A deletion mutant ndv200 of the Bacillus thuringiensis vip3BR insecticidal toxin gene is a prospective candidate for the next generation of genetically modified crop plants resistant to lepidopteran insect damage.

Main conclusion Ectopic expression of a deletion mutant ( ndv200 ) of Bacillus thuringiensis vip3BR gene in tobacco plant provided almost complete protection against major crop pests cotton boll worm ( Helicoverpa armigera ), black cut worm ( Agrotis ipsilon ) and cotton leaf worm ( Spodoptera littoralis ). Whereas vip3BR transgenic tobacco plant failed to protect themselves from these insects and showed resistance towards cotton leaf worm only. An analogous form of the Bacillus thuringiensis vip3Aa insecticidal toxin gene, named vip3BR, was identified and characterized, and exhibited similar attributes to the well-known Vip3Aa toxin. Vip3BR possessed broad-spectrum lepidopteran-specific insecticidal properties effective against most major crop pests of the Indian subcontinent. A Vip3BR toxin protein N-terminal deletion mutant, Ndv200, showed increased insecticidal potency relative to the native toxin, which conferred efficacy against four major crop pests, including cotton boll worm (Helicoverpa armigera), black cut worm (Agrotis ipsilon), cotton leaf worm (Spodoptera littoralis), and rice yellow stem borer (Scirpophaga incertulas). Ligand blot analysis indicated the Ndv200 toxin recognized the same larval midgut receptors as the native Vip3BR toxin, but differed from receptors recognized by Cry1A toxins. In the present study, we tested the prospect of the vip3BR and ndv200 toxin gene as candidate in development of insect-resistant genetically engineered crop plants by generating transgenic tobacco plant. The study revealed that the ndv200 mutant of vip3BR insecticidal toxin gene is a strong and prospective candidate for the next generation of genetically modified crop plants resistant to lepidopteran insects.