HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplementary material Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Yan, Q. Articles by Zhang, L.-Q. Search for Related Content PubMed PubMed Citation Articles by Yan, Q. Articles by Zhang, L.-Q. Agricola Articles by Yan, Q. Articles by Zhang, L.-Q.

Regulation of the PcoI/PcoR quorum-sensing system in Pseudomonas fluorescens 2P24 by the PhoP/PhoQ two-component system

Department of Plant Pathology, China Agricultural University, Beijing 100193, China

Correspondence
Li-Qun Zhang
zhanglq{at}cau.edu.cn

A quorum-sensing locus, pcoI/pcoR, which is involved in the regulation of root colonization and plant disease-suppressive ability, was previously identified in Pseudomonas fluorescens 2P24. In this study, we performed random mutagenesis using mini-Tn5 in order to screen the upstream transcriptional regulators of pcoI, a biosynthase gene responsible for the synthesis of N-acylhomoserine lactone signal molecules. Two mutants, PM400 and PM410, with elevated pcoI gene promoter activity, were identified from 10 000 insertion clones. The amino acid sequences of the interrupted genes in these two mutants were highly similar to PhoQ, a sensor protein of the two-component regulatory system PhoP/PhoQ, which responds to environmental Mg²⁺ starvation and regulates virulence in Salmonella typhimurium and antimicrobial peptide resistance in Pseudomonas aeruginosa. The promoter activity of pcoI was also induced under low-Mg²⁺ conditions in the 2P24 strain of P. fluorescens. Deletion mutagenesis and complementation experiments demonstrated that the transcription of pcoI was negatively regulated by the sensor PhoQ but positively regulated by the response regulator PhoP. Genetic evidence also indicated that transcription of the outer-membrane protein gene oprH was induced by Mg²⁺ starvation through regulation of the wild-type PhoP/PhoQ system. Additionally, PhoQ was involved in biofilm formation by 2P24 under low-Mg²⁺ conditions through a PhoP-independent pathway.

The GenBank/EMBL/DDBJ accession number for the DNA sequence containing the oprH, phoP and phoQ genes of P. fluorescens 2P24 is EU569830.

Supplementary material is available with the online version of this paper.