The GrrSA-Csr global regulatory system plays a critical role in Erwinia amylovora virulence

V. Ancona, Y. Zhao

Research output: Chapter in Book/Report/Conference proceedingChapter


The fire blight pathogen Erwinia amylovora requires a functional type III secretion system (T3SS) and the production of the exopolysaccharide amylovoran to cause disease. The GacS/GacA two-component system is widely conserved among gammaproteobacteria and is a global regulator of virulence factors. This system positively regulates non-coding small regulatory RNA csrB, which in turn binds to CsrA, a translational regulator. In this study, we characterized the grrA, csrB and csrA mutants. Results showed that the grrA and csrB mutants had similar phenotypes: both were hypermotile, produced a higher amount of amylovoran, and had increased expression of T3SS genes in vivo. In contrast, the csrA mutant exhibited the opposite phenotypes, including non-motility, no amylovoran production and no expression of T3SS genes. Furthermore, the csrA mutant did not induce hypersensitive response on non-host tobacco plants neither caused disease on immature pear fruit and apple shoots, indicating that CsrA is a positive regulator of virulence factors. These findings suggest that negative regulation of virulence by GrrS/GrrA acts through csrB, which likely binds to CsrA, antagonizing its positive effect on T3SS gene expression, flagellar formation and amylovoran production.

Original languageEnglish (US)
Title of host publicationXIII International Workshop on Fire Blight
EditorsT.H.M. Smits, E. Holliger, F. Rezzonico
PublisherInternational Society for Horticultural Science
Number of pages6
ISBN (Electronic)9789462610460
StatePublished - Oct 29 2014

Publication series

NameActa Horticulturae
ISSN (Print)0567-7572


  • RNA binding protein
  • Small non-coding RNA
  • Two-component system

ASJC Scopus subject areas

  • Horticulture


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