Comprehensive overexpression analysis of cyclic-di-GMP signalling proteins in the phytopathogen Pectobacterium atrosepticum reveals diverse effects on motility and virulence phenotypes

Microbiology (Reading). 2014 Jul;160(Pt 7):1427-1439. doi: 10.1099/mic.0.076828-0. Epub 2014 Apr 23.


Bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) is a ubiquitous bacterial signalling molecule produced by diguanylate cyclases of the GGDEF-domain family. Elevated c-di-GMP levels or increased GGDEF protein expression is frequently associated with the onset of sessility and biofilm formation in numerous bacterial species. Conversely, phosphodiesterase-dependent diminution of c-di-GMP levels by EAL- and HD-GYP-domain proteins is often accompanied by increased motility and virulence. In this study, we individually overexpressed 23 predicted GGDEF, EAL or HD-GYP-domain proteins encoded by the phytopathogen Pectobacterium atrosepticum strain SCRI1043. MS-based detection of c-di-GMP and 5'-phosphoguanylyl-(3'-5')-guanosine in these strains revealed that overexpression of most genes promoted modest 1-10-fold changes in cellular levels of c-di-GMP, with the exception of the GGDEF-domain proteins ECA0659 and ECA3374, which induced 1290- and 7660-fold increases, respectively. Overexpression of most EAL domain proteins increased motility, while overexpression of most GGDEF domain proteins reduced motility and increased poly-β-1,6-N-acetyl-glucosamine-dependent flocculation. In contrast to domain-based predictions, overexpression of the EAL protein ECA3549 or the HD-GYP protein ECA3548 increased c-di-GMP concentrations and reduced motility. Most overexpression constructs altered the levels of secreted cellulases, pectinases and proteases, confirming c-di-GMP regulation of virulence in Pe. atrosepticum. However, there was no apparent correlation between virulence-factor induction and the domain class expressed or cellular c-di-GMP levels, suggesting that regulation was in response to specific effectors within the network, rather than total c-di-GMP concentration. Finally, we demonstrated that the cellular localization patterns vary considerably for GGDEF/EAL/HD-GYP proteins, indicating it is a likely factor restricting specific interactions within the c-di-GMP network.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Computational Biology
  • Cyclic GMP / analogs & derivatives*
  • Cyclic GMP / analysis
  • Cyclic GMP / metabolism
  • Gene Expression
  • Gene Expression Regulation, Bacterial*
  • Pectobacterium / genetics*
  • Pectobacterium / pathogenicity
  • Pectobacterium / physiology*
  • Phenotype
  • Plant Diseases / microbiology*
  • Plant Tubers / microbiology
  • Recombinant Fusion Proteins
  • Signal Transduction*
  • Solanum tuberosum / microbiology*
  • Virulence


  • Bacterial Proteins
  • Recombinant Fusion Proteins
  • bis(3',5')-cyclic diguanylic acid
  • Cyclic GMP