Permethrin induction of multiple cytochrome P450 genes in insecticide resistant mosquitoes, Culex quinquefasciatus

Insect cytochrome P450s are known to play important roles in detoxifying xenobiotics compounds, including insecticides and plant toxins. An interesting feature of some insect P450 genes is that their expression can be induced by both exogenous and endogenous compounds, a phenomenon known as induction. It has been suggested that the induction of P450s and their activities in insects is involved in the development of insecticide resistance. In the present study, we characterized the permethrin induction profiles on the expression of multiple P450 genes, which had been previously identified up-regulated in mosquitoes, in different mosquitoes strains of Culex quinquefasciatus ranging from susceptible (S-Lab strain), field  parental strains (HAmCq^G0 and MAmCq^G0), to highly resistant permethrin selected strains (HAmCq^G8  and  MAmCq^G6). Induction of multiple P450 expression was identified when the mosquitoes were treated with permethrin at the concentration that cause 50% mortality of test mosquitoes, i.e., LC₅₀.. The highest induction level of P450 gene expression was identified in highly resistant mosquitoes of HAmCq^G8 and MAmCq^G6, followed by the filed strains of HAmCq^G0 and MAmCq^G0. Our finding suggests the importance of induction of multiple P450 gene expression in the detoxification of permethrin, thus in turn, resulting in the development of resistance in mosquitoes.