Cloning and characterization of a novel Cry1A toxin from Bacillus thuringiensis with high toxicity to the Asian corn borer and other lepidopteran insects

A novel cry1A was cloned from Bacillus thuringiensis strain BT8 and expressed in the B. thuringiensis acrystalliferous mutant HD73-. The gene, designated cry1Ah1, encoded a protein with a molecular weight of 134 kDa. Reverse transcriptase-PCR and Western blotting showed that Cry1Ah was expressed in the host strain BT8. The toxin expressed in HD73- exhibited high toxicity against lepidopteran larvae of Ostrinia furnacalis, Helicoverpa armigera, Chilo suppressalis, and Plutella xylostella. The 50% lethal concentrations (LC50s) were 0.05, 1.48, 0.98 µg g-1 and 1.52 µg mL-1, respectively. The LC50s of Cry1Ah were significantly lower than that of Cry1Ac for H. armigera, C. suppressalis, and O. furnacalis, and lower than that of Cry1Ab and Cry1Ie for Ostrinia furnacalis. The high toxicity against a range of pest species makes this novel toxin a potential candidate for insect biocontrol.