Binding of Bacillus thuringiensis proteins to a laboratory-selected line of Heliothis virescens

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 20; pp. 8930 - 8933
• Main Authors: MacIntosh, S.C. (Monsanto Agricultural Company, Saint Lousi, MO), Stone, T.B, Jokerst, R.S, Fuchs, R.L
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 15.10.1991; National Acad Sciences
• Subjects: Animals; BACILLUS THURINGIENSIS; Bacillus thuringiensis - genetics; Bacillus thuringiensis - metabolism; BACTERIA; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacterial Proteins - pharmacology; Bacterial Toxins; Bacteriology; Binding, Competitive; Biological and medical sciences; Digestive System - metabolism; Endotoxins; Fundamental and applied biological sciences. Psychology; Genes, Bacterial; HELIOTHIS VIRESCENS; Hemolysin Proteins; Insect colonies; Insect control; Insect development; Insect genetics; Insect larvae; Insect pests; Insect proteins; INSECTICIDAS; INSECTICIDE; Kinetics; Larva; Lepidoptera; Lepidoptera - drug effects; Lepidoptera - metabolism; Microbiology; Microvilli - metabolism; Mode of action; Noctuidae; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Pest Control, Biological; Protein Binding; PROTEINAS; PROTEINAS UNICELULARES; PROTEINE; PROTEINE MICROBIOLOGIQUE; Receptors; RESISTANCE AUX PRODUITS CHIMIQUES; RESISTENCIA QUIMICA; Heliothis virescens; Insecticide; Insecta; Bacillus thuringiensis; Bacillaceae; Biological activity; Proteins; Brush border; Membrane receptor; Binding capacity; Sensitivity resistance; Bacillales; Arthropoda; Lepidoptera; Bacteria; Noctuidae; Invertebrata; Mechanism of action
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.20.8930

A laboratory-selected colony of Heliothis virescens displaying a 20- to 70-fold level of resistance to Bacillus thuringiensis proteins was evaluated to identify mechanism(s) of resistance. Brush-border membrane vesicles were isolated from larval midgut epithelium from the susceptible and resistant strains of H. virescens. Two B. thuringiensis proteins, CryIA(b) and CryIA(c), were iodinated and shown to specifically bind to brush-border membrane vesicles of both insect strains. Multiple changes in the receptor-binding parameters were seen in the resistant strain as compared with the susceptible strain. A 2- to 4-fold reduction in binding affinity was accompanied by a 4- to 6-fold increase in binding-site concentration for both proteins. Although these two B. thuringiensis proteins competed for the same high-affinity binding site, competition experiments revealed different receptor specificity toward these proteins in the resistant H. virescens line. The H. virescens strains were not sensitive to a coleopteran-active protein, CryIIIA, nor did these proteins compete with the CryIA proteins for binding. Complexity of the mechanism of resistance is consistent with the complex mode of action of B. thuringiensis proteins.