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DNA Distortion by the Burkholderia thailandensis Transcriptional Regulator FusR2 Is Abolished by Fusaric Acid Binding

George C Nwokocha1, Nabanita Bhattacharyya1, Erin N LeBoeuf1

  • 1Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States.

Biochemistry
|December 3, 2025
PubMed

Insights

Bacteria like Burkholderia thailandensis can resist toxic fusaric acid produced by Fusarium fungi. Fusaric acid triggers a regulatory mechanism involving FusR2, which controls genes for defense and antifungal compound production.

Area of Science:

  • Microbiology
  • Plant Pathology
  • Molecular Biology

Background:

  • Fusaric acid, a toxic metabolite from *Fusarium* species, causes plant wilt and aids fungal competition against soil bacteria.
  • Understanding bacterial resistance mechanisms is crucial for controlling *Fusarium* wilt.
  • *Burkholderia thailandensis* possesses a predicted fusaric acid-binding transporter (FusC2) within an operon including isochorismatase (*isoC*) and a MarR-family transcription factor.

Purpose of the Study:

  • To investigate the regulatory mechanism by which *Burkholderia thailandensis* responds to fusaric acid.
  • To characterize the role of the FusR2 transcription factor in the *fusR2-isoC-fusC2* operon.
  • To elucidate how fusaric acid induces the expression of defense-related genes.

Main Methods:

  • Electrophoretic mobility shift assays (EMSAs) to assess FusR2 binding to the operon promoter.
  • DNase I footprinting to analyze DNA conformational changes induced by FusR2.
  • Thermal shift assays to detect direct binding of fusaric acid to FusR2.
  • Gene expression analysis to determine the effect of fusaric acid on operon transcription.

Main Results:

  • FusR2 specifically binds to the *fusR2-isoC-fusC2* operon promoter, inducing significant DNA conformational changes.
  • Fusaric acid induces the expression of the *fusR2-isoC-fusC2* operon and binds directly to FusR2.
  • Fusaric acid binding to FusR2 alters the DNA-bound conformation, facilitating RNA polymerase binding and transcription initiation.
  • The operon's genes encode an efflux pump and an enzyme for antifungal metabolite production.

Conclusions:

  • FusR2 acts as a transcriptional regulator, modulating DNA conformation to control gene expression.
  • Fusaric acid triggers a regulatory cascade by binding to FusR2, leading to the expression of bacterial defense mechanisms.
  • This mechanism allows *B. thailandensis* to mitigate the toxic effects of fusaric acid and potentially compete in environments with *Fusarium* species.

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