Drosophila melanogaster NADPH-cytochrome P450 oxidoreductase: pronounced expression in antennae may be related to odorant clearance.

Insects perceive a large number of airborne chemicals as olfactory components mainly through the antenna. It is thought that detection of the odorants by specific receptors is followed by a degradative pathway that clears the olfactory organ from accumulating chemicals. In Drosophila, a number of P450 monooxygenases are involved in the metabolism of foreign chemicals [Dunkov et al. (1996) Cytochrome P450 gene cluster in Drosophila melanogaster, Mol. Gen. Genet. 251, 290-297]. NADPH-cytochrome P450 oxidoreductases serve to transfer reducing equivalents to P450 monooxygenases. We isolated cDNA and genomic clones coding for a Drosophila NADPH cytochrome P450 oxidoreductase (CPR). The largest cDNA of 2471 nucleotides in length contained an open reading frame of 693 amino acids that includes the putative CPR sequence. CPR is a single copy gene as shown by genomic Southern hybridisation and maps to the cytogenetic map position 26C on the second chromosome. Comparison of genomic and cDNA CPR sequences revealed a gene structure that is split into at least six exons. The CPR protein sequence is almost identical with that of house fly and remarkably conserved when compared to vertebrates and yeast. RNA expression is high in embryos and antennae as compared to adult heads, adult bodies and larvae. High expression in antennae may reflect the putative function in olfactory clearance.