Researchers at St Petersburg State University have discovered a central mechanism in the evolution of Cry toxins, insecticidal proteins produced by the soil bacterium Bacillus thuringiensis. The study, published in The ISME Journal, was led by doctoral student Anton Shikov and Professor Kirill Antonets, working with the Research Institute for Agricultural Microbiology.
These toxins target pests such as caterpillars, beetles and mosquitoes and underpin more than half of the plant-protection products on the global market. They are considered safe for humans, warm-blooded animals and beneficial insects such as bees, but they need to keep evolving because insects gradually adapt.
The team concluded that site-specific recombination, in which DNA exchanges well-defined regions encoding parts of the protein, plays a central role in creating new toxins, challenging the view that homologous recombination was the key process. Through large-scale bioinformatic analysis, they identified conserved DNA regions that appear to trigger these exchanges and a bacterial enzyme that is likely responsible.
According to the authors, the findings offer a unified explanation for how new toxins arise and could help predict the efficacy and specificity of new variants. In the long term, the work could support the design of biological plant-protection agents that target harmful insects while keeping people and the environment safe.
