Adaptive evolution of cry genes in Bacillus thuringiensis: implications for their specificity determination

Area of Science:

• * Molecular biology and evolutionary genetics.
• * Biochemistry and entomology.

Background:

• * The Cry gene family from Bacillus thuringiensis encodes proteins with specific insecticidal activity.
• * Cry proteins are crucial for pest control, with research focusing on their structure-function relationships and target specificity.
• * Specific residues and domains are known to be vital for Cry protein interaction with insect receptors.

Purpose of the Study:

• * To investigate adaptive evolution in Cry proteins using a maximum likelihood method.
• * To identify specific amino acid residues under positive selection.
• * To correlate identified residues with insect specificity determination and functional divergence.

Main Methods:

• * Maximum likelihood analysis to detect positive selection in Cry protein sequences.
• * Integration of existing mutagenesis data.
• * Comparative analysis of identified positively selected sites with known functional domains.

Main Results:

• * Identification of 24 residues under positive selection in Cry proteins.
• * All identified residues are located within Domain II or Domain III.
• * These residues are strongly implicated in determining insect specificity.

Conclusions:

• * Adaptive evolution, particularly positive selection, plays a significant role in Cry protein diversification.
• * The identified residues are critical for insect specificity and may be driven by an evolutionary "arms race" with insects.
• * These positively selected sites offer valuable targets for future structural and functional studies of Cry proteins.