title: Toxin stability improvement and toxicity increase against dipteran and lepidopteran larvae of Bacillus thuringiensis crystal protein Cry2Aa.
abstract: BACKGROUND
  Bacillus thuringiensis δ-endotoxins are the most widely used biopesticides for controlling economically important crop pests and disease vectors. Improving their efficacy is of great benefit. Here, an improvement in Cry2Aa δ-endotoxin toxicity was attempted via a cry gene over expression system using P20 from B. thuringiensis israelensis.
  
  
  RESULTS
  The coexpression of Cry2Aa with P20 resulted in a seven fold increase in its production yield in B. thuringiensis. Generated crystals proved to be significantly more toxic (505.207 µg g-1, 1.99 mg L-1and 1.49 mg L-1) than the P20-lacking control (720.78 µg g-1, 705.69 mg L-1and 508.51 mg L-1) against Ephestia kuehniella, Aedes aegypti and Culex pipiens larvae respectively. In vitro, processing experiments revealed a P20-mediated protection of Cry2Aa against degradation under larval gut conditions. Thus, P20 could promote the maintenance of a tightly packaged conformation of Cry2Aa toxins in the larval midgut upon correct activation and binding to its membrane receptors.
  
  
  CONCLUSIONS
  Based on their resistance against excessive proteolysis, Cry2Aa δ-endotoxins, produced in the presence of P20, could be considered as a successful control agent for E. kuehniella and an effective alternative for mosquito control, implying its possible exploitation in pest management programmes. © 2016 Society of Chemical Industry.
authors.affiliation: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
authors.forename: Jihen
authors.initials: J
authors.lastname: Elleuch
authors.affiliation: Department of Biological and Environmental Sciences, College of Arts Sciences, Qatar University, Doha, Qatar.
authors.forename: Samir
authors.initials: S
authors.lastname: Jaoua
authors.affiliation: Institut de Recherche pour le Développement (IRD), UMR MIVEGEC (UM1-UM2-CNRS 5290-IRD 224) Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Laboratoire de Lutte contre les Insectes Nuisibles (LIN), Montpellier, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Ginibre
authors.affiliation: Institut de Recherche pour le Développement (IRD), UMR MIVEGEC (UM1-UM2-CNRS 5290-IRD 224) Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Laboratoire de Lutte contre les Insectes Nuisibles (LIN), Montpellier, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Chandre
authors.affiliation: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
authors.forename: Slim
authors.initials: S
authors.lastname: Tounsi
authors.affiliation: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia. raida.zribi@cbs.rnrt.tn.
authors.forename: Raida Z
authors.initials: RZ
authors.lastname: Zghal
mesh_terms: D000330:Aedes / Q000187:drug effects; D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics / Q000378:metabolism; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology*; D003465:Culex / Q000187:drug effects; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004731:Endotoxins / Q000235:genetics* / Q000494:pharmacology*; D005786:Gene Expression Regulation; D006460:Hemolysin Proteins / Q000235:genetics* / Q000494:pharmacology*; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects*; D007915:Lepidoptera / Q000187:drug effects; D009032:Mosquito Control / Q000379:methods; D015202:Protein Engineering / Q000379:methods*; D055550:Protein Stability; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; D011994:Recombinant Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Cry2Aa toxin; P20 helper protein; larvicidal activity improvement; protection against excessive proteolysis