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Budil J, Štenclová P, Kromka A, Lišková P. Development of the Pseudomonas syringae pv. morsprunorum Biofilm Monitored in Real Time Using Attenuated Total Reflection Fourier Transform Infrared Measurements in a Flow Cell Chamber. APPLIED SPECTROSCOPY 2023; 77:500-512. [PMID: 36898963 DOI: 10.1177/00037028231165057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Biofilms of sessile Pseudomonas syringae cells formed on top of plant host's leaves or fruits allow surviving harsh environmental conditions (desiccation) and improve their resistance to antibacterial treatments of crops. A better understanding of these biofilms can help minimize their effect on harvests. In the present study, infrared attenuated total reflection spectroscopy coupled with optical and confocal laser scanning microscopy has been applied for the first time to analyze Pseudomonas syringae pathovar morsprunorum biofilm development in real time. The biofilm development was observed within a spectral window 4000-800 cm-1 under constant flow conditions for 72 h. The kinetics of representative integrated band areas (nucleic acids with polysaccharides at 1141-1006 cm-1, amino acid side chains with free fatty acids at 1420-1380 cm-1, proteins at 1580-1490 cm-1, and lipids with proteins at 2935-2915 cm-1) were analyzed with regard to the observed biofilm structure and the following P. syringae biofilm developmental stages were attributed: The inoculation phase, washing of weakly attached bacteria closely followed by recolonization of the vacated surface, the restructuration phase, and finally the maturation phase.
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Affiliation(s)
- Jakub Budil
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
- Department of Semiconductors, Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Pavla Štenclová
- Department of Semiconductors, Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Alexander Kromka
- Department of Semiconductors, Institute of Physics of the Czech Academy of Sciences, Prague, Czech Republic
| | - Petra Lišková
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Prague, Czech Republic
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Classification of the plant-associated lifestyle of Pseudomonas strains using genome properties and machine learning. Sci Rep 2022; 12:10857. [PMID: 35760985 PMCID: PMC9237127 DOI: 10.1038/s41598-022-14913-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Accepted: 06/15/2022] [Indexed: 12/30/2022] Open
Abstract
The rhizosphere, the region of soil surrounding roots of plants, is colonized by a unique population of Plant Growth Promoting Rhizobacteria (PGPR). Many important PGPR as well as plant pathogens belong to the genus Pseudomonas. There is, however, uncertainty on the divide between beneficial and pathogenic strains as previously thought to be signifying genomic features have limited power to separate these strains. Here we used the Genome properties (GP) common biological pathways annotation system and Machine Learning (ML) to establish the relationship between the genome wide GP composition and the plant-associated lifestyle of 91 Pseudomonas strains isolated from the rhizosphere and the phyllosphere representing both plant-associated phenotypes. GP enrichment analysis, Random Forest model fitting and feature selection revealed 28 discriminating features. A test set of 75 new strains confirmed the importance of the selected features for classification. The results suggest that GP annotations provide a promising computational tool to better classify the plant-associated lifestyle.
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Inoue Y, Takikawa Y. Primers for specific detection and identification of Pseudomonas syringae pv. maculicola and P. cannabina pv. alisalensis. Appl Microbiol Biotechnol 2021; 105:1575-1584. [PMID: 33511445 DOI: 10.1007/s00253-021-11118-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 12/29/2020] [Accepted: 01/16/2021] [Indexed: 10/22/2022]
Abstract
Bacterial leaf spot and bacterial leaf blight are global threats to the cultivation of cruciferous vegetables, and it is necessary to develop methods to easily detect, identify, and distinguish the causative pathogens Pseudomonas syringae pv. maculicola (Psm) and P. cannabina pv. alisalensis (Pca). Here, we used the sequence specificity of the exchangeable effector loci flanking the hrp gene cluster to design primers that can help detect and discriminate between Psm and Pca. Primers common to both bacteria (hrpK_fw1 and hrpK_fw2) were designed within hrpK at the end of the hrp gene cluster. Psm-specific primers (MAC_rv1 and MAC_rv2) were designed in hopPtoB1 and Pca-specific primers (ALS_rv1 and ALS_rv2) were designed in hopX1 adjacent to hrpK. PCR using hrpK_fw1 and MAC_rv1 or hrpK_fw2 and MAC_rv2 amplified DNA fragments of only Psm, P. syringae pv. tomato (causal agent of tomato bacterial speck), and P. syringae pv. spinaciae (causal agent of spinach bacterial leaf spot), among 76 strains of phytopathogenic bacteria. PCR using hrpK_fw1 and ALS_rv1 or hrpK_2 and ALS_rv2 amplified DNA fragments of only Pca. Multiplex PCR with these primers could easily distinguish Psm and Pca from bacterial colonies isolated on growth media and detect the pathogen in symptomatic leaves. Multiplex nested PCR with the primers detected contamination in one Psm- and/or one Pca-infected seeds in 1000 seeds. These results suggest that these PCR primers could help detect and discriminate Psm and Pca. KEY POINTS: • We investigated Pseudomonas syringae pv. maculicola and P. cannabina pv. alisalensis. • Novel primers common to both bacteria were designed following genome comparison. • Multiplex PCR with new primers could discriminate Psm and Pca.
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Affiliation(s)
- Yasuhiro Inoue
- Central Region Agricultural Research Center, National Agriculture and Food Research Organization (NARO), Tsukuba, Ibaraki, Japan.
| | - Yuichi Takikawa
- Laboratory of Plant Pathology, Graduate School of Agriculture, and Graduate School of Science and Technology, Shizuoka University, Shizuoka, Shizuoka, Japan
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Jayaraman J, Yoon M, Applegate ER, Stroud EA, Templeton MD. AvrE1 and HopR1 from Pseudomonas syringae pv. actinidiae are additively required for full virulence on kiwifruit. MOLECULAR PLANT PATHOLOGY 2020; 21:1467-1480. [PMID: 32969167 PMCID: PMC7548996 DOI: 10.1111/mpp.12989] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 08/14/2020] [Accepted: 08/14/2020] [Indexed: 06/01/2023]
Abstract
Pseudomonas syringae pv. actinidiae ICMP 18884 biovar 3 (Psa3) produces necrotic lesions during infection of its kiwifruit host. Bacterial growth in planta and lesion formation are dependent upon a functional type III secretion system (T3S), which translocates multiple effector proteins into host cells. Associated with the T3S locus is the conserved effector locus (CEL), which has been characterized and shown to be essential for the full virulence in other P. syringae pathovars. Two effectors at the CEL, hopM1 and avrE1, as well as an avrE1-related non-CEL effector, hopR1, have been shown to be redundant in the model pathogen P. syringae pv. tomato DC3000 (Pto), a close relative of Psa. However, it is not known whether CEL-related effectors are required for Psa pathogenicity. The Psa3 allele of hopM1, and its associated chaperone, shcM, have diverged significantly from their orthologs in Pto. Furthermore, the CEL effector hopAA1-1, as well as a related non-CEL effector, hopAA1-2, have both been pseudogenized. We have shown that HopM1 does not contribute to Psa3 virulence due to a truncation in shcM, a truncation conserved in the Psa lineage, probably due to the need to evade HopM1-triggered immunity in kiwifruit. We characterized the virulence contribution of CEL and related effectors in Psa3 and found that only avrE1 and hopR1, additively, are required for in planta growth and lesion production. This is unlike the redundancy described for these effectors in Pto and indicates that these two Psa3 genes are key determinants essential for kiwifruit bacterial canker disease.
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Affiliation(s)
- Jay Jayaraman
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
- Bio‐Protection Research CentreLincolnNew Zealand
| | - Minsoo Yoon
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
| | - Emma R. Applegate
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
- School of Biological SciencesUniversity of AucklandAucklandNew Zealand
- Present address:
AgResearch Ltd., Grasslands Research CentrePalmerston NorthNew Zealand
| | - Erin A. Stroud
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
- School of Biological SciencesUniversity of AucklandAucklandNew Zealand
| | - Matthew D. Templeton
- The New Zealand Institute for Plant and Food Research LimitedAucklandNew Zealand
- Bio‐Protection Research CentreLincolnNew Zealand
- School of Biological SciencesUniversity of AucklandAucklandNew Zealand
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Ho J, Zhao M, Wojcik S, Taiaroa G, Butler M, Poulter R. The application of the CRISPR–Cas9 system in Pseudomonas syringae pv. actinidiae. J Med Microbiol 2020; 69:478-486. [DOI: 10.1099/jmm.0.001124] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Introduction.Pseudomonas syringaepv. actinidiae (Psa) has emerged as a major bacterial pathogen of kiwifruit cultivation throughout the world.Aim.We aim to introduce a CRISPR–Cas9 system, a commonly used genome editing tool, into Psa. The protocols may also be useful in otherPseudomonasspecies.Methodology.Using standard molecular biology techniques, we modified plasmid pCas9, which carries the CRISPR–Cas9 sequences fromStreptococcus pyogenes,for use in Psa. The final plasmid, pJH1, was produced in a series of steps and is maintained with selection in bothEscherichia coliand Psa.Results.We have constructed plasmids carrying a CRISPR–Cas9 system based on that ofS. pyogenes, which can be maintained, under selection, in Psa. We have shown that the gene targeting capacity of the CRISPR–Cas9 system is active and that the Cas9 protein is able to cleave the targeted sites. The Cas9 was directed to several different sites in theP. syringaegenome. Using Cas9 we have generated Psa transformants that no longer carry the native plasmid present in Psa, and other transformants that lack the integrative, conjugative element, Pac_ICE1. Targeting of a specific gene, a chromosomal non-ribosomal peptide synthetase, led to gene knockouts with the transformants having deletions encompassing the target site.Conclusion.We have constructed shuttle plasmids carrying a CRISPR–Cas9 system that are maintained in bothE. coliandP. syringaepv. actinidiae. We have used this gene editing system to eliminate features of the accessory genome (plasmids or ICEs) from Psa and to target a single chromosomal gene.
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Affiliation(s)
- Joycelyn Ho
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Min Zhao
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Samuel Wojcik
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - George Taiaroa
- Microbiological Diagnostic Unit Public Health Laboratory, Department of Microbiology and Immunology, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Melbourne, Australia
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Margi Butler
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Russell Poulter
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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Abstract
Pseudomonas syringae is one of the best-studied plant pathogens and serves as a model for understanding host-microorganism interactions, bacterial virulence mechanisms and host adaptation of pathogens as well as microbial evolution, ecology and epidemiology. Comparative genomic studies have identified key genomic features that contribute to P. syringae virulence. P. syringae has evolved two main virulence strategies: suppression of host immunity and creation of an aqueous apoplast to form its niche in the phyllosphere. In addition, external environmental conditions such as humidity profoundly influence infection. P. syringae may serve as an excellent model to understand virulence and also of how pathogenic microorganisms integrate environmental conditions and plant microbiota to become ecologically robust and diverse pathogens of the plant kingdom.
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SAWADA H, KONDO K, NAKAUNE R. Novel biovar (biovar 6) of Pseudomonas syringae pv. actinidiae causing bacterial canker of kiwifruit ( Actinidia deliciosa) in Japan. ACTA ACUST UNITED AC 2016. [DOI: 10.3186/jjphytopath.82.101] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Affiliation(s)
- H. SAWADA
- Genetic Resources Center, National Agriculture and Food Research Organization
| | - K. KONDO
- Nagano Fruit-Tree Experiment Station
- Agricultural Administration Department, Nagano Prefectural Government
| | - R. NAKAUNE
- Institute of Fruit Tree and Tea Science, National Agriculture and Food Research Organization
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Balmant KM, Parker J, Yoo MJ, Zhu N, Dufresne C, Chen S. Redox proteomics of tomato in response to Pseudomonas syringae infection. HORTICULTURE RESEARCH 2015; 2:15043. [PMID: 26504582 PMCID: PMC4591677 DOI: 10.1038/hortres.2015.43] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 08/20/2015] [Accepted: 08/20/2015] [Indexed: 05/21/2023]
Abstract
Unlike mammals with adaptive immunity, plants rely on their innate immunity based on pattern-triggered immunity (PTI) and effector-triggered immunity (ETI) for pathogen defense. Reactive oxygen species, known to play crucial roles in PTI and ETI, can perturb cellular redox homeostasis and lead to changes of redox-sensitive proteins through modification of cysteine sulfhydryl groups. Although redox regulation of protein functions has emerged as an important mechanism in several biological processes, little is known about redox proteins and how they function in PTI and ETI. In this study, cysTMT proteomics technology was used to identify similarities and differences of protein redox modifications in tomato resistant (PtoR) and susceptible (prf3) genotypes in response to Pseudomonas syringae pv tomato (Pst) infection. In addition, the results of the redox changes were compared and corrected with the protein level changes. A total of 90 potential redox-regulated proteins were identified with functions in carbohydrate and energy metabolism, biosynthesis of cysteine, sucrose and brassinosteroid, cell wall biogenesis, polysaccharide/starch biosynthesis, cuticle development, lipid metabolism, proteolysis, tricarboxylic acid cycle, protein targeting to vacuole, and oxidation-reduction. This inventory of previously unknown protein redox switches in tomato pathogen defense lays a foundation for future research toward understanding the biological significance of protein redox modifications in plant defense responses.
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Affiliation(s)
- Kelly Mayrink Balmant
- Department of Biology, Genetics Institute, University of Florida, Gainesville, FL, USA
- Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL, USA
| | - Jennifer Parker
- Department of Biology, Genetics Institute, University of Florida, Gainesville, FL, USA
- Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL, USA
| | - Mi-Jeong Yoo
- Department of Biology, Genetics Institute, University of Florida, Gainesville, FL, USA
| | - Ning Zhu
- Department of Biology, Genetics Institute, University of Florida, Gainesville, FL, USA
| | - Craig Dufresne
- Thermo Fisher Scientific, 1400 Northpoint Parkway, West Palm Beach, FL, USA
| | - Sixue Chen
- Department of Biology, Genetics Institute, University of Florida, Gainesville, FL, USA
- Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL, USA
- Interdisciplinary Center for Biotechnology Research, University of Florida, Gainesville, FL, USA
- E-mail:
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9
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Tampakaki AP. Commonalities and differences of T3SSs in rhizobia and plant pathogenic bacteria. FRONTIERS IN PLANT SCIENCE 2014; 5:114. [PMID: 24723933 PMCID: PMC3973906 DOI: 10.3389/fpls.2014.00114] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2014] [Accepted: 03/11/2014] [Indexed: 05/19/2023]
Abstract
Plant pathogenic bacteria and rhizobia infect higher plants albeit the interactions with their hosts are principally distinct and lead to completely different phenotypic outcomes, either pathogenic or mutualistic, respectively. Bacterial protein delivery to plant host plays an essential role in determining the phenotypic outcome of plant-bacteria interactions. The involvement of type III secretion systems (T3SSs) in mediating animal- and plant-pathogen interactions was discovered in the mid-80's and is now recognized as a multiprotein nanomachine dedicated to trans-kingdom movement of effector proteins. The discovery of T3SS in bacteria with symbiotic lifestyles broadened its role beyond virulence. In most T3SS-positive bacterial pathogens, virulence is largely dependent on functional T3SSs, while in rhizobia the system is dispensable for nodulation and can affect positively or negatively the mutualistic associations with their hosts. This review focuses on recent comparative genome analyses in plant pathogens and rhizobia that uncovered similarities and variations among T3SSs in their genetic organization, regulatory networks and type III secreted proteins and discusses the evolutionary adaptations of T3SSs and type III secreted proteins that might account for the distinguishable phenotypes and host range characteristics of plant pathogens and symbionts.
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Affiliation(s)
- Anastasia P. Tampakaki
- *Correspondence: Anastasia P. Tampakaki, Laboratory of General and Agricultural Microbiology, Department of Crop Science, Agricultural University of Athens, Iera Odos 75, Votanikos, 11855, Athens, Greece e-mail:
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10
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Lewis JD, Lee A, Ma W, Zhou H, Guttman DS, Desveaux D. The YopJ superfamily in plant-associated bacteria. MOLECULAR PLANT PATHOLOGY 2011; 12:928-37. [PMID: 21726386 PMCID: PMC6640427 DOI: 10.1111/j.1364-3703.2011.00719.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Bacterial pathogens employ the type III secretion system to secrete and translocate effector proteins into their hosts. The primary function of these effector proteins is believed to be the suppression of host defence responses or innate immunity. However, some effector proteins may be recognized by the host and consequently trigger a targeted immune response. The YopJ/HopZ/AvrRxv family of bacterial effector proteins is a widely distributed and evolutionarily diverse family, found in both animal and plant pathogens, as well as plant symbionts. How can an effector family effectively promote the virulence of pathogens on hosts from two separate kingdoms? Our understanding of the evolutionary relationships among the YopJ superfamily members provides an excellent opportunity to address this question and to investigate the functions and virulence strategies of a diverse type III effector family in animal and plant hosts. In this work, we briefly review the literature on YopJ, the archetypal member from Yersinia pestis, and discuss members of the superfamily in species of Pseudomonas, Xanthomonas, Ralstonia and Rhizobium. We review the molecular and cellular functions, if known, of the YopJ homologues in plants, and highlight the diversity of responses in different plant species, with a particular focus on the Pseudomonas syringae HopZ family. The YopJ superfamily provides an excellent foundation for the study of effector diversification in the context of wide-ranging, co-evolutionary interactions.
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Affiliation(s)
- Jennifer D Lewis
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
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Perrett CA, Lin DYW, Zhou D. Interactions of bacterial proteins with host eukaryotic ubiquitin pathways. Front Microbiol 2011; 2:143. [PMID: 21772834 PMCID: PMC3131157 DOI: 10.3389/fmicb.2011.00143] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 06/16/2011] [Indexed: 12/20/2022] Open
Abstract
Ubiquitination is a post-translational modification in which one or more 76 amino acid polypeptide ubiquitin molecules are covalently linked to the lysine residues of target proteins. Ubiquitination is the main pathway for protein degradation that governs a variety of eukaryotic cellular processes, including the cell-cycle, vesicle trafficking, antigen presentation, and signal transduction. Not surprisingly, aberrations in the system have been implicated in the pathogenesis of many diseases including inflammatory and neurodegenerative disorders. Recent studies have revealed that viruses and bacterial pathogens exploit the host ubiquitination pathways to gain entry and to aid their survival/replication inside host cells. This review will summarize recent developments in understanding the biochemical and structural mechanisms utilized by bacterial pathogens to interact with the host ubiquitination pathways.
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Affiliation(s)
| | - David Yin-Wei Lin
- Department of Biological Sciences, Purdue UniversityWest Lafayette, IN, USA
| | - Daoguo Zhou
- Department of Biological Sciences, Purdue UniversityWest Lafayette, IN, USA
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12
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Lee JS, Cha JY, Baik HS. Plant Cell Contact-Dependent Virulence Regulation of hrp Genes in Pseudomonas syringae pv. tabaci 11528. ACTA ACUST UNITED AC 2011. [DOI: 10.5352/jls.2011.21.2.227] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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13
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O'Brien HE, Thakur S, Guttman DS. Evolution of plant pathogenesis in Pseudomonas syringae: a genomics perspective. ANNUAL REVIEW OF PHYTOPATHOLOGY 2011; 49:269-89. [PMID: 21568703 DOI: 10.1146/annurev-phyto-072910-095242] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The phytopathogenic bacterium Pseudomonas syringae causes serious diseases in a wide range of important crop plants, with recent severe outbreaks on the New Zealand kiwifruit crop and among British horse chestnut trees. Next-generation genome sequencing of over 25 new strains has greatly broadened our understanding of how this species adapts to a diverse range of plant hosts. Not unexpectedly, the genomes were found to be highly dynamic, and extensive polymorphism was found in the distribution of type III secreted effectors (T3SEs) and other virulence-associated genes, even among strains within the same pathovar. An underexplored area brought to light by these data is the specific metabolic adaptations required for growth on woody hosts. These studies provide a tremendous wealth of candidates for more refined functional characterization, which is greatly enhancing our ability to disentangle the web of host-pathogen interactions that determine disease outcomes.
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Affiliation(s)
- Heath E O'Brien
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, M5S 3B2 Canada
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14
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Macho AP, Guevara CM, Tornero P, Ruiz-Albert J, Beuzón CR. The Pseudomonas syringae effector protein HopZ1a suppresses effector-triggered immunity. THE NEW PHYTOLOGIST 2010; 187:1018-1033. [PMID: 20636323 DOI: 10.1111/j.1469-8137.2010.03381.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
*The Pseudomonas syringae pv syringae type III effector HopZ1a is a member of the HopZ effector family of cysteine-proteases that triggers immunity in Arabidopsis. This immunity is dependent on HopZ1a cysteine-protease activity, and independent of known resistance genes. We have previously shown that HopZ1a-triggered immunity is partially additive to that triggered by AvrRpt2. These partially additive effects could be caused by at least two mechanisms: their signalling pathways share a common element(s), or one effector interferes with the response triggered by the other. *Here, we investigate the molecular basis for the partially additive effect displayed by AvrRpt2- and HopZ1a-triggered immunities, by analysing competitive indices, hypersensitive response and symptom induction, PR-1 accumulation, expression of PR genes, and systemic acquired resistance (SAR) induction. *Partially additive effects between these defence responses require HopZ1a cysteine-protease activity, and also take place between HopZ1a and AvrRps4 or AvrRpm1-triggered responses. We establish that HopZ1a-triggered immunity is independent of salicylic acid (SA), EDS1, jasmonic acid (JA) and ethylene (ET)-dependent pathways, and show that HopZ1a suppresses the induction of PR-1 and PR-5 associated with P. syringae pv tomato (Pto)-triggered effector-triggered immunity (ETI)-like defences, AvrRpt2-triggered immunity, and Pto or Pto (avrRpt2) activation of SAR, and that suppression requires HopZ1a cysteine-protease activity. *Our results indicate that HopZ1a triggers an unusual resistance independent of known pathways and suppresses SA and EDS1-dependent resistance.
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Affiliation(s)
- Alberto P Macho
- Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain
| | - Carlos M Guevara
- Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain
| | - Pablo Tornero
- Instituto de Biología Molecular y Celular de Plantas (Universidad Politécnica de Valencia - CSIC) Avda de los Naranjos s/n. Valencia E-46022, Spain
| | - Javier Ruiz-Albert
- Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain
| | - Carmen R Beuzón
- Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain
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15
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Translocation of NopP by Sinorhizobium fredii USDA257 into Vigna unguiculata root nodules. Appl Environ Microbiol 2010; 76:3758-61. [PMID: 20382805 DOI: 10.1128/aem.03122-09] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Sinorhizobium fredii is a nitrogen-fixing legume symbiont that stimulates the formation of root nodules. S. fredii nodulation of roots is influenced by Nop proteins, which are secreted through a type III secretion system (T3SS). We demonstrate that S. fredii injects NopP into Vigna unguiculata nodules in a T3SS-dependent manner.
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16
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Morgan RL, Zhou H, Lehto E, Nguyen N, Bains A, Wang X, Ma W. Catalytic domain of the diversified Pseudomonas syringae type III effector HopZ1 determines the allelic specificity in plant hosts. Mol Microbiol 2010; 76:437-55. [PMID: 20233307 DOI: 10.1111/j.1365-2958.2010.07107.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The type III secretion systems (T3SS) and secreted effectors (T3SEs) are essential virulence factors in Gram-negative bacteria. During the arms race, plants have evolved resistance (R) genes to detect specific T3SEs and activate defence responses. However, this immunity can be efficiently defeated by the pathogens through effector evolution. HopZ1 of the plant pathogen Pseudomonas syringae is a member of the widely distributed YopJ T3SE family. Three alleles are known to be present in P. syringae, with HopZ1a most resembling the ancestral allelic form. In this study, molecular mechanisms underlying the sequence diversification-enabled HopZ1 allelic specificity is investigated. Using domain shuffling experiments, we present evidence showing that a central domain upstream of the conserved catalytic cysteine residue determines HopZ1 recognition specificity. Random and targeted mutagenesis identified three amino acids involved in HopZ1 allelic specificity. Particularly, the exchange of cysteine141 in HopZ1a with lysine137 at the corresponding position in HopZ1b abolished HopZ1a recognition in soybean. This position is under strong positive selection, suggesting that the cysteine/lysine mutation might be a key step driving the evolution of HopZ1. Our data support a model in which sequence diversification imposed by the plant R gene-associated immunity has driven HopZ1 evolution by allowing allele-specific substrate-binding.
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Affiliation(s)
- Robyn L Morgan
- Center for Plant Cell Biology, Department of Plant Pathology and Microbiology, University of California, Riverside, CA 92521, USA
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17
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Clarke CR, Cai R, Studholme DJ, Guttman DS, Vinatzer BA. Pseudomonas syringae strains naturally lacking the classical P. syringae hrp/hrc Locus are common leaf colonizers equipped with an atypical type III secretion system. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2010; 23:198-210. [PMID: 20064063 DOI: 10.1094/mpmi-23-2-0198] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Pseudomonas syringae is best known as a plant pathogen that causes disease by translocating immune-suppressing effector proteins into plant cells through a type III secretion system (T3SS). However, P. syringae strains belonging to a newly described phylogenetic subgroup (group 2c) are missing the canonical P. syringae hrp/hrc cluster coding for a T3SS, flanking effector loci, and any close orthologue of known P. syringae effectors. Nonetheless, P. syringae group 2c strains are common leaf colonizers and grow on some tested plant species to population densities higher than those obtained by other P. syringae strains on nonhost species. Moreover, group 2c strains have genes necessary for the production of phytotoxins, have an ice nucleation gene, and, most interestingly, contain a novel hrp/hrc cluster, which is only distantly related to the canonical P. syringae hrp/hrc cluster. This hrp/hrc cluster appears to encode a functional T3SS although the genes hrpK and hrpS, present in the classical P. syringae hrp/hrc cluster, are missing. The genome sequence of a representative group 2c strain also revealed distant orthologues of the P. syringae effector genes avrE1 and hopM1 and the P. aeruginosa effector genes exoU and exoY. A putative life cycle for group 2c P. syringae is discussed.
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Affiliation(s)
- Christopher R Clarke
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Latham Hall, Ag Quad Lane, Blacksburg 24061, USA
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18
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Kim SH, Kwon SI, Saha D, Anyanwu NC, Gassmann W. Resistance to the Pseudomonas syringae effector HopA1 is governed by the TIR-NBS-LRR protein RPS6 and is enhanced by mutations in SRFR1. PLANT PHYSIOLOGY 2009; 150:1723-32. [PMID: 19525323 PMCID: PMC2719129 DOI: 10.1104/pp.109.139238] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2009] [Accepted: 06/09/2009] [Indexed: 05/18/2023]
Abstract
The Pseudomonas syringae-Arabidopsis (Arabidopsis thaliana) interaction is an extensively studied plant-pathogen system. Arabidopsis possesses approximately 150 putative resistance genes encoding nucleotide binding site (NBS) and leucine-rich repeat (LRR) domain-containing proteins. The majority of these belong to the Toll/Interleukin-1 receptor (TIR)-NBS-LRR (TNL) class. Comparative studies with the coiled-coil-NBS-LRR genes RPS2, RPM1, and RPS5 and isogenic P. syringae strains expressing single corresponding avirulence genes have been particularly fruitful in dissecting specific and common resistance signaling components. However, the major TNL class is represented by a single known P. syringae resistance gene, RPS4. We previously identified hopA1 from P. syringae pv syringae strain 61 as an avirulence gene that signals through ENHANCED DISEASE SUSCEPTIBILITY1, indicating that the corresponding resistance gene RPS6 belongs to the TNL class. Here we report the identification of RPS6 based on a forward-genetic screen and map-based cloning. Among resistance proteins of known function, the deduced amino acid sequence of RPS6 shows highest similarity to the TNL resistance protein RAC1 that determines resistance to the oomycete pathogen Albugo candida. Similar to RPS4 and other TNL genes, RPS6 generates alternatively spliced transcripts, although the alternative transcript structures are RPS6 specific. We previously characterized SRFR1 as a negative regulator of avrRps4-triggered immunity. Interestingly, mutations in SRFR1 also enhanced HopA1-triggered immunity in rps6 mutants. In conclusion, the cloning of RPS6 and comparisons with RPS4 will contribute to a closer dissection of the TNL resistance pathway in Arabidopsis.
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Affiliation(s)
- Sang Hee Kim
- Division of Plant Sciences and Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211-7310, USA
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19
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Wroblewski T, Caldwell KS, Piskurewicz U, Cavanaugh KA, Xu H, Kozik A, Ochoa O, McHale LK, Lahre K, Jelenska J, Castillo JA, Blumenthal D, Vinatzer BA, Greenberg JT, Michelmore RW. Comparative large-scale analysis of interactions between several crop species and the effector repertoires from multiple pathovars of Pseudomonas and Ralstonia. PLANT PHYSIOLOGY 2009; 150:1733-49. [PMID: 19571308 PMCID: PMC2719141 DOI: 10.1104/pp.109.140251] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Accepted: 06/23/2009] [Indexed: 05/18/2023]
Abstract
Bacterial plant pathogens manipulate their hosts by injection of numerous effector proteins into host cells via type III secretion systems. Recognition of these effectors by the host plant leads to the induction of a defense reaction that often culminates in a hypersensitive response manifested as cell death. Genes encoding effector proteins can be exchanged between different strains of bacteria via horizontal transfer, and often individual strains are capable of infecting multiple hosts. Host plant species express diverse repertoires of resistance proteins that mediate direct or indirect recognition of bacterial effectors. As a result, plants and their bacterial pathogens should be considered as two extensive coevolving groups rather than as individual host species coevolving with single pathovars. To dissect the complexity of this coevolution, we cloned 171 effector-encoding genes from several pathovars of Pseudomonas and Ralstonia. We used Agrobacterium tumefaciens-mediated transient assays to test the ability of each effector to induce a necrotic phenotype on 59 plant genotypes belonging to four plant families, including numerous diverse accessions of lettuce (Lactuca sativa) and tomato (Solanum lycopersicum). Known defense-inducing effectors (avirulence factors) and their homologs commonly induced extensive necrosis in many different plant species. Nonhost species reacted to multiple effector proteins from an individual pathovar more frequently and more intensely than host species. Both homologous and sequence-unrelated effectors could elicit necrosis in a similar spectrum of plants, suggesting common effector targets or targeting of the same pathways in the plant cell.
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Affiliation(s)
- Tadeusz Wroblewski
- Genome Center and Department of Plant Sciences, University of California, Davis, California 95616, USA
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20
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Zhou H, Morgan RL, Guttman DS, Ma W. Allelic variants of the Pseudomonas syringae type III effector HopZ1 are differentially recognized by plant resistance systems. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2009; 22:176-89. [PMID: 19132870 DOI: 10.1094/mpmi-22-2-0176] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The bacterial plant pathogen Pseudomonas syringae depends on the type III secretion system and type III-secreted effectors to cause disease in plants. HopZ is a diverse family of type III effectors widely distributed in P. syringae isolates. Among the HopZ homologs, HopZ1 is ancient to P. syringae and has been shown to be under strong positive selection driven by plant resistance-imposed selective pressure. Here, we characterized the virulence and avirulence functions of the three HopZ1 alleles in soybean and Nicotiana benthamiana. In soybean, HopZ1 alleles have distinct functions: HopZ1a triggers defense response, HopZ1b promotes bacterial growth, and HopZ1c has no observable effect. In N. benthamiana, HopZ1a and HopZ1b both induce plant defense responses. However, they appear to trigger different resistance pathways, evidenced by two major differences between HopZ1a- and HopZ1b-triggered hypersensitive response (HR): i) the putative N-acylation sites had no effect on HopZ1a-triggered cell death, whereas it greatly enhanced HopZ1b-triggered cell death; and ii) the HopZ1b-triggered HR, but not the HopZ1a-triggered HR, was suppressed by another HopZ homolog, HopZ3. We previously demonstrated that HopZ1a most resembled the ancestral allelic form of HopZ1; therefore, this new evidence suggested that differentiated resistance systems have evolved in plant hosts to adapt to HopZ1 diversification in P. syringae.
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Affiliation(s)
- Huanbin Zhou
- Department of Plant Pathology and Microbiology, University of California, Riverside 92521, USA
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21
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Almeida NF, Yan S, Lindeberg M, Studholme DJ, Schneider DJ, Condon B, Liu H, Viana CJ, Warren A, Evans C, Kemen E, Maclean D, Angot A, Martin GB, Jones JD, Collmer A, Setubal JC, Vinatzer BA. A draft genome sequence of Pseudomonas syringae pv. tomato T1 reveals a type III effector repertoire significantly divergent from that of Pseudomonas syringae pv. tomato DC3000. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2009; 22:52-62. [PMID: 19061402 DOI: 10.1094/mpmi-22-1-0052] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Diverse gene products including phytotoxins, pathogen-associated molecular patterns, and type III secreted effectors influence interactions between Pseudomonas syringae strains and plants, with additional yet uncharacterized factors likely contributing as well. Of particular interest are those interactions governing pathogen-host specificity. Comparative genomics of closely related pathogens with different host specificity represents an excellent approach for identification of genes contributing to host-range determination. A draft genome sequence of Pseudomonas syringae pv. tomato T1, which is pathogenic on tomato but nonpathogenic on Arabidopsis thaliana, was obtained for this purpose and compared with the genome of the closely related A. thaliana and tomato model pathogen P. syringae pv. tomato DC3000. Although the overall genetic content of each of the two genomes appears to be highly similar, the repertoire of effectors was found to diverge significantly. Several P. syringae pv. tomato T1 effectors absent from strain DC3000 were confirmed to be translocated into plants, with the well-studied effector AvrRpt2 representing a likely candidate for host-range determination. However, the presence of avrRpt2 was not found sufficient to explain A. thaliana resistance to P. syringae pv. tomato T1, suggesting that other effectors and possibly type III secretion system-independent factors also play a role in this interaction.
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Affiliation(s)
- Nalvo F Almeida
- Virginia Bioinformatics Institute, Virginia Tech, Blacksburg, VA 24061, USA
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22
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Mohr TJ, Liu H, Yan S, Morris CE, Castillo JA, Jelenska J, Vinatzer BA. Naturally occurring nonpathogenic isolates of the plant pathogen Pseudomonas syringae lack a type III secretion system and effector gene orthologues. J Bacteriol 2008; 190:2858-70. [PMID: 18263729 PMCID: PMC2293242 DOI: 10.1128/jb.01757-07] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2007] [Accepted: 01/28/2008] [Indexed: 12/28/2022] Open
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.
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Affiliation(s)
- Toni J Mohr
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Latham Hall, Ag Quad Lane, Blacksburg, VA 24061, USA
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23
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Lewis JD, Abada W, Ma W, Guttman DS, Desveaux D. The HopZ family of Pseudomonas syringae type III effectors require myristoylation for virulence and avirulence functions in Arabidopsis thaliana. J Bacteriol 2008; 190:2880-91. [PMID: 18263728 PMCID: PMC2293245 DOI: 10.1128/jb.01702-07] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 01/28/2008] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas syringae utilizes the type III secretion system to translocate effector proteins into plant cells, where they can contribute to the pathogen's ability to infect and cause disease. Recognition of these effectors by resistance proteins induces defense responses that typically include a programmed cell death reaction called the hypersensitive response. The YopJ/HopZ family of type III effector proteins is a common family of effector proteins found in animal- and plant-pathogenic bacteria. The HopZ family in P. syringae includes HopZ1a(PsyA2), HopZ1b(PgyUnB647), HopZ1c(PmaE54326), HopZ2(Ppi895A) and HopZ3(PsyB728a). HopZ1a is predicted to be most similar to the ancestral hopZ allele and causes a hypersensitive response in multiple plant species, including Arabidopsis thaliana. Therefore, it has been proposed that host defense responses have driven the diversification of this effector family. In this study, we further characterized the hypersensitive response induced by HopZ1a and demonstrated that it is not dependent on known resistance genes. Further, we identified a novel virulence function for HopZ2 that requires the catalytic cysteine demonstrated to be required for protease activity. Sequence analysis of the HopZ family revealed the presence of a predicted myristoylation sequence in all members except HopZ3. We demonstrated that the myristoylation site is required for membrane localization of this effector family and contributes to the virulence and avirulence activities of HopZ2 and HopZ1a, respectively. This paper provides insight into the selective pressures driving virulence protein evolution by describing a detailed functional characterization of the diverse HopZ family of type III effectors with the model plant Arabidopsis.
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Affiliation(s)
- Jennifer D Lewis
- Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario M5S 3B2, Canada
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24
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Whalen M, Richter T, Zakhareyvich K, Yoshikawa M, Al-Azzeh D, Adefioye A, Spicer G, Mendoza LL, Morales CQ, Klassen V, Perez-Baron G, Toebe CS, Tzovolous A, Gerstman E, Evans E, Thompson C, Lopez M, Ronald PC. Identification of a host 14-3-3 Protein that Interacts with Xanthomonas effector AvrRxv. PHYSIOLOGICAL AND MOLECULAR PLANT PATHOLOGY 2008; 72:46-55. [PMID: 21796232 PMCID: PMC3142867 DOI: 10.1016/j.pmpp.2008.05.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
AvrRxv is a member of a family of pathogen effectors present in pathogens of both plant and mammalian species. Xanthomonas campestris pv. vesicatoria strains carrying AvrRxv induce a hypersensitive response (HR) in the tomato cultivar Hawaii 7998. Using a yeast two-hybrid screen, we identified a 14-3-3 protein from tomato that interacts with AvrRxv called AvrRxv Interactor 1 (ARI1). The interaction was confirmed in vitro with affinity chromatography. Using mutagenesis, we identified a 14-3-3-binding domain in AvrRxv and demonstrated that a mutant in that domain showed concomitant loss of interaction with ARI1 and HR-inducing activity in tomato. These results demonstrate that the AvrRxv bacterial effector recruits 14-3-3 proteins for its function within host cells. AvrRxv homologues YopP and YopJ from Yersinia do not have AvrRxv-specific HR-inducing activity when delivered into tomato host cells by Agrobacterium. Although YopP itself cannot induce HR, its C-terminal domain containing the catalytic residues can replace that of AvrRxv in an AvrRxv-YopP chimera for HR-inducing activity. Phylogenetic analysis indicates that the sequences encoding the C-termini of family members are evolving independently from those encoding the N-termini. Our results support a model in which there are three functional domains in proteins of the family, translocation, interaction, and catalytic.
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Affiliation(s)
- Maureen Whalen
- Crop Improvement and Utilization Unit, Western Regional Research Center, ARS USDA, 800 Buchanan Street, Albany, CA 94710, US
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
- Corresponding author. Crop Improvement and Utilization Unit, Western Regional Research Center, ARS USDA, 800 Buchanan Street, Albany, CA 94710, USA. Tel.: +1 510 559 5950; fax: + 1 510 559 5818. (M.C. Whalen), (P.C. Ronald)
| | - Todd Richter
- Department of Plant Pathology, University of California at Davis, One Shields Ave, Davis CA 95616, USA
| | - Kseniya Zakhareyvich
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Masayasu Yoshikawa
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Dana Al-Azzeh
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Adeshola Adefioye
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Greg Spicer
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Laura L. Mendoza
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Christine Q. Morales
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Vicki Klassen
- Department of Biology, City College of San Francisco, 50 Phelan Avenue, San Francisco, CA 94112, USA
| | - Gina Perez-Baron
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Carole S. Toebe
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
- Department of Biology, City College of San Francisco, 50 Phelan Avenue, San Francisco, CA 94112, USA
| | - Ageliki Tzovolous
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Emily Gerstman
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Erika Evans
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Cheryl Thompson
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Mary Lopez
- Biology Department, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132, USA
| | - Pamela C. Ronald
- Department of Plant Pathology, University of California at Davis, One Shields Ave, Davis CA 95616, USA
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25
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Araki H, Innan H, Kreitman M, Bergelson J. Molecular evolution of pathogenicity-island genes in Pseudomonas viridiflava. Genetics 2007; 177:1031-41. [PMID: 17720907 PMCID: PMC2034611 DOI: 10.1534/genetics.107.077925] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The bacterial pathogen Pseudomonas viridiflava possesses two pathogenicity islands (PAIs) that share many gene homologs, but are structurally and phenotypically differentiated (T-PAI and S-PAI). These PAIs are paralogous, but only one is present in each isolate. While this dual presence/absence polymorphism has been shown to be maintained by balancing selection, little is known about the molecular evolution of individual genes on the PAIs. Here we investigate genetic variation of 12 PAI gene loci (7 on T-PAI and 5 on S-PAI) in 96 worldwide isolates of P. viridiflava. These genes include avirulence genes (hopPsyA and avrE), their putative chaperones (shcA and avrF), and genes encoding the type III outer proteins (hrpA, hrpZ, and hrpW). Average nucleotide diversities in these genes (pi = 0.004-0.020) were close to those in the genetic background. Large numbers of recombination events were found within PAIs and a sign of positive selection was detected in avrE. These results suggest that the PAI genes are evolving relatively freely from each other on the PAIs, rather than as a single unit under balancing selection. Evolutionarily stable PAIs may be preferable in this species because preexisting genetic variation enables P. viridiflava to respond rapidly to natural selection.
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Affiliation(s)
- Hitoshi Araki
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois 60637, USA.
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26
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Nimchuk ZL, Fisher EJ, Desveaux D, Chang JH, Dangl JL. The HopX (AvrPphE) family of Pseudomonas syringae type III effectors require a catalytic triad and a novel N-terminal domain for function. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:346-57. [PMID: 17427805 DOI: 10.1094/mpmi-20-4-0346] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Many gram-negative plant pathogenic bacteria employ type III secretion systems to deliver effector proteins directly into the host cell during infection. On susceptible hosts, type III effectors aid pathogen growth by manipulating host defense pathways. On resistant hosts, some effectors can activate specific host disease resistance (R) genes, leading to generation of rapid and effective immune responses. The biochemical basis of these processes is poorly understood. The HopX (AvrPphE) family is a widespread type III effector among phytopathogenic bacteria. We determined that HopX family members are modular proteins composed of a conserved putative cysteine-based catalytic triad and a conserved potential target/cofactor interaction domain. HopX is soluble in host cells. Putative catalytic triad residues are required for avirulence activity on resistant bean hosts and for the generation of a cell-death response in specific Arabidopsis genotypes. The putative target/cofactor interaction domain is also required for these activities. Our data suggest that specific interaction with and modification of a cytosolic host target drives HopX recognition in resistant hosts and may contribute to virulence in susceptible hosts. Surprisingly, the Legionella pneumophila genome was found to contain a protein with similarity to HopX in sequence and domain arrangement, suggesting that these proteins might also contribute to animal pathogenesis and could be delivered to plant and animal hosts by diverse secretion systems.
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Affiliation(s)
- Zachary L Nimchuk
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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27
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Jakob K, Kniskern JM, Bergelson J. The role of pectate lyase and the jasmonic acid defense response in Pseudomonas viridiflava virulence. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:146-58. [PMID: 17313166 DOI: 10.1094/mpmi-20-2-0146] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Pseudomonas viridiflava is a common pathogen of Arabidopsis thaliana in wild populations, yet very little is known about mechanisms of resistance and virulence in this interaction. We examined the induced defense response of A. thaliana to several strains of P. viridiflava collected from this host by quantifying the expression of PR-1 and LOX2/PDF1.2, which serve as markers for induction of the salicylic and jasmonic acid (JA) pathways, respectively. Growth of these strains then was assessed on Col-0, the fad3/7/8 and coil-1 mutants deficient in JA- and ethylene (ET)-induced defense responses, and the sid2-1 mutant deficient in salicylic acid-induced defense responses. All strains of P. viridiflava induced high expression of LOX2 and PDF1.2 on Col-0. In contrast, PR-1 expression was delayed and reduced relative to PDF1.2 expression. Additionally, three of four P. viridiflava strains were more virulent on fad3/7/8 relative to Col-0, whereas all strains were more virulent on coil-1 relative to Col-0, indicating that P. viridiflava generally may be suppressed by JA/ET-mediated defense responses. In contrast, no increase in the growth of P. viridiflava strains was observed in the sid2-1 mutant relative to Col-0. Parallel experiments were performed with the closely related P. syringae pv. tomato for comparative purposes. In addition, we assessed the role of pectate lyase and the alternative sigma factor HrpL in P. viridiflava virulence on A. thaliana and found that pectate lyase activity is correlated with virulence, whereas the removal of pectate lyase or HrpL significantly reduced virulence.
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Affiliation(s)
- Katrin Jakob
- Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago 60637, USA
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28
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Lindeberg M, Cartinhour S, Myers CR, Schechter LM, Schneider DJ, Collmer A. 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. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:1151-8. [PMID: 17073298 DOI: 10.1094/mpmi-19-1151] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
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.
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Affiliation(s)
- Magdalen Lindeberg
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA
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29
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Schechter LM, Vencato M, Jordan KL, Schneider SE, Schneider DJ, Collmer A. Multiple approaches to a complete inventory of Pseudomonas syringae pv. tomato DC3000 type III secretion system effector proteins. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:1180-92. [PMID: 17073301 DOI: 10.1094/mpmi-19-1180] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Pseudomonas syringae pv. tomato DC3000 is a pathogen of tomato and Arabidopsis that translocates virulence effector proteins into host cells via a type III secretion system (T3SS). Many effector-encoding hypersensitive response and pathogenicity (Hrp) outer protein (hop) genes have been identified previously in DC3000 using bioinformatic methods based on Hrp promoter sequences and characteristic N-terminal amino acid patterns that are associated with T3SS substrates. To approach completion of the Hop/effector inventory in DC3000, 44 additional candidates were tested by the Bordetella pertussis calmodulin-dependent adenylate cyclase (Cya) translocation reporter assay; 10 of the high-probability candidates were confirmed as T3SS substrates. Several previously predicted hop genes were tested for their ability to be expressed in an HrpL-dependent manner in culture or to be expressed in planta. The data indicate that DC3000 harbors 53 hop/avr genes and pseudogenes (encoding both injected effectors and T3SS substrates that probably are released to the apoplast); 33 of these genes are likely functional in DC3000, 12 are nonfunctional members of valid Hop families, and 8 are less certain regarding their production at functional levels. Growth of DC3000 in tomato and Arabidopsis Col-0 was not impaired by constitutive expression of repaired versions of two hops that were disrupted naturally by transposable elements or of hop genes that are naturally cryptic. In summary, DC3000 carries a complex mixture of active and inactive hop genes, and the hop genes in P. syringae can be identified efficiently by bioinformatic methods; however, a precise inventory of the subset of Hops that are important in pathogenesis awaits more knowledge based on mutant phenotypes and functions within plants.
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Affiliation(s)
- Lisa M Schechter
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA
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Ma W, Dong FFT, Stavrinides J, Guttman DS. Type III effector diversification via both pathoadaptation and horizontal transfer in response to a coevolutionary arms race. PLoS Genet 2006; 2:e209. [PMID: 17194219 PMCID: PMC1713259 DOI: 10.1371/journal.pgen.0020209] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Accepted: 10/25/2006] [Indexed: 11/21/2022] Open
Abstract
The concept of the coevolutionary arms race holds a central position in our understanding of pathogen–host interactions. Here we identify the molecular mechanisms and follow the stepwise progression of an arms race in a natural system. We show how the evolution and function of the HopZ family of type III secreted effector proteins carried by the plant pathogen Pseudomonas syringae are influenced by a coevolutionary arms race between pathogen and host. We surveyed 96 isolates of P. syringae and identified three homologs (HopZ1, HopZ2, and HopZ3) distributed among ∼45% of the strains. All alleles were sequenced and their expression was confirmed. Evolutionary analyses determined that the diverse HopZ1 homologs are ancestral to P. syringae, and have diverged via pathoadaptive mutational changes into three functional and two degenerate forms, while HopZ2 and HopZ3 have been brought into P. syringae via horizontal transfer from other ecologically similar bacteria. A PAML selection analysis revealed that the C terminus of HopZ1 is under strong positive selection. Despite the extensive genetic variation observed in this family, all three homologs have cysteine–protease activity, although their substrate specificity may vary. The introduction of the ancestral hopZ1 allele into strains harboring alternate alleles results in a resistance protein-mediated defense response in their respective hosts, which is not observed with the endogenous allele. These data indicate that the P. syringae HopZ family has undergone allelic diversification via both pathoadaptive mutational changes and horizontal transfer in response to selection imposed by the host defense system. This genetic diversity permits the pathogen to avoid host defenses while still maintaining a virulence-associated protease, thereby allowing it to thrive on its current host, while simultaneously impacting its host range. Pathogens and their hosts impose reciprocal selective pressures on each other, such that the improvement of one selects for the improvement of the other. Pathogens that are able to evolve increasingly effective methods of attacking their hosts select for hosts that are able to mount increasingly effective defenses against pathogen attack. This coevolutionary interaction is commonly referred to as an arms race, or the Red Queen Principle, taken from Lewis Carroll's Through the Looking Glass, and What Alice Found There, in which Alice and the Red Queen had to run as fast as they could simply to stay in the same place. Many pathogenic bacteria rely on specialized virulence proteins, called type III secreted effectors (T3SEs), to cause disease. These proteins are injected into the cells of the host, and often act to disrupt the host defense response. This study shows how the HopZ family of T3SEs in the pathogen Pseudomonas syringae evolves in response to coevolutionary selective pressures imposed by its plant hosts. The authors identify the version of the hopZ gene that is most similar to the one carried by the ancestral strain, and then show how this version has been modified by mutation and selection in response to the host defense systems. They also identify genes related to hopZ from other species that were brought into P. syringae presumably in response to this same host-imposed selective pressure. Finally, the authors show how the genetic diversity in this gene family permits the pathogen to avoid host defenses while still maintaining an important virulence-associated function. This study provides a clearer picture of the molecular interactions that drive coevolutionary interactions, and insight into how ecological processes play out at the molecular and evolutionary scale.
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Affiliation(s)
- Wenbo Ma
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada, 2 Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
| | - Frederick F. T Dong
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada, 2 Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
| | - John Stavrinides
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada, 2 Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
| | - David S Guttman
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada, 2 Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
- * To whom correspondence should be addressed. E-mail:
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Vinatzer BA, Teitzel GM, Lee MW, Jelenska J, Hotton S, Fairfax K, Jenrette J, Greenberg JT. The type III effector repertoire of Pseudomonas syringae pv. syringae B728a and its role in survival and disease on host and non-host plants. Mol Microbiol 2006; 62:26-44. [PMID: 16942603 DOI: 10.1111/j.1365-2958.2006.05350.x] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The bacterial plant pathogen Pseudomonas syringae injects a large repertoire of effector proteins into plant cells using a type III secretion apparatus. Effectors can trigger or suppress defences in a host-dependent fashion. Host defences are often accompanied by programmed cell death, while interference with defences is sometimes associated with cell death suppression. We previously predicted the effector repertoire of the sequenced bean pathogen P. syringae pv. syringae (Psy) B728a using bioinformatics. Here we show that PsyB728a is also pathogenic on the model plant species Nicotiana benthamiana (tobacco). We confirm our effector predictions and clone the nearly complete PsyB728a effector repertoire. We find effectors to have different cell death-modulating activities and distinct roles during the infection of the susceptible bean and tobacco hosts. Unexpectedly, we do not find a strict correlation between cell death-eliciting and defence-eliciting activity and between cell death-suppressing activity and defence-interfering activity. Furthermore, we find several effectors with quantitative avirulence activities on their susceptible hosts, but with growth-promoting effects on Arabidopsis thaliana, a species on which PsyB728a does not cause disease. We conclude that P. syringae strains may have evolved large effector repertoires to extend their host ranges or increase their survival on various unrelated plant species.
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Affiliation(s)
- Boris A Vinatzer
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Fralin Biotechnology Center, West Campus Drive, Blacksburg, VA 24061-0346, USA
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Genka H, Baba T, Tsuda M, Kanaya S, Mori H, Yoshida T, Noguchi MT, Tsuchiya K, Sawada H. Comparative analysis of argK-tox clusters and their flanking regions in phaseolotoxin-producing Pseudomonas syringae pathovars. J Mol Evol 2006; 63:401-14. [PMID: 16927007 DOI: 10.1007/s00239-005-0271-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2005] [Accepted: 04/27/2006] [Indexed: 11/29/2022]
Abstract
DNA fragments containing argK-tox clusters and their flanking regions were cloned from the chromosomes of Pseudomonas syringae pathovar (pv.) actinidiae strain KW-11 (ACT) and P. syringae pv. phaseolicola strain MAFF 302282 (PHA), and then their sequences were determined. Comparative analysis of these sequences and the sequences of P. syringae pv. tomato DC3000 (TOM) (Buell et al., Proc Natl Acad Sci USA 100:10181-10186, 2003) and pv. syringae B728a (SYR) (Feil et al., Proc Natl Acad Sci USA 102:11064-11069, 2005) revealed that the chromosomal backbone regions of ACT and TOM shared a high similarity to each other but presented a low similarity to those of PHA and SYR. Nevertheless, almost-identical DNA regions of about 38 kb were confirmed to be present on the chromosomes of both ACT and PHA, which we named "tox islands." The facts that the GC content of such tox islands was 6% lower than that of the chromosomal backbone regions of P. syringae, and that argK-tox clusters, which are considered to be of exogenous origin based on our previous studies (Sawada et al., J Mol Evol 54:437-457, 2002), were confirmed to be contained within the tox islands, suggested that the tox islands were an exogenous, mobile genetic element inserted into the chromosomes of P. syringae strains. It was also predicted that the tox islands integrated site-specifically into the homologous sites of the chromosomes of ACT and PHA in the same direction, respectively, wherein 34 common gene coding sequences (CDSs) existed. Furthermore, at the left end of the tox islands were three CDSs, which encoded polypeptides and had similarities to the members of the tyrosine recombinase family, suggesting that these putative site-specific recombinases were involved in the recent horizontal transfer of tox islands.
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Affiliation(s)
- Hiroyuki Genka
- Graduate School of Life Sciences, Tohoku University, Sendai, Japan
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Fletcher J, Bender C, Budowle B, Cobb WT, Gold SE, Ishimaru CA, Luster D, Melcher U, Murch R, Scherm H, Seem RC, Sherwood JL, Sobral BW, Tolin SA. Plant pathogen forensics: capabilities, needs, and recommendations. Microbiol Mol Biol Rev 2006; 70:450-71. [PMID: 16760310 PMCID: PMC1489535 DOI: 10.1128/mmbr.00022-05] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A biological attack on U.S. crops, rangelands, or forests could reduce yield and quality, erode consumer confidence, affect economic health and the environment, and possibly impact human nutrition and international relations. Preparedness for a crop bioterror event requires a strong national security plan that includes steps for microbial forensics and criminal attribution. However, U.S. crop producers, consultants, and agricultural scientists have traditionally focused primarily on strategies for prevention and management of diseases introduced naturally or unintentionally rather than on responding appropriately to an intentional pathogen introduction. We assess currently available information, technologies, and resources that were developed originally to ensure plant health but also could be utilized for postintroduction plant pathogen forensics. Recommendations for prioritization of efforts and resource expenditures needed to enhance our plant pathogen forensics capabilities are presented.
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Affiliation(s)
- J Fletcher
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.
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Gürlebeck D, Thieme F, Bonas U. Type III effector proteins from the plant pathogen Xanthomonas and their role in the interaction with the host plant. JOURNAL OF PLANT PHYSIOLOGY 2006; 163:233-55. [PMID: 16386329 DOI: 10.1016/j.jplph.2005.11.011] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2005] [Accepted: 11/15/2005] [Indexed: 05/05/2023]
Abstract
Pathogenicity of Xanthomonas campestris pathovar (pv.) vesicatoria and most other Gram-negative bacterial plant pathogens largely depends on a type III secretion (TTS) system which is encoded by hypersensitive response and pathogenicity (hrp) genes. These genes are induced in the plant and are essential for the bacterium to be virulent in susceptible hosts and for the induction of the hypersensitive response (HR) in resistant host and non-host plants. The TTS machinery secretes proteins into the extracellular milieu and effector proteins into the plant cell cytosol. In the plant, the effectors presumably interfere with cellular processes to the benefit of the pathogen or have an avirulence activity that betrays the bacterium to the plant surveillance system. Type III effectors were identified by their avirulence activity, co-regulation with the TTS system and homology to known effectors. A number of effector proteins are members of families, e.g., the AvrBs3 family in Xanthomonas. AvrBs3 localizes to the nucleus of the plant cell where it modulates plant gene expression. Another family that is also present in Xanthomonas is the YopJ/AvrRxv family. The latter proteins appear to act as SUMO cysteine proteases in the host. Here, we will present an overview about the regulation of the TTS system and its substrates and discuss the function of the AvrRxv and AvrBs3 family members in more detail.
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Affiliation(s)
- Doreen Gürlebeck
- Institute of Genetics, Martin-Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle, Germany.
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Jackson RW, Preston GM, Rainey PB. Genetic characterization of Pseudomonas fluorescens SBW25 rsp gene expression in the phytosphere and in vitro. J Bacteriol 2006; 187:8477-88. [PMID: 16321952 PMCID: PMC1317024 DOI: 10.1128/jb.187.24.8477-8488.2005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
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.
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Affiliation(s)
- Robert W Jackson
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, United Kingdom.
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Franza T, Mahé B, Expert D. Erwinia chrysanthemi requires a second iron transport route dependent of the siderophore achromobactin for extracellular growth and plant infection. Mol Microbiol 2005; 55:261-75. [PMID: 15612933 DOI: 10.1111/j.1365-2958.2004.04383.x] [Citation(s) in RCA: 130] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Full virulence of the pectinolytic enterobacterium Erwinia chrysanthemi strain 3937 depends on the production in planta of the catechol-type siderophore chrysobactin. Under iron-limited conditions, E. chrysanthemi synthesizes a second siderophore called achromobactin belonging to the hydroxy/carboxylate class of siderophore. In this study, we cloned and functionally characterized a 13 kb long operon comprising seven genes required for the biosynthesis (acs) and extracellular release (yhcA) of achromobactin, as well as the gene encoding the specific outer membrane receptor for its ferric complex (acr). The promoter of this operon was negatively regulated by iron. In a fur null mutant, transcriptional fusions to the acsD and acsA genes were constitutively expressed. Band shift assays showed that the purified E. chrysanthemi Fur repressor protein specifically binds in vitro to the promoter region of the acsF gene confirming that the metalloregulation of the achromobactin operon is achieved directly by Fur. The temporal production of achromobactin in iron-depleted bacterial cultures was determined: achromobactin is produced before chrysobactin and its production decreases as that of chrysobactin increases. Pathogenicity tests performed on African violets showed that achromobactin production contributes to the virulence of E. chrysanthemi. Thus, during infection, synthesis of these two different siderophores allows E. chrysanthemi cells to cope with the fluctuations of iron availability encountered within plant tissues. Interestingly, iron transport mediated by achromobactin or a closely related siderophore probably exists in other phytopathogenic bacterial species such as Pseudomonas syringae.
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Affiliation(s)
- Thierry Franza
- Laboratoire de Pathologie Végétale, UMR 217 INRA/INA P-G/UPMC, 16 rue Claude Bernard, 75005 Paris, France
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37
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Vinatzer BA, Jelenska J, Greenberg JT. Bioinformatics correctly identifies many type III secretion substrates in the plant pathogen Pseudomonas syringae and the biocontrol isolate P. fluorescens SBW25. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:877-88. [PMID: 16134900 DOI: 10.1094/mpmi-18-0877] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The plant pathogen Pseudomonas syringae causes disease by secreting a potentially large set of virulence proteins called effectors directly into host cells, their environment, or both, using a type III secretion system (T3SS). Most P. syringae effectors have a common upstream element called the hrp box, and their N-terminal regions have amino acids biases, features that permit their bioinformatic prediction. One of the most prominent biases is a positive serine bias. We previously used the truncated AvrRpt2(81-255) effector containing a serine-rich stretch from amino acids 81 to 100 as a T3SS reporter. Region 81 to 100 of this reporter does not contribute to the secretion or translocation of AvrRpt2 or to putative effector protein chimeras. Rather, the serine-rich region from the N-terminus of AvrRpt2 is important for protein accumulation in bacteria. Most of the N-terminal region (amino acids 15 to 100) is not essential for secretion in culture or delivery to plants. However, portions of this sequence may increase the efficiency of AvrRpt2 secretion, delivery to plants, or both. Two effectors previously identified with the AvrRpt2(81-255) reporter were secreted in culture independently of AvrRpt2, validating the use of the C terminus of AvrRpt2 as a T3SS reporter. Finally, using the reduced AvrRpt2(101-255) reporter, we confirmed seven predicted effectors from P. syringae pv. tomato DC3000, four from P. syringae pv. syringae B728a, and two from P. fluorescens SBW25.
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Affiliation(s)
- Boris A Vinatzer
- Department of Molecular Genetics and Cell Biology, The University of Chicago, 1103 East 57th Street, EBC410, Chicago, IL 60637, USA.
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Rose LE, Langley CH, Bernal AJ, Michelmore RW. Natural variation in the Pto pathogen resistance gene within species of wild tomato (Lycopersicon). I. Functional analysis of Pto alleles. Genetics 2005; 171:345-57. [PMID: 15944360 PMCID: PMC1456525 DOI: 10.1534/genetics.104.039339] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Disease resistance to the bacterial pathogen Pseudomonas syringae pv. tomato (Pst) in the cultivated tomato, Lycopersicon esculentum, and the closely related L. pimpinellifolium is triggered by the physical interaction between plant disease resistance protein, Pto, and the pathogen avirulence protein, AvrPto. To investigate the extent to which variation in the Pto gene is responsible for naturally occurring variation in resistance to Pst, we determined the resistance phenotype of 51 accessions from seven species of Lycopersicon to isogenic strains of Pst differing in the presence of avrPto. One-third of the plants displayed resistance specifically when the pathogen expressed AvrPto, consistent with a gene-for-gene interaction. To test whether this resistance in these species was conferred specifically by the Pto gene, alleles of Pto were amplified and sequenced from 49 individuals and a subset (16) of these alleles was tested in planta using Agrobacterium-mediated transient assays. Eleven alleles conferred a hypersensitive resistance response (HR) in the presence of AvrPto, while 5 did not. Ten amino acid substitutions associated with the absence of AvrPto recognition and HR were identified, none of which had been identified in previous structure-function studies. Additionally, 3 alleles encoding putative pseudogenes of Pto were isolated from two species of Lycopersicon. Therefore, a large proportion, but not all, of the natural variation in the reaction to strains of Pst expressing AvrPto can be attributed to sequence variation in the Pto gene.
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Affiliation(s)
- Laura E Rose
- Center for Population Biology, University of California, Davis, California 95616, USA.
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Lindeberg M, Stavrinides J, Chang JH, Alfano JR, Collmer A, Dangl JL, Greenberg JT, Mansfield JW, Guttman DS. Proposed guidelines for a unified nomenclature and phylogenetic analysis of type III Hop effector proteins in the plant pathogen Pseudomonas syringae. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:275-82. [PMID: 15828679 DOI: 10.1094/mpmi-18-0275] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Pathovars of Pseudomonas syringae interact with their plant hosts via the action of Hrp outer protein (Hop) effector proteins, injected into plant cells by the type III secretion system (TTSS). Recent availability of complete genome sequences for a number of P. syringae pathovars has led to a significant increase in the rate of effector discovery. However, lack of a systematic nomenclature has resulted in multiple names being assigned to the same Hop, unrelated Hops designated by the same alphabetic character, and failure of name choices to reflect consistent standards of experimental confirmation or phylogenetic relatedness. Therefore, specific experimental and bioinformatic criteria are proposed for proteins to be designated as Hops. A generic Hop name structure, HopXY#pv strain, also is proposed, wherein family membership is indicated by the alphabetic characters, subgroup membership numerically, and source pathovar and strain in subscript. Guidelines are provided for phylogenetic characterization and name selection for Hops that are novel, related to previously characterized Hops, chimeras, pseudogenes, truncations, or nonexpressed alleles. Phylogenetic analyses of previously characterized Hops are described, the results of which have been used to guide their integration into the proposed nomenclature.
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Affiliation(s)
- Magdalen Lindeberg
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA
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Petnicki-Ocwieja T, van Dijk K, Alfano JR. The hrpK operon of Pseudomonas syringae pv. tomato DC3000 encodes two proteins secreted by the type III (Hrp) protein secretion system: HopB1 and HrpK, a putative type III translocator. J Bacteriol 2005; 187:649-63. [PMID: 15629936 PMCID: PMC543549 DOI: 10.1128/jb.187.2.649-663.2005] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas syringae is a gram-negative bacterial plant pathogen that is dependent on a type III protein secretion system (TTSS) and the effector proteins it translocates into plant cells for pathogenicity. The P. syringae TTSS is encoded by hrp-hrc genes that reside in a central region of a pathogenicity island (Pai). Flanking one side of this Pai is the exchangeable effector locus (EEL). We characterized the transcriptional expression of the open reading frames (ORFs) within the EEL of P. syringae pv. tomato DC3000. One of these ORFs, PSPTO1406 (hopB1) is expressed in the same transcriptional unit as hrpK. Both HopB1 and HrpK were secreted in culture and translocated into plant cells via the TTSS. However, the translocation of HrpK required its C-terminal half. HrpK shares low similarity with a putative translocator, HrpF, from Xanthomonas campestris pv. vesicatoria. DC3000 mutants lacking HrpK were significantly reduced in disease symptoms and multiplication in planta, whereas DC3000 hopB1 mutants produced phenotypes similar to the wild type. Additionally, hrpK mutants were reduced in their ability to elicit the hypersensitive response (HR), a programmed cell death associated with plant defense. The reduced HR phenotype exhibited by hrpK mutants was complemented by hrpK expressed in bacteria but not by HrpK transgenically expressed in tobacco, suggesting that HrpK does not function inside plant cells. Further experiments identified a C-terminal transmembrane domain within HrpK that is required for HrpK translocation. Taken together, HopB1 is a type III effector and HrpK plays an important role in the TTSS and is a putative type III translocator.
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Affiliation(s)
- Tanja Petnicki-Ocwieja
- Plant Science Initiative, The Beadle Center for Genetic Research, University of Nebraska, 1901 Vine St., Lincoln, NE 68588-0660, USA
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Rezzonico F, Défago G, Moënne-Loccoz Y. Comparison of ATPase-encoding type III secretion system hrcN genes in biocontrol fluorescent Pseudomonads and in phytopathogenic proteobacteria. Appl Environ Microbiol 2004; 70:5119-31. [PMID: 15345390 PMCID: PMC520869 DOI: 10.1128/aem.70.9.5119-5131.2004] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Type III protein secretion systems play a key role in the virulence of many pathogenic proteobacteria, but they also occur in nonpathogenic, plant-associated bacteria. Certain type III protein secretion genes (e.g., hrcC) have been found in Pseudomonas sp. strain SBW25 (and other biocontrol pseudomonads), but other type III protein secretion genes, such as the ATPase-encoding gene hrcN, have not been found. Using both colony hybridization and a PCR approach, we show here that hrcN is nevertheless present in many biocontrol fluorescent pseudomonads. The phylogeny of biocontrol Pseudomonas strains based on partial hrcN sequences was largely congruent with the phylogenies derived from analyses of rrs (encoding 16S rRNA) and, to a lesser extent, biocontrol genes, such as phlD (for 2,4-diacetylphloroglucinol production) and hcnBC (for HCN production). Most biocontrol pseudomonads clustered separately from phytopathogenic proteobacteria, including pathogenic pseudomonads, in the hrcN tree. The exception was strain KD, which clustered with phytopathogenic pseudomonads, such as Pseudomonas syringae, suggesting that hrcN was acquired from the latter species. Indeed, strain KD (unlike strain SBW25) displayed the same organization of the hrpJ operon, which contains hrcN, as P. syringae. These results indicate that the occurrence of hrcN in most biocontrol pseudomonads is not the result of recent horizontal gene transfer from phytopathogenic bacteria, although such transfer might have occurred for a minority of biocontrol strains.
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Affiliation(s)
- Fabio Rezzonico
- Phytopathology Group, Institute of Plant Sciences, Swiss Federal Institute of Technology, Zürich, Switzerland
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Yang B, White FF. Diverse members of the AvrBs3/PthA family of type III effectors are major virulence determinants in bacterial blight disease of rice. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:1192-200. [PMID: 15553245 DOI: 10.1094/mpmi.2004.17.11.1192] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
AvrXa7 is a member of the avBs3/pthA gene family and the only known type III secretion system effector gene from Xanthomonas oryzae pv. oryzae with a major contribution to bacterial growth and lesion formation in bacterial blight disease of rice. We examined the general requirement for effectors of the AvrBs3/PthA family in bacterial blight of rice by identifying effectors from diverse strains of the pathogen. Inactivation of single effector genes in representative strains from Japan, Korea, and the Philippines resulted in severely limited growth in plants. Five strains harbored one gene of the avrBs3/pthA family, while one strain had two genes with the equivalent virulence activity of avrXa7. Sequence analysis revealed three genes with unique repeat arrangements in comparison to avrXa7. Comparison of the repetitive regions revealed a potential motif for the group that was also present in the repetitive region of avrBs3. However, the repetitive region of avrBs3 could not support virulence activity but, in combination with the C-terminal coding region of avrXa7, triggered a Xa7-dependent avirulence reaction. The results revealed diverse members of the avrBs3/pthA gene family with virulence activity in X. oryzae pv. oryzae and supported the hypothesis that bacterial blight disease of rice is highly dependent on a single class of type III effectors. The results also indicated that avrXa7 avirulence specificity is separable from virulence activity.
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Affiliation(s)
- Bing Yang
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66502, USA
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Mazurier S, Lemunier MÃ, Siblot SÃ, Mougel C, Lemanceau P. Distribution and diversity of type III secretion system-like genes in saprophytic and phytopathogenic fluorescent pseudomonads. FEMS Microbiol Ecol 2004; 49:455-67. [DOI: 10.1016/j.femsec.2004.04.019] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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44
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Bretz JR, Hutcheson SW. Role of type III effector secretion during bacterial pathogenesis in another kingdom. Infect Immun 2004; 72:3697-705. [PMID: 15213109 PMCID: PMC427461 DOI: 10.1128/iai.72.7.3697-3705.2004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Affiliation(s)
- James R Bretz
- Department of Cell Biology and Molecular Genetics, Microbiology Bldg., University of Maryland, College Park, MD 20742, USA
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Rojas CM, Ham JH, Schechter LM, Kim JF, Beer SV, Collmer A. The Erwinia chrysanthemi EC16 hrp/hrc gene cluster encodes an active Hrp type III secretion system that is flanked by virulence genes functionally unrelated to the Hrp system. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:644-53. [PMID: 15195947 DOI: 10.1094/mpmi.2004.17.6.644] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Erwinia chrysanthemi is a host-promiscuous plant pathogen that possesses a type III secretion system (TTSS) similar to that of the host-specific pathogens E. amylovora and Pseudomonas syringae. The regions flanking the TTSS-encoding hrp/hrc gene clusters in the latter pathogens encode various TTSS-secreted proteins. DNA sequencing of the complete E. chrysanthemi hrp/hrc gene cluster and approximately 12 kb of the flanking regions (beyond the previously characterized hecA adhesin gene in the left flank) revealed that the E. chrysanthemi TTSS genes were syntenic and similar (>50% amino-acid identity) with their E. amylovora orthologs. However, the hrp/hrc cluster was interrupted by a cluster of four genes, only one of which, a homolog of lytic transglycosylases, is implicated in TTSS functions. Furthermore, the regions flanking the hrp/hrc cluster lacked genes that were likely to encode TTSS substrates. Instead, some of the genes in these regions predict ABC transporters and methyl-accepting chemotaxis proteins that could have alternative roles in virulence. Mutations affecting all of the genes in the regions flanking or interrupting the hrp/hrc cluster were constructed in E. chrysanthemi CUCPB5047, a mutant whose reduced pectolytic capacity can enhance the phenotype of minor virulence factors. Mutants were screened in witloof chicory leaves and then in potato tubers and Nicotiana clevelandii seedlings. Mu dII1734 insertion in one gene, designated virA, resulted in strongly reduced virulence in all three tests. virA is immediately downstream of hecA, has an unusually low G+C content of 38%, and predicts an unknown protein of 111 amino acids. The E. chrysanthemi TTSS was shown to be active by its ability to translocate AvrPto-Cya (a P. syringae TTSS effector fused to an adenylate cyclase reporter that is active in the presence of eukaryote calmodulin) into N. benthamiana leaf cells. However, VirA(1-61)-Cya was not translocated into plant cells, and virA expression was not affected by mutations in E. chrysanthemi Hrp regulator genes hrpL and hrpS. Thus, the 44-kb region of the E. chrysanthemi EC16 genome that is centered on the hrplhrc cluster encodes a potpourri of virulence factors, but none of these appear to be a TTSS effector.
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Affiliation(s)
- Clemencia M Rojas
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853-4203, USA
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Shan L, Oh HS, Chen J, Guo M, Zhou J, Alfano JR, Collmer A, Jia X, Tang X. The HopPtoF locus of Pseudomonas syringae pv. tomato DC3000 encodes a type III chaperone and a cognate effector. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:447-455. [PMID: 15141948 DOI: 10.1094/mpmi.2004.17.5.447] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Type III secretion systems are highly conserved among gram-negative plant and animal pathogenic bacteria. Through the type III secretion system, bacteria inject a number of virulence proteins into the host cells. Analysis of the whole genome sequence of Pseudomonas syringae pv. tomato DC3000 strain identified a locus, named HopPtoF, that is homologous to the avirulence gene locus avrPphF in P. syringae pv. phaseolicola. The HopPtoF locus harbors two genes, ShcF(Pto) and HopF(Pto), that are preceded by a single hrp box promoter. We present evidence here to show that ShcF(Pto) and HopF(Pto) encode a type III chaperone and a cognate effector, respectively. ShcF(Pto) interacts with and stabilizes the HopF(Pto) protein in the bacterial cell. Translation of HopF(Pto) starts at a rare initiation codon ATA that limits the synthesis of the HopF(Pto) protein to a low level in bacterial cells.
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Affiliation(s)
- Libo Shan
- Department of Plant Pathology, Kansas State University, Manhattan 66506-5502, USA
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Oguiza JA, Rico A, Rivas LA, Sutra L, Vivian A, Murillo J. Pseudomonas syringae pv. phaseolicola can be separated into two genetic lineages distinguished by the possession of the phaseolotoxin biosynthetic cluster. MICROBIOLOGY-SGM 2004; 150:473-482. [PMID: 14766926 DOI: 10.1099/mic.0.26635-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The bean (Phaseolus spp.) plant pathogen Pseudomonas syringae pv. phaseolicola is characterized by the ability to produce phaseolotoxin (Tox(+)). We recently reported that the majority of the Spanish P. syringae pv. phaseolicola population is unable to synthesize this toxin (Tox(-)). These Tox(-) isolates appear to lack the entire DNA region for the biosynthesis of phaseolotoxin (argK-tox gene cluster), as shown by PCR amplification and DNA hybridization using DNA sequences specific for separated genes of this cluster. Tox(+) and Tox(-) isolates also showed genomic divergence that included differences in ERIC-PCR and arbitrarily primed-PCR profiles. Tox(+) isolates showed distinct patterns of IS801 genomic insertions and contained a chromosomal IS801 insertion that was absent from Tox(-) isolates. Using a heteroduplex mobility assay, sequence differences were observed only among the intergenic transcribed spacer of the five rDNA operons of the Tox(-) isolates. The techniques used allowed the unequivocal differentiation of isolates of P. syringae pv. phaseolicola from the closely related soybean (Glycine max) pathogen, P. syringae pv. glycinea. Finally, a pathogenicity island that is essential for the pathogenicity of P. syringae pv. phaseolicola on beans appears to be conserved among Tox(+), but not among Tox(-) isolates, which also lacked the characteristic large plasmid that carries this pathogenicity island. It is proposed that the results presented here justify the separation of the Tox(+) and Tox(-) P. syringae pv. phaseolicola isolates into two distinct genetic lineages, designated Pph1 and Pph2, respectively, that show relevant genomic differences that include the pathogenicity gene complement.
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Affiliation(s)
- José A Oguiza
- Instituto de Agrobiotecnología y Recursos Naturales, CSIC-UPNA, and Laboratorio de Patología Vegetal, Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain
| | - Arantza Rico
- Instituto de Agrobiotecnología y Recursos Naturales, CSIC-UPNA, and Laboratorio de Patología Vegetal, Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain
| | - Luis A Rivas
- Instituto de Agrobiotecnología y Recursos Naturales, CSIC-UPNA, and Laboratorio de Patología Vegetal, Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain
| | - Laurent Sutra
- UMR de Pathologie Végétale INRA-INH-Université, Beaucouzé, 49071 France
| | - Alan Vivian
- Centre for Research in Plant Science, University of the West of England, Coldharbour Lane, Bristol BS16 1QY, UK
| | - Jesús Murillo
- Instituto de Agrobiotecnología y Recursos Naturales, CSIC-UPNA, and Laboratorio de Patología Vegetal, Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain
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Gropp SJ, Guttman DS. The PCR amplification and characterization of entire Pseudomonas syringae hrp/hrc clusters. MOLECULAR PLANT PATHOLOGY 2004; 5:137-140. [PMID: 20565590 DOI: 10.1111/j.1364-3703.2004.00212.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
SUMMARY We describe the use of degenerate primers to amplify the core hrp/hrc region of P. syringae pv. phaseolicola NPS3121. 18 826 bp were amplified using long-range PCR, digested and shotgun sequenced. Sequence analysis finds a hypervariable region between the hrpU and hrpC operons, and indications of positive selection on the hrpE locus. The primers were also shown to work on four other, widely divergent P. syringae strains. These primers should be of great utility for the characterization of hrp/hrc clusters from any P. syringae strain.
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Losada L, Sussan T, Pak K, Zeyad S, Rozenbaum I, Hutcheson SW. Identification of a novel Pseudomonas syringae Psy61 effector with virulence and avirulence functions by a HrpL-dependent promoter-trap assay. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:254-262. [PMID: 15000392 DOI: 10.1094/mpmi.2004.17.3.254] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The hrp pathogenicity island of Pseudomonas syringae encodes a type III secretion system (TTSS) that translocates effectors into plant cells. Most genes encoding effectors are dispersed in the P. syringae genome. Regardless of location, all are regulated coordinately by the alternative sigma factor HrpL. An HrpL-dependent promoter-trap assay was developed to screen genomic libraries of P. syringae strains for promoters whose activity in Escherichia coli is dependent on an inducible hrpL construct. Twenty-two HrpL-dependent promoter fragments were isolated from P. syringae Psy61 that included promoters for known HrpL-dependent genes. One fragment also was isolated that shared no similarity with known genes but retained a near consensus HrpL-dependent promoter. The sequence of the region revealed a 375-amino acid open reading frame encoding a 40.5-kDa product that was designated HopPsyL. HopPsyL was structurally similar to other secreted effectors and carried a putative chloroplast-targeting signal and two predicted transmembrane domains. HopPsyL':'AvrRpt2 fusions were translocated into host cells via the P. syringae pv. tomato DC3000 hrp TTSS. A hopPsyL::kan mutant of Psy61 exhibited strongly reduced virulence in Phaseolus vulgaris cv. Kentucky Wonder, but did not appear to act as a defense response suppressor. The ectopically expressed gene reduced the virulence of Pseudomonas syringae DC3000 transformants in Arabidopsis thaliana Col-0. The gene was shown to be conserved in 6 of 10 P. syringae pv. syringae strains but was not detected in 35 strains of other pathovars. HopPsyL appears to be a novel TTSS-dependent effector that functions as a host-species-specific virulence factor in Psy61.
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Affiliation(s)
- L Losada
- Department of Cell Biology and Molecular Genetics, Microbiology Bldg, University of Maryland, College Park 20742, USA
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50
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Alfano JR, Collmer A. Type III secretion system effector proteins: double agents in bacterial disease and plant defense. ANNUAL REVIEW OF PHYTOPATHOLOGY 2004; 42:385-414. [PMID: 15283671 DOI: 10.1146/annurev.phyto.42.040103.110731] [Citation(s) in RCA: 500] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Many phytopathogenic bacteria inject virulence effector proteins into plant cells via a Hrp type III secretion system (TTSS). Without the TTSS, these pathogens cannot defeat basal defenses, grow in plants, produce disease lesions in hosts, or elicit the hypersensitive response (HR) in nonhosts. Pathogen genome projects employing bioinformatic methods to identify TTSS Hrp regulon promoters and TTSS pathway targeting signals suggest that phytopathogenic Pseudomonas, Xanthomonas, and Ralstonia spp. harbor large arsenals of effectors. The Hrp TTSS employs customized cytoplasmic chaperones, conserved export components in the bacterial envelope (also used by the TTSS of animal pathogens), and a more specialized set of TTSS-secreted proteins to deliver effectors across the plant cell wall and plasma membrane. Many effectors can act as molecular double agents that betray the pathogen to plant defenses in some interactions and suppress host defenses in others. Investigations of the functions of effectors within plant cells have demonstrated the plasma membrane and nucleus as subcellular sites for several effectors, revealed some effectors to possess cysteine protease or protein tyrosine phosphatase activity, and provided new clues to the coevolution of bacterium-plant interactions.
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Affiliation(s)
- James R Alfano
- The Plant Science Initiative and the Department of Plant Pathology, University of Nebraska, Lincoln, Nebraska, 68588-0660, USA.
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