Submitted to: Molecular and Cellular Proteomics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/27/2002
Publication Date: 9/1/2003
Citation: CANDAS, M., LOSEVA, O., OPPERT, B.S., KOSARAJU, P., BULLA, L.A. INSECT RESISTANCE TO BACILLUS THURINGIENSIS: ALTERATIONS IN THE INDIANMEAL MOTH LARVAL GUT PROTEOME. Molecular and Cellular Proteomics 2.1: 19-28. 2003. Interpretive Summary: Insect resistance to the microbial insecticides from Bacillus thuringiensis (Bt) is a major problem facing farmers and industries involved in the organic as well as transgenic control of insect pests. We studied the complete gut proteome (i.e., all of the proteins expressed in the midgut) of the Indianmeal moth in colonies susceptible and resistant to Bt. Differences in protein expression included increased and decreased levels of some proteins, and one protein was shifted in it's gel migration pattern. The overall picture suggests that the stress response to Bt insecticides involves a shift in oxidative metabolism. Therefore, resistance to Bt is complex. This information can be used to understand how insects develop resistance to Bt, to delay resistance development, as well as to identify new targets for insect control.
Technical Abstract: Insect resistance to the Cry toxins of Bacillus thuringiensis (Bt) has been examined previously using a number of traditional biochemical and molecular techniques. In this study, we utilized a proteomic approach involving two-dimensional differential gel electrophoresis, mass spectrometry and function-based activity profiling to examine changes in the gut proteins from the larvae of an Indianmeal moth (IMM, Plodia interpunctella) colony exhibiting resistance to Bt. We found a number of changes in the levels of midgut proteins that indicated increased glutathione utilization, elevation in oxidative metabolism and differential maintenance of energy balance within the midgut epithelial cells of the Bt-resistant IMM larva. Additionally, the electrophoretic migration pattern of a low-molecular mass acidic protein, an ortholog of F1F0-ATPase, was altered in the Bt-resistant insect indicating that variations in amino acid content or modifications of certain proteins also are important components of resistance in this colony. Furthermore, there was a dramatic decrease in the level of chymotrypsin-like proteinase in the membrane of the Bt-resistant larva that corresponded to a reduction in soluble proteinase activity, as was previously reported in this Bt-resistant colony. The proteomic analysis of larval gut proteins provided a useful approach for consolidating protein changes and physiological events associated with insect resistance to Bt. Our results support the hypothesis that physiological adaptation of insects and resistance to Bt is multi-faceted, including protein modification and changes in the synthesis of specific larval gut proteins. Increased oxidative metabolism may be an adaptive response of insects that undergo survival challenge and thus mediate detoxification as well as higher rates of generalized and localized mutations that enhance resistance and provide survival advantage.