Autosomal linkage, expression profiles, and thefunctionalstudy of cytochrome P450 genes in insecticide resistant house flies, Musca domestica

Cytochrome P450-mediated resistance in house flies has been extensively documented and several P450 genes have been identified constitutively up-regulated in highly insecticide resistant strains. In the current study, we conducted a whole transcriptome analysis of gene expression for a total of 84 cytochrome P450 genes in seven house fly strains and lines, including one multiple-insecticide resistant strain ALHF, two insecticide-susceptible strains, CS and aabys, and four house fly lines with different autosome combinations from ALHF, generated from crosses of ALHF and aabys. Our study revealed that 18 cytochrome P450 genes were co-up-regulated in ALHF compared to two insecticide-susceptible strains. The expression of these up-regulated genes varied when autosomes1, 2, and/or 5 from ALHF were replaced by the corresponding autosomes from aabys, highlighting the interaction and regulation features among the different autosomes in insecticide resistanceof house flies. Functional studies of two up-regulated P450 genes, CYP6A9and CYP6A36, in the P450 transgenic lines of Drosophila melanogaster revealed an increased tolerance of the Drosophila transgenic lines to permethrin, further confirming the importance of these up-regulated P450 genes in detoxification of insecticides. Taken together, our study provides a global pictureof P450 gene expression, regulation, interaction, and function in insecticide resistant house flies.