Identification of CYP genes in Mytilus (mussel) and Crassostrea (oyster) species: first approach to the full complement of cytochrome P450 genes in bivalves.

Understanding the fate and effects of organic chemicals in animals requires knowledge of cytochrome P450 (CYP) genes, which thus far are poorly known in bivalve mollusks. We searched for CYP sequences in EST databases for Mytilus and Crassostrea species, lophotrochozoan representatives of the protostomes. From ESTs averaging ca. 924bp, we identified 58 CYP genes in Mytilus californianus and 39 CYP genes in Crassostrea gigas. The sequences fell in all known animal CYP clans, and collectively they clustered in phylogenetic analysis with vertebrate CYP families 1, 2, 3, 4, 17, 20, 26 and 27. As in deuterostomes, a majority of the sequences fell in Clan 2. The CYP sequences found thus far in bivalves suggest a diversity consistent with that found in many other animal species. The present description of mollusk genes provides the overall framework for classification of any additional bivalve sequences. The sequences identified also will be useful in obtaining full-length sequences and in designing primers for analysis of expression of mussel and oyster CYP genes, or for recombinant protein expression to identify potential substrates for the bivalve CYP proteins, and understand their roles in xenobiotic detoxification and physiology of bivalves.