Lack of RsmA-mediated control results in constant hypervirulence, cell elongation, and hyperflagellation in Pectobacterium wasabiae

PLoS One. 2013;8(1):e54248. doi: 10.1371/journal.pone.0054248. Epub 2013 Jan 23.

Abstract

The posttranscriptional regulator RsmA controls the production of plant cell wall degrading enzymes (PCWDE) and cell motility in the Pectobacterium genus of plant pathogens. In this study the physiological role of gene regulation by RsmA is under investigation. Disruption of rsmA gene of the Pectobacterium wasabiae strain, SCC3193 resulted in 3-fold decrease in growth rate and increased virulence. The comparison of mRNA levels of the rsmA(-) mutant and wild-type using a genome-wide microarray showed, that genes responsible for successful infection, i.e. virulence factors, motility, butanediol fermentation, various secretion systems etc. were up-regulated in the rsmA(-) strain. The rsmA(-) strain exhibited a higher propensity to swarm and produce PCWDE compared to the wild-type strain. Virulence experiments in potato tubers demonstrated that in spite of its more efficient tissue maceration, the rsmA(-) strain's ability to survive within the host is reduced and the infection site is taken over by resident bacteria. Taken together, in the absence of RsmA, cells revert to a constitutively infective phenotype characterized by expression of virulence factors and swarming. We hypothesize that lack of control over these costly energetic processes results in decreased growth rate and fitness. In addition, our findings suggest a relationship between swarming and virulence in plant pathogens.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Chemotaxis / physiology
  • Flagella / genetics*
  • Flagella / metabolism
  • Gene Deletion
  • Gene Expression Regulation, Bacterial
  • Metabolic Networks and Pathways / genetics*
  • Pectobacterium / genetics*
  • Pectobacterium / growth & development
  • Pectobacterium / metabolism
  • Pectobacterium / pathogenicity*
  • Plant Diseases / microbiology
  • Repressor Proteins / genetics*
  • Repressor Proteins / metabolism
  • Solanum tuberosum / microbiology
  • Virulence
  • Virulence Factors / genetics*
  • Virulence Factors / metabolism

Substances

  • Bacterial Proteins
  • Repressor Proteins
  • Virulence Factors

Grants and funding

This work was funded by grants SF0180088s08 and SF0180166s08 from the Estonian Ministry of Education and Research; by the EU through the European Regional Development Fund through the Estonian Centre of Excellence in Genomics and through the Center of Excellence in Chemical Biology; by Academy of Finland grants (Center of Excellence program 2006–2011 grants 213509, 129628, and grants 136470, 120821 and 128566); by University of Helsinki; by Biocentrum Helsinki; by Biocenter Finland; by Finnish Doctoral Program in Plant Science. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.