Skip to Main Content
Changes in protease activity and Cry3Aa toxin binding in the Colorado potato beetle: implications for insect resistance to Bacillus thuringiensis toxinsAuthor(s): Olga Loseva; Mohamed Ibrahim; Mehmet Candas; C. Noah Koller; Leah S. Bauer; Lee A. Jr. Bulla
Source: Insect Biochemistry and Molecular Biology. 32: 567?577.
Publication Series: Scientific Journal (JRNL)
Station: Northern Research Station
PDF: View PDF (208.03 KB)
DescriptionWidespread commercial use of Bacillus thuringiensis Cry toxins to control pest insects has increased the likelihood for development of insect resistance to this entomopathogen. In this study, we investigated protease activity profiles and toxin-binding capacities in the midgut of a strain of Colorado potato beetle (CPB) that has developed resistance to the Cry3Aa toxin of B. thuringiensis subsp. tenebrionis. Histological examination revealed that the structural integrity of the midgut tissue in the toxin-resistant (R) insect was retained whereas the same tissue was devastated by toxin action in the susceptible (S) strain. Function-based activity profiling using zymographic gels showed specific proteolytic bands present in midgut extracts and brush border membrane vesicles (BBMV) of the R strain not apparent in the S strain. Aminopeptidase activity associated with insect midgut was higher in the R strain than in the S strain. Enzymatic processing of toxin did not differ in either strain and, apparently, is not a factor in resistance. BBMV from the R strain bound ~60% less toxin than BBMV from the S strain, whereas the kinetics of toxin saturation of BBMV was 30 times less in the R strain than in the S strain. However, homologous competition inhibition binding of 125I-Cry3Aa to BBMV did not reveal any differences in binding affinity (Kd~0.1 µM) between the S and R strains. The results indicate that resistance by the CPB to the Cry3Aa toxin correlates with specific alterations in protease activity in the midgut as well as with decreased toxin binding. We believe that these features reflect adaptive responses that render the insect refractory to toxin action, making this insect an ideal model to study host innate responses and adaptive changes brought on by bacterial toxin interaction.
- Check the Northern Research Station web site to request a printed copy of this publication.
- Our on-line publications are scanned and captured using Adobe Acrobat.
- During the capture process some typographical errors may occur.
- Please contact Sharon Hobrla, firstname.lastname@example.org if you notice any errors which make this publication unusable.
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationLoseva, Olga; Ibrahim, Mohamed; Candas, Mehmet; Koller, C. Noah; Bauer, Leah S.; Bulla, Lee A. Jr. 2002. Changes in protease activity and Cry3Aa toxin binding in the Colorado potato beetle: implications for insect resistance to Bacillus thuringiensis toxins. Insect Biochemistry and Molecular Biology. 32: 567?577.
KeywordsColorado potato beetle, Bacillus thuringiensis, Cry3Aa, protease, resistance
- Comparative analysis of Bacillus thuringiensis toxin binding to gypsy moth, browntail moth, and douglas-fir tussock moth midgut tissue sections using fluorescence microscopy
- Bacillus thuringiensis toxins trigger receptor shedding from gypsy moth midgut cells
- Bacillus thuringiensis pore-forming toxins trigger massive shedding of GPI-anchored aminopeptidase N from gypsy moth midgut epithelial cells
XML: View XML