Gene Involved in Transcriptional Activation of the
 hrp
 Regulatory Gene
 hrpG
 in
 Xanthomonas oryzae
 pv. oryzae

Tsuge, Seiji; Nakayama, Tsuneyoshi; Terashima, Shinsaku; Ochiai, Hirokazu; Furutani, Ayako; Oku, Takashi; Tsuno, Kazunori; Kubo, Yasuyuki; Kaku, Hisatoshi

doi:10.1128/jb.00006-06

Cited by 50 publications

(47 citation statements)

References 41 publications

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“…A recent paper reports that a putative transcriptional regulator gene, named trh (transcriptional regulator for hrp), is involved in expression of HrpG in X. oryzae pv. oryzae (74). Putting these results together, the orphan regulator HrpG might function as part of multiple regulatory systems rather than interacting with a single cognate HK that senses external stimuli.…”

Section: Discussionmentioning

confidence: 99%

TheXanthomonas oryzaepv. oryzae PhoPQ Two-Component System Is Required for AvrXA21 Activity,hrpGExpression, and Virulence

et al. 2008

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The rice pathogen recognition receptor, XA21, confers resistance to Xanthomonas oryzae pv. oryzae strains producing the type one system-secreted molecule, AvrXA21. X. oryzae pv. oryzae requires a regulatory twocomponent system (TCS) called RaxRH to regulate expression of eight rax (required for AvrXA21 activity) genes and to sense population cell density. To identify other key components in this critical regulatory circuit, we assayed proteins expressed in a raxR gene knockout strain. This survey led to the identification of the phoP gene encoding a response regulator that is up-regulated in the raxR knockout strain. Next we generated a phoP knockout strain and found it to be impaired in X. oryzae pv. oryzae virulence and no longer able to activate the response regulator HrpG (hypersensitive reaction and pathogenicity G) in response to low levels of Ca 2؉ . The impaired virulence of the phoP knockout strain can be partially complemented by constitutive expression of hrpG, indicating that PhoP controls a key aspect of X. oryzae pv. oryzae virulence through regulation of hrpG. A gene encoding the cognate putative histidine protein kinase, phoQ, was also isolated. Growth curve analysis revealed that AvrXA21 activity is impaired in a phoQ knockout strain as reflected by enhanced growth of this strain in rice lines carrying XA21. These results suggest that the X. oryzae pv. oryzae PhoPQ TCS functions in virulence and in the production of AvrXA21 in partnership with RaxRH.

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Section: Discussionmentioning

confidence: 99%

TheXanthomonas oryzaepv. oryzae PhoPQ Two-Component System Is Required for AvrXA21 Activity,hrpGExpression, and Virulence

et al. 2008

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“…However, we previously found that another H-NS protein, XrvB, negatively regulates hrpG expression (25). In addition, the GntR family transcriptional regulator Trh and the two-component signal transduction system PhoP/PhoQ have also been reported to be involved in the transcriptional regulation of hrpG (26,27). Thus, not only the phosphorylation of the first key hrp regulator, HrpG, followed by the activation of the second key hrp regulator, HrpX, but also the transcriptional regulation of hrpG are likely to be important, although the transcriptional regulation of hrpG by the regulators that have been identified so far is probably all indirect.…”

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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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“…oryzae (17,18). A novel regulatory gene, trh, was identified as a positive regulator of HrpG both under in vitro hrp-inducing conditions and in planta (52). Also, HrpX was reported to be regulated by the expression of some other effectors.…”

Section: Discussionmentioning

confidence: 99%

“…(7,11,12,15,50,52,56,57). It was reported that hrpG itself was shown to be regulated by other regulators.…”

Section: Discussionmentioning

confidence: 99%

KdgR, an IClR Family Transcriptional Regulator, Inhibits Virulence Mainly by Repression of hrp Genes in Xanthomonas oryzae pv. oryzae

Islam

Hirata

et al. 2011

Journal of Bacteriology

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KdgR has been reported to negatively regulate the genes involved in degradation and metabolization of pectic acid and other extracellular enzymes in soft-rotting Erwinia spp. through direct binding to their promoters. The possible involvement of a KdgR orthologue in virulence by affecting the expression of extracellular enzymes in Xanthomonas oryzae pv. oryzae, the causal agent of rice blight disease, was examined by comparing virulence and regulation of extracellular enzymes between the wild type (WT) and a strain carrying a mutation in putative kdgR (⌬Xoo0310 mutant). This putative kdgR mutant of X. oryzae pv. oryzae showed increased pathogenicity on rice without affecting the regulation of extracellular enzymes, such as amylase, cellulase, xylanase, and protease. However, the mutant carrying a mutation in an ortholog of xpsL, which encodes the functional secretion machinery for the extracellular enzymes, showed a dramatic decrease in pathogenicity on rice. Both mutants of kdgR and of xpsL orthologs showed higher expression of two major hrp regulatory genes, hrpG and hrpX, and the genes in the hrp operons when grown in hrp-inducing medium. Thus, both genes were shown to be involved in repression of hrp genes. The kdgR ortholog was thought to suppress virulence mainly by repressing the expression of hrp genes without affecting the expression of extracellular enzymes, unlike findings for the kdgR gene in soft-rotting Erwinia spp. On the other hand, xpsL was confirmed to be involved in virulence by promoting the secretion of extracellular enzymes in spite of repressing the expression of the hrp genes.

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Gene Involved in Transcriptional Activation of the hrp Regulatory Gene hrpG in Xanthomonas oryzae pv. oryzae

Cited by 50 publications

References 41 publications

TheXanthomonas oryzaepv. oryzae PhoPQ Two-Component System Is Required for AvrXA21 Activity,hrpGExpression, and Virulence

TheXanthomonas oryzaepv. oryzae PhoPQ Two-Component System Is Required for AvrXA21 Activity,hrpGExpression, and Virulence

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

KdgR, an IClR Family Transcriptional Regulator, Inhibits Virulence Mainly by Repression of hrp Genes in Xanthomonas oryzae pv. oryzae

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