scholarly journals The proteasome acts as a hub for local and systemic plant immunity in Arabidopsis thaliana and constitutes a virulence target of Pseudomonas syringae type-III effector proteins

2016 ◽  
Author(s):  
Suayib Üstün ◽  
Arsheed Sheikh ◽  
Selena Gimenez-Ibanez ◽  
Alexandra Jones ◽  
Vardis Ntoukakis ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Bacterial Growth ◽  
Plant Immunity ◽  
Effector Proteins ◽  
Proteasome Activity ◽  
General Strategy ◽  
Dependent Manner ◽  
Type Iii Effector ◽  
Type Iii ◽  
Proteasome Subunits

AbstractRecent evidence suggests that the ubiquitin-proteasome system (UPS) is involved in several aspects of plant immunity and a range of plant pathogens subvert the UPS to enhance their virulence. Here, we show that proteasome activity is strongly induced during basal defense in Arabidopsis and mutant lines defective in proteasome subunits RPT2a and RPN12a support increased bacterial growth of virulent Pseudomonas syringae DC3000 (Pst), strains in local leaves. Both proteasome subunits are required for PTI events such as production of reactive oxygen species and mitogen-activated protein kinases signaling as well as for defense gene expression. Furthermore, analysis of bacterial growth after a secondary infection of systemic leaves revealed that the establishment of systemic-acquired resistance (SAR) is impaired in proteasome mutants, suggesting that the proteasome plays an important role in defense priming and SAR. In addition, we show that Pst inhibits proteasome activity in a type-III secretion dependent manner. A systematic screen for type-III effector proteins from Pst for their ability to interfere with proteasome activity revealed HopM1, HopAO1, HopA1 and HopG1 as candidates. Identification of proteins interacting with HopM1 by mass-spectrometry indicate that HopM1 resides in a complex together with several E3 ubiquitin ligases and proteasome subunits, supporting the hypothesis that HopM1 associates with the proteasome leading to its inhibition. We conclude that the proteasome is an essential component of the plant immune system and that some pathogens have developed a general strategy to overcome proteasome-mediated defense.One sentence summaryThe proteasome is required for local and systemic immune responses and is targeted by Pseudomonas type-III effectors

scholarly journals Identification of Novel Type III Secretion Effectors in Xanthomonas oryzae pv. oryzae

2009 ◽  
Vol 22 (1) ◽  
pp. 96-106 ◽  
Author(s):  
Ayako Furutani ◽  
Minako Takaoka ◽  
Harumi Sanada ◽  
Yukari Noguchi ◽  
Takashi Oku ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Pathogenic Bacteria ◽  
Regulatory Protein ◽  
Effector Proteins ◽  
Xanthomonas Oryzae ◽  
Dependent Manner ◽  
Plant Pathogenic Bacteria ◽  
Type Iii ◽  
Genes Encoding

Many gram-negative bacteria secrete so-called effector proteins via a type III secretion (T3S) system. Through genome screening for genes encoding potential T3S effectors, 60 candidates were selected from rice pathogen Xanthomonas oryzae pv. oryzae MAFF311018 using these criteria: i) homologs of known T3S effectors in plant-pathogenic bacteria, ii) genes with expression regulated by hrp regulatory protein HrpX, or iii) proteins with N-terminal amino acid patterns associated with T3S substrates of Pseudomonas syringae. Of effector candidates tested with the Bordetella pertussis calmodulin-dependent adenylate cyclase reporter for translocation into plant cells, 16 proteins were translocated in a T3S system-dependent manner. Of these 16 proteins, nine were homologs of known effectors in other plant-pathogenic bacteria and seven were not. Most of the effectors were widely conserved in Xanthomonas spp.; however, some were specific to X. oryzae. Interestingly, all these effectors were expressed in an HrpX-dependent manner, suggesting coregulation of effectors and the T3S system. In X. campestris pv. vesicatoria, HpaB and HpaC (HpaP in X. oryzae pv. oryzae) have a central role in recruiting T3S substrates to the secretion apparatus. Secretion of all but one effector was reduced in both HpaB– and HpaP– mutant strains, indicating that HpaB and HpaP are widely involved in efficient secretion of the effectors.

scholarly journals Pseudomonas syringae Two-Component Response Regulator RhpR Regulates Promoters Carrying an Inverted Repeat Element

2010 ◽  
Vol 23 (7) ◽  
pp. 927-939 ◽  
Author(s):  
Xin Deng ◽  
Lefu Lan ◽  
Yanmei Xiao ◽  
Megan Kennelly ◽  
Jian-Min Zhou ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Inverted Repeat ◽  
Response Regulator ◽  
Effector Proteins ◽  
Dependent Manner ◽  
Type Iii ◽  
Regulatory Cascade ◽  
Two Component ◽  
Genes Encoding ◽  
Element Activity

The two-component system RhpRS was identified in Pseudomonas syringae as a regulator of the genes encoding the type III secretion system and type III effector proteins (together called the T3 genes). In the absence of the sensor kinase RhpS, the response regulator RhpR represses the induction of the T3 gene regulatory cascade consisting of hrpRS, hrpL, and the T3 genes in a phosphorylation-dependent manner. The repressor activity of RhpR is inhibited by RhpS, which presumably acts as a phosphatase under the T3 gene inducing conditions. Here, we show that RhpR binds and induces its own promoter in a phosphorylation-dependent manner. Deletion and mutagenesis analyses revealed an inverted repeat (IR) element, GTATC-N6-GATAC, in the rhpR promoter that confers the RhpR-dependent induction. Computational search of the P. syringae genomes for the putative IR elements and Northern blot analysis of the genes with a putative IR element in the promoter region uncovered five genes that were upregulated and two genes that were downregulated in an RhpR-dependent manner. Two genes that were strongly induced by RhpR were assayed for the IR element activity in gene regulation and, in both cases, the IR element mediated the RhpR-dependent gene induction. Chromatin immunoprecipitation assays indicated that RhpR binds the promoters containing a putative IR element but not the hrpR and hrpL promoters that do not have an IR element, suggesting that RhpR indirectly regulates the transcriptional cascade of hrpRS, hrpL, and the T3 genes.

scholarly journals The Majority of the Type III Effector Inventory of Pseudomonas syringae pv. tomato DC3000 Can Suppress Plant Immunity

2009 ◽  
Vol 22 (9) ◽  
pp. 1069-1080 ◽  
Author(s):  
Ming Guo ◽  
Fang Tian ◽  
Yashitola Wamboldt ◽  
James R. Alfano
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Immunity ◽  
In Planta ◽  
Tomato Dc3000 ◽  
Type Iii Effector ◽  
Type Iii Effectors ◽  
Type Iii ◽  
Molecular Pattern ◽  
Effector Triggered Immunity ◽  
Type Iii Protein Secretion

The Pseudomonas syringae type III protein secretion system (T3SS) and the type III effectors it injects into plant cells are required for plant pathogenicity and the ability to elicit a hypersensitive response (HR). The HR is a programmed cell death that is associated with effector-triggered immunity (ETI). A primary function of P. syringae type III effectors appears to be the suppression of ETI and pathogen-associated molecular pattern–triggered immunity (PTI), which is induced by conserved molecules on microorganisms. We reported that seven type III effectors from P. syringae pv. tomato DC3000 were capable of suppressing an HR induced by P. fluorescens(pHIR11) and have now tested 35 DC3000 type III effectors in this assay, finding that the majority of them can suppress the HR induced by HopA1. One newly identified type III effector with particularly strong HR suppression activity was HopS2. We used the pHIR11 derivative pLN1965, which lacks hopA1, in related assays and found that a subset of the type III effectors that suppressed HopA1-induced ETI also suppressed an ETI response induced by AvrRpm1 in Arabidopsis thaliana. A. thaliana plants expressing either HopAO1 or HopF2, two type III effectors that suppressed the HopA1-induced HR, were reduced in the flagellin-induced PTI response as well as PTI induced by other PAMPs and allowed enhanced in planta growth of P. syringae. Collectively, our results suggest that the majority of DC3000 type III effectors can suppress plant immunity. Additionally, the construct pLN1965 will likely be a useful tool in determining whether other type III effectors or effectors from other types of pathogens can suppress either ETI, PTI, or both.

scholarly journals Pseudomonas syringae type III effector HopAF1 suppresses plant immunity by targeting methionine recycling to block ethylene induction

2016 ◽  
Vol 113 (25) ◽  
pp. E3577-E3586 ◽  
Author(s):  
Erica J. Washington ◽  
M. Shahid Mukhtar ◽  
Omri M. Finkel ◽  
Li Wan ◽  
Mark J. Banfield ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Pathogens ◽  
Plant Immunity ◽  
Ethylene Biosynthesis ◽  
Host Protein ◽  
Loss Of Function ◽  
Type Iii Effector ◽  
Type Iii ◽  
Host Defense Response ◽  
Molecular Patterns

HopAF1 is a type III effector protein of unknown function encoded in the genomes of several strains of Pseudomonas syringae and other plant pathogens. Structural modeling predicted that HopAF1 is closely related to deamidase proteins. Deamidation is the irreversible substitution of an amide group with a carboxylate group. Several bacterial virulence factors are deamidases that manipulate the activity of specific host protein substrates. We identified Arabidopsis methylthioadenosine nucleosidase proteins MTN1 and MTN2 as putative targets of HopAF1 deamidation. MTNs are enzymes in the Yang cycle, which is essential for the high levels of ethylene biosynthesis in Arabidopsis. We hypothesized that HopAF1 inhibits the host defense response by manipulating MTN activity and consequently ethylene levels. We determined that bacterially delivered HopAF1 inhibits ethylene biosynthesis induced by pathogen-associated molecular patterns and that Arabidopsis mtn1 mtn2 mutant plants phenocopy the effect of HopAF1. Furthermore, we identified two conserved asparagines in MTN1 and MTN2 from Arabidopsis that confer loss of function phenotypes when deamidated via site-specific mutation. These residues are potential targets of HopAF1 deamidation. HopAF1-mediated manipulation of Yang cycle MTN proteins is likely an evolutionarily conserved mechanism whereby HopAF1 orthologs from multiple plant pathogens contribute to disease in a large variety of plant hosts.

scholarly journals The type III effector HopF2Pto targets Arabidopsis RIN4 protein to promote Pseudomonas syringae virulence

2010 ◽  
Vol 107 (5) ◽  
pp. 2349-2354 ◽  
Author(s):  
Mike Wilton ◽  
Rajagopal Subramaniam ◽  
James Elmore ◽  
Corinna Felsensteiner ◽  
Gitta Coaker ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Immunity ◽  
Effector Proteins ◽  
Type Iii ◽  
Pathogen Effector ◽  
Effector Triggered Immunity ◽  
Type Iii Secretion Effector ◽  
Virulence Target

Plant immunity can be induced by two major classes of pathogen-associated molecules. Pathogen- or microbe-associated molecular patterns (PAMPs or MAMPs) are conserved molecular components of microbes that serve as “non-self” features to induce PAMP-triggered immunity (PTI). Pathogen effector proteins used to promote virulence can also be recognized as “non-self” features or induce a “modified-self” state that can induce effector-triggered immunity (ETI). The Arabidopsis protein RIN4 plays an important role in both branches of plant immunity. Three unrelated type III secretion effector (TTSE) proteins from the phytopathogen Pseudomonas syringae, AvrRpm1, AvrRpt2, and AvrB, target RIN4, resulting in ETI that effectively restricts pathogen growth. However, no pathogenic advantage has been demonstrated for RIN4 manipulation by these TTSEs. Here, we show that the TTSE HopF2Pto also targets Arabidopsis RIN4. Transgenic plants conditionally expressing HopF2Pto were compromised for AvrRpt2-induced RIN4 modification and associated ETI. HopF2Pto interfered with AvrRpt2-induced RIN4 modification in vitro but not with AvrRpt2 activation, suggestive of RIN4 targeting by HopF2Pto. In support of this hypothesis, HopF2Pto interacted with RIN4 in vitro and in vivo. Unlike AvrRpm1, AvrRpt2, and AvrB, HopF2Pto did not induce ETI and instead promoted P. syringae growth in Arabidopsis. This virulence activity was not observed in plants genetically lacking RIN4. These data provide evidence that RIN4 is a major virulence target of HopF2Pto and that a pathogenic advantage can be conveyed by TTSEs that target RIN4.

scholarly journals Pseudomonas syringae Exchangeable Effector Loci: Sequence Diversity in Representative Pathovars and Virulence Function in P. syringae pv. syringae B728a

2003 ◽  
Vol 185 (8) ◽  
pp. 2592-2602 ◽  
Author(s):  
Wen-Ling Deng ◽  
Amos H. Rehm ◽  
Amy O. Charkowski ◽  
Clemencia M. Rojas ◽  
Alan Collmer
Keyword(s):  
Pseudomonas Syringae ◽  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Brown Spot ◽  
Dependent Manner ◽  
Type Iii ◽  
Effector Genes

ABSTRACT Pseudomonas syringae is a plant pathogen whose pathogenicity and host specificity are thought to be determined by Hop/Avr effector proteins injected into plant cells by a type III secretion system. P. syringae pv. syringae B728a, which causes brown spot of bean, is a particularly well-studied strain. The type III secretion system in P. syringae is encoded by hrp (hypersensitive response and pathogenicity) and hrc (hrp conserved) genes, which are clustered in a pathogenicity island with a tripartite structure such that the hrp/hrc genes are flanked by a conserved effector locus and an exchangeable effector locus (EEL). The EELs of P. syringae pv. syringae B728a, P. syringae strain 61, and P. syringae pv. tomato DC3000 differ in size and effector gene composition; the EEL of P. syringae pv. syringae B728a is the largest and most complex. The three putative effector proteins encoded by the P. syringae pv. syringae B728a EEL—HopPsyC, HopPsyE, and HopPsyV—were demonstrated to be secreted in an Hrp-dependent manner in culture. Heterologous expression of hopPsyC, hopPsyE, and hopPsyV in P. syringae pv. tabaci induced the hypersensitive response in tobacco leaves, demonstrating avirulence activity in a nonhost plant. Deletion of the P. syringae pv. syringae B728a EEL strongly reduced virulence in host bean leaves. EELs from nine additional strains representing nine P. syringae pathovars were isolated and sequenced. Homologs of avrPphE (e.g., hopPsyE) and hopPsyA were particularly common. Comparative analyses of these effector genes and hrpK (which flanks the EEL) suggest that the EEL effector genes were acquired by horizontal transfer after the acquisition of the hrp/hrc gene cluster but before the divergence of modern pathovars and that some EELs underwent transpositions yielding effector exchanges or point mutations producing effector pseudogenes after their acquisition.

scholarly journals Identification and Functional Analysis of Type III Effector Proteins in Mesorhizobium loti

2010 ◽  
Vol 23 (2) ◽  
pp. 223-234 ◽  
Author(s):  
Shin Okazaki ◽  
Saori Okabe ◽  
Miku Higashi ◽  
Yoshikazu Shimoda ◽  
Shusei Sato ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Rhizobium Leguminosarum ◽  
Plant Pathogens ◽  
Effector Proteins ◽  
Sequence Motif ◽  
Shikimate Kinase ◽  
Model Legume ◽  
Type Iii Effector ◽  
Mesorhizobium Loti ◽  
Type Iii

Mesorhizobium loti MAFF303099, a microsymbiont of the model legume Lotus japonicus, possesses a cluster of genes (tts) that encode a type III secretion system (T3SS). In the presence of heterologous nodD from Rhizobium leguminosarum and a flavonoid naringenin, we observed elevated expression of the tts genes and secretion of several proteins into the culture medium. Inoculation experiments with wild-type and T3SS mutant strains revealed that the presence of the T3SS affected nodulation at a species level within the Lotus genus either positively (L. corniculatus subsp. frondosus and L. filicaulis) or negatively (L. halophilus and two other species). By inoculating L. halophilus with mutants of various type III effector candidate genes, we identified open reading frame mlr6361 as a major determinant of the nodulation restriction observed for L. halophilus. The predicted gene product of mlr6361 is a protein of 3,056 amino acids containing 15 repetitions of a sequence motif of 40 to 45 residues and a shikimate kinase-like domain at its carboxyl terminus. Homologues with similar repeat sequences are present in the hypersensitive-response and pathogenicity regions of several plant pathogens, including strains of Pseudomonas syringae, Ralstonia solanacearum, and Xanthomonas species. These results suggest that L. halophilus recognizes Mlr6361 as potentially pathogen derived and subsequently halts the infection process.

scholarly journals A remorin from Nicotiana benthamiana interacts with the Pseudomonas type-III effector protein HopZ1a and is phosphorylated by the immune-related kinase PBS1

2018 ◽  
Author(s):  
Philip Albers ◽  
Suayib Üstün ◽  
Katja Witzel ◽  
Max Kraner ◽  
Frederik Börnke
Keyword(s):  
Plasma Membrane ◽  
Pseudomonas Syringae ◽  
Nicotiana Benthamiana ◽  
Effector Proteins ◽  
Effector Protein ◽  
Type Iii Effector ◽  
Defense Signaling ◽  
Type Iii ◽  
Transient Overexpression

AbstractThe plasma membrane is at the interface of plant-pathogen interactions and thus many bacterial type-III effector proteins (T3Es) target membrane-associated processes to interfere with immunity. The Pseudomonas syringae T3E is a host cell plasma membrane (PM)-localized effector protein that has several immunity associated host targets but also activates effector triggered immunity (ETI) in resistant backgrounds. Although HopZ1a has been shown to interfere with early defense signaling at the PM, no dedicated plasma membrane-associated HopZ1a target protein has been identified until now. We show here, that HopZ1a interacts with the PM-associated remorin protein NbREM4 from Nicotiana benthamiana in several independent assays. NbREM4 re-localizes to membrane sub-domains after treatment with the bacterial elicitor flg22 and transient overexpression of NbREM4 in N. benthamiana induces the expression of a subset of defense related genes. We can further show that NbREM4 interacts with the immune-related receptor-like cytoplasmic kinase PBS1 and is phosphorylated by PBS1 on several residues in vitro. Thus, we conclude that NbREM4 is associated with early defense signaling at the PM. The possible relevance of the HopZ1a/NbREM4 interaction for HopZ1a virulence and avirulence functions is discussed.

scholarly journals Pseudomonas syringae evades phagocytosis in animal cells through type III effector-mediated inhibition of the LIM kinase-cofilin system

2018 ◽  
Author(s):  
Sung-Jin Yoon ◽  
Soohyun Lee ◽  
Jun-Seob Kim ◽  
Sang-Hyun Lee ◽  
Song Choi ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Pathogenic Bacteria ◽  
Actin Polymerization ◽  
Plant Immunity ◽  
Direct Interaction ◽  
Effector Proteins ◽  
Animal Cells ◽  
Lim Kinase ◽  
Plant Pathogenic Bacteria ◽  
Type Iii

ABSTRACTCertain animal and plant pathogenic bacteria have developed virulence factors (including effector proteins) that enable them to overcome host immunity. A plant pathogen, Pseudomonas syringae pv. tomato (Pto), secretes a large repertoire of effectors into plant cells via a type III secretory apparatus, thereby suppressing plant immunity. Here, we show that exposure to Pto caused sepsis in mice. Surprisingly, the effector HopQ1 disrupted phagocytosis by inhibiting actin rearrangement via a direct interaction with the LIM domain of the animal target protein LIM kinase, a key regulator of actin polymerization. The results provide new insights into cross-kingdom pathogenicity of bacteria. The current studies demonstrate that certain plant pathogenic bacteria such as Pto can be fatal in animals due to cross-kingdom host immune suppression.

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