Submitted to: Journal of Insect Biochemistry and Molecular Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2004
Publication Date: 10/16/2004
Citation: Li, H., Oppert, B.S., Higgins, R.A., Huang, F., Zhu, K.Y., Buschman, L.L. 2004. Comparative analysis of proteinase activities of bacillus thuringiensis-resistant and -susceptible ostrinia nubilalis (lepidoptera: crambidae). Journal of Insect Biochemistry and Molecular Biology 34: 753-762. Interpretive Summary: Transgenic corn with genes encoding insecticidal proteins from Bacillus thuringiensis (Bt) control a major corn pest, the European corn borer. Bt-resistant populations of European corn borer may reduce the efficacy of transgenic corn. This paper describes the digestive proteinases of the European corn borer which process the toxin to an active form. Proteinases in Bt-resistant European corn borer were less active resulting in lower levels of activated toxin. Understanding how insects adapt to Bt toxins and become less sensitive will provide the information for scientists, regulatory agencies, and extension to effectively manage resistance to Bt in the field.
Technical Abstract: Proteinase activities were compared in soluble and membrane fractions of gut tissues of Bacillus thuringiensis-resistant and -susceptible Ostrinia nubilalis larvae. The soluble trypsin-like proteinase activity of the resistant strain was reduced 56%, significantly lower than that of the susceptible strain. Serine proteinases from soluble fractions of Bt-susceptible larvae were more active than those of Bt-resistant larvae. In addition, the number and relative molecular masses of soluble and membrane proteinases were different. However, there were no significant differences in the activities of selected serine proteinases and aminopeptidases extracted from Bt-susceptible and -resistant gut membranes. Cry1Ab protoxin processing by soluble proteinase extracts of the resistant strain was reduced 20-30% when compared to that of the susceptible strain. Reduced protoxin processing due to the reduced activities of Bt protoxin activation proteinases may be associated with resistance to Bt toxin in this resistant O. Nubilalis strain.