Virulence of the Phytopathogen
            <i>Pseudomonas syringae</i>
            pv. Maculicola Is
            <i>rpoN</i>
            Dependent

Hendrickson, Erik L.; Guevera, Pablo; Peñaloza‐Vázquez, Alejandro; Shao, Jing; Bender, Carol L.; Ausubel, Frederick M.

doi:10.1128/jb.182.12.3498-3507.2000

Cited by 54 publications

(57 citation statements)

References 96 publications

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“…Because of the HrpS-NtrC homology, it seemed likely that a P. syringae homologue of rpoN would be required for activation of the hrp gene cluster. Circumstantial evidence in support of this conclusion was provided by our findings presented in the accompanying study that the rpoN gene of P. syringae is required for pathogenesis and the HR (32).…”

supporting

confidence: 68%

“…However, pHRPLC had no effect on other rpoN phenotypes, such as nonmotility and the inability to utilize nitrate as a sole nitrogen source (data not shown). As shown in the accompanying study (32), constitutive hrpL expression also did not restore expression of the phytotoxin coronatine, suggesting that ES4326 rpoN::Km r (pHRPLC) phenotypes are most likely due to the specific activation of hrp and avrRpt2 genes. Interestingly, as shown in Fig.…”

Section: Vol 182 2000 Rpon Activation Of Hrp Genes In P Syringae 3511mentioning

confidence: 93%

“…However, rpoN is often found to control multiple functions, including flagellar synthesis and nitrogen utilization (41,50,60). Moreover, P. syringae pathovars produce a number of toxins, including syringomycins, tabtoxin, phaseolotoxin, tagetitoxin, and coronatine (6), and we have found that rpoN is required for the expression of coronatine (32). Therefore, rpoN might be involved in the regulation of a number of virulence factors in addition to the hrp cluster, and our finding that rpoN mutants are nonpathogenic is not definitive evidence that rpoN regulates hrp gene expression.…”

mentioning

confidence: 97%

“…In contrast, ES4326 carrying the avirulence gene avrRpt2 elicits a visible HR about 16 h after infiltration, and its multiplication in planta is 50-to 100-fold less than ES4326 (16). In the accompanying publication, we describe the isolation and characterization of an ES4326 rpoN mutant (32). We describe here experiments examining the effect of the rpoN mutant on hrp and avr gene regulation in ES4326.…”

mentioning

confidence: 99%

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The Alternative Sigma Factor RpoN Is Required for hrp Activity in Pseudomonas syringae pv. Maculicola and Acts at the Level of hrpL Transcription

2000

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␤-Glucuronidase (uidA) reporter gene fusions were constructed for the hrpZ, hrpL, and hrpS genes from the phytopathogen Pseudomonas syringae pv. maculicola strain ES4326. These reporters, as well as an avrRpt2-uidA fusion, were used to measure transcriptional activity in ES4326 and a ES4326 rpoN mutant. rpoN was required for the expression of avrRpt2, hrpZ, and hrpL in vitro in minimal media and in vivo when infiltrated into Arabidopsis thaliana leaves. In contrast, the expression of hrpS was essentially the same in wild-type and rpoN mutant strains. Constitutive expression of hrpL in an rpoN mutant restored hrpZ transcription to wild-type levels, restored the hypersensitive response when infiltrated into tobacco (Nicotiana tobacum), and partially restored the elicitation of virulence-related symptoms but not growth when infiltrated into Arabidopsis leaves. These data indicate that rpoN-mediated control of hrp gene expression acts at the level of hrpL and that in planta growth of P. syringae is not required for the elicitation of disease symptoms.In gram-negative bacteria, transcriptional activation in response to external stimuli often involves the alternative sigma factor 54 (1, 50). 54 , which is encoded by rpoN, works in conjunction with members of the NtrC superfamily of transcriptional activators (1, 50). Among the different enzymatic pathways under 54 control are those responsible for nitrogen utilization, dicarboxylate transport, xylene degradation, and hydrogen utilization (8,39,47,79).In the case of some phytopathogenic bacterial species, rpoN has been implicated indirectly as a regulator of a large cluster of pathogenicity-related genes known as the hrp gene cluster (17,27). For example, Pseudomonas syringae pv. syringae strain 61 contains a 25-kb hrp cluster consisting of 27 genes arranged as follows : hrpKL, hrpJ, hrcV, hrpQ, hrcN, hrpOP, hrcQRSTU, hrpVT, hrcC, hrpGF, hrpED, hrcJ, hrpBZA, and hrpSR (11,33). The acronym hrp stands for hypersensitive response and pathogenicity. The genes within the hrp cluster are required not only for pathogenicity but also for elicitation of the plant resistance reaction known as the hypersensitive response (HR) (44, 45). The HR involves rapid, localized plant cell death, which is triggered by a gene-for-gene interaction between a particular avirulence (avr) gene in the pathogen and a corresponding resistance gene in the host (21, 56). The widely conserved members of the hrp cluster, designated hrc, show significant homology to members of the Yersinia type III secretory pathway and in the new simplified nomenclature bear the letter designation of the corresponding Yersinia gene (9). (The exception is hrcV, which is homologous to the Yersinia lcrD genes.)Sequence analysis of the hrp cluster in P. syringae pv. phaseolicola suggested that 54 would be required for hrp gene expression in conjunction with the hrpRS genes, which are required for expression of the remaining hrp genes in the cluster (17, 27). hrpR and hrpS encode proteins that contain the domain conserved ...

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supporting

confidence: 68%

Section: Vol 182 2000 Rpon Activation Of Hrp Genes In P Syringae 3511mentioning

confidence: 93%

mentioning

confidence: 97%

mentioning

confidence: 99%

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The Alternative Sigma Factor RpoN Is Required for hrp Activity in Pseudomonas syringae pv. Maculicola and Acts at the Level of hrpL Transcription

2000

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“…During the infection process, P. syringae controls gene expression via global regulators such as the gacA/gacS two-component regulatory system (Chatterjee et al, 2003) and rpoN (Hendrickson et al, 2000;Totten et al, 1990). Therefore, cross-talk between the major regulatory systems and transcriptional activators must be coordinated.…”

Section: Discussionmentioning

confidence: 99%

AlgR functions in algC expression and virulence in Pseudomonas syringae pv. syringae

et al. 2004

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Pseudomonas syringae pv. syringae strain FF5 is a phytopathogen associated with a rapid dieback on ornamental pear trees. P. syringae and the human pathogen Pseudomonas aeruginosa produce the exopolysaccharide alginate, a copolymer of mannuronic and guluronic acid. In P. aeruginosa, the response regulator AlgR (AlgR1) is required for transcription of algC and algD, which encode key enzymes in the alginate biosynthetic pathway. In P. syringae FF5, however, algR is not required for the activation of algD. Interestingly, algR mutants of P. syringae remain nonmucoid, indicating an undefined role for this response regulator in alginate biosynthesis. In the current study, the algC promoter region was cloned from P. syringae pv. syringae strain FF5, and sequence analysis of the algC promoter indicated the presence of potential binding sites for AlgR and s 54 , the alternative sigma factor encoded by rpoN. The algC promoter from P. syringae FF5 (PsalgC) was cloned upstream of a promoterless glucuronidase gene (uidA), and the PsalgC-uidA transcriptional fusion was used to monitor algC expression in strains FF5.32 (algR mutant of P. syringae FF5) and PG4180.K2 (rpoN mutant of P. syringae pv. glycinea PG4180). Expression of the PsalgC-uidA fusion was fourfold lower in both the algR and rpoN mutants as compared to respective wild-type strains, indicating that both AlgR and s 54 are required for full activation of algC transcription in P. syringae pv. syringae. AlgR from P. syringae was successfully overproduced in Escherichia coli as a C-terminal translational fusion to the maltose-binding protein (MBP). Gel shift experiments indicated that MBP-AlgR binds strongly to the algC promoter region. Biological assays demonstrated that the algR mutant was significantly impaired in both pathogenicity and epiphytic fitness as compared to the wild-type strain. These results, along with the gene expression studies, indicate that AlgR has a positive role in the activation of algC in P. syringae and contributes to both virulence and epiphytic fitness. Furthermore, the symptoms observed with wild-type P. syringae FF5 suggest that this strain can move systemically in leaf tissue, and that a functional copy of algR is required for systemic movement.

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Detection of the phytotoxin coronatine by ELISA and localization in infected plant tissue

Zhao

Jones

Sutherland

et al. 2001

Physiological and Molecular Plant Pathology

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Virulence of the Phytopathogen Pseudomonas syringae pv. Maculicola Is rpoN Dependent

Cited by 54 publications

References 96 publications

The Alternative Sigma Factor RpoN Is Required for hrp Activity in Pseudomonas syringae pv. Maculicola and Acts at the Level of hrpL Transcription

The Alternative Sigma Factor RpoN Is Required for hrp Activity in Pseudomonas syringae pv. Maculicola and Acts at the Level of hrpL Transcription

AlgR functions in algC expression and virulence in Pseudomonas syringae pv. syringae

Detection of the phytotoxin coronatine by ELISA and localization in infected plant tissue

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