Overexpression of Cytochrome P450 CYP6D1 Is Associated with Monooxygenase-Mediated Pyrethroid Resistance in House Flies from Georgia

Abstract

CYP6D1 is a house fly cytochrome P450 that catalyzes metabolism of pyrethroid insecticides. Overexpression of CYP6D1 is responsible for monooxygenase-mediated pyrethroid resistance in the LPR (Learn pyrethroid resistant) house fly strain, which was originally collected in New York State. To determine whether CYP6D1 is involved in monooxygenase-mediated pyrethroid resistance in other populations, we obtained two pyrethroid-resistant strains from Georgia and investigated the relationship between piperonyl butoxide suppressible permethrin resistance and CYP6D1 gene expression. The Georgia strain, collected from a poultry facility in about 1983, showed no PBO suppressible permethrin resistance and CYP6D1 was not overexpressed. The NG98-u strain, collected from a poultry facility in Georgia State in 1998, showed PBO suppressible resistance and CYP6D1 mRNA was overexpressed. Furthermore, the level of resistance and CYP6D1 mRNA increased after only two generations of permethrin selection. Overall, the synergistic ratios were well correlated with the expression of CYP6D1. CYP6D1 protein detected by immunoblotting was well correlated with CYP6D1 mRNA expression. These results suggest that increased expression of CYP6D1 in the resistant flies collected from Georgia in 1998 is due to increased transcription of the gene (as has been identified in LPR) and that CYP6D1-mediated pyrethroid resistance is found in house flies from both New York and Georgia.