Target modification as a molecular mechanism of pyrethroid resistance in Drosophila melanogaster

“Knock down” resistance (kdr) to the pyrethroid deltamethrin was investigated using susceptible (Tübingen) and resistant (TübingenDDT) strains of Drosophila melanogaster. Toxicological and pharmacological data show that resistance involves a modification of the affinity of the insecticide for its receptor site on the voltage-dependent sodium channel. Genetic studies indicate that the kdr factor is linked to the second chromosome where one sodium channel gene, sch, is located. Cloning and sequencing the alleles of this gene from both strains revealed a single substitution that may be responsible for the loss of toxicity of deltamethrin in the resistant strain.