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Bacillus thuringiensis pathogenicity islands encode regulatory circuits controlling insecticidal Cry toxin expression
Bowen Zhang1,2, Zhiyu Liu1,2, Hang Zhang1,2
1National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China.
Plos Pathogens
|July 29, 2026
Summary
Bacillus thuringiensis (Bt) VipR regulator activates insecticidal gene expression during vegetative growth, coordinating toxin production and enhancing biological pest control. This discovery offers new avenues for engineering improved Bt strains.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Bacillus thuringiensis (Bt) produces insecticidal Cry and Vip3 proteins for biological pest control.
- Toxin gene expression is typically linked to sporulation, but Vip3 is produced during vegetative growth, indicating different regulatory mechanisms.
- Pathogenicity Islands (PAIs) in Bt often contain toxin genes, but their regulatory roles are not fully understood.
Purpose of the Study:
- To investigate the regulatory mechanisms of insecticidal gene expression during the vegetative phase in Bacillus thuringiensis.
- To identify novel transcriptional regulators encoded within Bt Pathogenicity Islands (PAIs).
- To explore the role of these regulators in coordinating toxin production and enhancing insecticidal activity.
Main Methods:
- Identification and characterization of the VipR transcriptional regulator from BtPAI-1.
- Analysis of VipR's effect on the transcription of vip3A and cry genes in Bt strains HD-1 and CT-43.
- Phylogenetic analysis to determine the distribution of vipR in Bt strains.
- Heterologous expression of vipR in different Bt strains (BGSC 4J5, HD-73) to assess its function.
Main Results:
- VipR, encoded by BtPAI-1, acts as a transcriptional activator of insecticidal genes, including vip3A and certain cry genes, during vegetative growth.
- VipR promotes premature Cry protein accumulation and increases insecticidal activity in Bt strains HD-1 and CT-43.
- VipR also influences the vegetative-phase expression of cry9Aa genes in strain BGSC 4AE1.
- Phylogenetic analysis shows vipR is prevalent in about one-third of Bt strains and associated with PAIs.
- Heterologous expression of vipR activates vegetative-phase cry transcription independently of sporulation-specific sigma factors.
Conclusions:
- VipR plays a crucial role in coordinating the vegetative-phase expression of insecticidal genes in Bt.
- BtPAI-1 encodes not only insecticidal determinants but also regulatory functions that control their expression.
- These findings provide insights into the regulatory architecture of Bt PAIs and potential for engineering enhanced Bt strains for pest control.
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