title: The distinct quorum sensing hierarchy of las and rhl in Pseudomonas sp. M18.
abstract: Pseudomonas sp. M18 is a rhizosphere isolate capable of producing two kinds of antifungal agents: phenazine-1-carboxylic acid (PCA) and pyoluteorin. Recently, the two well-studied quorum sensing (QS) systems of Pseudomonas aeruginosa, LasR/LasI and RhlR/RhlI, have also been identified in this strain. However, in this study, through the use of lacZ translational fusion expression analysis and acyl-homoserine lactone thin-layer chromatography (TLC) bioassays, we clearly display a more complex and distinctive hierarchy of the las and rhl QS systems in strain M18. In this QS cascade, expression of rhlI was negatively controlled by the LasR/LasI QS system. In contrast with lasI, which negatively regulated the rhlR induction, lasR exerted a positive influence on rhlR expression during the log-phase. This interrelationship indicated that the response regulators (LasR and RhlR) of the QS system are expressed independently of their cognate synthases (LasI and RhlI). Furthermore, the las system also modulated the timing and magnitude of the rhlI and rhlR maximal expression. In addition, our data imply that the lasR gene exerts its negative control on PCA production through modulation of rhlI expression. Thus, interactions between the two QS systems are strain specific.
authors.affiliation: College of Life Science and Biotechnology, Shanghai Jiao Tong University, Shanghai, People's Republic of China. jishunlu@gmail.com
authors.forename: Jishun
authors.initials: J
authors.lastname: Lu
authors.forename: Xianqing
authors.initials: X
authors.lastname: Huang
authors.forename: Mingyue
authors.initials: M
authors.lastname: Zhang
authors.forename: Sainan
authors.initials: S
authors.lastname: Li
authors.forename: Haixia
authors.initials: H
authors.lastname: Jiang
authors.forename: Yuquan
authors.initials: Y
authors.lastname: Xu
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000096:biosynthesis; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002855:Chromatography, Thin Layer; D015964:Gene Expression Regulation, Bacterial; D008025:Ligases / Q000235:genetics / Q000378:metabolism; D010619:Phenazines / Q000378:metabolism; D011549:Pseudomonas / Q000235:genetics / Q000502:physiology*; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000502:physiology*; D053038:Quorum Sensing; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C081237:LasI protein, Pseudomonas aeruginosa; C092312:N-butyrylhomoserine lactone; C104908:N-hexanoyl-L-homoserine lactone; D010619:Phenazines; D014157:Transcription Factors; D037521:Virulence Factors; C037165:1-phenazinecarboxylic acid; D008025:Ligases; C096955:RHLI protein, Pseudomonas aeruginosa; D015107:4-Butyrolactone