Identification of a putative cognate sensor kinase for the two‐component response regulator <scp>HrpG</scp>, a key regulator controlling the expression of the <scp>hrp</scp> genes in <scp>X</scp>anthomonas campestris pv. campestris

Li, Ruifang; Lu, Guang‐Tao; Li, Lei; Su, Hui-Zhao; Feng, Guo-fang; Chen, Ya; He, Yanan; Jiang, Bo-Le; Tang, Dongjie

doi:10.1111/1462-2920.12207

Cited by 64 publications

(134 citation statements)

References 53 publications

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“…To monitor signaling through CroR, Phos-tag SDS-PAGE was optimized to separate phosphorylated CroR (CroR-P) from nonphosphorylated CroR, as has been done for other RRs (40)(41)(42)(43)(44). Figure 1A demonstrates that two species of CroR can be detected after Phos-tag SDS-PAGE when a strain carrying wild-type (WT) CroRS is treated with vancomycin, a known stimulant of CroRS activity (lanes 2 to 3).…”

Section: Analysis Of Gene Expression By Quantitative Reverse Transcrimentioning

confidence: 99%

Functional Dissection of the CroRS Two-Component System Required for Resistance to Cell Wall Stressors in Enterococcus faecalis

Kellogg

Kristich

2016

J Bacteriol

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Bacteria use two-component signal transduction systems (TCSs) to sense and respond to environmental changes via a conserved phosphorelay between a sensor histidine kinase and its cognate response regulator. The opportunistic pathogen Enterococcus faecalis utilizes a TCS comprised of the histidine kinase CroS and the response regulator CroR to mediate resistance to cell wall stresses such as cephalosporin antibiotics, but the molecular details by which CroRS promotes cephalosporin resistance have not been elucidated. Here, we analyzed mutants of E. faecalis carrying substitutions in CroR and CroS to demonstrate that phosphorylated CroR drives resistance to cephalosporins, and that CroS exhibits kinase and phosphatase activities to control the level of CroR phosphorylation in vivo. Deletion of croS in various lineages of E. faecalis revealed a CroS-independent mechanism for CroR phosphorylation and led to the identification of a noncognate histidine kinase capable of influencing CroR (encoded by OG1RF_12162; here called cisS). Further analysis of this TCS network revealed that both systems respond to cell wall stress. IMPORTANCETCSs allow bacteria to sense and respond to many different environmental conditions. The opportunistic pathogen Enterococcus faecalis utilizes the CroRS TCS to mediate resistance to cell wall stresses, including clinically relevant antibiotics such as cephalosporins and glycopeptides. In this study, we use genetic and biochemical means to investigate the relationship between CroRS signaling and cephalosporin resistance in E. faecalis cells. Through this, we uncovered a signaling network formed between the CroRS TCS and a previously uncharacterized TCS that also responds to cell wall stress. This study provides mechanistic insights into CroRS signaling and cephalosporin resistance in E. faecalis. Although Enterococcus faecalis is a normal commensal of the gut microbiome, it poses a serious risk to humans as an opportunistic pathogen. A major risk factor for the pathogenic transition of enterococci is therapy with broad-spectrum cephalosporin antibiotics. Cephalosporins are commonly used to treat bacterial infections; however, nearly all enterococcal isolates are resistant to these compounds. This intrinsic resistance allows for the expansion of resident enterococcal populations during cephalosporin treatment, which is thought to promote dissemination from the gastrointestinal tract, enabling enterococci to establish infections (1, 2). With the emergence of multidrug-resistant isolates of E. faecalis, few options for treating infections are available. Therefore, understanding the mechanisms that support cephalosporin resistance in E. faecalis is crucial for designing new therapies that limit growth during cephalosporin treatment or that can be used as adjuvants with cephalosporins to treat E. faecalis infections. An essential determinant of cephalosporin resistance in E. faecalis is the CroRS two-component system (TCS), consisting of CroS (a transmembrane sensor-histidine kinase) and ...

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Section: Analysis Of Gene Expression By Quantitative Reverse Transcrimentioning

confidence: 99%

Functional Dissection of the CroRS Two-Component System Required for Resistance to Cell Wall Stressors in Enterococcus faecalis

Kellogg

Kristich

2016

J Bacteriol

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“…vesicatoria (17). Recently, Li et al (18) discovered the cognate sensor kinase for HrpG, named HpaS, in X. campestris pv. campestris, though a homolog of HpaS is not encoded in the genome of X. oryzae pv.…”

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confidence: 99%

GamR, the LysR-Type Galactose Metabolism Regulator, Regulates hrp Gene Expression via Transcriptional Activation of Two Key hrp Regulators, HrpG and HrpX, in Xanthomonas oryzae pv. oryzae

Rashid

Ikawa

Tsuge

2016

Appl Environ Microbiol

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Xanthomonas oryzae pv. oryzae is the causal agent of bacterial leaf blight of rice. For the virulence of the bacterium, the hrp genes, encoding components of the type III secretion system, are indispensable. The expression of hrp genes is regulated by two key hrp regulators, HrpG and HrpX: HrpG regulates hrpX, and HrpX regulates other hrp genes. Several other regulators have been shown to be involved in the regulation of hrp genes. Here, we found that a LysR-type transcriptional regulator that we named GamR, encoded by XOO_2767 of X. oryzae pv. oryzae strain MAFF311018, positively regulated the transcription of both hrpG and hrpX, which are adjacent to each other but have opposite orientations, with an intergenic upstream region in common. In a gel electrophoresis mobility shift assay, GamR bound directly to the middle of the upstream region common to hrpG and hrpX. The loss of either GamR or its binding sites decreased hrpG and hrpX expression. Also, GamR bound to the upstream region of either a galactose metabolism-related gene (XOO_2768) or a galactose metabolism-related operon (XOO_2768 to XOO_2771) located next to gamR itself and positively regulated the genes. The deletion of the regulator gene resulted in less bacterial growth in a synthetic medium with galactose as a sole sugar source. Interestingly, induction of the galactose metabolismrelated gene was dependent on galactose, while that of the hrp regulator genes was galactose independent. Our results indicate that the LysR-type transcriptional regulator that regulates the galactose metabolism-related gene(s) also acts in positive regulation of two key hrp regulators and the following hrp genes in X. oryzae pv. oryzae. IMPORTANCEThe expression of hrp genes encoding components of the type III secretion system is essential for the virulence of many plantpathogenic bacteria, including Xanthomonas oryzae pv. oryzae. It is specifically induced during infection. Research has revealed that in this bacterium, hrp gene expression is controlled by two key hrp regulators, HrpG and HrpX, along with several other regulators in the complex regulatory network, but the details remain unclear. Here, we found that a novel LysR-type transcriptional activator, named GamR, functions as an hrp regulator by directly activating the transcription of both hrpG and hrpX. Interestingly, GamR also regulates a galactose metabolism-related gene (or operon) in a galactose-dependent manner, while the regulation of hrpG and hrpX is independent of the sugar. Our finding of a novel hrp regulator that directly and simultaneously regulates two key hrp regulators provides new insights into an important and complex regulation system of X. oryzae pv. oryzae hrp genes. In several plant-pathogenic bacteria, hrp genes are essential for bacterial pathogenicity (1). The hrp genes generally comprise more than 20 genes and are clustered in the genome of each bacterium. The genes mainly encode components of a type III secretion apparatus, through which the bacteria secrete numerous proteins, s...

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“…For example, the OM portion of HpaS presumably senses plant stimuli during the early stages of infection and transphosphorylates HrpG (13). As noted in our model, the activated form of HrpG may function via an unknown factor to activate HrcT expression via promoter T3.…”

Section: Discussionmentioning

confidence: 64%

“…In addition to the regulators HrpG, HrpX, and HrpD6 (2,11,12), additional two-component regulatory system (TCS) proteins have been shown to modulate expression of the T3SS in Xanthomonas spp. For example, Li and coworkers (13) recently identified HpaS, the histidine protein kinase that interacts with HrpG via phosphorylation. Other regulators of the TCS include Trh and HpaR1, which were shown to positively regulate the expression of hrpG (43,44).…”

Section: Discussionmentioning

confidence: 99%

“…The hrp genes in group II, which includes Ralstonia solanacearum and Xanthomonas spp., are regulated by HrpG and HrpX (the latter protein is designated HrpB in Ralstonia) (9)(10)(11)(12). HrpG is an OmpR family protein that belongs to response regulators of the two-component signal transduction system and putatively receives phosphorylation from HpaS (12,13). HrpX is an AraC-type transcriptional activator that forms a homodimer and contains a helix-turn-helix (HTH) motif (11).…”

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confidence: 99%

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HrcT Is a Key Component of the Type III Secretion System in Xanthomonas spp. and Also Regulates the Expression of the Key hrp Transcriptional Activator HrpX

Liu

Zou

Xue

et al. 2014

Appl Environ Microbiol

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The type III secretion system (T3SS), encoded by hrp (hypersensitive response and pathogenicity) genes in Gram-negative phytopathogenic bacteria, delivers repertoires of T3SS effectors (T3SEs) into plant cells to trigger the hypersensitive response (HR) in nonhost or resistant-host plants and promote pathogenicity in susceptible plants. The expression of hrp genes in Xanthomonas is regulated by two key regulatory proteins, HrpG and HrpX. However, the interactions between hrp gene products in directing T3SE secretion are largely unknown. Here we demonstrated that HrcT of X. oryzae pv. oryzicola functions as a T3SS component and positively regulates the expression of hrpX. Transcription of hrcT occurs via two distinct promoters; one (T1) is with the hrpB operon and the second (T3) within hrpB7 Via either promoter T1 or T3, the defect in Hrp phenotype by hrcT deletion was corrected in the presence of hrcT only from Xanthomonas species but not from other phytopathogenic bacteria. An N-terminally truncated HrcT was able to bind the hrpX promoter and activate the expression of hrpX, supporting that HrcT is a positive regulator of hrpX. A revised model showing the regulatory interactions between HrcT, HrpX, and HrpG is proposed.

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Identification of a putative cognate sensor kinase for the two‐component response regulator HrpG, a key regulator controlling the expression of the hrp genes in Xanthomonas campestris pv. campestris

Cited by 64 publications

References 53 publications

Functional Dissection of the CroRS Two-Component System Required for Resistance to Cell Wall Stressors in Enterococcus faecalis

Functional Dissection of the CroRS Two-Component System Required for Resistance to Cell Wall Stressors in Enterococcus faecalis

GamR, the LysR-Type Galactose Metabolism Regulator, Regulates hrp Gene Expression via Transcriptional Activation of Two Key hrp Regulators, HrpG and HrpX, in Xanthomonas oryzae pv. oryzae

HrcT Is a Key Component of the Type III Secretion System in Xanthomonas spp. and Also Regulates the Expression of the Key hrp Transcriptional Activator HrpX

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