Overproduction of the Bacillus thuringiensis Vip3Aa16 toxin and study of its insecticidal activity against the carob moth Ectomyelois ceratoniae

• Published in: Journal of invertebrate pathology Vol. 127; pp. 127 - 129
• Main Authors: Boukedi, Hanen, Ben Khedher, Saoussen, Triki, Nesrine, Kamoun, Fakher, Saadaoui, Imen, Chakroun, Maissa, Tounsi, Slim, Abdelkefi-Mesrati, Lobna
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2015
• Subjects: Animals; Bacillus thuringiensis; Bacterial Proteins - toxicity; Ectomyelois ceratoniae; Escherichia coli; Insecticides - toxicity; Moths - drug effects; Toxicity; Vip3Aa16; Vip3Aa16; Ectomyelois ceratoniae; Toxicity; Bacillus thuringiensis; Escherichia coli
• ISSN: 0022-2011; 1096-0805
• DOI: 10.1016/j.jip.2015.03.013

[Display omitted] •The Vip3a16 toxin production was improved 21-fold compared to the starting conditions.•Vip3Aa16 toxin was active against Ectomyelois ceratoniae with an LC50 of 40ng/cm2.•The toxin attacks the midgut with cellular disintegration and larvae death which allowed the protection of stored dates. The vip3Aa16 gene of Bacillus thuringiensis strain BUPM95 was cloned and expressed in Escherichia coli. Optimization of Vip3A16 protein expression was conducted using Plackett–Burman design and response surface methodology. Accordingly, the optimum Vip3A16 toxin production was 170μg/ml at 18h post-induction time and 39°C post-induction temperature. This corresponds to an improvement of 21times compared to the starting conditions. The insecticidal activity, evaluated against Ectomyelois ceratoniae, displayed an LC50 value of 40ng/cm2 and the midgut histopathology of Vip3Aa16 fed larvae showed vacuolization of the cytoplasm, brush border membrane destruction, vesicle formation in the apical region and cellular disintegration.