Characterization of the Xylella fastidiosa PD1671 gene encoding degenerate c-di-GMP GGDEF/EAL domains, and its role in the development of Pierce's disease

PLoS One. 2015 Mar 26;10(3):e0121851. doi: 10.1371/journal.pone.0121851. eCollection 2015.

Abstract

Xylella fastidiosa is an important phytopathogenic bacterium that causes many serious plant diseases including Pierce's disease of grapevines. X. fastidiosa is thought to induce disease by colonizing and clogging xylem vessels through the formation of cell aggregates and bacterial biofilms. Here we examine the role in X. fastidiosa virulence of an uncharacterized gene, PD1671, annotated as a two-component response regulator with potential GGDEF and EAL domains. GGDEF domains are found in c-di-GMP diguanylate cyclases while EAL domains are found in phosphodiesterases, and these domains are for c-di-GMP production and turnover, respectively. Functional analysis of the PD1671 gene revealed that it affected multiple X. fastidiosa virulence-related phenotypes. A Tn5 PD1671 mutant had a hypervirulent phenotype in grapevines presumably due to enhanced expression of gum genes leading to increased exopolysaccharide levels that resulted in elevated biofilm formation. Interestingly, the PD1671 mutant also had decreased motility in vitro but did not show a reduced distribution in grapevines following inoculation. Given these responses, the putative PD1671 protein may be a negative regulator of X. fastidiosa virulence.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics*
  • Biofilms
  • Cyclic GMP / analogs & derivatives
  • Cyclic GMP / metabolism
  • Extracellular Space / enzymology
  • Extracellular Space / metabolism
  • Gene Expression Regulation, Bacterial
  • Molecular Sequence Data
  • Mutation
  • Plant Diseases / microbiology*
  • Polymers / metabolism
  • Protein Interaction Domains and Motifs / genetics*
  • Sequence Alignment
  • Virulence / genetics
  • Xylella / genetics*
  • Xylella / metabolism
  • Xylella / pathogenicity

Substances

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

Grants and funding

Support was provided by the University of California Pierce’s Disease Research Grants Program #2010-287 and #SA7465 to PM, HCH, and TJB [http://www.piercesdisease.org/grants/manage], and Nanobiotechnology Center, an STC program of the National Science Foundation, under agreement no. ECS-304 9876771 to HCH. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.