Fatty acid DSF binds and allosterically activates histidine kinase RpfC of phytopathogenic bacterium Xanthomonas campestris pv. campestris to regulate quorum-sensing and virulence

The gram-negative bacterium Xanthomonas campestris pv. campestris is the causal agent of black rot disease of cruciferous plants. Its genome encodes a large repertoire of two-component signal transduction systems (TCSTSs), which consist of histidine kinases and response regulators (RR) to monitor and respond to environmental stimuli. To investigate the biological functions of these TCSTS genes, we aimed to inactivate all 54 RR genes in X. campestris pv. campestris ATCC 33913, and successfully generated 51 viable mutants using the insertion inactivation method. Plant inoculation identified two novel response regulator genes (XCC1958 and XCC3107) that are involved in virulence of this strain. Genetic complementation demonstrated that XCC3107, designated as vgrR (virulence and growth regulator), also affects bacterial growth and activity of extracellular proteases. In addition, we assessed the survival of these mutants under various stresses, including osmotic stress, high sodium concentration, heat shock, and sodium dodecyl sulfate exposure, and identified a number of genes that may be involved in the general stress response of X. campestris pv. campestris. Mutagenesis and phenotypic characterization of RR genes in this study will facilitate future studies on signaling networks in this important phytopathogenic bacterium.

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Xanthomonas campestris FabH is required for branched-chain fatty acid and DSF-family quorum sensing signal biosynthesis

Scientific Reports ◽

10.1038/srep32811 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 8

Author(s):

Yong-Hong Yu ◽

Zhe Hu ◽

Hui-Juan Dong ◽

Jin-Cheng Ma ◽

Hai-Hong Wang

Keyword(s):

Fatty Acid ◽

Quorum Sensing ◽

Xanthomonas Campestris ◽

Chain Fatty Acid ◽

Branched Chain

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Requirement of a mip-Like Gene for Virulence in the Phytopathogenic Bacterium Xanthomonas campestris pv. campestris

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-20-0021 ◽

2007 ◽

Vol 20 (1) ◽

pp. 21-30 ◽

Cited By ~ 28

Author(s):

Ning Zang ◽

Dong-Jie Tang ◽

Mei-Liang Wei ◽

Yong-Qiang He ◽

Baoshan Chen ◽

...

Keyword(s):

Virulence Factors ◽

Legionella Pneumophila ◽

Xanthomonas Campestris ◽

Bacterial Pathogen ◽

Replication Capacity ◽

Human Pathogens ◽

Extracellular Proteases ◽

Ppiase Activity ◽

Phytopathogenic Bacterium ◽

Xanthomonas Campestris Pv Campestris

Macrophage infectivity potentiators (Mips) are FKBP domain-containing proteins reported as virulence factors in several human pathogens, such as members of genera Legionella, Salmonella and Chlamydia. The putative peptidyl-prolyl cis-trans isomerase (PPIase) encoded by XC2699 of the plant bacterial pathogen Xanthomonas campestris pv. campestris 8004 exhibits a 49% similarity at the aminoacid level to the Mip protein of Legionella pneumophila. This mip-like gene, XC2699, was overexpressed in Es-cherichia coli and the purified (His)6-tagged Mip-like protein encoded by XC2699 exhibited a PPIase activity specifically inhibited by FK-506. A mutation in the mip-like gene XC2699 led to significant reductions in virulence and replication capacity in the host plant Chinese radish (Raphanus sativus L. var. radiculus Pers.). Furthermore, the production of exopolysaccharide and the activity of extracellular proteases, virulence factors X. campestris pv. campestris, were significantly decreased in the mip-like mutant. These results reveal that the mip-like gene is involved in the pathogenesis of X. campestris pv. campestris through an effect on the production of these virulence factors.

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BDSF is a degradation-prone quorum-sensing signal detected by the histidine kinase RpfC of Xanthomonas campestris pv. campestris

10.1101/2022.01.03.474871 ◽

2022 ◽

Author(s):

Xiu-Qi Tian ◽

Yao Wu ◽

Zhen Cai ◽

Wei Qian

Keyword(s):

Quorum Sensing ◽

Histidine Kinase ◽

Xanthomonas Campestris ◽

Bacterial Species ◽

Life Stage ◽

Structural Analog ◽

Fatty Acyl ◽

Coa Ligase ◽

Bacterial Quorum

Diffusible signal factors (DSFs) are medium-chain fatty acids that induce bacterial quorum sensing. Among these compounds, BDSF is a structural analog of DSF that is commonly detected in bacterial species (e.g., Xanthomonas, Pseudomonas, and Burkholderia). Additionally, BDSF contributes to the interkingdom communication regulating fungal life stage transitions. How BDSF is sensed in Xanthomonas spp. and the functional diversity between BDSF and DSF remain unclear. In this study, we generated genetic and biochemical evidence that BDSF is a low-active regulator of X. campestris pv. campestris quorum sensing, whereas trans-BDSF seems not a signaling compound. BDSF is detected by the sensor histidine kinase RpfC. Although BDSF has relatively low physiological activities, it binds to the RpfC sensor with a high affinity and activates RpfC autophosphorylation to a level that is similar to that induced by DSF in vitro. The inconsistency in the physiological and biochemical activities of BDSF is not due to RpfC–RpfG phosphorylation or RpfG hydrolase. Neither BDSF nor DSF controls the phosphotransferase and phosphatase activities of RpfC or the ability of RpfG hydrolase to degrade the bacterial second messenger cyclic di-GMP. We demonstrated that BDSF is prone to degradation by RpfB, a critical fatty acyl-CoA ligase involved in the turnover of DSF-family signals. rpfB mutations lead to substantial increases in BDSF-induced quorum sensing. Although DSF and BDSF are similarly detected by RpfC, our data suggest that their differential degradation in cells is the major factor responsible for the diversity in their physiological effects.

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