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Putative transcription antiterminator RfaH contributes to Erwinia amylovora virulence
Sara M Klee1,2, Judith P Sinn1, Jeremy Held1,3
1Department of Plant Pathology and Environmental Microbiology, The Pennsylvania State University, University Park, Pennsylvania, USA.
Molecular Plant Pathology
|August 5, 2022
Summary
The transcription antiterminator RfaH is crucial for Erwinia amylovora virulence, specifically by preventing premature termination in amylovoran and lipopolysaccharide operons, essential for fire blight disease.
Area of Science:
- Bacteriology
- Plant Pathology
- Molecular Biology
Background:
- Erwinia amylovora causes fire blight, a destructive disease in apple and pear trees.
- Amylovoran exopolysaccharide and lipopolysaccharides are key virulence factors for E. amylovora.
- Virulence factor production is often regulated by genes organized in operons.
Purpose of the Study:
- To investigate the role of the predicted transcription antiterminator RfaH in E. amylovora virulence.
- To determine if RfaH influences the expression of virulence-associated operons.
- To elucidate the specific mechanism by which RfaH affects gene expression and pathogenicity.
Main Methods:
- Genetic manipulation to create an E. amylovora ΔrfaH mutant.
- RNA sequencing to analyze transcriptional polarity in wild-type and mutant strains.
- In vitro assays to measure amylovoran and lipopolysaccharide production.
- Assessment of bacterial virulence in apple fruitlets and tree shoots.
Main Results:
- Full virulence of E. amylovora depends on RfaH.
- RfaH suppresses transcriptional polarity in the amylovoran and lipopolysaccharide operons.
- Amylovoran and lipopolysaccharide production were significantly reduced in ΔrfaH mutants.
- Expression of type VI secretion cluster 1 was also reduced in ΔrfaH mutants.
Conclusions:
- E. amylovora RfaH is essential for virulence by specifically preventing operon polarity in virulence factor gene clusters.
- RfaH directly regulates the expression of amylovoran and lipopolysaccharide operons, impacting virulence.
- The findings highlight RfaH as a critical regulator in the pathogenicity of E. amylovora.
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