Constitutive overexpression of the cytochrome P450 gene CYP6A1 in a house fly strain with metabolic resistance to insecticides

Messenger RNA levels of the cytochrome P450 gene CYP6A1 were measured in the insecticide resistant Diazinon-R 'Rutgers' strain and in the susceptible strain sbo of the house fly with a cloned cDNA probe. The constitutive expression of the CYP6A1 gene was at least 10 times higher in the Rutgers strain than in the sbo strain. In both strains, CYP6A1 was inducible by phenobarbital treatment of the flies. Analysis of genomic DNA from the two strains indicated that there was no amplification of the CYP6A1 gene in the Rutgers strain. A developmental analysis revealed that CYP6A1 is expressed larvae and adults, and very low levels of CYP6A1 mRNA were detected in eggs and pupae. The constitutive overexpression of CYP6A1 in the Rutgers strain was observed in both larvae and adults. Crosses between the Rutgers strain and the multiply marked sbo strain revealed that the high constitutive expression of CYP6A1 in the Rutgers strain is controlled by one or more loci located on chromosome II.