Open AccessThe Transcriptional Activator rfiA Is Quorum-Sensing Regulated by Cotranscription with the luxI Homolog pcoI and Is Essential for Plant Virulence in Pseudomonas corrugata
Author(s) -
Grazia Licciardello,
Iris Bertani,
Laura Steindler,
P. Bella,
Vittorio Venturi,
Vittoria Catara
Publication year - 2009
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi-22-12-1514
Subject(s) - autoinducer , quorum sensing , biology , operon , virulence , mutant , gene , bacillus megaterium , genetics , microbiology and biotechnology , bacteria
The gram-negative phytopathogen Pseudomonas corrugata has an acyl-homoserine lactone (AHL) quorum-sensing (QS) system called PcoI/PcoR that is involved in virulence on tomato. This work identifies, downstream of pcoI, a gene designated rfiA, which we demonstrate is directly linked to QS by cotranscription with pcoI. The deduced RfiA protein contains a DNA-binding domain characteristic of the LuxR family but lacks the autoinducer-binding terminus characteristic of the QS LuxR-family proteins. We also identified, downstream of rfiA, an operon designated pcoABC, encoding for the three components of a tripartite resistance nodulation-cell-division (RND) transporter system. The expression of pcoABC is regulated by RfiA. We found that lipodepsipeptide (LDP) production is cell density dependent and mutants of pcoI, pcoR, and rfiA are unable to inhibit the growth of the LDP-sensitive microorganisms Rhodotorula pilimanae and Bacillus megaterium. P. corrugata rfiA mutants were significantly reduced in their ability to cause necrosis development in tomato pith. In addition, it was established that PcoR in the absence of AHL also played a role in virulence on tomato. A model for the role of PcoI, PcoR, and RfiA in tomato pith necrosis is presented.