title: Identification and characterization of naturally occurring DSF-family quorum sensing signal turnover system in the phytopathogen Xanthomonas.
abstract: Molecules of the diffusible signal factor (DSF)-family are a class of quorum sensing (QS) signals used by the phytopathogens Xanthomonas. Studies during the last decade have outlined how Xanthomonas cells enter the QS phase. However, information on the mechanism underlying its exit from the QS phase is limited. RpfB has recently been reported as a fatty acyl-CoA ligase (FCL) that activates a wide range of fatty acids to their CoA esters in vitro. Here, we establish an improved quantification assay for DSF-family signals using liquid chromatography-mass spectrometry in X. campestris pv. campestris (Xcc). We first demonstrated that RpfB represents a naturally occurring DSF-family signal turnover system. RpfB effectively turns over DSF-family signals DSF and BDSF in vivo. RpfB FCL enzymatic activity is required for DSF and BDSF turnover. Deletion of rpfB slightly increased Xcc virulence in the Chinese radish and overexpression of rpfB significantly decreased virulence. We further showed that the expression of rpfB is growth phase-dependent, and its expression is significantly enhanced when Xcc cells enter the stationary phase. DSF regulates rpfB expression in a concentration-dependent manner. rpfB expression is also negatively regulated by the DSF signalling components RpfC, RpfG and Clp. The global transcription factor Clp directly binds to the AATGC-tgctgc-GCATC motif in the promoter region of rpfB to repress its expression. Finally, RpfB-dependent signal turnover system was detected in a wide range of bacterial species, suggesting that it is a conserved mechanism.
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Lian
authors.initials: L
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Xing-Yu
authors.initials: XY
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Sun
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning, 530004, China.
authors.forename: Li-Chao
authors.initials: LC
authors.lastname: Yang
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning, 530004, China.
authors.forename: Bo-Le
authors.initials: BL
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Shanghai Jiao Tong University, Shanghai, 200240, China.
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: He
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002853:Chromatography, Liquid; D005227:Fatty Acids / Q000378:metabolism; D017353:Gene Deletion; D013058:Mass Spectrometry; D010935:Plant Diseases / Q000382:microbiology*; D053038:Quorum Sensing / Q000235:genetics*; D031224:Raphanus / Q000382:microbiology*; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism; D037521:Virulence Factors / Q000378:metabolism; D016959:Xanthomonas campestris / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*
chemical_list: D000214:Acyl Coenzyme A; D001426:Bacterial Proteins; D005227:Fatty Acids; D014157:Transcription Factors; D037521:Virulence Factors