title: LysR family transcriptional regulator PqsR as repressor of pyoluteorin biosynthesis and activator of phenazine-1-carboxylic acid biosynthesis in Pseudomonas sp. M18.
abstract: The biocontrol rhizobacterium Pseudomonas sp. M18 can produce two different types of antibiotics, pyoluteorin (Plt) and phenazine-1-carboxylic acid (PCA), which are inhibitory to a number of soil-borne plant pathogens. The pqsR gene, identified in Pseudomonas sp. M18, encodes a LysR-type transcriptional regulator in the Pseudomonas quinolone signal (PQS)-mediated quorum-sensing (QS) system. Here we investigated the regulatory mechanisms of PqsR in PCA and Plt biosyntheses. The results clearly suggest that PqsR functions as a double-duty transcriptional regulator, either as a repressor of Plt biosynthesis or as an activator of PCA biosynthesis. The chromosomal inactivation of pqsR resulted in significant enhancement of Plt production and its genes expression, while almost full inhibition of PCA production and its genes expression. This was further confirmed by multiple pqsR gene dosage experiments, lacZ fusion reporter analysis, and semi-quantitative RT-PCR. Furthermore, PqsR had little effect on expression of the plt pathway-specific activator PltR, indicating that PqsR does not exert its negative regulation on Plt biosynthesis through the mediator PltR. In addition, the pqsR mutation did not have any obvious influence on production of RhlI directing N-acylhomoserine lactones (C4 and C8-HSLs). This result shows PqsR functions as a crucial transcriptional regulator independently of the rhl QS system.
authors.affiliation: Key Laboratory of Microbial Metabolism, Ministry of Education, College of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, PR China.
authors.forename: Jishun
authors.initials: J
authors.lastname: Lu
authors.forename: Xianqing
authors.initials: X
authors.lastname: Huang
authors.forename: Kang
authors.initials: K
authors.lastname: Li
authors.forename: Sainan
authors.initials: S
authors.lastname: Li
authors.forename: Mingyue
authors.initials: M
authors.lastname: Zhang
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Haixia
authors.initials: H
authors.lastname: Jiang
authors.forename: Yuquan
authors.initials: Y
authors.lastname: Xu
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D002876:Chromosomes, Bacterial / Q000648:ultrastructure; D018628:Gene Dosage; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D007763:Lac Operon; D008954:Models, Biological; D009154:Mutation; D010619:Phenazines / Q000737:chemistry; D010636:Phenols / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011549:Pseudomonas / Q000378:metabolism*; D011758:Pyrroles / Q000737:chemistry*; D012097:Repressor Proteins / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D010619:Phenazines; D010636:Phenols; D011758:Pyrroles; D012097:Repressor Proteins; D014157:Transcription Factors; C095503:pyoluteorin; C037165:1-phenazinecarboxylic acid; C073470:LysR protein, Bacteria