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Cyclic Di-GMP modulates the disease progression of Erwinia amylovora

Adam C Edmunds1, Luisa F Castiblanco, George W Sundin

  • 1Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA.

Journal of Bacteriology
|March 12, 2013
PubMed

Insights

Cyclic di-GMP (c-di-GMP) regulates Erwinia amylovora

Area of Science:

  • Microbiology
  • Molecular Biology
  • Plant Pathology

Background:

  • Cyclic di-GMP (c-di-GMP) is a crucial second messenger regulating diverse cellular functions in bacteria.
  • Diguanylate cyclase (DGC) and phosphodiesterase (PDE) enzymes control intracellular c-di-GMP levels.
  • The role of c-di-GMP in Erwinia amylovora, the causal agent of fire blight, was previously uncharacterized.

Purpose of the Study:

  • To investigate the function of c-di-GMP signaling in Erwinia amylovora.
  • To identify active DGCs in E. amylovora and their roles in regulating cellular processes and virulence.

Main Methods:

  • Identification and characterization of putative DGC genes (edc genes) in E. amylovora.
  • Assays to determine the enzymatic activity of identified DGCs.
  • Mutational analysis to assess the impact of DGCs on biofilm formation, motility, exopolysaccharide secretion, and plant infection.

Main Results:

  • Three E. amylovora DGC genes (edcA, edcC, edcE) encode active diguanylate cyclases.
  • c-di-GMP positively regulates amylovoran secretion and biofilm formation, while negatively impacting flagellar motility.
  • Deletion of biofilm-promoting DGCs led to increased tissue necrosis in pear and apple infection models, indicating a negative role of c-di-GMP in virulence.
  • c-di-GMP inhibited hrpA expression, a component of the type III secretion system.

Conclusions:

  • This study elucidates the first described role for c-di-GMP in E. amylovora.
  • c-di-GMP plays a complex role in E. amylovora pathogenesis, coordinating the downregulation of motility and type III secretion during infection.
  • The findings suggest that c-di-GMP signaling is a key regulator of E. amylovora virulence and host colonization.

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