Characterization of the Regulatory Process of Pyrethroid Resistance in the House Fly, Musca domestica

Abstract

The house fly, Musca domestica, is a major domestic, medical and veterinary pest that causes more than 100 human and animal intestinal diseases. The major barrier in the house fly control is their remarkable ability to develop not only resistance to the insecticide used against them, but also cross-resistance to unrelated classes of insecticides. The house fly has demonstrated to be a useful model to study and predict resistance in not only themselves but also other insect species. The current study generated the first reference transcriptome from the adult house fly and a whole transcriptome analysis was conducted for the multiple insecticide resistant strain ALHF (wild-type) and two insecticide susceptible strains: aabys (with morphological recessive markers) and CS (wild type) to gain valuable insights into the gene interaction and complex regulation in insecticide resistance of house flies. A total of 1316 genes were identified as being co-up-regulated in ALHF in comparison to both aabys and CS. The majority of these up-regulated genes fell within the three key detailed function categories: redox detailed function category in metabolism, signal transduction and kinases/phosphatases in regulation, and proteases in intra-cellular processes. Genetic linkage analysis with house fly lines comparing different autosomal combinations from ALHF revealed that the up-regulation of gene expression occurred mainly through the co-regulation of factors among multiple autosomes, especially between autosomes 2 and 5, suggesting that signaling transduction cascades controlled by GPCRs, protein kinase/phosphates and proteases may be involved in the regulation of P450 and carboxylesterase gene expression. To characterize the cytochrome P450 and carboxylesterase genes that play important roles in the pyrethroid resistance of house flies, 86 P450 and 26 carboxylesterase genes were selected based on our whole transcriptome analysis of the house fly to conduct the expression profile analysis in different house fly strains with different levels of permethrin resistance and autosome combinations. Our study showed that multiple P450 and carboxylesterase genes were co-up-regulated in insecticide-resistant house flies compared to -susceptible house flies, and the expression of these genes was regulated by cis or trans regulatory factors/genes, which were mainly on autosomes 1, 2 and 5. Transgenic expression analysis of selected P450 and carboxylesterase genes in Drosophila melanogaster demonstrated that elevated expression of these genes confers different levels of resistance to permethrin in the transgenic Drosophila. Homology modeling and permethrin docking analysis further suggested potential ability of these genes to metabolize permethrin. Taken together, the study provides a global picture of P450 and carboxylesterase gene expression, regulation, autosomal interaction, and function in insecticide resistance of house flies, indicating multiple genes are co-responsible for detoxification of insecticides, and multiple mechanisms co-work on the development of insecticide resistance in house flies.