Molecular Mechanism for the Insecticidal Activity of Bacillus Thuringiensis

Bacillus thuringiensis crystal proteins are highly toxic to certain species of lepidopteran insects but are much less toxic to other lepidoteran species and usually have significantly lower toxicity to non-lepidopteran species. In addition, some lepidopteran species that initially were susceptible to Bacillus thuringiensis have developed resistance. Understanding the molecular mechanism for the insecticidal activity of Bacillus thuringiensis crystal proteins represents a significant area of research accomplishment. One rationale for this research is that such understanding will assist efforts to improve the toxicity of crystal proteins through protein engineering. Protein engineering efforts have been aided by two important findings on the mechanism of toxicity of crystal proteins. Briefly stated these findings are 1) Bacillus thuringiensis crystal proteins bind to cells lining the insect midgut; 2) Bound proteins form pores causing colloid osmotic lysis of the insect gut cells. It is presumed that lysis of gut cells results in insect death. This proposal will explore promising avenues of research which will add to the understanding of the mechanism of toxicity of Bacillus thuringiensis crystal proteins.