A transgenic approach for controlling Lygus in cotton

Area of Science:

• Agricultural Entomology
• Molecular Biology
• Plant Biotechnology

Background:

• Lygus species are significant pests of cotton, causing economic losses.
• Commercial Bacillus thuringiensis (Bt) cotton is ineffective against Lygus species.
• Previous attempts using Cry51Aa2 protein in transgenic cotton showed limited efficacy.

Purpose of the Study:

• To enhance the insecticidal activity of the Cry51Aa2 protein against Lygus species.
• To develop improved transgenic cotton expressing a variant Cry51Aa2 protein for pest control.

Main Methods:

• Protein crystallography and modeling were used to guide amino acid substitutions in Cry51Aa2.
• Site-directed mutagenesis was employed to create variant proteins.
• Transgenic cotton plants expressing the optimized protein (Cry51Aa2.834_16) were generated and tested.
• Whole-plant caged field trials were conducted to evaluate efficacy against Lygus populations.

Main Results:

• Limited amino acid substitutions resulted in a >200-fold increase in insecticidal activity of Cry51Aa2 against Lygus species.
• Transgenic cotton expressing Cry51Aa2.834_16 (event MON88702) reduced Lygus populations by up to 30-fold in field trials.
• The optimized protein demonstrated significantly enhanced efficacy compared to the wild-type Cry51Aa2.

Conclusions:

• Optimized Cry51Aa2 variants show high insecticidal activity against Lygus species.
• Transgenic cotton expressing the variant protein offers a promising strategy for Lygus pest management.
• This development could lead to reduced insecticide use and associated environmental benefits in cotton production.