RESUMO
The kdr insecticide resistance trait in the house fly, Musca domestica, confers resistance to the rapid paralysis (knockdown) and lethal effects of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and pyrethroids. Flies with the kdr trait exhibit reduced neuronal sensitivity to these compounds, which are known to act at voltage-sensitive sodium channels of nerve membranes. To test the hypothesis that a mutation in a voltage-sensitive sodium channel gene confers the kdr phenotype, we have cloned genomic DNA corresponding to a segment of the house fly homologue of the para sodium channel gene of Drosophila melanogaster, identified restriction-site polymorphisms within this segment between the kdr strain 538ge and an inbred insecticide-susceptible lab stain, and developed a sensitive polymerase chain reaction-based diagnostic procedure to determine the sodium channel genotype of individual flies. A genetic linkage analysis performed with these molecular markers shows that the kdr trait is tightly linked (within about 1 map unit) to the voltage-sensitive sodium channel gene segment exhibiting the DNA sequence polymorphism. These findings provide genetic evidence for a mutation at or near a voltage-sensitive sodium channel gene as the basis for kdr resistance.
