The Sodium Channel Gene Expression on the Kdr Locus in the House Fly, Musca domestica and the Mosquito, Culex quinquefasciatus

Abstract

A point mutation of leucine to phenylalanine (L-to-F), resulting from a single nucleotide substitution in the sodium-channel of insects, is associated with pyrethroid resistance. In this study, to understand genetic basis of sodium channel mutations in resistance, 14 house fly lines with different autosomal combinations were generated from crosses of resistant and susceptible house flies. This study, for the first time, mapped the sodium channel gene on autosome 3, factors on which were demonstrated to be involved in the elevated levels of resistance. In addition, two copies of the sodium channel gene of mosquitoes were identified. A strong correlation among the frequency of the resistant allele at the L-to-F site at the DNA level, the frequency of L-to-F allelic expression at the RNA level, and the levels of pyrethroid resistance suggests that one of the two copies is a functional sodium channel gene in mosquitoes, which is involved in insecticide resistance.