Binding site alteration is responsible for field-isolated resistance to Bacillus thuringiensis Cry2A insecticidal proteins in two Helicoverpa species
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Binding site alteration is responsible for field-isolated resistance to Bacillus thuringiensis Cry2A insecticidal proteins in two Helicoverpa species

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Binding site alteration is responsible for field-isolated resistance to Bacillus thuringiensis Cry2A insecticidal proteins in two Helicoverpa species

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dc.contributor.author Caccia, Silvia
dc.contributor.author Hernández Rodríguez, Carmen Sara
dc.contributor.author Mahon, Rod J.
dc.contributor.author Downes, Sharon
dc.contributor.author James, William
dc.contributor.author Bautsoens, Nadine
dc.contributor.author Van Rie, Jeroen
dc.contributor.author Ferré Manzanero, Juan
dc.date.accessioned 2010-07-13T07:56:35Z
dc.date.available 2010-07-13T07:56:35Z
dc.date.issued 2010
dc.identifier.uri http://hdl.handle.net/10550/15982
dc.description.abstract Background Evolution of resistance by target pests is the main threat to the long-term efficacy of crops expressing Bacillus thuringiensis (Bt) insecticidal proteins. Cry2 proteins play a pivotal role in current Bt spray formulations and transgenic crops and they complement Cry1A proteins because of their different mode of action. Their presence is critical in the control of those lepidopteran species, such as Helicoverpa spp., which are not highly susceptible to Cry1A proteins. In Australia, a transgenic variety of cotton expressing Cry1Ac and Cry2Ab (Bollgard II) comprises at least 80% of the total cotton area. Prior to the widespread adoption of Bollgard II, the frequency of alleles conferring resistance to Cry2Ab in field populations of Helicoverpa armigera and Helicoverpa punctigera was significantly higher than anticipated. Colonies established from survivors of F2 screens against Cry2Ab are highly resistant to this toxin, but susceptible to Cry1Ac. Methodology/Principal Findings Bioassays performed with surface-treated artificial diet on neonates of H. armigera and H. punctigera showed that Cry2Ab resistant insects were cross-resistant to Cry2Ae while susceptible to Cry1Ab. Binding analyses with 125I-labeled Cry2Ab were performed with brush border membrane vesicles from midguts of Cry2Ab susceptible and resistant insects. The results of the binding analyses correlated with bioassay data and demonstrated that resistant insects exhibited greatly reduced binding of Cry2Ab toxin to midgut receptors, whereas no change in 125I-labeled-Cry1Ac binding was detected. As previously demonstrated for H. armigera, Cry2Ab binding sites in H. punctigera were shown to be shared by Cry2Ae, which explains why an alteration of the shared binding site would lead to cross-resistance between the two Cry2A toxins. Conclusion/Significance This is the first time that a mechanism of resistance to the Cry2 class of insecticidal proteins has been reported. Because we found the same mechanism of resistance in multiple strains representing several field populations, we conclude that target site alteration is the most likely means that field populations evolve resistance to Cry2 proteins in Helicoverpa spp. Our work also confirms the presence in the insect midgut of specific binding sites for this class of proteins. Characterizing the Cry2 receptors and their mutations that enable resistance could lead to the development of molecular tools to monitor resistance in the field. en
dc.language.iso en en
dc.relation http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2848615/pdf/pone.0009975.pdf en
dc.source Caccia, S; Hernández-Rodríguez, C.S.; Mahon, R.J.; Downes, S.; James, W.; Bautsoens, N.; Van Rie, J.; Ferré, J. Binding site alteration is responsible for field-isolated resistance to Bacillus thuringiensis Cry2A insecticidal proteins in two Helicoverpa species. En PLoS ONE 5(4), 2010,: e9975. en
dc.subject Bacillus thuringiensis; Binding site alteration; Helicoverpa species en
dc.title Binding site alteration is responsible for field-isolated resistance to Bacillus thuringiensis Cry2A insecticidal proteins in two Helicoverpa species en
dc.type info:eu-repo/semantics/article en
dc.type info:eu-repo/semantics/publishedVersion en
dc.subject.unesco UNESCO::CIENCIAS DE LA VIDA::Biología de insectos (Entomología)::Entomología general en
dc.identifier.doi 10.1371/journal.pone.0009975 en
dc.description.private silcac@uv.es; ferrej@uv.es en
dc.identifier.idgrec 057965 en

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