Isolation and sequence analysis of a cDNA clone for a pyrethroid inducible cytochrome P450 from Helicoverpa armigera

The complete coding sequence and parts of the 3' and 5' noncoding regions of a mRNA coding for a cytochrome P450 from Helicoverpa armigera have been obtained. The sequence is most similar to members of family CYP6, in particular that obtained from Papilio polyxenes, CYP6B1, and has been labeled CYP6B2 accordingly. The original cDNA was obtained by screening a cDNA library with an oligonucleotide specific for the amino acid sequence surrounding the cysteine residue involved in heme binding, present in the other known insect sequences. This sequence is also present in mammalian members of family CYP3. The highly conserved nature of this particular sequence suggests that this approach may allow the easy and direct identification of cDNA clones specific for members of this particular cytochrome P450 family from a wide variety of species of invertebrates and, possibly, vertebrates. The cDNA hybridizes to two major mRNAs of 2.1 and 1.8 kb in length. Induction studies indicate that the smaller mRNA is inducible by phenobarbital while the larger mRNA is inducible by the pyrethroid insecticide permethrin. Both the evolution of this particular family of cytochrome P450 genes and its potential involvement in the development of resistance to pyrethroids is discussed.