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06:30
Bioassays for Monitoring Insecticide Resistance
Published on: December 30, 2010
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Continuous evolution of Bacillus thuringiensis toxins overcomes insect resistance
Ahmed H Badran1,2, Victor M Guzov3, Qing Huai3
1Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Nature
|April 28, 2016
Summary
Scientists evolved Bacillus thuringiensis (Bt) toxins to overcome insect resistance. New Bt toxin variants bind insect receptors, effectively killing resistant pests and preserving crop protection.
Area of Science:
- Biochemistry
- Molecular Biology
- Entomology
Background:
- Bacillus thuringiensis (Bt) δ-endotoxins are crucial insecticidal proteins for engineered crops.
- Insect resistance to Bt toxins threatens the sustainability of this pest control method.
Purpose of the Study:
- To evolve novel Bt toxin variants with enhanced binding affinity to insect receptors.
- To overcome existing insect resistance mechanisms against Bt toxins.
Main Methods:
- Phage-assisted continuous evolution (PACE) was employed to rapidly evolve high-affinity protein-protein interactions.
- Variants of the Cry1Ac Bt toxin were evolved to bind the cadherin-like receptor (TnCAD) from Trichoplusia ni.
Main Results:
- Evolved Cry1Ac variants demonstrated high-affinity binding to TnCAD (dissociation constant Kd = 11-41 nM).
- These variants effectively killed insect cells expressing TnCAD, which were resistant to wild-type Cry1Ac.
- Evolved toxins were up to 335-fold more potent against Cry1Ac-resistant T. ni insects compared to wild-type Cry1Ac.
Conclusions:
- Engineered Bt toxins with novel receptor affinities can surmount insect resistance.
- This approach restores the efficacy of Bt toxins against resistant insect populations, approaching wild-type potency.
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