HrpS Is a Global Regulator on Type III Secretion System (T3SS) and Non-T3SS Genes in Pseudomonas savastanoi pv. phaseolicola

Mol Plant Microbe Interact. 2018 Dec;31(12):1232-1243. doi: 10.1094/MPMI-02-18-0035-R. Epub 2018 Sep 14.


The type III secretion system (T3SS) is the main machinery for Pseudomonas savastanoi and other gram-negative bacteria to invade plant cells. HrpR and HrpS form a hetero-hexamer, which activates the expression of HrpL, which induces all T3SS genes by binding to a 'hrp box' in promoters. However, the individual molecular mechanism of HrpR or HrpS has not been fully understood. Through chromatin immunoprecipitation coupled to high-throughput DNA sequencing, we found that HrpR, HrpS, and HrpL had four, 47, and 31 targets on the genome, respectively. HrpS directly bound to the promoter regions of a group of T3SS genes and non-T3SS genes. HrpS independently regulated these genes in a hrpL deletion strain. Additionally, a HrpS-binding motif (GTGCCAAA) was identified, which was verified by electrophoretic mobility shift assay and lux-reporter assay. HrpS also regulated motility and biofilm formation in P. savastanoi. The present study strongly suggests that HrpS alone can work as a global regulator on both T3SS and non-T3SS genes in P. savastanoi. [Formula: see text] Copyright © 2018 The Author(s). This is an open-access article distributed under the CC BY-NC-ND 4.0 International license .

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Biofilms / growth & development*
  • Chromatin Immunoprecipitation
  • DNA-Binding Proteins
  • Electrophoretic Mobility Shift Assay
  • Gene Expression Regulation, Bacterial*
  • Genes, Reporter
  • High-Throughput Nucleotide Sequencing
  • Models, Biological
  • Nucleotide Motifs
  • Point Mutation
  • Promoter Regions, Genetic / genetics
  • Pseudomonas / genetics*
  • Pseudomonas / metabolism
  • Sequence Analysis, DNA
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Type III Secretion Systems / genetics*
  • Type III Secretion Systems / metabolism


  • Bacterial Proteins
  • DNA-Binding Proteins
  • Transcription Factors
  • Type III Secretion Systems