scholarly journals A DeoR-Type Transcription Regulator Is Required for Sugar-Induced Expression of Type III Secretion-Encoding Genes in Pseudomonas syringae pv. tomato DC3000

2020 ◽  
Vol 33 (3) ◽  
pp. 509-518 ◽  
Author(s):  
Sydney E. Turner ◽  
Yin-Yuin Pang ◽  
Megan R. O’Malley ◽  
Alexandra J. Weisberg ◽  
Valerie N. Fraser ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Molecular Mechanisms ◽  
In Planta ◽  
Induced Expression ◽  
Tn5 Transposon ◽  
Type Iii ◽  
Genes Encoding ◽  
Tn5 Mutant ◽  
Encoding Genes

The type III secretion system (T3SS) of plant-pathogenic Pseudomonas syringae is essential for virulence. Genes encoding the T3SS are not constitutively expressed and must be induced upon infection. Plant-derived metabolites, including sugars such as fructose and sucrose, are inducers of T3SS-encoding genes, yet the molecular mechanisms underlying perception of these host signals by P. syringae are unknown. Here, we report that sugar-induced expression of type III secretion A (setA), predicted to encode a DeoR-type transcription factor, is required for maximal sugar-induced expression of T3SS-associated genes in P. syringae DC3000. From a Tn5 transposon mutagenesis screen, we identified two independent mutants with insertions in setA. When both setA::Tn5 mutants were cultured in minimal medium containing fructose, genes encoding the T3SS master regulator HrpL and effector AvrRpm1 were expressed at lower levels relative to that of a wild-type strain. Decreased hrpL and avrRpm1 expression also occurred in a setA::Tn5 mutant in response to glucose, sucrose, galactose, and mannitol, demonstrating that setA is genetically required for T3SS induction by many different sugars. Expression of upstream regulators hrpR/S and rpoN was not altered in setA::Tn5, indicating that SetA positively regulates hrpL expression independently of increased transcription of these genes. In addition to decreased response to defined sugar signals, a setA::Tn5 mutant had decreased T3SS deployment during infection and was compromised in its ability to grow in planta and cause disease. These data suggest that SetA is necessary for P. syringae to effectively respond to T3SS-inducing sugar signals encountered during infection.

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 Molecular mechanisms of two-component system RhpRS regulating type III secretion system in Pseudomonas syringae

2014 ◽  
Vol 42 (18) ◽  
pp. 11472-11486 ◽  
Author(s):  
Xin Deng ◽  
Haihua Liang ◽  
Kai Chen ◽  
Chuan He ◽  
Lefu Lan ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Molecular Mechanisms ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Two Component System ◽  
Component System ◽  
Type Iii ◽  
Two Component

scholarly journals Multiple Xanthomonas euvesicatoria Type III Effectors Inhibit flg22-Triggered Immunity

2016 ◽  
Vol 29 (8) ◽  
pp. 651-660 ◽  
Author(s):  
Georgy Popov ◽  
Malou Fraiture ◽  
Frederic Brunner ◽  
Guido Sessa
Keyword(s):  
Pseudomonas Syringae ◽  
Map Kinases ◽  
Molecular Mechanisms ◽  
Inducible Promoter ◽  
Effector Proteins ◽  
Host Cells ◽  
In Planta ◽  
Callose Deposition ◽  
Type Iii ◽  
Xanthomonas Euvesicatoria

Xanthomonas euvesicatoria is the causal agent of bacterial spot disease in pepper and tomato. X. euvesicatoria bacteria interfere with plant cellular processes by injecting effector proteins into host cells through the type III secretion (T3S) system. About 35 T3S effectors have been identified in X. euvesicatoria 85-10, and a few of them were implicated in suppression of pattern-triggered immunity (PTI). We used an Arabidopsis thaliana pathogen-free protoplast–based assay to identify X. euvesicatoria 85-10 effectors that interfere with PTI signaling induced by the bacterial peptide flg22. Of 33 tested effectors, 17 inhibited activation of a PTI-inducible promoter. Among them, nine effectors also interfered with activation of an abscisic acid–inducible promoter. However, effectors that inhibited flg22-induced signaling did not affect phosphorylation of mitogen-activated protein (MAP) kinases acting downstream of flg22 perception. Further investigation of selected effectors revealed that XopAJ, XopE2, and XopF2 inhibited activation of a PTI-inducible promoter by the bacterial peptide elf18 in Arabidopsis protoplasts and by flg22 in tomato protoplasts. The effectors XopF2, XopE2, XopAP, XopAE, XopH, and XopAJ inhibited flg22-induced callose deposition in planta and enhanced disease symptoms caused by attenuated Pseudomonas syringae bacteria. Finally, selected effectors were found to localize to various plant subcellular compartments. These results indicate that X. euvesicatoria bacteria utilize multiple T3S effectors to suppress flg22-induced signaling acting downstream or in parallel to MAP kinase cascades and suggest they act through different molecular mechanisms.

scholarly journals Components of the Pseudomonas syringae Type III Secretion System Can Suppress and May Elicit Plant Innate Immunity

2010 ◽  
Vol 23 (6) ◽  
pp. 727-739 ◽  
Author(s):  
Hye-Sook Oh ◽  
Duck Hwan Park ◽  
Alan Collmer
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Leaf Tissue ◽  
Secretion System ◽  
Colony Development ◽  
Plant Responses ◽  
In Planta ◽  
Callose Deposition ◽  
Type Iii

The type III secretion system (T3SS) of Pseudomonas syringae translocates into plant cells multiple effectors that suppress pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI). P. syringae pv. tomato DC3000 no longer delivers the T3SS translocation reporter AvrPto-Cya in Nicotiana benthamiana leaf tissue in which PTI was induced by prior inoculation with P. fluorescens(pLN18). Cosmid pLN18 expresses the T3SS system of P. syringae pv. syringae 61 but lacks the hopA1Psy61 effector gene. P. fluorescens(pLN18) expressing HrpHPtoDC3000 or HopP1PtoDC3000, two T3SS-associated putative lytic transglycosylases, suppresses PTI, based on multiple assays involving DC3000 challenge inoculum (AvrPto-Cya translocation, hypersensitive response elicitation, and colony development in planta) or on plant responses (vascular dye uptake or callose deposition). Analysis of additional mutations in pHIR11 derivatives revealed that the pLN18-encoded T3SS elicits a higher level of reactive oxygen species (ROS) than does P. fluorescens without a T3SS, that enhanced ROS production is dependent on the HrpK1 translocator, and that HopA1Psy61 suppresses ROS elicitation attributable to both the P. fluorescens PAMPs and the presence of a functional T3SS.

scholarly journals Negative Regulation of the Hrp Type III Secretion System in Pseudomonas syringae pv. phaseolicola

2010 ◽  
Vol 23 (5) ◽  
pp. 682-701 ◽  
Author(s):  
Inmaculada Ortiz-Martín ◽  
Richard Thwaites ◽  
John W. Mansfield ◽  
Carmen R. Beuzón
Keyword(s):  
Gene Expression ◽  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Pathogenic Bacteria ◽  
In Planta ◽  
Secretion Systems ◽  
Type Iii ◽  
Type Iii Secretion Systems ◽  
Bacterial Fitness

Many plant-pathogenic bacteria require type III secretion systems (T3SS) to cause disease in compatible hosts and to induce the hypersensitive response in resistant plants. T3SS gene expression is induced within the plant and responds to host and environmental factors. In Pseudomonas syringae, expression is downregulated by the Lon protease in rich medium and by HrpV under inducing conditions. HrpV acts as an anti-activator by binding HrpS. HrpG, which can also bind HrpV, has been reported to act as an anti-anti-activator. Previous studies have used mostly in vitro inducing conditions, different pathovars, and methodology. We have used single and double lon and hrpV mutants of P. syringae pv. phaseolicola 1448a, as well as strains ectopically expressing the regulators, to examine their role in coordinating expression of the T3SS. We applied real-time polymerase chain reaction to analyze gene expression both in vitro and in planta, and assessed bacterial fitness using competitive indices. Our results indicate that i) Lon downregulates expression of the hrp/hrc genes in all conditions, probably by constitutively degrading naturally unstable HrpR; ii) HrpV and HrpT downregulate expression of the hrp/hrc genes in all conditions; and iii) HrpG has an additional, HrpV-independent role, regulating expression of the hrpC operon.

scholarly journals Naturally Occurring Nonpathogenic Isolates of the Plant Pathogen Pseudomonas syringae Lack a Type III Secretion System and Effector Gene Orthologues

2008 ◽  
Vol 190 (8) ◽  
pp. 2858-2870 ◽  
Author(s):  
Toni J. Mohr ◽  
Haijie Liu ◽  
Shuangchun Yan ◽  
Cindy E. Morris ◽  
José A. Castillo ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Plant Diseases ◽  
In Planta ◽  
Type Iii ◽  
Effector Gene

ABSTRACT Pseudomonas syringae causes plant diseases, and the main virulence mechanism is a type III secretion system (T3SS) that translocates dozens of effector proteins into plant cells. Here we report the existence of a subgroup of P. syringae isolates that do not cause disease on any plant species tested. This group is monophyletic and most likely evolved from a pathogenic P. syringae ancestor through loss of the T3SS. In the nonpathogenic isolate P. syringae 508 the genomic region that in pathogenic P. syringae strains contains the hrp-hrc cluster coding for the T3SS and flanking effector genes is absent. P. syringae 508 was also surveyed for the presence of effector orthologues from the closely related pathogenic strain P. syringae pv. syringae B728a, but none were detected. The absence of the hrp-hrc cluster and effector orthologues was confirmed for other nonpathogenic isolates. Using the AvrRpt2 effector as reporter revealed the inability of P. syringae 508 to translocate effectors into plant cells. Adding a plasmid-encoded T3SS and the P. syringae pv. syringae 61 effector gene hopA1 increased in planta growth almost 10-fold. This suggests that P. syringae 508 supplemented with a T3SS could be used to determine functions of individual effectors in the context of a plant infection, avoiding the confounding effect of other effectors with similar functions present in effector mutants of pathogenic isolates.

scholarly journals Transcriptional Regulation of Components of the Type III Secretion System and Effectors in Pseudomonas syringae pv. phaseolicola

2004 ◽  
Vol 17 (11) ◽  
pp. 1250-1258 ◽  
Author(s):  
R. Thwaites ◽  
P. D. Spanu ◽  
N. J. Panopoulos ◽  
C. Stevens ◽  
J. W. Mansfield
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Plant Cell Wall ◽  
Type Iii Secretion System ◽  
Regulatory Elements ◽  
Secretion System ◽  
Mrna Levels ◽  
In Planta ◽  
Type Iii ◽  
Effector Genes

Quantitative real-time polymerase chain reaction was used with specific TaqMan probes to examine transcription of selected hrp and effector genes in Pseudomonas syringae pv. phaseolicola strains 1448A (race 6) and 1449B (race 7). Transcripts examined were from genes encoding the regulators hrpR and hrpL, core structural components of the type III secretion system (TTSS) hrcC, hrcJ, hrcN, hrcU, and hrpA; the first open-reading frame of each hrp operon, including hrpF, hrpJ, hrpP, and hrpY; and also secreted effectors hrpZ, avrPphE, avrPphF, and virPphA. All genes were induced by incubation in a minimal medium and showed patterns of expression indicating regulation by HrpRS and HrpL. Basal mRNA levels and the timing of accumulation of transcripts after induction differed significantly, suggesting the operation of additional regulatory elements. However, no clear transcriptional hierarchy emerged to explain the ordered construction of the TTSS. Quantitative analysis confirmed that the rates and levels of transcript accumulation within the first 2 h after inoculation were considerably higher in planta than in vitro, and indicated that plant cell wall contact may enhance transcription of TTSS and effector genes in P. syringae pv. phaseolicola. The low-abundance hrcU mRNA had a half-life of 16.5 min, whereas other transcripts had half-lives between 3 and 8 min.

scholarly journals Transcriptional profiling of three Pseudomonas syringae pv. actinidiae biovars reveals different responses to apoplast-like conditions related to strain virulence

2020 ◽  
Author(s):  
Elodie Vandelle ◽  
Teresa Colombo ◽  
Alice Regaiolo ◽  
Tommaso Libardi ◽  
Vanessa Maurizio ◽  
...  
Keyword(s):  
Gene Expression ◽  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Molecular Basis ◽  
Expression Profiles ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Type Iii ◽  
Genes Encoding ◽  
Operon Regulation

AbstractPseudomonas syringae pv. actinidiae (Psa) is a phytopathogen that causes devastating bacterial canker in kiwifruit. Among five biovars defined by genetic, biochemical and virulence traits, Psa3 is the most aggressive and is responsible for the most recent reported outbreaks, but the molecular basis of its heightened virulence is unclear. We therefore designed the first P. syringae multi-strain whole-genome microarray, encompassing biovars Psa1, Psa2 and Psa3 and the well-established model P. syringae pv. tomato, and analyzed early bacterial responses to an apoplast-like minimal medium. Transcriptomic profiling revealed (i) the strong activation in Psa3 of all hrp/hrc cluster genes, encoding components of the type III secretion system required for bacterial pathogenicity and involved in responses to environmental signals; (ii) potential repression of the hrp/hrc cluster in Psa2; and (iii) activation of flagellum-dependent cell motility and chemotaxis genes in Psa1. The detailed investigation of three gene families encoding upstream regulatory proteins (histidine kinases, their cognate response regulators, and proteins with diguanylate cyclase and/or phosphodiesterase domains) indicated that c-di-GMP may be a key regulator of virulence in Psa biovars. The gene expression data were supported by the quantification of biofilm formation. Our findings suggest that diverse early responses to the host apoplast, even among bacteria belonging to the same pathovar, can lead to different virulence strategies and may explain the differing outcomes of infections. Based on our detailed structural analysis of hrp operons, we also propose a revision of hrp cluster organization and operon regulation in P. syringae.Author summaryPseudomonas syringae pv. actinidiae (Psa) is a bacterial pathogen that infects kiwifruit crops. Recent outbreaks have been particularly devastating due to the emergence of a new biovar (Psa3), but the molecular basis of its virulence is unknown so it is difficult to develop mitigation strategies. In this study, we compared the gene expression profiles of Psa3 and various less-virulent biovars in an environment that mimics early infection, to determine the basis of pathogenicity. Genes involved in the assembly and activity of the type III secretion system, which is crucial for the secretion of virulence effectors, were strongly upregulated in Psa3 while lower or not expressed in the other biovars. We also observed the Psa3-specific expression of genes encoding upstream signaling components, confirming that strains of the same bacterial pathovar can respond differently to early contact with their host. Finally, our data suggested a key role in Psa virulence switch ability for the small chemical signaling molecule c-di-GMP, which suppresses the expression of virulence genes. This effect of c-di-GMP levels on Psa3 virulence should be further investigated and confirmed to develop new mitigation methods to target this pathway.

scholarly journals Closing the Circle on the Discovery of Genes Encoding Hrp Regulon Members and Type III Secretion System Effectors in the Genomes of Three Model Pseudomonas syringae Strains

2006 ◽  
Vol 19 (11) ◽  
pp. 1151-1158 ◽  
Author(s):  
Magdalen Lindeberg ◽  
Samuel Cartinhour ◽  
Christopher R. Myers ◽  
Lisa M. Schechter ◽  
David J. Schneider ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Active Member ◽  
Tomato Dc3000 ◽  
Type Iii ◽  
Effector Genes ◽  
Genes Encoding

Pseudomonas syringae strains translocate large and distinct collections of effector proteins into plant cells via the type III secretion system (T3SS). Mutations in T3SS-encoding hrp genes are unable to elicit the hypersensitive response or pathogenesis in nonhost and host plants, respectively. Mutations in individual effectors lack strong phenotypes, which has impeded their discovery. P. syringae effectors are designated Hop (Hrp outer protein) or Avr (avirulence) proteins. Some Hop proteins are considered to be extracellular T3SS helpers acting at the plant-bacterium interface. Identification of complete sets of effectors and related proteins has been enabled by the application of bioinformatic and high-throughput experimental techniques to the complete genome sequences of three model strains: P. syringae pv. tomato DC3000, P. syringae pv. phaseolicola 1448A, and P. syringae pv. syringae B728a. Several recent papers, including three in this issue of Molecular Plant-Microbe Interactions, address the effector inventories of these strains. These studies establish that active effector genes in P. syringae are expressed by the HrpL alternative sigma factor and can be predicted on the basis of cis Hrp promoter sequences and N-terminal amino-acid patterns. Among the three strains analyzed, P. syringae pv. tomato DC3000 has the largest effector inventory and P. syringae pv. syringae B728a has the smallest. Each strain has several effector genes that appear inactive. Only five of the 46 effector families that are represented in these three strains have an active member in all of the strains. Web-based community resources for managing and sharing growing information on these complex effector arsenals should help future efforts to understand how effectors promote P. syringae virulence.

scholarly journals Bioinformatics-Enabled Identification of the HrpL Regulon and Type III Secretion System Effector Proteins of Pseudomonas syringae pv. phaseolicola 1448A

2006 ◽  
Vol 19 (11) ◽  
pp. 1193-1206 ◽  
Author(s):  
Monica Vencato ◽  
Fang Tian ◽  
James R. Alfano ◽  
C. Robin Buell ◽  
Samuel Cartinhour ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Host Cells ◽  
Candidate Gene Approach ◽  
Type Iii Effectors ◽  
Type Iii ◽  
Genes Encoding

The ability of Pseudomonas syringae pv. phaseolicola to cause halo blight of bean is dependent on its ability to translocate effector proteins into host cells via the hypersensitive response and pathogenicity (Hrp) type III secretion system (T3SS). To identify genes encoding type III effectors and other potential virulence factors that are regulated by the HrpL alternative sigma factor, we used a hidden Markov model, weight matrix model, and type III targeting-associated patterns to search the genome of P. syringae pv. phaseolicola 1448A, which recently was sequenced to completion. We identified 44 high-probability putative Hrp promoters upstream of genes encoding the core T3SS machinery, 27 candidate effectors and related T3SS substrates, and 10 factors unrelated to the Hrp system. The expression of 13 of these candidate HrpL regulon genes was analyzed by real-time polymerase chain reaction, and all were found to be upregulated by HrpL. Six of the candidate type III effectors were assayed for T3SS-dependent translocation into plant cells using the Bordetella pertussis calmodulin-dependent adenylate cyclase (Cya) translocation reporter, and all were translocated. PSPPH1855 (ApbE-family protein) and PSPPH3759 (alcohol dehydrogenase) have no apparent T3SS-related function; however, they do have homologs in the model strain P. syringae pv. tomato DC3000 (PSPTO2105 and PSPTO0834, respectively) that are similarly upregulated by HrpL. Mutations were constructed in the DC3000 homologs and found to reduce bacterial growth in host Arabidopsis leaves. These results establish the utility of the bioinformatic or candidate gene approach to identifying effectors and other genes relevant to pathogenesis in P. syringae genomes.

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