Novel point mutations in the German cockroach para sodium channel gene areassociated with knockdown resistance (kdr) to pyrethroid insecticides

Knockdown resistance (kdr) to pyrethroid insecticides has been attributed t o point mutations in the para sodium channel gene in more than a half dozen insect pest species. In this study, we identified two novel para mutations in five highly resistant kdr-type German cockroach strains. The two mutati ons, from glutamic acid (E434) to lysine (K434) and from cysteine (C764) to arginine (R764), respectively, are located in the first intracellular link er connecting domains I and II. E434K is located near the beginning of the linker (closest to domain I), whereas C764R is found toward the end of the linker (closest to domain II). Two additional mutations from aspartic acid (D58) to glycine (G58), and from proline (P1880) to leucine (L1888), respec tively, were found in one of the resistant strains. The four mutations coex ist with the previously identified leucine to phenylalanine (L993F) kdr mut ation in IIS6, and are present only in the highly resistant individuals of a given strain. These findings suggest that these mutations might be respon sible for high levels of knockdown resistance toward pyrethroid insecticide s in the German cockroach. (C) 2000 Elsevier Science Ltd. All rights reserv ed.