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Applied and Environmental Microbiology, April 2006, p. 2594-2600, Vol. 72, No. 4
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.4.2594-2600.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Toxicity and Mode of Action of Bacillus thuringiensis Cry Proteins in the Mediterranean Corn Borer, Sesamia nonagrioides (Lefebvre)

Joel González-Cabrera,¹ Gema P. Farinós,² Silvia Caccia,³ Mercedes Díaz-Mendoza,² Pedro Castañera,² Maria Giovanna Leonardi,³ Barbara Giordana,³ and Juan Ferré^1*

Departamento de Genética, Facultad de CC. Biológicas, Universidad de Valencia, Valencia, Spain,¹ Departamento de Biología de Plantas, Laboratorio de Interacciones Planta-Insecto, Centro de Investigaciones Biológicas-C.S.I.C., Madrid, Spain,² Dipartimento di Biologia, Università degli Studi di Milano, Milan, Italy³

Received 17 November 2005/ Accepted 25 January 2006

Sesamia nonagrioides is one of the most damaging pests of corn in Spain and other Mediterranean countries. Bt corn expressing the Bacillus thuringiensis Cry1Ab toxin is being grown on about 58,000 ha in Spain. Here we studied the mode of action of this Cry protein on S. nonagrioides (binding to specific receptors, stability of binding, and pore formation) and the modes of action of other Cry proteins that were found to be active in this work (Cry1Ac, Cry1Ca, and Cry1Fa). Binding assays were performed with ¹²⁵I- or biotin-labeled toxins and larval brush border membrane vesicles (BBMV). Competition experiments indicated that these toxins bind specifically and that Cry1Aa, Cry1Ab, and Cry1Ac share a binding site. Cry1Ca and Cry1Fa bind to different sites. In addition, Cry1Fa binds to Cry1A's binding site with very low affinity and vice versa. Binding of Cry1Ab and Cry1Ac was found to be stable over time, which indicates that the observed binding is irreversible. The pore-forming activity of Cry proteins on BBMV was determined using the voltage-sensitive fluorescent dye DiSC₃(5). Membrane permeability increased in the presence of the active toxins Cry1Ab and Cry1Fa but not in the presence of the nonactive toxin Cry1Da. In terms of resistance management, based on our results and the fact that Cry1Ca is not toxic to Ostrinia nubilalis, we recommend pyramiding of Cry1Ab with Cry1Fa in the same Bt corn plant for better long-term control of corn borers.

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* Corresponding author. Mailing address: Departamento de Genética, Facultad de CC. Biológicas, Dr. Moliner 50, 46100-Burjassot, Valencia, Spain. Phone: (34) 96 354 4506. Fax: (34) 96 354 3029. E-mail: Juan.Ferre{at}uv.es.

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Applied and Environmental Microbiology, April 2006, p. 2594-2600, Vol. 72, No. 4
0099-2240/06/$08.00+0     doi:10.1128/AEM.72.4.2594-2600.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Rodrigo-Simon, A., Caccia, S., Ferre, J. (2008). Bacillus thuringiensis Cry1Ac Toxin-Binding and Pore-Forming Activity in Brush Border Membrane Vesicles Prepared from Anterior and Posterior Midgut Regions of Lepidopteran Larvae. Appl. Environ. Microbiol. 74: 1710-1716 [Abstract] [Full Text]