Engineering of Bacillus thuringiensis Cry2Ab toxin for improved insecticidal activity

Area of Science:

• Biochemistry
• Molecular Biology
• Entomology

Background:

• Bacillus thuringiensis Cry2Ab toxin is a key bioinsecticide for controlling lepidopteran pests.
• Genetic engineering offers a route to enhance the efficacy of existing bioinsecticides.

Purpose of the Study:

• To engineer Bacillus thuringiensis Cry2Ab toxin for improved insecticidal activity.
• To elucidate the molecular mechanisms underlying enhanced Cry2Ab activity.

Main Methods:

• Site-specific saturation mutagenesis was employed to generate Cry2Ab variants.
• The insecticidal activity of variants was assessed against Plutella xylostella.
• Proteolytic activation, oligomerization, and pore-formation activities were evaluated.

Main Results:

• Variant L183I exhibited significantly lower LC50 (0.129 µg/cm²) compared to wild-type Cry2Ab (0.267 µg/cm²).
• Proteolytic activation of L183I was comparable to wild-type Cry2Ab.
• Variant L183I demonstrated enhanced oligomerization and pore-formation activities.

Conclusions:

• Increased oligomerization and pore-formation correlate with enhanced insecticidal activity of Cry2Ab.
• Oligomerization and pore-formation can serve as indicators for Cry2Ab toxin efficacy.
• The L183I variant shows promise for future development of Cry2Ab-based bioinsecticides.