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Published Online November 1, 2007
Science DOI: 10.1126/science.1146453

Reports

Submitted on June 13, 2007
Accepted on September 19, 2007

Engineering Modified Bt Toxins to Counter Insect Resistance

Mario Soberón 1*, Liliana Pardo-López 1, Idalia López 1, Isabel Gómez 1, Bruce E. Tabashnik 2, Alejandra Bravo 1*

1 Instituto de Biotecnología, Universidad Nacional Autónoma de México. Apdo. postal 510-3, Cuernavaca 62250, Morelos, Mexico.
2 Department of Entomology, University of Arizona, Tucson, AZ, USA.

* To whom correspondence should be addressed.
Mario Soberón , E-mail: mario{at}ibt.unam.mx
Alejandra Bravo , E-mail: bravo{at}ibt.unam.mx

Evolution of insect resistance threatens the effectiveness of Bacillus thuringiensis (Bt) toxins that are widely used in sprays and transgenic crops. Resistance to Bt toxins in some insects is linked with mutations that disrupt a toxin-binding cadherin protein. We show that susceptibility to Bt toxin Cry1Ab was reduced by cadherin gene silencing with RNA interference in Manduca sexta, confirming cadherin’s role in Bt toxicity. Native Cry1A toxins required cadherin to form oligomers, but modified Cry1A toxins lacking one alpha-helix did not. The modified toxins killed cadherin-silenced M. sexta and Bt-resistant Pectinophora gossypiella that had cadherin deletion mutations. Our findings suggest that cadherin promotes Bt toxicity by facilitating toxin oligomerization and demonstrate that the modified Bt toxins may be useful against pests resistant to standard Bt toxins.


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
The Outlook for Protein Engineering in Crop Improvement.
A. G. Rao (2008)
Plant Physiology 147, 6-12
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Bacillus thuringiensis Cry1Ac Toxin-Binding and Pore-Forming Activity in Brush Border Membrane Vesicles Prepared from Anterior and Posterior Midgut Regions of Lepidopteran Larvae.
A. Rodrigo-Simon, S. Caccia, and J. Ferre (2008)
Appl. Envir. Microbiol. 74, 1710-1716
   Abstract »    Full Text »    PDF »
Biotechnological Prospects for Engineering Insect-Resistant Plants.
J. A. Gatehouse (2008)
Plant Physiology 146, 881-887
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Science. ISSN 0036-8075 (print), 1095-9203 (online)