Comparative characterization of two putative duplicated sodium channel genes in the red flour beetle, Tribolium castaneum.

The insect voltage-gated sodium channel is the primary target of pyrethroids and novel efficient insecticides such as indoxacarb and metaflumizone. In this study, we cloned and characterized two putative sodium channel genes, TcNav1 and TcNav2, in Tribolium castaneum. The composite TcNav1 and TcNav2 encode a protein of 2045 and 2037 amino acid residues, sharing 76.1% and 75.5% amino acid identity with Drosophila para, respectively. Comparative analysis of genomic organization showed that TcNav1 and TcNav2 contain 26 and 27 exons, respectively. Analysis of the expression patterns showed that the mRNA levels of TcNav1 and TcNav2 were predominantly expressed in the head. RNAi-mediated knockdown of both TcNav1 and TcNav2 adversely affected adult emergence and significantly decreased sensitivity to deltamethrin. Significantly reduced pupation rate and sensitivity to beta-cypermethrin were observed after injection of siRNA targeting TcNav1 but not TcNav2. Taken together, we provide evidence that sodium channel gene has undergone duplication in T. castaneum, resulting in diversified developmental and toxicological functions.