Characterization of five ECF sigma factors in the genome of Pseudomonas syringae pv. syringae B728a

PLoS One. 2013;8(3):e58846. doi: 10.1371/journal.pone.0058846. Epub 2013 Mar 14.

Abstract

Pseudomonas syringae pv. syringae B728a, a bacterial pathogen of bean, utilizes large surface populations and extracellular signaling to initiate a fundamental change from an epiphytic to a pathogenic lifestyle. Extracytoplasmic function (ECF) sigma (σ) factors serve as important regulatory factors in responding to various environmental signals. Bioinformatic analysis of the B728a genome revealed 10 ECF sigma factors. This study analyzed deletion mutants of five previously uncharacterized ECF sigma factor genes in B728a, including three FecI-type ECF sigma factors (ECF5, ECF6, and ECF7) and two ECF sigma factors placed in groups ECF11 and ECF18. Transcriptional profiling by qRT-PCR analysis of ECF sigma factor mutants was used to measure expression of their associated anti-sigma and outer membrane receptor proteins, and expression of genes associated with production of extracellular polysaccharides, fimbriae, glycine betaine and syringomycin. Notably, the B728aΔecf7 mutant displayed reduced swarming and had decreased expression of CupC fimbrial genes. Growth and pathogenicity assays, using a susceptible bean host, revealed that none of the tested sigma factor genes are required for in planta growth and lesion formation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / biosynthesis
  • Bacterial Proteins / genetics*
  • Biological Transport / drug effects
  • Biological Transport / genetics
  • Environment
  • Extracellular Space / drug effects
  • Extracellular Space / genetics
  • Fabaceae / microbiology
  • Fimbriae, Bacterial / genetics
  • Fimbriae, Bacterial / metabolism
  • Gene Expression Regulation, Bacterial / drug effects
  • Genome, Bacterial / drug effects
  • Genome, Bacterial / genetics*
  • Iron / metabolism
  • Oxidative Stress / drug effects
  • Oxidative Stress / genetics
  • Phenotype
  • Polysaccharides / metabolism
  • Pseudomonas syringae / cytology
  • Pseudomonas syringae / drug effects
  • Pseudomonas syringae / genetics*
  • Pseudomonas syringae / physiology
  • Regulon / genetics
  • Sequence Deletion
  • Sigma Factor / deficiency
  • Sigma Factor / genetics*
  • Stress, Physiological / drug effects
  • Stress, Physiological / genetics
  • Toluene / pharmacology

Substances

  • Bacterial Proteins
  • Polysaccharides
  • Sigma Factor
  • syringomycin
  • Toluene
  • Iron

Grants and funding

This work was supported by Texas A&M University AgriLife Research project no. H-8832. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.