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The Transcription Factor SsSR Mediates Ergosterol Biosynthesis and Virulence in Sclerotinia sclerotiorum

Summary

Scientists discovered that a specific protein called SsSR acts as a master switch controlling how dangerous a fungus called Sclerotinia sclerotiorum becomes when attacking plants. Unlike other protein switches that make the fungus grow faster, this one specifically controls the fungus’s ability to cause infection by managing the production of ergosterol, a critical component of the fungus’s cell membranes. This discovery could lead to new ways to protect crops like oilseed rape from this devastating disease.

Background

Sclerotinia sclerotiorum is a necrotrophic pathogenic fungus affecting over 700 plant species, causing significant agricultural losses. Previous research has focused on oxalic acid, cell-wall degrading enzymes, and secreted proteins in understanding pathogenesis. Transcription factors play critical roles in regulating fungal virulence, but their specific functions in S. sclerotiorum remain largely unexplored.

Objective

This study identifies and characterizes a transcription factor SsSR that specifically regulates S. sclerotiorum virulence through ergosterol biosynthesis. The research aims to determine how SsSR regulates downstream genes, particularly SsCYP51, and how this regulatory pathway influences infection capacity and stress tolerance.

Results

Deletion of SsSR did not affect growth or acid production but significantly reduced virulence and stress tolerance. SsSR deletion resulted in reduced ergosterol content and compromised cell membrane integrity. SsSR undergoes phosphorylation during infection and regulates SsCYP51 expression, with phosphorylation sites being essential for virulence. Overexpression of SsCYP51 in SsSR mutants partially restored virulence, confirming SsCYP51 as a key downstream target.

Conclusion

SsSR is a transcription factor that specifically regulates S. sclerotiorum virulence independently of growth by controlling ergosterol biosynthesis through SsCYP51 regulation. Phosphorylation of SsSR is essential for its transcriptional activity and the pathogen’s ability to infect plants. This represents the first transcription factor shown to specifically regulate virulence rather than growth in S. sclerotiorum, offering a novel target for disease control.
  • Published in:Journal of Fungi,
  • Study Type:Original Research,
  • Source: 40985441
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