Improved insecticidal activity of Vip3Ca protein through enhanced processing and receptor affinity

Area of Science:

• Biochemistry
• Molecular Biology
• Entomology

Background:

• Bacillus thuringiensis Vip3 proteins are potent insecticides against lepidopteran pests.
• The Vip3C subfamily, including Vip3Ca, exhibits limited natural insecticidal activity.
• Enhancing Vip3Ca's efficacy is crucial for broader pest control applications.

Purpose of the Study:

• To improve the insecticidal activity of Vip3Ca by enhancing its processing and receptor binding.
• To engineer Vip3Ca mutants with increased potency against lepidopteran pests.

Main Methods:

• Constructed Vip3Ca protease cleavage site mutants based on Vip3Aa.
• Introduced specific residue substitutions (G302K, N390K, Q468K) to improve binding affinity.
• Assessed processing efficiency in S. frugiperda midgut protease extracts.
• Evaluated insecticidal activity against various lepidopteran larvae (S. frugiperda, H. armigera, S. litura, S. exigua, O. furnacalis).

Main Results:

• Four out of five protease cleavage site mutants showed increased processing and enhanced toxicity against S. frugiperda.
• Selected mutants demonstrated improved activity against H. armigera, S. litura, and S. exigua.
• Residue substitutions increased Vip3Ca binding affinity to S. frugiperda BBMVs by 1.52- to 1.96-fold.
• Combined mutants exhibited significantly higher insecticidal activity, with increases up to 12.30-fold against O. furnacalis.

Conclusions:

• Optimizing both protein processing and receptor binding affinity effectively enhances Vip3Ca insecticidal activity.
• Engineered Vip3Ca mutants show significantly improved potency, offering a promising strategy for pest control.
• Findings provide insights for functional optimization of other Vip3 protein family members.