title: Increase of the Bacillus thuringiensis secreted toxicity against lepidopteron larvae by homologous expression of the vip3LB gene during sporulation stage.
abstract: The Vegetative insecticidal Vip3A proteins display a wide range of insecticidal spectrum against several agricultural insect pests. The fact that the expression of vip3 genes occurs only during the vegetative growth phase of Bacillus thuringiensis is a limiting factor in term of production level. Therefore, extending the synthesis of the Vip proteins to the sporulation phase is a good alternative to reach high levels of toxin synthesis. In this study, we have demonstrated that the maximal production of the secreted Vip3LB (also called Vip3Aa16) during the growth of the wild-type strain B. thuringiensis BUPM 95 is reached at the end of the vegetative growth phase, and that the protein remains relatively stable in the culture supernatant during the late sporulation stages. The vip3LB gene was cloned and expressed under the control of the sporulation dependant promoters BtI and BtII in B. thuringiensis BUPM 106 (Vip3(-)) and BUPM 95 (Vip3(+)) strains. The examination of the culture supernatants during the sporulation phase evidenced the synthesis of Vip3LB and its toxicity against the second-instars larvae of the Lepidopteron insect Spodoptera littoralis for the recombinant BUPM 106. Moreover, there was an increase of the Vip3LB synthesis level and an enhancement of the oral toxicity for the recombinant BUPM 95 resulting from the expression of the vip3LB gene during both the vegetative and sporulation phases and the relative stability of the Vip3LB protein.
authors: Laboratory of Biopesticides, Centre of Biotechnology of Sfax, University of Sfax, PO Box 1177, 3018 Sfax, Tunisia.
authors: Sameh
authors: S
authors: Sellami
authors: Kaïs
authors: K
authors: Jamoussi
authors: Emna
authors: E
authors: Dabbeche
authors: Samir
authors: S
authors: Jaoua
mesh_terms: D000818:Animals; D019677:Artificial Gene Fusion; D001413:Bacillus thuringiensis / Q000254:growth & development* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000633:toxicity*; D001835:Body Weight / Q000187:drug effects; D003001:Cloning, Molecular; D015870:Gene Expression; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000382:microbiology; D011401:Promoter Regions, Genetic; D055550:Protein Stability; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000633:toxicity; D018411:Spodoptera / Q000187:drug effects* / Q000382:microbiology
chemical_list: D001426:Bacterial Proteins; D007306:Insecticides; D011994:Recombinant Proteins; C544995:vip3LB protein, Bacillus thuringiensis