A novel cytochrome P450 1D1 gene in Nile tilapia fish (Oreochromis niloticus): partial cDNA cloning and expression following benzo-a-pyrene exposure

To understand the detoxification and bioactivation mechanisms for organic contaminants, it is essential to identify the cytochrome P450 (CYP) complement. Therefore, this study aimed to clone a partial cDNA sequence of the novel CYP1D1 gene from the fish Oreochromis niloticus and examine whether intraperitoneal injection of benzo-a-pyrene (BaP), a potent AHR agonist, is capable of inducing CYP1D1 mRNA expression in different tilapia fish tissues. The cloned nucleotide sequence consisted of 713 bp representing a portion of the tilapia CYP1D1 cDNA ORF, encoding 237 amino acids. Amino acid sequence comparison of O. niloticus CYP1D1 with the sequences of CYP1D1 from other species showed that this gene shared the highest identity of 81% with Fundulus heteroclitus CYP1D1. Furthermore, analysis of the percent identities shared by the deduced amino acid sequence of O. niloticus CYP1D1 with the sequences of CYP1 from other species revealed that the highest identities were shared with fish CYP1As. Real-time PCR results revealed that the highest expression level of CYP1D1 mRNA was found in muscles, followed by gills, liver, and intestine, while there was no detectable expression recorded in bile acid. These results indicate that tilapia CYP1D1 plays an important role in the metabolism of xenobiotics, expanding our knowledge regarding the diversity of CYP1 genes in this important model fish species.