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The global response regulator ExpA controls virulence gene expression through RsmA-mediated and RsmA-independent
Applied and Environmental Microbiology
|January 21, 2014
Summary
ExpA (GacA) and RsmA are key regulators of virulence in Pectobacterium wasabiae. This study reveals a significant overlap in their gene regulation, indicating ExpA largely influences virulence through RsmA.
Area of Science:
- Microbiology
- Plant Pathology
- Molecular Biology
Background:
- ExpA (GacA) regulates virulence genes, including plant cell wall-degrading enzymes (PCWDEs), in Pectobacterium wasabiae.
- ExpA homologues in related bacteria modulate virulence partly via RsmA, an RNA-binding regulator.
Purpose of the Study:
- To determine the overlap between ExpA and RsmA regulons in P. wasabiae.
- To understand how ExpA and RsmA coordinate virulence gene expression and bacterial phenotypes.
Main Methods:
- Microarray analysis to compare transcriptomes of wild-type, expA mutant, rsmA mutant, and expA rsmA double mutant strains.
- Quantitative reverse transcription PCR (qRT-PCR) for validating microarray data.
- Phenotypic assays assessing growth, motility, PCWDE production, and in planta virulence.
Main Results:
- Extensive overlap found between ExpA and RsmA regulons, suggesting ExpA primarily acts through RsmA.
- ExpA independently regulates genes involved in electron transport and oligogalacturonide metabolism.
- Phenotypic changes correlated with transcriptome data, linking regulation to bacterial functions.
Conclusions:
- ExpA's impact on P. wasabiae fitness and virulence is substantially mediated by RsmA.
- ExpA also possesses RsmA-independent regulatory functions, highlighting a complex regulatory network.
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