title: Insecticidal spectrum and mode of action of the Bacillus thuringiensis Vip3Ca insecticidal protein.
abstract: The Vip3Ca protein, discovered in a screening of Spanish collections of Bacillus thuringiensis, was known to be toxic to Chrysodeixis chalcites, Mamestra brassicae and Trichoplusia ni. In the present study, its activity has been tested with additional insect species and we found that Cydia pomonella is moderately susceptible to this protein. Vip3Ca (of approximately 90kDa) was processed to an approximately 70kDa protein when incubated with midgut juice in all tested species. The kinetics of proteolysis correlated with the susceptibility of the insect species to Vip3Ca. The activation was faster to slower in the following order: M. brassicae (susceptible), Spodoptera littoralis (moderately susceptible), Agrotis ipsilon and Ostrinia nubilalis (slightly susceptible). Processing Vip3Ca by O. nubilalis or M. brassicae midgut juice did not significantly changed its toxicity to either insect species, indicating that the low susceptibility of O. nubilalis is not due to a problem in the midgut processing of the toxin. M. brassicae larvae fed with Vip3Ca showed binding of this toxin to the apical membrane of the midgut epithelial cells. Histopathological inspection showed sloughing of the epithelial cells with further disruption, which suggests that the mode of action of Vip3Ca is similar to that described for Vip3Aa. Biotin-labeled Vip3Ca and Vip3Aa bound specifically to M. brassicae brush border membrane vesicles and both toxins competed for binding sites. This result suggests that insects resistant to Vip3A may also be cross-resistant to Vip3C, which has implications for Insect Resistance Management (IRM).
authors.affiliation: Estructura de Recerca Interdisciplinar en Biotecnología y Biomedicina (ERI BIOTECMED), Departamento de Genética, Facultad de Ciencias Biológicas, Universitat de València, 46100 Burjassot, Spain.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Gomis-Cebolla
authors.affiliation: Instituto de Agrobiotecnología, CSIC-UPNA, Gobierno de Navarra, Avda. de Pamplona nº 123, 31192 Mutilva, Navarra, Spain; Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain.
authors.forename: Iñigo
authors.initials: I
authors.lastname: Ruiz de Escudero
authors.affiliation: Estructura de Recerca Interdisciplinar en Biotecnología y Biomedicina (ERI BIOTECMED), Departamento de Genética, Facultad de Ciencias Biológicas, Universitat de València, 46100 Burjassot, Spain.
authors.forename: Natalia Mara
authors.initials: NM
authors.lastname: Vera-Velasco
authors.affiliation: Estructura de Recerca Interdisciplinar en Biotecnología y Biomedicina (ERI BIOTECMED), Departamento de Genética, Facultad de Ciencias Biológicas, Universitat de València, 46100 Burjassot, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Hernández-Martínez
authors.affiliation: Estructura de Recerca Interdisciplinar en Biotecnología y Biomedicina (ERI BIOTECMED), Departamento de Genética, Facultad de Ciencias Biológicas, Universitat de València, 46100 Burjassot, Spain.
authors.forename: Carmen Sara
authors.initials: CS
authors.lastname: Hernández-Rodríguez
authors.affiliation: Instituto de Agrobiotecnología, CSIC-UPNA, Gobierno de Navarra, Avda. de Pamplona nº 123, 31192 Mutilva, Navarra, Spain.
authors.forename: Tomás
authors.initials: T
authors.lastname: Ceballos
authors.affiliation: Instituto de Agrobiotecnología, CSIC-UPNA, Gobierno de Navarra, Avda. de Pamplona nº 123, 31192 Mutilva, Navarra, Spain; Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain.
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Palma
authors.affiliation: Estructura de Recerca Interdisciplinar en Biotecnología y Biomedicina (ERI BIOTECMED), Departamento de Genética, Facultad de Ciencias Biológicas, Universitat de València, 46100 Burjassot, Spain.
authors.forename: Baltasar
authors.initials: B
authors.lastname: Escriche
authors.affiliation: Instituto de Agrobiotecnología, CSIC-UPNA, Gobierno de Navarra, Avda. de Pamplona nº 123, 31192 Mutilva, Navarra, Spain; Laboratorio de Entomología Agrícola y Patología de Insectos, Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain.
authors.forename: Primitivo
authors.initials: P
authors.lastname: Caballero
authors.affiliation: Estructura de Recerca Interdisciplinar en Biotecnología y Biomedicina (ERI BIOTECMED), Departamento de Genética, Facultad de Ciencias Biológicas, Universitat de València, 46100 Burjassot, Spain. Electronic address: juan.ferre@uv.es.
authors.forename: Juan
authors.initials: J
authors.lastname: Ferré
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism*; D007305:Insecticide Resistance; D007306:Insecticides; D009036:Moths; D010572:Pest Control, Biological / Q000379:methods
chemical_list: D001426:Bacterial Proteins; D007306:Insecticides; C447139:Vip3A protein, Bacillus thuringiensis
keywords: Bioinsecticides; Crop protection; Histological localization; Insect pest control; Vegetative insecticidal proteins