What is it about?
Bacillus thuringiensis (Bt) is a naturally occurring bacterium widely used in agriculture because it produces proteins that kill insect pests while remaining safe for humans and most beneficial organisms. For decades, scientists believed that these insecticidal Cry proteins were produced mainly after Bt began forming spores. In this study, we discovered that Bt starts producing Cry proteins much earlier than previously thought. We identified a regulatory protein called VipR that directly switches on the expression of several insecticidal genes during the vegetative growth stage, before sporulation begins. This early activation allows Cry proteins to accumulate sooner, giving the bacterium stronger insecticidal activity during the early stages of growth. We also found that this regulatory mechanism is associated with a pathogenicity island (BtPAI-1), a cluster of toxin-related genes present in many Bt strains. Our findings reveal a previously unrecognized stage of toxin regulation in Bt and provide new insights into how this important biocontrol bacterium coordinates toxin production throughout its life cycle.
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Why is it important?
Bt-based biopesticides are among the most widely used environmentally friendly alternatives to chemical insecticides. Understanding how Bt regulates toxin production is essential for improving its effectiveness and developing next-generation microbial insecticides. Our study overturns the traditional view that Cry toxins are produced only during sporulation by demonstrating that toxin production begins much earlier through a previously unrecognized regulatory pathway. These findings improve our understanding of Bt biology and provide a molecular framework for engineering strains with enhanced insecticidal activity. The work may also inspire new strategies for improving biological pest control while reducing reliance on chemical pesticides.
Perspectives
For many years, Cry toxins were considered classic sporulation-associated proteins. During this project, one of the most exciting moments was realizing that Bt had been producing these toxins much earlier than we expected. This unexpected observation led us to uncover a previously unknown regulatory circuit involving VipR. I hope this work encourages researchers to look beyond traditional models of bacterial gene regulation and inspires new ideas for improving biological pest control. It has also been a rewarding collaboration among researchers with complementary expertise, making this project especially meaningful to me.
Kai Wang
Huazhong Agriculture University
Read the Original
This page is a summary of: Bacillus thuringiensis pathogenicity islands encode regulatory circuits controlling insecticidal Cry toxin expression during vegetative growth, PLoS Pathogens, July 2026, PLOS,
DOI: 10.1371/journal.ppat.1014476.
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