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Identification and characterization of naturally occurring DSF ‐family quorum sensing signal turnover system in the phytopathogen X anthomonas
Author(s) -
Zhou Lian,
Wang XingYu,
Sun Shuang,
Yang LiChao,
Jiang BoLe,
He YaWen
Publication year - 2015
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12999
Subject(s) - quorum sensing , biology , virulence , xanthomonas campestris , transcription factor , swarming motility , microbiology and biotechnology , gene , genetics , biochemistry
Summary Molecules of the diffusible signal factor ( DSF )‐family are a class of quorum sensing ( QS ) signals used by the phytopathogens X anthomonas . Studies during the last decade have outlined how X anthomonas 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 ( X cc ). 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 rpf B slightly increased X cc virulence in the C hinese radish and overexpression of rpf B significantly decreased virulence. We further showed that the expression of rpf B is growth phase‐dependent, and its expression is significantly enhanced when X cc cells enter the stationary phase. DSF regulates rpf B expression in a concentration‐dependent manner. rpf B expression is also negatively regulated by the DSF signalling components RpfC , RpfG and C lp. The global transcription factor C lp directly binds to the AATGC ‐tgctgc‐ GCATC motif in the promoter region of rpf B 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.