RNA Interference to Control Asian Corn Borer Using dsRNA from a Novel Glutathione-S-Transferase Gene of Ostrinia furnacalis (Lepidoptera: Crambidae).

Glutathione-S-transferases (GST) comprise a multifunctional protein superfamily, which plays important roles as detoxifiers and antioxidants in insects. The GST in Asian corn borer has not been previously characterized. In this study, we cloned, characterized, and expressed the complete GST genes from the midgut of Asian corn borer. Furthermore, we designed htL4440-OfGST vector to exploit this gene for RNA interference (RNAi) strategy to control this pest. A complete GST cDNA sequence in Asian corn borer was obtained by reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends technology. The gene was 887bp in length and contained a 705bp open reading frame and 5' UTR and 3' UTR lengths of 89 and 93bp, respectively. The putative sequence encoded a putative 234 amino acid residue peptide and had a predicted molecular weight of ~26kDa. The GST protein of Asian corn borer is hydrophilic and may have a 30 amino acid signal peptide with a cleavage site between L30 and K31. A recombination vector pET28a-OfGST was constructed for purification and antibody preparation. Western blotting analysis showed that this protein reached the maximum expression level around 24 h in Asian corn borer larvae fed the plant toxin 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one. A second vector, htL4440-OfGST, was constructed to generate the dsRNA of the GST gene. A larval feeding bioassay showed that the expressed dsRNA significantly reduced the detoxification ability of Asian corn borer larvae and increased mortality rate up to 54%. Our data indicated that GST plays very important roles in detoxifying in Asian corn borer and can be used as an RNAi method to control this pest in the field.