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Title: Rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae produces multiple DSF-family signals in regulation of virulence factor production
Authors: He, Y.-W
Wu, J
Cha, J.-S
Zhang, L.-H 
Keywords: B diffusible signal factor
bacterial protein
C diffusible signal factor
cell enzyme
diffusible signal factor
EPS protein
rpfB protein
rpfC protein
rpfG protein
rppfF protein
unclassified drug
unsaturated fatty acid
virulence factor
xylan endo 1,3 beta xylosidase
bacterial protein
virulence factor
bacterial blight
bacterial strain
bacterial virulence
computer model
controlled study
culture medium
enzyme activity
fatty acid synthesis
gene cluster
genetic transcription
mass spectrometry
nuclear magnetic resonance
quorum sensing
signal transduction
wild type
Xanthomonas campestris
xanthomonas oryzae
gene expression regulation
multigene family
plant disease
signal transduction
Bacteria (microorganisms)
Xanthomonas oryzae pv. oryzae
Bacterial Proteins
Gene Expression Regulation, Bacterial
Multigene Family
Oryza sativa
Plant Diseases
Signal Transduction
Virulence Factors
Issue Date: 2010
Citation: He, Y.-W, Wu, J, Cha, J.-S, Zhang, L.-H (2010). Rice bacterial blight pathogen Xanthomonas oryzae pv. oryzae produces multiple DSF-family signals in regulation of virulence factor production. BMC Microbiology 10 : 187. ScholarBank@NUS Repository.
Rights: Attribution 4.0 International
Abstract: Background. Xanthomonas oryzae pv. oryzae (Xoo) is the causal agent of rice bacterial blight disease. Xoo produces a range of virulence factors, including EPS, extracellular enzyme, iron-chelating siderophores, and type III-secretion dependent effectors, which are collectively essential for virulence. Genetic and genomics evidence suggest that Xoo might use the diffusible signal factor (DSF) type quorum sensing (QS) system to regulate the virulence factor production. However, little is known about the chemical structure of the DSF-like signal(s) produced by Xoo and the factors influencing the signal production. Results. Xoo genome harbours an rpf cluster comprising rpfB, rpfF, rpfC and rpfG. The proteins encoded by these genes are highly homologous to their counterparts in X. campestris pv. campestris (Xcc), suggesting that Xcc and Xoo might use similar mechanisms for DSF biosynthesis and autoregulation. Consistent with in silico analysis, the rpfF mutant was DSF-deficient and the rpfC mutant produced about 25 times higher DSF-like activity than the wild type Xoo strain KACC10331. From the supernatants of rpfC mutant, we purified three compounds showing strong DSF-like activity. Mass spectrometry and NMR analysis revealed that two of them were the previously characterized DSF and BDSF; the third one was a novel unsaturated fatty acid with 2 double bonds and was designated as CDSF in this study. Further analysis showed that all the three DSF-family signals were synthesized via the enzyme RpfF encoded by Xoo2868. DSF and BDSF at a final concentration of 3 M to the rpfF mutant could fully restore its extracellular xylanase activity and EPS production to the wild type level, but CDSF was less active than DSF and BDSF in induction of EPS and xylanase. DSF and CDSF shared a similar cell density-dependent production time course with the maximum production being detected at 42 h after inoculation, whereas the maximum production of BDSF was observed at 36 h after inoculation. When grown in a rich medium such as YEB, LB, PSA, and NYG, Xoo produced all the three signals with the majority being DSF. Whereas in nutritionally poor XOLN medium Xoo only produced BDSF and DSF but the majority was BDSF. Conclusions. This study demonstrates that Xoo and Xcc share the conserved mechanisms for DSF biosynthesis and autoregulation. Xoo produces DSF, BDSF and CDSF signals in rich media and CDSF is a novel signal in DSF-family with two double bonds. All the three DSF-family signals promote EPS production and xylanase activity in Xoo, but CDSF is less active than its analogues DSF and BDSF. The composition and ratio of the three DSF-family signals produced by Xoo are influenced by the composition of culture media. © 2010 He et al; licensee BioMed Central Ltd.
Source Title: BMC Microbiology
ISSN: 14712180
DOI: 10.1186/1471-2180-10-187
Rights: Attribution 4.0 International
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