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Applied and Environmental Microbiology, July 2006, p. 4796-4804, Vol. 72, No. 7
0099-2240/06/$08.00+0     doi:10.1128/AEM.02861-05
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Molecular and Insecticidal Characterization of a Cry1I Protein Toxic to Insects of the Families Noctuidae, Tortricidae, Plutellidae, and Chrysomelidae

Iñigo Ruiz de Escudero,¹ Anna Estela,² Manuel Porcar,^1, Clara Martínez,^1, José A. Oguiza,¹ Baltasar Escriche,² Juan Ferré,² and Primitivo Caballero^1*

Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain,¹ Departamento de Genética, Universitat de València, 46100 Burjassot, Spain²

Received 6 December 2005/ Accepted 8 May 2006

The most notable characteristic of Bacillus thuringiensis is its ability to produce insecticidal proteins. More than 300 different proteins have been described with specific activity against insect species. We report the molecular and insecticidal characterization of a novel cry gene encoding a protein of the Cry1I group with toxic activity towards insects of the families Noctuidae, Tortricidae, Plutellidae, and Chrysomelidae. PCR analysis detected a DNA sequence with an open reading frame of 2.2 kb which encodes a protein with a molecular mass of 80.9 kDa. Trypsin digestion of this protein resulted in a fragment of ca. 60 kDa, typical of activated Cry1 proteins. The deduced sequence of the protein has homologies of 96.1% with Cry1Ia1, 92.8% with Cry1Ib1, and 89.6% with Cry1Ic1. According to the Cry protein classification criteria, this protein was named Cry1Ia7. The expression of the gene in Escherichia coli resulted in a protein that was water soluble and toxic to several insect species. The 50% lethal concentrations for larvae of Earias insulana, Lobesia botrana, Plutella xylostella, and Leptinotarsa decemlineata were 21.1, 8.6, 12.3, and 10.0 µg/ml, respectively. Binding assays with biotinylated toxins to E. insulana and L. botrana midgut membrane vesicles revealed that Cry1Ia7 does not share binding sites with Cry1Ab or Cry1Ac proteins, which are commonly present in B. thuringiensis-treated crops and commercial B. thuringiensis-based bioinsecticides. We discuss the potential of Cry1Ia7 as an active ingredient which can be used in combination with Cry1Ab or Cry1Ac in pest control and the management of resistance to B. thuringiensis toxins.

Present address: Institut Cavanilles de Biodiversitat i Biologia Evolutiva, Universitat de València, Apartado Postal 22085, 46071 Paterna, Spain.

Present address: Institut Curie, UMR 144 CNRS Equipe de Morphogénèse Cellulaire et Progression Tumorale, 75005 Paris, France.

This article has been cited by other articles:

• Ruiz de Escudero, I., Estela, A., Escriche, B., Caballero, P. (2007). Potential of the Bacillus thuringiensis Toxin Reservoir for the Control of Lobesia botrana (Lepidoptera: Tortricidae), a Major Pest of Grape Plants. Appl. Environ. Microbiol. 73: 337-340 [Abstract] [Full Text]