Xenobiotic transcription factors initiate the cytochrome P450-mediated insecticide resistance in Tribolium castaneum

Insecticide resistance is a global problem.  Resistance leads to genetic changes in response to the selection pressure. One of the several ways by which insects detoxify the xenobiotic compounds such as insecticides, is by up-regulation of cytochrome P450 genes. Previous studies have shown that the constitutive overexpression of brain specific CYP6BQ9 gene is the key mediator of the deltamethrin resistance observed in the QTC279 strain of Tribolium castaneum. The expression of this gene is 200-fold higher in the resistant strain (QTC279) as compared to that in susceptible strain, but the molecular basis for CYP6BQ9 overexpression is unknown. The current study focused on identifying the xenobiotic transcription factors involved in deltamethrin resistance as well as finding the binding sites for these transcription factors.  RNAi mediated knockdown of the probable xenobiotic transcription factors showed that heterodimer partners cap ‘n’ collar C (CncC) and muscle aponeurosis fibromatosis (Maf) were involved in regulation of not only CYP6BQ9 gene but multiple genes in the CYP6BQ cluster. Moreover, the CncC and Maf knockdown beetles showed 100% mortality in deltamethrin bioassay.  Further, the promoter analysis studies using the luciferase assay identified the binding site for CncC and Maf as GCAGTAn in the promoters of CYP6BQ genes.  Overall, these data identified both transcription factors involved in deltamethrin resistance as well as the binding site where these transcription factors bind to regulate CYP6BQ9 genes.