title: Involvement of the processing step in the susceptibility/tolerance of two lepidopteran larvae to Bacillus thuringiensis Cry1Aa toxin.
abstract: Bacillus thuringiensis (Bt) Cry1A toxins are known for their effectiveness against lepidopteran insects. In this study, the entomopathogenic activity of Cry1Aa was investigated against two lepidopteran larvae causing serious threat to various crops, Spodoptera littoralis and Tuta absoluta. Contrarily to S. littoralis, which showed low susceptibility to Cry1Aa (40% mortality with 1μg/cm(2)), T. absoluta was very sensitive to this delta-endotoxin (LC50 of 95.8ng/cm(2)). The different steps in the mode of action of this toxin on the two larvae were studied with the aim to understand the origin of their difference of susceptibility. Activation of the 130kDa Cry1Aa protein by T. absoluta larvae juice generated a 65kDa active toxin, whereas S. littoralis gut juice led to a complete degradation of the protoxin. The study of the interaction of the brush border membrane vesicles (BBMV) with purified biotinylated Cry1Aa toxin revealed six and seven toxin binding proteins in T. absoluta and S. littoralis BBMV, respectively. Midgut histopathology of Cry1Aa fed larvae demonstrated approximately similar damage caused by the toxin in the two larvae midguts. These results suggest that the activation step was strongly involved in the difference of susceptibility of the two larvae to Cry1Aa.
authors.affiliation: Team of Biopesticides (LPIP), Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia. Electronic address: dammak_mar@yahoo.fr.
authors.forename: Mariam
authors.initials: M
authors.lastname: Dammak
authors.affiliation: Team of Biopesticides (LPIP), Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
authors.forename: Saoussen Ben
authors.initials: SB
authors.lastname: Khedher
authors.affiliation: Team of Biopesticides (LPIP), Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
authors.forename: Hanen
authors.initials: H
authors.lastname: Boukedi
authors.affiliation: Unit of Entomology (UR13A-GR09), Regional Research Center on Horticulture and Organic Agriculture, University of Sousse, Chott-Mariem, 4042, Tunisia.
authors.forename: Ikbel
authors.initials: I
authors.lastname: Chaib
authors.affiliation: Unit of Entomology (UR13A-GR09), Regional Research Center on Horticulture and Organic Agriculture, University of Sousse, Chott-Mariem, 4042, Tunisia.
authors.forename: Asma
authors.initials: A
authors.lastname: Laarif
authors.affiliation: Team of Biopesticides (LPIP), Centre of Biotechnology of Sfax, University of Sfax, P.O. Box 1177, 3018 Sfax, Tunisia.
authors.forename: Slim
authors.initials: S
authors.lastname: Tounsi
mesh_terms: D000818:Animals; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000494:pharmacology*; D004731:Endotoxins / Q000494:pharmacology*; D006460:Hemolysin Proteins / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects* / Q000254:growth & development; D007915:Lepidoptera / Q000254:growth & development*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Activation; Binding; Cry1Aa; Histopathological effect; Lepidopteran larvae; Toxicity