Systematic Mutagenesis of All Predicted gntR Genes in Xanthomonas campestris pv. campestris Reveals a GntR Family Transcriptional Regulator Controlling Hypersensitive Response and Virulence

An, Shi-Qi; Lu, Guang Tao; Su, Huidong; Li, Rui Fang; He, Yong Qiang; Jiang, Bo; Tang, Dong Jie; Tang, Ji Liang

doi:10.1094/mpmi-08-10-0180

Cited by 33 publications

(47 citation statements)

References 46 publications

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“…To confirm this idea, we quantified the expression of several hrp operons ( hrpB , hrpC , hrpF ), and hrpX and hrpG , the key regulators of T3SS. This was achieved by using promoterless‐ gusA transcriptional fusion reporters that we have deployed in previous studies (An et al , ; Cui et al , ; Huang et al , ). Here we constructed a group of reporter plasmids for hrpB , hrpC , hrpF , hrpX and hrpG where the promoter sequence fused in front of the gusA gene so that the activity of gusA (Huang et al , ).…”

Section: Resultsmentioning

confidence: 99%

“…oryzae (Liu et al , ; Rashid et al , ), a T3SS component HrcT positively regulates the expression of hrpX via binding to its promoter in X. oryzae pv. oryzicola (Liu et al , ), and the zinc uptake regulator Zur and a GntR family transcriptional regulator HpaR1 indirectly control the expression of hrp genes via HrpX and HrpG, respectively, in Xcc (An et al , ; Huang et al , ). Here our experimental evidences suggest a novel regulatory pathway control T3SS in Xcc .…”

Section: Discussionmentioning

confidence: 99%

“…The zinc uptake regulator (Zur), a key regulator of zinc homeostasis belonging to the Fur family of transcription factors, positively regulates the hrp gene expression via HrpX (Huang et al , ). HpaR1 ( hrp ‐associated regulator), a global regulator belonging to the YtrA subfamily of the GntR family, appears to indirectly regulate the expression of hrp genes via HrpG (An et al , ). In addition, HpaP, a novel regulatory protein with ATPase and phosphatase activity, regulates the expression of hrp genes by controlling the expression of hrpX .…”

Section: Introductionmentioning

confidence: 99%

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Flp, a Fis‐like protein, contributes to the regulation of type III secretion and virulence processes in the phytopathogen Xanthomonas campestris pv. campestris

Leng

Qin

et al. 2019

Molecular Plant Pathology

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Summary The ability of the plant pathogen Xanthomonas campestris pv. campestris ( Xcc ) to cause disease is dependent on its ability to adapt quickly to the host environment during infection. Like most bacterial pathogens, Xcc has evolved complex regulatory networks that ensure expression and regulation of their virulence genes. Here, we describe the identification and characterization of a Fis‐like protein (named Flp), which plays an important role in virulence and type III secretion system (T3SS) gene expression in Xcc . Deletion of flp caused reduced virulence and hypersensitive response (HR) induction of Xcc and alterations in stress tolerance. Global transcriptome analyses revealed the Flp had a broad regulatory role and that most T3SS HR and pathogenicity ( hrp ) genes were down‐regulated in the flp mutant. β ‐glucuronidase activity assays implied that Flp regulates the expression of hrp genes via controlling the expression of hrpX . More assays confirmed that Flp binds to the promoter of hrpX and affected the transcription of hrpX directly. Interestingly, the constitutive expression of hrpX in the flp mutant restored the HR phenotype but not full virulence. Taken together, the findings describe the unrecognized regulatory role of Flp protein that controls hrp gene expression and pathogenesis in Xcc .

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flp, a Fis‐like protein, contributes to the regulation of type III secretion and virulence processes in the phytopathogen Xanthomonas campestris pv. campestris

Leng

Qin

et al. 2019

Molecular Plant Pathology

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“…Zur, a key regulator for zinc homeostasis, positively influenced the expression of hrp operons via hrpX but not hrpG (47). HpaR1 is a GntR family transcriptional activator that regulates the expression of all five operons in the hrp cluster via HrpG (48). It seems unlikely that the unknown regulator for HrcT is one of the preceding TCSs, particularly because the expression of hrpG is repressed by Trh, HpaR1, ColS/ColR, Zur, and HpaR, and the expression of hrcT is occasionally HrpG independent and HrpX dependent (Fig.…”

Section: Discussionmentioning

confidence: 99%

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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“…HR test was performed as described previously [32]. The Xcc nonhost plant pepper ECW-10R ( Capsicum annuum cv.…”

Section: Methodsmentioning

confidence: 99%

RpfC regulates the expression of the key regulator hrpX of the hrp/T3SS system in Xanthomonas campestris pv. campestris

Jiang

Liu

et al. 2018

BMC Microbiol

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BackgroundThe Gram-negative phytopathogenic bacterium Xanthomonas campestris pv. campestris recruits the hrp/T3SS system to inject pathogenicity effector proteins into host cells and uses the rpf/DSF cell-cell signaling system to regulate the expression of virulence factors such as extracellular enzymes and polysaccharide. Whether these two systems have any connection is unknown.MethodsPositive regulator candidates affecting hrpX expression were identified by sacB strategy. The transcriptional expression was determined by qRT-PCR and GUS activity analysis. Transcriptome analysis was performed by RNA deep-sequencing. The hypersensitive response (HR) was determined in the nonhost plant pepper ECW-10R and electrolyte leakage assay.ResultsMutation of the gene encoding the sensor RpfC of the rpf/DSF system significantly reduced the expression of hrpX, the key regulator of the hrp/T3SS system, all of the genes in the hrp cluster and most reported type III effector genes. Mutation of rpfG did not affect the expression of hrpX. The rpfC mutant showed a delayed and weakened HR induction.ConclusionsRpfC positively regulates the expression of hrpX independent of RpfG, showing a complex regulatory network linking the rpf/DSF and hrp/T3SS systems.Electronic supplementary materialThe online version of this article (10.1186/s12866-018-1233-5) contains supplementary material, which is available to authorized users.

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Systematic Mutagenesis of All Predicted gntR Genes in Xanthomonas campestris pv. campestris Reveals a GntR Family Transcriptional Regulator Controlling Hypersensitive Response and Virulence

Cited by 33 publications

References 46 publications

Flp, a Fis‐like protein, contributes to the regulation of type III secretion and virulence processes in the phytopathogen Xanthomonas campestris pv. campestris

Flp, a Fis‐like protein, contributes to the regulation of type III secretion and virulence processes in the phytopathogen Xanthomonas campestris pv. campestris

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

RpfC regulates the expression of the key regulator hrpX of the hrp/T3SS system in Xanthomonas campestris pv. campestris

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