Related Experiment Videos
VsrA, a second two-component sensor regulating virulence genes of Pseudomonas solanacearum
M A Schell1, T P Denny, J Huang
1Department of Plant Pathology, University of Georgia, Athens 30602-2605.
Molecular Microbiology
|February 1, 1994
Summary
A new gene, vsrA, is crucial for Pseudomonas solanacearum to produce virulence factors like EPS I and EXPs, causing wilt disease in plants. This discovery reveals dual two-component sensors controlling EPS I production.
Area of Science:
- Microbiology
- Plant Pathology
- Molecular Biology
Background:
- Pseudomonas solanacearum causes bacterial wilt disease.
- Virulence factors, including extracellular polysaccharides (EPS I) and proteins (EXPs), are key to disease development.
- Regulation of these factors involves transcriptional regulators like PhcA and sensor histidine kinases like VsrB.
Purpose of the Study:
- To characterize a novel genetic locus, vsrA, involved in virulence factor production and disease development in P. solanacearum.
- To elucidate the role of vsrA in the regulation of EPS I and EXPs.
- To understand the contribution of vsrA to the in planta growth and pathogenicity of P. solanacearum.
Main Methods:
- Analysis of eps::lacZ reporter gene expression in vsrA mutants under various growth conditions.
- Characterization of extracellular protein profiles in vsrA mutants.
- In planta pathogenicity assays using stem inoculation of tomato plants with vsrA mutants.
- Cloning and subcloning of the vsrA gene.
- PhoA fusion analysis and subcellular localization studies in E. coli maxicells.
- Nucleotide sequence analysis of the vsrA gene.
Main Results:
- vsrA is essential for maximal transcription of eps genes, which are involved in EPS I production.
- eps transcription and EPS I production in vsrA mutants are condition-dependent, ranging from 3-17% of wild-type levels.
- vsrA inactivation significantly reduces the production of specific EXPs (28, 48, and 66 kDa) and alters the production of others.
- vsrA mutants exhibit drastically reduced pathogenicity and in planta growth compared to wild-type strains.
- The vsrA gene product is a 53 kDa membrane-associated protein with homology to histidine kinase domains, suggesting it's part of a two-component regulatory system.
Conclusions:
- vsrA plays a critical role in regulating EPS I and EXP production, essential for P. solanacearum virulence.
- The findings indicate that EPS I production is simultaneously controlled by at least two distinct two-component sensor systems (VsrB and VsrA).
- This dual regulation provides a more complex regulatory network for virulence factor production in P. solanacearum.