levels of lipopolysaccharide (LPS)-binding protein 1,3-glucan and cavorting genes were higher in oysters exposed to the combined diets in all treatments compared to the non-toxic diet at day three, which was probably related with an activation of the oysters' immediate immune response during the first 24 h. Protein 44 interferon-induced gene expression level was repressed in treatments with the highest dinoflagellate concentration and overexpressed in the diet with equal dinoflagellate concentration. Interaction protein-Toll and immunoglobulin gene transcript levels reached the highest values at day seven in oysters exposed to all combined diets. Then, the immune defense appeared to be activated in oyster spat as a response of toxins and/or extra-cellular compounds produced by the dinoflagellates.