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Cross-resistance and mechanism of resistance to Cry1Ab toxin from Bacillus thuringiensis in a field-derived strain of European corn borer, Ostrinia nubilalis
Authors:Crespo André L B  Rodrigo-Simón Ana  Siqueira Herbert A A  Pereira Eliseu J G  Ferré Juan  Siegfried Blair D
Affiliation:a Department of Entomology, University of Nebraska, Lincoln, NE 68583-0816, USA
b Department of Genetics, University of Valencia, Dr. Moliner 50, 46100 Burjassot (Valencia), Spain
c Departamento de Agronomia-Entomologia, Universidade Federal Rural de Pernambuco, Recife, PE 52171-900, Brazil
d Departamento de Biologia Animal, Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil
Abstract:
The cross-resistance spectrum and biochemical mechanism of resistance to the Bacillus thuringiensis Cry1Ab toxin was studied in a field-derived strain of Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) that was further selected in the laboratory for high levels (>1000-fold) of resistance to Cry1Ab. The resistant strain exhibited high levels of cross-resistance to Cry1Ac and Cry1Aa but only low levels of cross-resistance (<4-fold) to Cry1F. In addition, there was no significant difference between the levels of resistance to full-length and trypsin-activated Cry1Ab protein. No differences in activity of luminal gut proteases or altered proteolytic processing of the toxin were observed in the resistant strain. Significantly reduced binding of radiolabeled Cry1Aa was observed in the resistant strain whereas binding of Cry1Ab and Cry1Ac was practically the same in both resistant and susceptible strains. The interpretation of the overall data seems to suggest the involvement of an alteration in the binding of Cry1A toxins to a common receptor, which is more clearly revealed by the binding assays using radiolabeled Cry1Aa.
Keywords:Bacillus thuringiensis   Bt maize   Ostrinia nubilalis   Resistance   Toxin binding   Luminal gut proteases
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