Identification of a novel P450 gene belonging to the CYP4 family in the clam Ruditapes philippinarum, and analysis of basal- and benzo(a)pyrene-induced mRNA expression levels in selected tissues

A novel full-length cDNA encoding a CYP4 protein was initially cloned from the clam, Ruditapes philippinarum. The nucleotide sequence contained an open reading frame coding for 442 amino acids and the deduced amino acid sequence showed 42.6–49.1% identity with other species CYP4s. The phylogenetic analysis demonstrated that the clam CYP4 was clustered within the CYP4s branch. The clam CYP4 mRNA expression was detected in gill, digestive gland, adductor muscle and mantle, and highest transcription level was observed in digestive gland compared to other tissues. Quantitative real-time RT-PCR analysis revealed that there was no notable change in CYP4 mRNA expression in gill of R. philippinarum exposure to benzo(a)pyrene (BaP), while the mRNA expression was induced significantly in the digestive gland of the clam by 0.2 ppb (μg L−1) BaP (p < 0.05). The results suggest that CYP4 of the clam may serve as a useful biomarker of marine environmental PAH pollution.

► A novel CYP4 gene in the clam Ruditapes philippinarum was identified.
► The deduced amino acid sequence shares common characteristics with other CYP members.
► The gene expression level of CYP4 in BaP-stressed clams was increased significantly.
► The clam CYP4 may be a potential biomarker for PAHs exposure in aquatic environment.