Insect resistance to Bacillus thuringiensis (Bt) toxins has been examined using a number of traditional biochemical and molecular approaches. The limitation of each approach has been the assessment of individual steps in the toxin mode of action. Toxin binding studies have focused on toxin interactions with the membrane, and proteinase studies have centered on the activation and/or degradation of toxin. To overcome these shortcomings, we have used proteome analyses to understand physiological changes in a resistant insect, obtaining information related to the overall condition promoting resistance. A comparison of gut epithelial proteins in Bt-susceptible and -resistant Indianmeal moth, Plodia interpunctella, was performed using dual-fluorescent labeling, two-dimensional gel electrophoresis, and mass spectrometry (MALDI-TOF). A significant decrease in a chymotrypsin-like proteinase was observed in the Bt-resistant colony, which agrees with previous reports of proteinase deficiencies in this insect colony. Increases were observed in the levels of a vacuolar ATPase and an aminopeptidase in larvae from the Bt-resistant colony. In Bt-susceptible larvae, an unidentified acidic protein of low molecular mass localized to a different area of the gel than the same protein from Bt-resistant larvae. Therefore, up and down regulation of protein expression, as well as chemical alteration to proteins resulting in altered migration patterns, are all components of the physiological adaptations in this resistant insect. These data confirm that resistance to Bt is multifactorial in this colony of Bt-resistant P. interpunctella. Alterations in the protein expression profile contribute to the sustained resistance state, providing protection to the entomopathogenic effects of Bt.
Species 1: Lepidoptera Pyralidae Plodia interpunctella (Indian meal moth)
Keywords: Proteomics, Bt resistance
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