A valine421 to methionine mutation in IS6 of the hscp voltage-gated sodium channel associated with pyrethroid resistance in Heliothis virescens F.

Multiple mutations in a locus encoding a voltage-gated sodium channel have been predicted for pyrethroid resistance in insects. Previously we reported a mutation associated with pyrethroid resistance, Leu1029 to His, in domain II transmembrane segment S6 (IIS6) of the Heliothis virescens F. sodium channel (para homologue) hscp locus. Sequence analysis of additional resistance haplotypes 5' to this mutation in the hscp locus has uncovered a G to A transition leading to a Val to Met mutation at amino acid position 421 in IS6 (V421M, numbering from Drosophila para). The V421M mutation is found only in a unique resistant haplotype, but not in two susceptible and a distinct resistant haplotype carrying the L1029H mutation. Implications of this finding in the evolution and mechanisms of pyrethroid resistance are discussed.