Analysis, of Cry2A proteins encoded by genes cloned from indigenous isolates of Bacillus thuringiensis for toxicity against Helicoverpa armigera

摘要

The Cry2A proteins of Bacillus thuringiensis are promising candidates for management of resistance development in insects due to their differences from the currently used Cry1A proteins, in structure and insecticidal mechanism. The Cry2Aa and Cry2Ab proteins isolated from recombinant Escherichia coli strains harbouring indigenous cry2Aa and cry2Ab genes under the control of T7 promoter were tested for toxicity against Helicoverpa armigera (Hubner). In artificial diet bioassay, inclusions containing Cry2Aa and urea-solubilized Cry2Aa protein showed 100% mortality of H. armigera at a concentration of 650 and 100 ng ml(-1) after 48 and 72 h respectively. On the other hand., the Cry2Ab protein inclusions as well as urea-solubilized Cry2Ab protein were not toxic to H. armigera, probably due to lack of solubility in alkaline condition and improper folding after urea solubilization.