Chimeric vip3Aa16TC Gene Encoding the Toxic Core of the Vegetative Insecticidal Protein Enhanced Bacillus thuringiensis Entomopathogenicity

Abstract

Vip3 insecticidal protein is produced by Bacillus thuringiensis during the vegetative stage. Its proteolysis by the midgut juice of susceptible larvae formed four major products of approximately 66, 45, 33 and 22 kDa. In this study, we cloned the vip3Aa16TC DNA encoding the “Vip3Aa16 toxic core (TC)” of 33 kDa corresponding to the Vip3Aa16 region from amino acid 200 to 456. The vip3Aa16TC chimeric gene carried by the pHT-vip3Aa16TC plasmid was under the control of the sporulation dependent promoters (BtI-BtII) and the Shine Dalgarno sequence of cry1Ac gene as well as the cry1Ia gene terminator. Western-blot analysis of the culture supernatants of the recombinant B. thuringiensis strain detected Vip3Aa16TC after growing for 14 to 56 h proving that this protein can be produced without the Vip3 amino- and carboxy-terminal regions. Interestingly, the preservation of the Vip3Aa16TC toxicity against the polyphagous lepidopteran Spodoptera littoralis makes it a promising polypeptide for the pest biological control.

Keywords

• Bacillus thuringiensis
• Spodoptera littoralis
• Vip3Aa16TC