Cloning and characterization of truncated cry1Ab gene from a new indigenous isolate of Bacillus thuringiensis

The insecticidal crystal protein(s) encoded by cry gene(s) of Bacillus thuringiensis (Bt) have been used for insect control both as biopesticides and in transgenic plants. A new 3'-truncated cry1Ab gene was cloned from an indigenous isolate of Bt, A19-31. Nucleotide sequencing and homology search revealed that the deduced amino acid sequence of Cry1Ab toxin of Bt strain A19-31 had a variation of two amino acid residues with the holotype sequence, Cry1Ab1. Expression of the 3'-truncated cry1Ab gene was studied in an acrystalliferous strain of Bt (4Q7). SDS-PAGE and immunostrip analysis of spore-crystal mixture revealed a low level expression of the 3'-truncated cry1Ab gene. Insecticidal activity assay showed that the recombinant 3'-truncated cry1Ab gene product was toxic to larvae of both Helicoverpa armigera and Spodoptera litura.