Regulation and Detection of Effectors Translocated by Pseudomonas syringae

Hutcheson, Steven W.; Bretz, James R.; Charity, James C.; Losada, Liliana; Sussan, Thomas E.

doi:10.1007/978-94-017-0133-4_16

Cited by 3 publications

(3 citation statements)

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“…RspV mutation does not affect rspU expression. HrpV negatively regulates TTSS gene expression in P. syringae, possibly by negatively regulating HrpS (20). In rich growth medium, mutation of hrpV in P. syringae pv.…”

Section: Vol 187 2005 Pseudomonas Fluorescens Rsp Gene Regulation 8483mentioning

confidence: 99%

“…HrpL controls a regulon consisting of hrp/hrc structural genes and effector genes by recognition of a specific promoter sequence upstream of the regulated genes (10,21,42,43). The hrpV gene, within the hrcC operon, encodes a negative regulator of hrp gene expression that is predicted to act above the level of hrpL expression, possibly binding to and affecting HrpS activity (20,32). Recently, Lon protease has been shown to negatively regulate hrp gene expression (4) by affecting the level of HrpR in bacterial cells and thus imposing stringent negative regulation.…”

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Genetic Characterization ofPseudomonas fluorescensSBW25rspGene Expression in the Phytosphere and In Vitro

2005

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The plant-colonizing Pseudomonas fluorescens strain SBW25 harbors a gene cluster (rsp) whose products show similarity to type III protein secretion systems found in plant and animal pathogens. Here we report a detailed analysis of the expression and regulation of the P. fluorescens rsp pathway, both in the phytosphere and in vitro. A combination of chromosomally integrated transcriptional reporter fusions, overexpressed regulatory genes, and specific mutants reveal that promoters controlling expression of rsp are actively transcribed in the plant rhizosphere but not (with the exception of the rspC promoter) in the phyllosphere. In synthetic medium, regulatory (rspL and rspR) and structural (rspU, plus the putative effector ropE) genes are poorly expressed; the rspC promoter is subject to an additional level of regulatory control. Ectopic expression of regulatory genes in wild-type and mutant backgrounds showed that RspR controls transcription of the alternate sigma factor, rspL, and that RspL controls expression of gene clusters encoding structural genes. Mutation of rspV did not affect RspR-mediated expression of rspU. A search for additional regulators revealed two candidates-one with a role in the conversion of alanine to pyruvate-suggesting that expression of rsp is partly dependent upon the metabolic status of the cell. Mutations in rsp regulators resulted in a significant reduction in competitive colonization of the root tips of sugar beet seedlings but also caused a marked increase in the lag phase of laboratory-grown cultures, indicating that rsp regulatory genes play a more significant general role in the function of P. fluorescens SBW25 than previously appreciated.The plant rhizosphere is a complex environment comprising organic matter and a plethora of microbes, some of which can affect plant health. Pathogens, such as Pythium ultimum, can hinder plant growth, whereas strains of Pseudomonas fluorescens, including P. fluorescens SBW25, can promote plant growth. The mechanism of plant growth promotion involves a combination of competition, antagonism of pathogens via the production of antimicrobial compounds, and induction of systemic resistance (15,16,31,34).To understand the interaction between P. fluorescens SBW25 and plants, SBW25 genes specifically activated in the plant environment were identified via a promoter trapping strategy (11,36). Approximately 100 rhizosphere-induced (rhi) genes have been identified and categorized into six groups: nutrient acquisition, stress response, attachment and surface colonization, antibiotic production, secretion, and unknown. One rhi gene (rhi-18) is hrcC (redesignated rscC), whose product is a component of a type III protein secretion system (TTSS) termed Rsp (33, 36) (Fig. 1).The P. fluorescens SBW25 rsp cluster exhibits a high level of synteny to the group I TTSS clusters of Pseudomonas syringae pv. tomato DC3000 and Erwinia amylovora and is genetically most similar to the P. syringae cluster. The cluster is organized into three putative transcriptional units...

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Section: Vol 187 2005 Pseudomonas Fluorescens Rsp Gene Regulation 8483mentioning

confidence: 99%

mentioning

confidence: 99%

Genetic Characterization ofPseudomonas fluorescensSBW25rspGene Expression in the Phytosphere and In Vitro

2005

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“…Recently we developed a method to identify candidate effectors genes by screening genomic libraries of P. syringae strains for promoters dependent upon HrpL for expression (Hutcheson et al ., 2003). During preliminary trials of this HrpL‐dependent promoter trap assay, the P. syringae pv.…”

Section: Introductionmentioning

confidence: 99%

A translocated protein tyrosine phosphatase of Pseudomonas syringae pv. tomato DC3000 modulates plant defence response to infection

Bretz

Mock

Charity

et al. 2003

Molecular Microbiology

116

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SummaryPseudomonas syringae strains translocate effector proteins into host cells via the hrp -encoded type III protein secretion system (TTSS) to facilitate pathogenesis in susceptible plants. However, the mechanisms by which pathogenesis is favoured by these effectors are not well understood. Individual strains express multiple effectors with apparently distinct activities that are co-ordinately regulated by the alternative sigma factor HrpL. Genes for several effectors were identified in the P. syringae pv. tomato DC3000 genome using a promoter trap assay to identify HrpLdependent promoters. In addition to orthologues of avrPphE and hrpW , an unusual allele of avrPphD was detected that carried an IS 52 insertion. Using this avrPphD ::IS 52 allele as a probe, a wild-type allele of avrPphD, hopPtoD1, and a chimeric homologue were identified in the DC3000 genome. This chimeric homologue, identified as HopPtoD2 in the annotated DC3000 genome, consisted of an amino terminal secretion domain similar to that of AvrPphD fused to a potential protein tyrosine phosphatase domain. Culture filtrates of strains expressing HopPtoD2 were able to dephosphorylate pNPP and two phosphotyrosine peptides. HopPtoD2 was shown to be translocated into Arabidopsis thaliana cells via the hrp -encoded TTSS. A D D D D hopPtoD2 mutant of DC3000 exhibited strongly reduced virulence in Arabidopsis thaliana . Ectopic expression of hopPtoD2 in P. syringae Psy61 that lacks a native hopPtoD2 orthologue delayed the development of several defence-associated responses including programmed cell death, active oxygen production and transcription of the pathogenesis-related gene PR1. The results indicate that HopPtoD2 is a translocated effector with protein tyrosine phosphatase activity that modulates plant defence responses.

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Genetic background of host—pathogen interaction betweenCucumis sativus L. andPseudomonas syringae pv.lachrymans

2009

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The interplay of plant resistance mechanisms and bacterial pathogenicity is very complex. This applies also to the interaction that takes place between the pathogen Pseudomonas syringae pv. lachrymans (Smith et Bryan) and the cucumber (Cucumis sativus L.) as its host plant. Research on P. syringae pv. lachrymans has led to the discovery of specific factors produced during pathogenesis, i.e. toxins or enzymes. Similarly, studies on cucumber have identified the specific types of plant resistance expressed, namely Systemic Acquired Resistance (SAR) or Induced Systemic Resistance (ISR). This paper presents a summary of the current state of knowledge about this particular host-pathogen interaction, with reference to general information about interactions of P. syringae pathovars with host plants.

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Regulation and Detection of Effectors Translocated by Pseudomonas syringae

Cited by 3 publications

References 20 publications

Genetic Characterization ofPseudomonas fluorescensSBW25rspGene Expression in the Phytosphere and In Vitro

Genetic Characterization ofPseudomonas fluorescensSBW25rspGene Expression in the Phytosphere and In Vitro

A translocated protein tyrosine phosphatase of Pseudomonas syringae pv. tomato DC3000 modulates plant defence response to infection

Genetic background of host—pathogen interaction betweenCucumis sativus L. andPseudomonas syringae pv.lachrymans

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