Expression and characterization of a recombinant Cry1Ac crystal protein fused with an insect-specific neurotoxin ω-ACTX-Hv1a in Bacillus thuringiensis.

In order to assess possible enhancement of biopesticide activity, the fusion gene of crystal protein gene cry1Ac with the insect-specific neurotoxin ω-ACTX-Hv1a gene and egfp was expressed in Bacillus thuringiensis acrystalliferous strain Cry-B under the control of the native gene expression system. The fusion recombinant Cry-B(1Ac-ACTX-EGFP) generally produced two or three small crystal-like inclusion bodies in each cell and the GFP signal could be clearly observed. A 166 kDa full-length fusion protein was identified by immunoblot analysis. Virulence of the fusion inclusions was at least fivefold higher toward larvae of Spodoptera exigua. These results demonstrated that a foreign protein could be expressed and accumulate as parasporal inclusions in B. thuringiensis by C-terminal fusion with the native endotoxin while retaining partial insecticidal activity.