LAUSR

Abstract Cytochrome P450s (CYPs) are present in almost all organisms and play critical roles in metabolism of endogenous substrates and detoxification of xenobiotic compounds. Oysters are a group of bivalves that are important in marine ecosystem and aquaculture program, adapting to the harsh environment in intertidal zones. The studies on CYPs and their potential involvement in dealing with toxic xenobiotics in oysters were limited. In the present study, we performed a multiple omics analyses and identified a full-set of 123 CYP genes in the Pacific oyster, Crassostrea gigas. These CYP genes were classified into 5 clans and 16 families. The phylogenetic tree constructed with other species showed extensive gene expansion of CYPs in the clan 2 and mitochondrial clan in the C. gigas. The amino acid sequence analysis showed conserved typical motifs of CYP genes. The expression profiles of CYPs quantified across different tissues (gill and digestive gland) at various time points (0d, 0.5d, 7d, 14d, 28d) revealed their roles in response to Cd exposure. Notably, CYP17A1-like_6 and CYP2C50 were expressed at significantly higher levels compared with other CYP genes, suggesting their crucial roles in the detoxification of Cd in the C. gigas. This work provides valuable information toward understanding of CYP-mediated detoxification of cadmium in mollusks, and will be important for surveillance of marine environment pollution and seafood safety.