Cytotoxic and lethal effects of recombinant β-BUTX-Lqq1a peptide against Lepidopteran insects and cell lines.

Extensive usage of synthetic chemical pesticides have collateral effect in harming the health, environment and development of resistance in insect pests. Scorpion produces variety of molecules that are specific to insects, mammals and to both. Insect specific molecules act as potential candidature as an alternative to synthetic chemical pesticides. We have successfully expressed and purified recombinant Scorpion Leiurus quinquestriatus quinquestriaus β-BUTX-Lqq1a toxin in bacterial system. Cytotoxic activity assay with the help of insect cell line Sf-21 from Spodoptera frugiperda reveals that mean IC50 1.72-3.0 μg ml -1 significantly reduced the cell proliferation when compared with control. Microscopic examination of treated Sf-21 cell lines also showed changes in the cell morphology such as cell membrane blebbing, cell shrinkage and granulated apoptotic bodies. When β-BUTX-Lqq1a was hemocoelly injected with various doses, significant reduction in survival of Helicoverpa armigera (LC50 = 0.13 μg insect-1) and Spodoptera litura (LC50 = 0.147 μg insect -1) were noticeable with immediate paralysis, and reduced feeding when compared with control. Toxicity with purified recombinant β-BUTX-Lqq1a protein towards insect cell line Sf-21 and major agricultural pest was demonstrated by various bioassays. Cytotoxicity and insect bioassay demonstrated the potential use of β-BUTX-Lqq1a protein as an effective insecticide against lepidopteran insects. These results strongly suggest that the development of rational insecticidal molecule against with significant promise.