A single amino acid change in the para sodium channel protein is associated with knockdown-resistance (kdr) to pyrethroid insecticides in German cockroach

Previous genetic and pharmacological studies suggest that knockdown-resistance (kdr) to pyrethroid insecticides likely results from a mutation(s) in the para sodium channel gene, In this study, para sodium channel genes from an insecticide-susceptible German cockroach strain, CSMA, and a kdr-type German cockroach strain, Ectiban-R, were cloned and sequenced, Comparison of the nucleotide sequences of papa(CSMA) and para(Ectiban-R) revealed two nucleotide differences at nt 1491 and nt 2979, respectively, Only the difference at nt 2979 (G in para(CSMA) and C in para(Ectiban-R)) resulted in an amino acid change (Leu(993) in CSMA and Phe(993) in Ectiban-R), Leu(993)/Phe(993) is located in the highly conserved membrane-spanning segment 6 of domain II (IIS6). Furthermore, reverse transcription-polymerase chain reaction (RT-PCR) sequence analysis using another two insecticide-susceptible and one kdr German cockroach strain, revealed that C-2979 was specifically associated with kdr resistant strains, whereas only G(2979) was present in all susceptible strains, These results suggest that a single amino acid change from Leu(993) to Phe(993) is responsible for the kdr-type resistance in German cockroach. The sequences reported in this paper have been deposited in the Genbank database (accession nos U73583 and U73584). (C) 1997 Elsevier Science Ltd.