Abstract：To find novel vip3 genes, the vip3-type genes in 72 Bt stains were identified by PCR method and high-resolution melting analysis(HRMA) system. The results indicated that three vip3 gene types, vip3Aa, vip3Af and vip3Ba were found in 18 positive strains. A full-length vip3 gene fragment, which obtained by PCR amplification with a pair of primers designed according to vip3-type gene sequences and DNA from T03B001(B. thuringiensis subsp. sumiyoshiensis) as template, was introduced into expression vector pEB and transformed into Escherichia coli Rosetta(DE3). At low temperatures, a peptide of 88 kD was expressed by IPTG induction. The encoded protein was composed of 789 amino acid rsidues. It shared a 96% sequence homology with Vip3Aa protein. This gene designated as vip3Aa39 by International Nomenclature Commitee of Bt endotoxin, GenBank accession No. was HMI17631. Vip3Aa11 protein was obtained in our previous study, 39 amino acid residues were found to be different between the Vip3Aa39 and Vip3Aa11 proteins. Insecticidal activities of soluble expressed products of vip3Aa39 and vip3Aa11 genes were tested against Agrotis ipsilon, Plutella xylostella, Helicoverpa armigera and Spodoptera exigua by feeding method. The bioassay results indicated that Vip3Aa39 had insecticidal activity against A.ipsilon with 50% lethal concentration(LC50) of 5.43 μg/mL compared to 73.62 μg/mL for Vip3Aa11; Vip3Aa39 showed insecticidal activity against P.xylostella with LC50 of 140.64 μg/mL while Vip3Aa11 protein had no activity against P.xylostella; Vip3Aa11 demonstrated insecticidal activity against H.armigera with LC50 of 35.18 μg/mL compared to 286.99 μg/mL for Vip3Aa39; Vip3Aa39 had insecticidal activity against S.exigua with LC50 of 2.02 μg/mL similar to 2.04 μg/mL for Vip3Aa11. The results indicated that insecticidal activity of Vip3Aa39 and Vip3Aa11 was different from each other against A.ipsilon, P.xylostella and H.armigera. Compared with the Vip3Aa11, Vip3Aa39 had high insecticidal activity against A.ipsilon and P.xylostella while showed low activity agaist H.armigera. Vip3Aa39 will provide more chocies to control agricultural pest, and it provide materials to study structure and insecticidal mechanism of the Vip3 protein.
