Cloning, characterization and expression of a novel haplotype cry2A-type gene from Bacillus thuringiensis strain SWK1, native to Himalayan valley Kashmir.

Bacillus thuringiensis (Bt) is a gram positive bacterium which is effectively being used in pest management strategies as an eco-friendly bioinsecticide. In the present study a new cry2A gene was cloned from a promising indigenous B. thuringiensis SWK1 strain previously characterized for its toxicity against Spodoptera litura and Helicoverpa armigera larvae. The nucleotide sequence of the cloned cry2A gene pointed out that the open reading frame has 1902 bases encoding a polypeptide of 634 amino acid residues with a probable molecular weight of 70kDa. Homology comparisons showed that the deduced amino acid sequence of Cry2A had a similarity of 94% compared to that of the known Cry2Aa protein in the NCBI database and this gene has been named as cry2Al1 by the B. thuringiensis δ-endotoxin Nomenclature Committee. cry2Al1 was ligated into pET 22b vector and expressed in Escherichia coli BL21 (DE3) pLysS under the control of T7 promoter induced by isopropyl-beta-d-thiogalactopyranoside (IPTG). SDS-PAGE analysis confirmed the expression of cry2Al1 as ∼65kDa protein. Insect pest bioassays with neonate larvae of S. litura and H. armigera showed that the purified Cry2Al1 are toxic to S. litura and H. armigera with LC50 2.448µg/ml and H. armigera with 3.374µg/ml respectively.

Cloning, characterization, and expression of a new cry2Ab gene from Bacillus thuringiensis strain 14-1.

Bacillus thuringiensis is the major source for transfer of genes to impart insect resistance in transgenic plants. Cry2A proteins of B. thuringiensis are promising candidates for management of resistance development in insects owing to their difference from the currently used Cry1A proteins, in structure and insecticidal mechanism. The cry2Ab gene was found to lack a functional promoter and, hence, is cryptic in nature. The cry2Ab7 gene was cloned from a new indigenous B. thuringiensis strain, 14-1. Nucleotide sequencing of the cry2Ab gene cloned from B. thuringiensis strain 14-1 revealed an open reading frame of 1902 bp. The deduced amino acid sequence of Cry2Ab of B. thuringiensis strain 14-1 showed a variation in three amino acid residues in comparison to the holotype sequence, Cry2Ab1. Expression of the newly cloned cry2Ab gene was studied in an acrystalliferous strain of B. thuringiensis (4Q7) by fusing the cry2Ab gene downstream of cry2Aa promoter and orf1 + orf2 sequences. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of a spore-crystal mixture obtained from transformants of B. thuringiensis strain 4Q7 showed production of Cry2Ab protein of about 65 kDa. Alkali solubilized Cry2Ab7 protein showed toxicity against Helicoverpa armigera neonates.