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Molecular and structural characterization of a novel Cry1D toxin from Bacillus thuringiensis with high toxicity to Spodoptera littoralis (Lepidoptera: Noctuidae)
- BenFarhat-Touzri, Dalel, Jemli, Sonia, Driss, Fatma, Tounsi, Slim
- International journal of biological macromolecules 2019 v.126 pp. 969-976
- Bacillus thuringiensis, Spodoptera littoralis, Western blotting, amino acids, genes, insecticidal properties, insecticidal proteins, juices, lethal concentration 50, midgut, molecular weight, open reading frames, pest control, polyacrylamide gel electrophoresis, proteolysis, toxicity
- The investigation of new Bacillus thuringiensis (Bt) insecticidal proteins (Cry) with specific toxicity is one of the alternative measures used for Lepidopteran pest control. In the present study, a new Cry toxin was identified from a promising Bt strain BLB250 which was previously selected for its high toxicity against Spodoptera littoralis. The corresponding gene, designated cry1D-250, was cloned. It showed an ORF of 3498bp, encoding a protein of 1165 amino acid residues with a putative molecular mass of 132kDa which was confirmed by SDS-PAGE and Western blot analyses. The corresponding toxin named Cry1D-250 showed a higher insecticidal activity towards S. littoralis than Cry1D-133 (LC50 of 224.4ngcm−2) with an LC50 of only 166ngcm−2. Besides to the 65kDa active toxin, proteolysis activation of Cry1D-133 protein with S. littoralis midgut juice generated an extra form of 56kDa, which was the result of a second cleavage. Via activation study and 3D structure analysis, novel substitutions found in the Cry1D-250 protein compared to Cry1D-133 toxin were shown to be involved in the protein stability and toxicity. Therefore, the Cry1D-250 toxin can be considered to be an effective alternative for the control of S. littoralis.