Distribution of flavin-containing monooxygenase gene expression in several teleost fish species using a cDNA sequence from the teleost rainbow trout (Oncorhynchus mykiss)

Flavin-containing monooxygenases (FMOs) play an important role in the xenobiotic biotransformation of numerous pesticides and hetero-atom containing compounds found in petroleum. Several lines of evidence suggest an osmoregulatory role for FMOs in euryhaline fish. Since very few non-mammalian FMO sequences are available, the primary goal of this study was to isolate gene(s) encoding FMO(s) from the euryhaline teleosts. The initial species examined was rainbow trout. Total RNA isolated from rainbow trout liver was subjected to a reverse transcription-polymerase chain reaction using degenerate primers derived from conserved regions of FMO1 proteins (between amino acid residues 27–32 and 304–309). PCR amplification resulted in a 842 bp electrophoretic band. The amino acid sequence deduced from this fragment demonstrated closest identity to rabbit hepatic FMO1 (96%) and pig FMO1 (85%). Using another pair of primers derived from the conserved FAD- and NADP- binding domains, a 400 bp band was obtained. The deduced amino acid sequence was 100% identical to the overlapping region of the 842 bp fragment and 96% homologous to rabbit FMO1. Genomic DNA from stenohaline and other euryhaline species will be screened with this cDNA in an attempt to better understand the phylogenetic and molecular evolution of this family of enzymes. (EPA grant No. R-823450-01-0).