Molecular characterization of a sodium channel gene in the rice leaffolder, Cnaphalocrocis medinalis (Guenée)

Abstract: Voltage-gated sodium channels are the targets of several important classes of synthetic insecticides including pyrethroids, indoxacarb and metaflumizone. The rice leaffolder, Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), is an important rice insect pest throughout Southeast Asia. In this study, we report the cDNA sequence (named as CmNav) of C. medinalis sodium channel α-subunit homologous to the para gene from Drosophila melanogaster. The 5643-bp contiguous CmNav gene sequence encoded 1877 amino acid residues, which spans the 5′ UTR and covers the open reading frame from the start codon to beyond the last transmembrane segment of transmembrane domain IV (IV S6). The deduced amino acid sequence of CmNav shares 79% identity with Drosophila para. All hallmarks of sodium channel proteins are conserved in the CmNav including an overall organization of four large hydrophobic domains and the sodium channel’s DEKA selectivity filter motif. In addition, two conserved alternative splicing sites were identified in the CmNav gene, which form the optional exon B and the mutually exclusive exon K/L, respectively. Diagnostic PCR showed that the inclusion frequencies of alternative exons differed between developmental stages or adult anatomical regions. [Copyright &y& Elsevier]