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Vadillo‐Dieguez A, Zeng Z, Mansfield JW, Grinberg NF, Lynn SC, Gregg A, Connell J, Harrison RJ, Jackson RW, Hulin MT. Genetic dissection of the tissue-specific roles of type III effectors and phytotoxins in the pathogenicity of Pseudomonas syringae pv. syringae to cherry. MOLECULAR PLANT PATHOLOGY 2024; 25:e13451. [PMID: 38590135 PMCID: PMC11002349 DOI: 10.1111/mpp.13451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/13/2024] [Accepted: 03/19/2024] [Indexed: 04/10/2024]
Abstract
When compared with other phylogroups (PGs) of the Pseudomonas syringae species complex, P. syringae pv. syringae (Pss) strains within PG2 have a reduced repertoire of type III effectors (T3Es) but produce several phytotoxins. Effectors within the cherry pathogen Pss 9644 were grouped based on their frequency in strains from Prunus as the conserved effector locus (CEL) common to most P. syringae pathogens; a core of effectors common to PG2; a set of PRUNUS effectors common to cherry pathogens; and a FLEXIBLE set of T3Es. Pss 9644 also contains gene clusters for biosynthesis of toxins syringomycin, syringopeptin and syringolin A. After confirmation of virulence gene expression, mutants with a sequential series of T3E and toxin deletions were pathogenicity tested on wood, leaves and fruits of sweet cherry (Prunus avium) and leaves of ornamental cherry (Prunus incisa). The toxins had a key role in disease development in fruits but were less important in leaves and wood. An effectorless mutant retained some pathogenicity to fruit but not wood or leaves. Striking redundancy was observed amongst effector groups. The CEL effectors have important roles during the early stages of leaf infection and possibly acted synergistically with toxins in all tissues. Deletion of separate groups of T3Es had more effect in P. incisa than in P. avium. Mixed inocula were used to complement the toxin mutations in trans and indicated that strain mixtures may be important in the field. Our results highlight the niche-specific role of toxins in P. avium tissues and the complexity of effector redundancy in the pathogen Pss 9644.
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Affiliation(s)
- Andrea Vadillo‐Dieguez
- NIABCambridgeUK
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
| | | | | | | | | | | | | | - Richard J. Harrison
- NIABCambridgeUK
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
- Faculty of Natural Sciences, Plant Science GroupWageningen University and ResearchWageningenNetherlands
- Present address:
Faculty of Natural Sciences, Plant Science GroupWageningen University and ResearchWageningenNetherlands
| | - Robert W. Jackson
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
| | - Michelle T. Hulin
- NIABCambridgeUK
- Department of Plant Soil & Microbial SciencesMichigan State UniversityEast LansingUSA
- Present address:
Department of Plant Soil & Microbial SciencesMichigan State UniversityEast LansingUSA
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2
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Wang MY, Chen JB, Wu R, Guo HL, Chen Y, Li ZJ, Wei LY, Liu C, He SF, Du MD, Guo YL, Peng YL, Jones JDG, Weigel D, Huang JH, Zhu WS. The plant immune receptor SNC1 monitors helper NLRs targeted by a bacterial effector. Cell Host Microbe 2023; 31:1792-1803.e7. [PMID: 37944492 DOI: 10.1016/j.chom.2023.10.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Revised: 09/01/2023] [Accepted: 10/06/2023] [Indexed: 11/12/2023]
Abstract
Plants deploy intracellular receptors to counteract pathogen effectors that suppress cell-surface-receptor-mediated immunity. To what extent pathogens manipulate intracellular receptor-mediated immunity, and how plants tackle such manipulation, remains unknown. Arabidopsis thaliana encodes three similar ADR1 class helper nucleotide-binding domain leucine-rich repeat receptors (ADR1, ADR1-L1, and ADR1-L2), which are crucial in plant immunity initiated by intracellular receptors. Here, we report that Pseudomonas syringae effector AvrPtoB suppresses ADR1-L1- and ADR1-L2-mediated cell death. ADR1, however, evades such suppression by diversifying into two ubiquitination sites targeted by AvrPtoB. The intracellular sensor SNC1 interacts with and guards the CCR domains of ADR1-L1/L2. Removal of ADR1-L1/L2 or delivery of AvrPtoB activates SNC1, which then signals through ADR1 to trigger immunity. Our work elucidates the long-sought-after function of SNC1 in defense, and also how plants can use dual strategies, sequence diversification, and a multi-layered guard-guardee system, to counteract pathogen's attack on core immunity functions.
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Affiliation(s)
- Ming-Yu Wang
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China
| | - Jun-Bin Chen
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China
| | - Rui Wu
- Department of Molecular Biology, Max Planck Institute for Biology Tübingen, 72076 Tübingen, Germany
| | - Hai-Long Guo
- Key Laboratory of Pest Monitoring and Green Management, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Yan Chen
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China
| | - Zhen-Ju Li
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China
| | - Lu-Yang Wei
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China
| | - Chuang Liu
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China
| | - Sheng-Feng He
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China
| | - Mei-Da Du
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China
| | - Ya-Long Guo
- State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - You-Liang Peng
- Key Laboratory of Pest Monitoring and Green Management, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, China Agricultural University, Beijing 100193, China
| | - Jonathan D G Jones
- The Sainsbury Laboratory, University of East Anglia, Norwich Research Park, Norwich NR4 7UH, UK
| | - Detlef Weigel
- Department of Molecular Biology, Max Planck Institute for Biology Tübingen, 72076 Tübingen, Germany; Institute for Bioinformatics and Medical Informatics, University of Tübingen, Tübingen, Germany
| | - Jian-Hua Huang
- The Sainsbury Laboratory, University of East Anglia, Norwich Research Park, Norwich NR4 7UH, UK.
| | - Wang-Sheng Zhu
- Key Laboratory of Surveillance and Management for Plant Quarantine Pests, Ministry of Agriculture and Rural Affairs, and College of Plant Protection, State Key Laboratory of Maize Bio-breeding, China Agricultural University, Beijing 100193, China.
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3
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Kvitko BH, Collmer A. Discovery of the Hrp Type III Secretion System in Phytopathogenic Bacteria: How Investigation of Hypersensitive Cell Death in Plants Led to a Novel Protein Injector System and a World of Inter-Organismal Molecular Interactions Within Plant Cells. PHYTOPATHOLOGY 2023; 113:626-636. [PMID: 37099273 DOI: 10.1094/phyto-08-22-0292-kd] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
In the early 1960s, Pseudomonas syringae and other host-specific phytopathogenic proteobacteria were discovered to elicit a rapid, resistance-associated death when infiltrated at high inoculum levels into nonhost tobacco leaves. This hypersensitive reaction (or response; HR) was a useful indicator of basic pathogenic ability. Research over the next 20 years failed to identify an elicitor of the HR but revealed that its elicitation required contact between metabolically active bacterial and plant cells. Beginning in the early 1980s, molecular genetic tools were applied to the HR puzzle, revealing the presence in P. syringae of clusters of hrp genes, so named because they are required for the HR and pathogenicity, and of avr genes, so named because their presence confers HR-associated avirulence in resistant cultivars of a host plant species. A series of breakthroughs over the next two decades revealed that (i) hrp gene clusters encode a type III secretion system (T3SS), which injects Avr (now "effector") proteins into plant cells, where their recognition triggers the HR; (ii) T3SSs, which are typically present in pathogenicity islands acquired by horizontal gene transfers, are found in many bacterial pathogens of plants and animals and inject many effector proteins, which are collectively essential for pathogenicity; and (iii) a primary function of phytopathogen effectors is to subvert non-HR defenses resulting from recognition of conserved microbial features presented outside of plant cells. In the 2000s, Hrp system research shifted to extracellular components enabling effector delivery across plant cell walls and plasma membranes, regulation, and tools for studying effectors. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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Affiliation(s)
- Brian H Kvitko
- Department of Plant Pathology, University of Georgia, 120 Carlton St., Athens, GA 30602
| | - Alan Collmer
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell University, 334 Plant Science Bldg., Ithaca, NY 14853
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4
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Cooperative virulence via the collective action of secreted pathogen effectors. Nat Microbiol 2023; 8:640-650. [PMID: 36782026 DOI: 10.1038/s41564-023-01328-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 01/13/2023] [Indexed: 02/15/2023]
Abstract
Although virulence is typically attributed to single pathogenic strains, here we investigated whether effectors secreted by a population of non-virulent strains could function as public goods to enable the emergence of collective virulence. We disaggregated the 36 type III effectors of the phytopathogenic bacterium Pseudomonas syringae strain PtoDC3000 into a 'metaclone' of 36 coisogenic strains, each carrying a single effector in an effectorless background. Each coisogenic strain was individually unfit, but the metaclone was collectively as virulent as the wild-type strain on Arabidopsis thaliana, suggesting that effectors can drive the emergence of cooperation-based virulence through their public action. We show that independently evolved effector suits can equally drive this cooperative behaviour by transferring the effector alleles native to the strain PmaES4326 into the conspecific but divergent strain PtoDC3000. Finally, we transferred the disaggregated PtoDC3000 effector arsenal into Pseudomonas fluorescens and show that their cooperative action was sufficient to convert this rhizosphere-inhabiting beneficial bacterium into a phyllosphere pathogen. These results emphasize the importance of microbial community interactions and expand the ecological scale at which disease may be attributed.
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5
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Beihammer G, Romero-Pérez A, Maresch D, Figl R, Mócsai R, Grünwald-Gruber C, Altmann F, Van Damme EJM, Strasser R. Pseudomonas syringae DC3000 infection increases glucosylated N-glycans in Arabidopsis thaliana. Glycoconj J 2023; 40:97-108. [PMID: 36269466 PMCID: PMC9925501 DOI: 10.1007/s10719-022-10084-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 09/26/2022] [Accepted: 09/29/2022] [Indexed: 11/04/2022]
Abstract
Studying the interaction between the hemibiotrophic bacterium Pseudomonas syringae pv. tomato DC3000 and Arabidopsis thaliana has shed light onto the various forms of mechanisms plants use to defend themselves against pathogen attack. While a lot of emphasis has been put on investigating changes in protein expression in infected plants, only little information is available on the effect infection plays on the plants N-glycan composition. To close this gap in knowledge, total N-glycans were enriched from P. syringae DC3000-infected and mock treated Arabidopsis seedlings and analyzed via MALDI-TOF-MS. Additionally, fluorescently labelled N-glycans were quantified via HPLC-FLD. N-glycans from infected plants were overall less processed and displayed increased amounts of oligomannosidic N-glycans. As multiple peaks for certain oligomannosidic glycoforms were detected upon separation via liquid chromatography, a porous graphitic carbon (PGC)-analysis was conducted to separate individual N-glycan isomers. Indeed, multiple different N-glycan isomers with masses of two N-acetylhexosamine residues plus 8, 9 or 10 hexoses were detected in the infected plants which were absent in the mock controls. Treatment with jack bean α-mannosidase resulted in incomplete removal of hexoses from these N-glycans, indicating the presence of glucose residues. This hints at the accumulation of misfolded glycoproteins in the infected plants, likely because of endoplasmic reticulum (ER) stress. In addition, poly-hexose structures susceptible to α-amylase treatment were found in the DC3000-infected plants, indicating alterations in starch metabolism due to the infection process.
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Affiliation(s)
- Gernot Beihammer
- Institute of Plant Biotechnology and Cell Biology, Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Andrea Romero-Pérez
- Laboratory of Biochemistry and Glycobiology, Department of Biotechnology, Ghent University, Ghent, Belgium
| | - Daniel Maresch
- Institute of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria
- Core Facility Mass Spectrometry, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Rudolf Figl
- Institute of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria
- Core Facility Mass Spectrometry, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Réka Mócsai
- Institute of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Clemens Grünwald-Gruber
- Institute of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria
- Core Facility Mass Spectrometry, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Friedrich Altmann
- Institute of Biochemistry, Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria
| | - Els J M Van Damme
- Laboratory of Biochemistry and Glycobiology, Department of Biotechnology, Ghent University, Ghent, Belgium
| | - Richard Strasser
- Institute of Plant Biotechnology and Cell Biology, Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Vienna, Austria.
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6
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Zhi T, Liu Q, Xie T, Ding Y, Hu R, Sun Y, Fan R, Long Y, Zhao Z. Identification of Genetic and Chemical Factors Affecting Type III Secretion System Expression in Pseudomonas syringae pv. actinidiae Biovar 3 Using a Luciferase Reporter Construct. PHYTOPATHOLOGY 2022; 112:1610-1619. [PMID: 35240868 DOI: 10.1094/phyto-09-21-0404-r] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The type III secretion system (T3SS) is a key factor in the pathogenesis of Pseudomonas syringae pv. actinidiae biovar 3 (Psa3), the causal agent of a global kiwifruit bacterial canker pandemic. To monitor the T3SS expression levels in Psa3, we constructed a luciferase reporter plasmid-expressing HrpAPsa3-NLuc fusion protein. The expression of HrpA-NLuc was induced in hrp-inducing conditions whereas the level of luciferase activity correlated with the expression of hrp/hrc genes in Psa3 confirmed the reliability of the reporter construct. Based on the readout of the NLuc reporter construct, three small molecule compounds 4-methoxy-cinnamic acid, sulforaphane, and ferulic acid were determined as T3SS inhibitors in Psa3, whereas sodium acetate was determined to be a T3SS inducer. Moreover, the aqueous extract of fruit inhibited the accumulation of HrpA-NLuc in Psa3 in medium and in planta. Additionally, the T3SS inhibitors suppress Psa3 virulence, whereas the T3SS inducer promotes Psa3 virulence on kiwifruit. Thus, our findings may provide clues to why the fruit is not infected by Psa3, and the Psa3 T3SS inhibitors have potential as alternatives to current nonspecific antimicrobials for disease management.
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Affiliation(s)
- Taihui Zhi
- Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
| | - Quanhong Liu
- Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
| | - Ting Xie
- Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
| | - Yue Ding
- Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
| | - Renjian Hu
- Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
| | - Yu Sun
- Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
| | - Rong Fan
- Kiwifruit Engineering and Technology Research Center, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
| | - Youhua Long
- Kiwifruit Engineering and Technology Research Center, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
| | - Zhibo Zhao
- Department of Plant Pathology, College of Agriculture, Guizhou University, Guiyang 550025, People's Republic of China
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7
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Yu X, Meng C, Tan X, Su Y, Cao Z, Hwang TS, Li L. RsmA3 modulates RpoS through the RetS-Gac-Rsm signaling pathway in response to H 2 O 2 stress in the phytopathogen Pseudomonas syringae. Environ Microbiol 2022; 24:4755-4770. [PMID: 35837862 DOI: 10.1111/1462-2920.16132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 05/27/2022] [Accepted: 07/06/2022] [Indexed: 11/28/2022]
Abstract
Reactive oxygen species are a fatal challenge to the plant pathogenic bacterium Pseudomonas syringae. In this study, we reveal that the global regulatory protein RsmA3 from the RetS-Gac/Rsm signaling pathway modulates RpoS in the early-log growth phase in the P. syringae wild-type strain MB03, thereby regulating oxidative tolerance to H2 O2 and ultimately affecting pathogenicity to the host plant. Following increased H2 O2 by external addition or endogenous induction by menadione, the resistance of the mutant strain ΔretS to H2 O2 is significantly enhanced due to rapid increases in the transcription of Rsm-related non-coding small RNAs (nc sRNAs), a sigma factor RpoS, and H2 O2 -detoxifying enzymes. Moreover, the ΔretS mutant is significantly less pathogenic in cucumber leaves. Seven Rsm-related nc sRNAs (namely, rsmZ, rsmY, and rsmX1-5 ) show functional redundancy in the RetS-Gac-Rsm signaling pathway. External addition of H2 O2 stimulates increases in the transcription of both rsmY and rsmZ. Thus, we propose a regulatory model of the RetS-Gac-Rsm signaling pathway in P. syringae MB03 for the regulation of H2 O2 tolerance and phytopathogenicity in the host plant.
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Affiliation(s)
- Xun Yu
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agriculture University, Wuhan, PR China
| | - Cui Meng
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agriculture University, Wuhan, PR China
| | - Xiaocheng Tan
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agriculture University, Wuhan, PR China
| | - Yuwei Su
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agriculture University, Wuhan, PR China
| | - Zhiping Cao
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agriculture University, Wuhan, PR China
| | - Tzann-Shun Hwang
- Graduate Institute of Biotechnology, Chinese Culture University, Taipei, Taiwan
| | - Lin Li
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agriculture University, Wuhan, PR China
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8
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Hemara LM, Jayaraman J, Sutherland PW, Montefiori M, Arshed S, Chatterjee A, Chen R, Andersen MT, Mesarich CH, van der Linden O, Yoon M, Schipper MM, Vanneste JL, Brendolise C, Templeton MD. Effector loss drives adaptation of Pseudomonas syringae pv. actinidiae biovar 3 to Actinidia arguta. PLoS Pathog 2022; 18:e1010542. [PMID: 35622878 PMCID: PMC9182610 DOI: 10.1371/journal.ppat.1010542] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Revised: 06/09/2022] [Accepted: 04/21/2022] [Indexed: 11/18/2022] Open
Abstract
A pandemic isolate of Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) has devastated kiwifruit orchards growing cultivars of Actinidia chinensis. In contrast, A. arguta (kiwiberry) is not a host of Psa3. Resistance is mediated via effector-triggered immunity, as demonstrated by induction of the hypersensitive response in infected A. arguta leaves, observed by microscopy and quantified by ion-leakage assays. Isolates of Psa3 that cause disease in A. arguta have been isolated and analyzed, revealing a 51 kb deletion in the exchangeable effector locus (EEL). This natural EEL-mutant isolate and strains with synthetic knockouts of the EEL were more virulent in A. arguta plantlets than wild-type Psa3. Screening of a complete library of Psa3 effector knockout strains identified increased growth in planta for knockouts of four effectors–AvrRpm1a, HopF1c, HopZ5a, and the EEL effector HopAW1a –suggesting a resistance response in A. arguta. Hypersensitive response (HR) assays indicate that three of these effectors trigger a host species-specific HR. A Psa3 strain with all four effectors knocked out escaped host recognition, but a cumulative increase in bacterial pathogenicity and virulence was not observed. These avirulence effectors can be used in turn to identify the first cognate resistance genes in Actinidia for breeding durable resistance into future kiwifruit cultivars. Clonally propagated monoculture crop plants facilitate the emergence and spread of new diseases. Plant pathogens cause disease by the secretion of effectors that function by repressing the host defense response. While the last few decades have seen a huge increase in our understanding of the role effectors play in mediating plant-pathogen interactions, the combinations of effectors required for the establishment of plant disease and that account for host specificity are less well understood. Breeding genetic resistance is often used to protect plants from disease but it is frequently evaded by rapidly evolving pathogens. Pseudomonas syringae pv. actinidiae (Psa) which causes bacterial canker disease of kiwifruit has spread rapidly throughout the world’s kiwifruit orchards, particularly those growing cultivars of Actinidia chinensis. Other Actinidia species including A. arguta display strong resistance conferred by recognition of effectors delivered by Psa. We explore the depth and dynamics of Psa effector recognition by A. arguta and show that there is a trade-off between losses of effector recognition by A. arguta versus the retention of pathogenicity. Our findings should aid in the understanding of how to breed durable resistance into perennial plants challenged by swiftly evolving pathogens.
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Affiliation(s)
- Lauren M. Hemara
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
- Bioprotection Aoteoroa, New Zealand
| | - Jay Jayaraman
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
- Bioprotection Aoteoroa, New Zealand
| | - Paul W. Sutherland
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
| | - Mirco Montefiori
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
| | - Saadiah Arshed
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
| | - Abhishek Chatterjee
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
| | - Ronan Chen
- The New Zealand Institute for Plant and Food Research Limited, Food Industry Science Centre, Palmerston North, New Zealand
| | - Mark T. Andersen
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
| | - Carl H. Mesarich
- Bioprotection Aoteoroa, New Zealand
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Otto van der Linden
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
| | - Minsoo Yoon
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
| | - Magan M. Schipper
- The New Zealand Institute for Plant and Food Research Limited, Ruakura Campus, Hamilton, New Zealand
| | - Joel L. Vanneste
- The New Zealand Institute for Plant and Food Research Limited, Ruakura Campus, Hamilton, New Zealand
| | - Cyril Brendolise
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
| | - Matthew D. Templeton
- The New Zealand Institute for Plant and Food Research Limited, Mt. Albert Research Centre, Auckland, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
- Bioprotection Aoteoroa, New Zealand
- * E-mail: ,
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9
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Metaeffector interactions modulate the type III effector-triggered immunity load of Pseudomonas syringae. PLoS Pathog 2022; 18:e1010541. [PMID: 35576228 PMCID: PMC9135338 DOI: 10.1371/journal.ppat.1010541] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Revised: 05/26/2022] [Accepted: 04/21/2022] [Indexed: 11/19/2022] Open
Abstract
The bacterial plant pathogen Pseudomonas syringae requires type III secreted effectors (T3SEs) for pathogenesis. However, a major facet of plant immunity entails the recognition of a subset of P. syringae’s T3SEs by intracellular host receptors in a process called Effector-Triggered Immunity (ETI). Prior work has shown that ETI-eliciting T3SEs are pervasive in the P. syringae species complex raising the question of how P. syringae mitigates its ETI load to become a successful pathogen. While pathogens can evade ETI by T3SE mutation, recombination, or loss, there is increasing evidence that effector-effector (a.k.a., metaeffector) interactions can suppress ETI. To study the ETI-suppression potential of P. syringae T3SE repertoires, we compared the ETI-elicitation profiles of two genetically divergent strains: P. syringae pv. tomato DC3000 (PtoDC3000) and P. syringae pv. maculicola ES4326 (PmaES4326), which are both virulent on Arabidopsis thaliana but harbour largely distinct effector repertoires. Of the 529 T3SE alleles screened on A. thaliana Col-0 from the P. syringae T3SE compendium (PsyTEC), 69 alleles from 21 T3SE families elicited ETI in at least one of the two strain backgrounds, while 50 elicited ETI in both backgrounds, resulting in 19 differential ETI responses including two novel ETI-eliciting families: AvrPto1 and HopT1. Although most of these differences were quantitative, three ETI responses were completely absent in one of the pathogenic backgrounds. We performed ETI suppression screens to test if metaeffector interactions contributed to these ETI differences, and found that HopQ1a suppressed AvrPto1m-mediated ETI, while HopG1c and HopF1g suppressed HopT1b-mediated ETI. Overall, these results show that P. syringae strains leverage metaeffector interactions and ETI suppression to overcome the ETI load associated with their native T3SE repertoires.
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10
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The Pseudomonas syringae type III effector HopG1 triggers necrotic cell death that is attenuated by AtNHR2B. Sci Rep 2022; 12:5388. [PMID: 35354887 PMCID: PMC8967837 DOI: 10.1038/s41598-022-09335-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 03/14/2022] [Indexed: 12/25/2022] Open
Abstract
The plant pathogenic bacterium Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) has become a paradigm to investigate plant-bacteria interactions due to its ability to cause disease in the model plant Arabidopsis thaliana. Pst DC3000 uses the type III secretion system to deliver type III secreted effectors (T3SEs) directly into the plant cytoplasm. Pst DC3000 T3SEs contribute to pathogenicity by suppressing plant defense responses and targeting plant’s physiological processes. Although the complete repertoire of effectors encoded in the Pst DC3000 genome have been identified, the specific function for most of them remains to be elucidated. Among those effectors, the mitochondrial-localized T3E HopG1, suppresses plant defense responses and promotes the development of disease symptoms. Here, we show that HopG1 triggers necrotic cell death that enables the growth of adapted and non-adapted pathogens. We further showed that HopG1 interacts with the plant immunity-related protein AtNHR2B and that AtNHR2B attenuates HopG1- virulence functions. These results highlight the importance of HopG1 as a multi-faceted protein and uncover its interplay with AtNHR2B.
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11
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Molecular and Genomic Characterization of the Pseudomonas syringae Phylogroup 4: An Emerging Pathogen of Arabidopsis thaliana and Nicotiana benthamiana. Microorganisms 2022; 10:microorganisms10040707. [PMID: 35456758 PMCID: PMC9030749 DOI: 10.3390/microorganisms10040707] [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: 02/28/2022] [Revised: 03/15/2022] [Accepted: 03/21/2022] [Indexed: 12/10/2022] Open
Abstract
Environmental fluctuations such as increased temperature, water availability, and air CO2 concentration triggered by climate change influence plant disease dynamics by affecting hosts, pathogens, and their interactions. Here, we describe a newly discovered Pseudomonas syringae strain found in a natural population of Arabidopsis thaliana collected from the southwest of France. This strain, called Psy RAYR-BL, is highly virulent on natural Arabidopsis accessions, Arabidopsis model accession Columbia 0, and tobacco plants. Despite the severe disease phenotype caused by the Psy RAYR-BL strain, we identified a reduced repertoire of putative Type III virulence effectors by genomic sequencing compared to P. syringae pv tomato (Pst) DC3000. Furthermore, hopBJ1Psy is found exclusively on the Psy RAYR-BL genome but not in the Pst DC3000 genome. The plant expression of HopBJ1Psy induces ROS accumulation and cell death. In addition, HopBJ1Psy participates as a virulence factor in this plant-pathogen interaction, likely explaining the severity of the disease symptoms. This research describes the characterization of a newly discovered plant pathogen strain and possible virulence mechanisms underlying the infection process shaped by natural and changing environmental conditions.
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12
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Eastman S, Smith T, Zaydman MA, Kim P, Martinez S, Damaraju N, DiAntonio A, Milbrandt J, Clemente TE, Alfano JR, Guo M. A phytobacterial TIR domain effector manipulates NAD + to promote virulence. THE NEW PHYTOLOGIST 2022; 233:890-904. [PMID: 34657283 PMCID: PMC9298051 DOI: 10.1111/nph.17805] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 09/15/2021] [Indexed: 05/06/2023]
Abstract
The Pseudomonas syringae DC3000 type III effector HopAM1 suppresses plant immunity and contains a Toll/interleukin-1 receptor (TIR) domain homologous to immunity-related TIR domains of plant nucleotide-binding leucine-rich repeat receptors that hydrolyze nicotinamide adenine dinucleotide (NAD+ ) and activate immunity. In vitro and in vivo assays were conducted to determine if HopAM1 hydrolyzes NAD+ and if the activity is essential for HopAM1's suppression of plant immunity and contribution to virulence. HPLC and LC-MS were utilized to analyze metabolites produced from NAD+ by HopAM1 in vitro and in both yeast and plants. Agrobacterium-mediated transient expression and in planta inoculation assays were performed to determine HopAM1's intrinsic enzymatic activity and virulence contribution. HopAM1 is catalytically active and hydrolyzes NAD+ to produce nicotinamide and a novel cADPR variant (v2-cADPR). Expression of HopAM1 triggers cell death in yeast and plants dependent on the putative catalytic residue glutamic acid 191 (E191) within the TIR domain. Furthermore, HopAM1's E191 residue is required to suppress both pattern-triggered immunity and effector-triggered immunity and promote P. syringae virulence. HopAM1 manipulates endogenous NAD+ to produce v2-cADPR and promote pathogenesis. This work suggests that HopAM1's TIR domain possesses different catalytic specificity than other TIR domain-containing NAD+ hydrolases and that pathogens exploit this activity to sabotage NAD+ metabolism for immune suppression and virulence.
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Affiliation(s)
- Samuel Eastman
- Department of Plant PathologyUniversity of Nebraska‐LincolnLincolnNE68583USA
| | - Thomas Smith
- Department of ChemistryUniversity of Nebraska‐LincolnLincolnNE68583USA
| | - Mark A. Zaydman
- Department of Pathology and ImmunologyWashington University School of MedicineSt LouisMO63110USA
| | - Panya Kim
- The Center for Plant Science InnovationUniversity of Nebraska‐LincolnLincolnNE68588USA
| | - Samuel Martinez
- School of Biological SciencesUniversity of Nebraska‐LincolnLincolnNE68583USA
| | - Neha Damaraju
- Department of Biomedical EngineeringWashington University in St LouisSt LouisMO63130USA
| | - Aaron DiAntonio
- Department of Developmental BiologyWashington University School of MedicineSt LouisMO63110USA
| | - Jeffrey Milbrandt
- Department of GeneticsWashington University School of MedicineSt LouisMO63110USA
| | - Thomas E. Clemente
- Department of Agriculture and HorticultureUniversity of Nebraska‐LincolnLincolnNE68583USA
| | - James R. Alfano
- Department of Plant PathologyUniversity of Nebraska‐LincolnLincolnNE68583USA
- The Center for Plant Science InnovationUniversity of Nebraska‐LincolnLincolnNE68588USA
| | - Ming Guo
- Department of Agriculture and HorticultureUniversity of Nebraska‐LincolnLincolnNE68583USA
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Yuan X, Hulin MT, Sundin GW. Effectors, chaperones, and harpins of the Type III secretion system in the fire blight pathogen Erwinia amylovora: a review. JOURNAL OF PLANT PATHOLOGY 2021; 103:25-39. [PMID: 0 DOI: 10.1007/s42161-020-00623-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 07/23/2020] [Indexed: 05/20/2023]
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14
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Dillon MM, Ruiz-Bedoya T, Bundalovic-Torma C, Guttman KM, Kwak H, Middleton MA, Wang PW, Horuz S, Aysan Y, Guttman DS. Comparative genomic insights into the epidemiology and virulence of plant pathogenic pseudomonads from Turkey. Microb Genom 2021; 7:000585. [PMID: 34227931 PMCID: PMC8477409 DOI: 10.1099/mgen.0.000585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2020] [Accepted: 04/16/2021] [Indexed: 12/31/2022] Open
Abstract
Pseudomonas is a highly diverse genus that includes species that cause disease in both plants and animals. Recently, pathogenic pseudomonads from the Pseudomonas syringae and Pseudomonas fluorescens species complexes have caused significant outbreaks in several agronomically important crops in Turkey, including tomato, citrus, artichoke and melon. We characterized 169 pathogenic Pseudomonas strains associated with recent outbreaks in Turkey via multilocus sequence analysis and whole-genome sequencing, then used comparative and evolutionary genomics to characterize putative virulence mechanisms. Most of the isolates are closely related to other plant pathogens distributed among the primary phylogroups of P. syringae, although there are significant numbers of P. fluorescens isolates, which is a species better known as a rhizosphere-inhabiting plant-growth promoter. We found that all 39 citrus blast pathogens cluster in P. syringae phylogroup 2, although strains isolated from the same host do not cluster monophyletically, with lemon, mandarin orange and sweet orange isolates all being intermixed throughout the phylogroup. In contrast, 20 tomato pith pathogens are found in two independent lineages: one in the P. syringae secondary phylogroups, and the other from the P. fluorescens species complex. These divergent pith necrosis strains lack characteristic virulence factors like the canonical tripartite type III secretion system, large effector repertoires and the ability to synthesize multiple bacterial phytotoxins, suggesting they have alternative molecular mechanisms to cause disease. These findings highlight the complex nature of host specificity among plant pathogenic pseudomonads.
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Affiliation(s)
- Marcus M. Dillon
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Present address: Department of Biology, University of Toronto at Mississauga, Mississauga, Ontario, Canada
| | - Tatiana Ruiz-Bedoya
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | | | - Kevin M. Guttman
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Haejin Kwak
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Maggie A. Middleton
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
| | - Pauline W. Wang
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
| | - Sumer Horuz
- Department of Plant Protection, Erciyes University, Kayseri, Turkey
| | - Yesim Aysan
- Department of Plant Protection, University of Çukurova, Adana, Turkey
| | - David S. Guttman
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
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15
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Li MSM, Piccoli DA, McDowell T, MacDonald J, Renaud J, Yuan ZC. Evaluating the biocontrol potential of Canadian strain Bacillus velezensis 1B-23 via its surfactin production at various pHs and temperatures. BMC Biotechnol 2021; 21:31. [PMID: 33926450 PMCID: PMC8082884 DOI: 10.1186/s12896-021-00690-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Accepted: 04/08/2021] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND Microorganisms, including Bacillus species are used to help control plant pathogens, thereby reducing reliance on synthetic pesticides in agriculture. Bacillus velezensis strain 1B-23 has been shown to reduce symptoms of bacterial disease caused by Clavibacter michiganensis subsp. michiganensis in greenhouse-grown tomatoes, with in vitro studies implicating the lipopeptide surfactin as a key antimicrobial. While surfactin is known to be effective against many bacterial pathogens, it is inhibitory to a smaller proportion of fungi which nonetheless cause the majority of crop diseases. In addition, knowledge of optimal conditions for surfactin production in B. velezensis is lacking. RESULTS Here, B. velezensis 1B-23 was shown to inhibit in vitro growth of 10 fungal strains including Candida albicans, Cochliobolus carbonum, Cryptococcus neoformans, Cylindrocarpon destructans Fusarium oxysporum, Fusarium solani, Monilinia fructicola, and Rhizoctonia solani, as well as two strains of C. michiganensis michiganensis. Three of the fungal strains (C. carbonum, C. neoformans, and M. fructicola) and the bacterial strains were also inhibited by purified surfactin (surfactin C, or [Leu7] surfactin C15) from B. velezensis 1B-23. Optimal surfactin production occurred in vitro at a relatively low temperature (16 °C) and a slightly acidic pH of 6.0. In addition to surfactin, B. velenzensis also produced macrolactins, cyclic dipeptides and minor amounts of iturins which could be responsible for the bioactivity against fungal strains which were not inhibited by purified surfactin C. CONCLUSIONS Our study indicates that B. velezensis 1B-23 has potential as a biocontrol agent against both bacterial and fungal pathogens, and may be particularly useful in slightly acidic soils of cooler climates.
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Affiliation(s)
- Michelle S M Li
- Department of Microbiology and Immunology, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada
| | - David A Piccoli
- Department of Microbiology and Immunology, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada
| | - Tim McDowell
- London Research and Development Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, N5V 4T3, Canada
| | - Jacqueline MacDonald
- Department of Microbiology and Immunology, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada
| | - Justin Renaud
- London Research and Development Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, N5V 4T3, Canada
| | - Ze-Chun Yuan
- Department of Microbiology and Immunology, University of Western Ontario, 1151 Richmond Street, London, Ontario, N6A 5B7, Canada. .,London Research and Development Centre, Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, N5V 4T3, Canada.
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16
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TaAP2-15, An AP2/ERF Transcription Factor, Is Positively Involved in Wheat Resistance to Puccinia striiformis f. sp. tritici. Int J Mol Sci 2021; 22:ijms22042080. [PMID: 33669850 PMCID: PMC7923241 DOI: 10.3390/ijms22042080] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2021] [Revised: 02/17/2021] [Accepted: 02/18/2021] [Indexed: 12/25/2022] Open
Abstract
AP2 transcription factors play a crucial role in plant development and reproductive growth, as well as response to biotic and abiotic stress. However, the role of TaAP2-15, in the interaction between wheat and the stripe fungus, Puccinia striiformis f. sp. tritici (Pst), remains elusive. In this study, we isolated TaAP2-15 and characterized its function during the interaction. TaAP2-15 was localized in the nucleus of wheat and N. benthamiana. Silencing of TaAP2-15 by barley stripe mosaic virus (BSMV)-mediated VIGS (virus-induced gene silencing) increased the susceptibility of wheat to Pst accompanied by enhanced growth of the pathogen (number of haustoria, haustorial mother cells and hyphal length). We confirmed by quantitative real-time PCR that the transcript levels of pathogenesis-related genes (TaPR1 and TaPR2) were down-regulated, while reactive oxygen species (ROS)-scavenging genes (TaCAT3 and TaFSOD3D) were induced accompanied by reduced accumulation of H2O2. Furthermore, we found that TaAP2-15 interacted with a zinc finger protein (TaRZFP34) that is a homolog of OsRZFP34 in rice. Together our findings demonstrate that TaAP2-15 is positively involved in resistance of wheat to the stripe rust fungus and provides new insights into the roles of AP2 in the host-pathogen interaction.
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17
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Arroyo-Velez N, González-Fuente M, Peeters N, Lauber E, Noël LD. From effectors to effectomes: Are functional studies of individual effectors enough to decipher plant pathogen infectious strategies? PLoS Pathog 2020; 16:e1009059. [PMID: 33270803 PMCID: PMC7714205 DOI: 10.1371/journal.ppat.1009059] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Noe Arroyo-Velez
- LIPM, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan, France
| | | | - Nemo Peeters
- LIPM, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan, France
| | | | - Laurent D. Noël
- LIPM, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan, France
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18
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Thordal-Christensen H. A holistic view on plant effector-triggered immunity presented as an iceberg model. Cell Mol Life Sci 2020; 77:3963-3976. [PMID: 32277261 PMCID: PMC7532969 DOI: 10.1007/s00018-020-03515-w] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/10/2020] [Accepted: 03/30/2020] [Indexed: 12/19/2022]
Abstract
The immune system of plants is highly complex. It involves pattern-triggered immunity (PTI), which is signaled and manifested through branched multi-step pathways. To counteract this, pathogen effectors target and inhibit individual PTI steps. This in turn can cause specific plant cytosolic nucleotide-binding leucine-rich repeat (NLR) receptors to activate effector-triggered immunity (ETI). Plants and pathogens have many genes encoding NLRs and effectors, respectively. Yet, only a few segregate genetically as resistance (R) genes and avirulence (Avr) effector genes in wild-type populations. In an attempt to explain this contradiction, a model is proposed where far most of the NLRs, the effectors and the effector targets keep one another in a silent state. In this so-called "iceberg model", a few NLR-effector combinations are genetically visible above the surface, while the vast majority is hidden below. Besides, addressing the existence of many NLRs and effectors, the model also helps to explain why individual downregulation of many effectors causes reduced virulence and why many lesion-mimic mutants are found. Finally, the iceberg model accommodates genuine plant susceptibility factors as potential effector targets.
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Affiliation(s)
- Hans Thordal-Christensen
- Department of Plant and Environmental Sciences, Copenhagen Plant Science Centre, University of Copenhagen, 1871, Frederiksberg C, Denmark.
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19
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Hulin MT, Jackson RW, Harrison RJ, Mansfield JW. Cherry picking by pseudomonads: After a century of research on canker, genomics provides insights into the evolution of pathogenicity towards stone fruits. PLANT PATHOLOGY 2020; 69:962-978. [PMID: 32742023 PMCID: PMC7386918 DOI: 10.1111/ppa.13189] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 03/09/2020] [Accepted: 03/23/2020] [Indexed: 05/10/2023]
Abstract
Bacterial canker disease is a major limiting factor in the growing of cherry and other Prunus species worldwide. At least five distinct clades within the bacterial species complex Pseudomonas syringae are known to be causal agents of the disease. The different pathogens commonly coexist in the field. Reducing canker is a challenging prospect as the efficacy of chemical controls and host resistance may vary against each of the diverse clades involved. Genomic analysis has revealed that the pathogens use a variable repertoire of virulence factors to cause the disease. Significantly, strains of P. syringae pv. syringae possess more genes for toxin biosynthesis and fewer encoding type III effector proteins. There is also a shared pool of key effector genes present on mobile elements such as plasmids and prophages that may have roles in virulence. By contrast, there is evidence that absence or truncation of certain effector genes, such as hopAB, is characteristic of cherry pathogens. Here we highlight how recent research, underpinned by the earlier epidemiological studies, is allowing significant progress in our understanding of the canker pathogens. This fundamental knowledge, combined with emerging insights into host genetics, provides the groundwork for development of precise control measures and informed approaches to breed for disease resistance.
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Affiliation(s)
| | - Robert W. Jackson
- Birmingham Institute of Forest Research (BIFoR), University of BirminghamBirminghamUK
- School of Biosciences, University of BirminghamBirminghamUK
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20
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Collmer A. James Robert Alfano, A Giant in Phytopathogenic Bacteria Effector Biology. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2020; 33:377-381. [PMID: 31990622 DOI: 10.1094/mpmi-12-19-0354-cr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The worldwide molecular plant-microbe interactions research community was significantly diminished in November 2019 by the death of James "Jim" Robert Alfano at age 56. Jim was a giant in our field, who gained key insights into plant pathogenesis using the model bacterial pathogen Pseudomonas syringae. As a mentor, collaborator, and, above all, a friend, I know Jim's many dimensions and accomplishments and, sadly, the depth of loss being felt by the many people around the world who were touched by him. In tracing the path of Jim's career, I will emphasize the historical context and impact of his advances and, finally, the essence of the person we will so miss.
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Affiliation(s)
- Alan Collmer
- School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, U.S.A
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21
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Gu Y, Wang J, Xia Z, Wei HL. Characterization of a Versatile Plant Growth-Promoting Rhizobacterium Pseudomonas mediterranea Strain S58. Microorganisms 2020; 8:E334. [PMID: 32120878 PMCID: PMC7143339 DOI: 10.3390/microorganisms8030334] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 02/17/2020] [Accepted: 02/25/2020] [Indexed: 01/30/2023] Open
Abstract
Plant growth-promoting rhizobacterial strain S58 was isolated from the tobacco rhizosphere. It showed strong antagonism against a battery of plant pathogenic fungi and bacteria, and controlled wheat sharp eyespot and tobacco wildfire diseases efficiently. Further tests showed that strain S58 solubilized organic phosphate and produced siderophore, protease, ammonia, and indole-3-acetic acid. In Arabidopsis thaliana, it promoted plant growth and changed root system architecture by restricting the growth of primary roots and increasing lateral root numbers. We relied on morphological, biochemical, physiological characteristics, and molecular phylogenic analysis to identify strain S58 as Pseudomonas mediterranea. The complete genome of strain S58 has a single circular chromosome of 6,150,838 bp with a 61.06% G+C content. The bacterial genome contained 5,312 predicted genes with an average length of 992.90 bp. A genome analysis suggested that P. mediterranea S58 was a rich cyclic lipopeptide (CLP)-producing strain that possessed seven non-ribosomal peptide gene clusters for CLP synthesis. Leaf inoculation of the bacterial culture and supernatants triggered cell death-like immunity in tobacco. Quantitative real-time PCR assays showed that the strain S58 induced the expression of pattern-triggered immunity and cell death marker genes, but not jasmonic acid marker genes. The results suggested that P. mediterranea S58 is a novel, versatile plant growth-promoting agent with multiple beneficial traits for plants.
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Affiliation(s)
- Yilin Gu
- Key Laboratory of Microbial Resources Collection and Preservation, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (Y.G.); (J.W.)
| | - Jing Wang
- Key Laboratory of Microbial Resources Collection and Preservation, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (Y.G.); (J.W.)
| | - Zhenyuan Xia
- Yunnan Academy of Tobacco Agricultural Science, Kunming 650021, China;
| | - Hai-Lei Wei
- Key Laboratory of Microbial Resources Collection and Preservation, Ministry of Agriculture and Rural Affairs, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China; (Y.G.); (J.W.)
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Méline V, Brin C, Lebreton G, Ledroit L, Sochard D, Hunault G, Boureau T, Belin E. A Computation Method Based on the Combination of Chlorophyll Fluorescence Parameters to Improve the Discrimination of Visually Similar Phenotypes Induced by Bacterial Virulence Factors. FRONTIERS IN PLANT SCIENCE 2020; 11:213. [PMID: 32174949 PMCID: PMC7055487 DOI: 10.3389/fpls.2020.00213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2019] [Accepted: 02/11/2020] [Indexed: 05/24/2023]
Abstract
Phenotyping biotic stresses in plant-pathogen interactions studies is often hindered by phenotypes that can hardly be discriminated by visual assessment. Particularly, single gene mutants in virulence factors could lack visible phenotypes. Chlorophyll fluorescence (CF) imaging is a valuable tool to monitor plant-pathogen interactions. However, while numerous CF parameters can be measured, studies on plant-pathogen interactions often focus on a restricted number of parameters. It could result in limited abilities to discriminate visually similar phenotypes. In this study, we assess the ability of the combination of multiple CF parameters to improve the discrimination of such phenotypes. Such an approach could be of interest for screening and discriminating the impact of bacterial virulence factors without prior knowledge. A computation method was developed, based on the combination of multiple CF parameters, without any parameter selection. It involves histogram Bhattacharyya distance calculations and hierarchical clustering, with a normalization approach to take into account the inter-leaves and intra-phenotypes heterogeneities. To assess the efficiency of the method, two datasets were analyzed the same way. The first dataset featured single gene mutants of a Xanthomonas strain which differed only by their abilities to secrete bacterial virulence proteins. This dataset displayed expected phenotypes at 6 days post-inoculation and was used as ground truth dataset to setup the method. The efficiency of the computation method was demonstrated by the relevant discrimination of phenotypes at 3 days post-inoculation. A second dataset was composed of transient expression (agrotransformation) of Type 3 Effectors. This second dataset displayed phenotypes that cannot be discriminated by visual assessment and no prior knowledge can be made on the respective impact of each Type 3 Effectors on leaf tissues. Using the computation method resulted in clustering the leaf samples according to the Type 3 Effectors, thereby demonstrating an improvement of the discrimination of the visually similar phenotypes. The relevant discrimination of visually similar phenotypes induced by bacterial strains differing only by one virulence factor illustrated the importance of using a combination of CF parameters to monitor plant-pathogen interactions. It opens a perspective for the identification of specific signatures of biotic stresses.
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Affiliation(s)
- Valérian Méline
- Emersys, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
- ImHorPhen, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
| | - Chrystelle Brin
- Emersys, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
| | - Guillaume Lebreton
- Phenotic Platform, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
| | - Lydie Ledroit
- Phenotic Platform, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
| | - Daniel Sochard
- Phenotic Platform, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
| | - Gilles Hunault
- ImHorPhen, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
- Laboratoire HIFIH, UPRES EA 3859, SFR 4208, Université d'Angers, Angers, France
| | - Tristan Boureau
- Emersys, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
- ImHorPhen, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
- Phenotic Platform, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
| | - Etienne Belin
- ImHorPhen, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
- Phenotic Platform, SFR 4207 QUASAV, IRHS, UMR1345, Université d'Angers, Angers, France
- Laboratoire Angevin de Recherche en Ingénierie des Systèmes, Université d'Angers, Angers, France
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23
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Kutschera A, Schombel U, Wröbel M, Gisch N, Ranf S. Loss of wbpL disrupts O-polysaccharide synthesis and impairs virulence of plant-associated Pseudomonas strains. MOLECULAR PLANT PATHOLOGY 2019; 20:1535-1549. [PMID: 31559681 PMCID: PMC6804347 DOI: 10.1111/mpp.12864] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Despite its importance for membrane stability and pathogenicity of mammalian pathogens, functions of the O-polysaccharide (OPS) of lipopolysaccharide (LPS) remain unclear in plant-associated bacteria. Genetic information about OPS biosynthesis in these bacteria is largely missing. Genome analysis of various plant-associated Pseudomonas strains revealed that one of the two known OPS biosynthesis clusters from Pseudomonas aeruginosa PAO1, the common polysaccharide antigen (CPA) gene cluster, is only conserved in some strains of the Pseudomonas fluorescens group. For the O-specific antigen (OSA) biosynthesis cluster, the putative genomic position could be identified, but orthologues of most functional important OSA biosynthesis enzymes could not be detected. Nevertheless, orthologues of the glycosyltransferase WbpL, required for initiation of CPA and OSA synthesis in P. aeruginosa PAO1, could be identified in the analysed Pseudomonas genomes. Knockout mutations of wbpL orthologues in Pseudomonas syringae pv. tomato DC3000 (Pst) and Pseudomonas cichorii ATCC10857/DSM50259 (Pci) resulted in strains lacking the OPS. Infection experiments of Arabidopsis thaliana plants revealed a reduced entry into the leaf apoplast after spray inoculation and a reduced apoplastic amplification of Pst ∆wbpL. Stab and spray inoculation of lettuce (Lactuca sativa) leaves with Pci ∆wbpL causes reduced infection symptoms compared to the wild-type strain. Furthermore, swarming motility was reduced in ∆wbpL mutants of Pst and Pci. This might be a possible reason for reduced bacterial titres after surface inoculation and reduced bacterial amplification in the plant. Our results imply that the presence of lipopolysaccharide OPS is required for efficient host colonization and full virulence of plant-pathogenic Pseudomonas bacteria.
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Affiliation(s)
- Alexander Kutschera
- Technical University of MunichPhytopathology, TUM School of Life Sciences Weihenstephan85354Freising‐WeihenstephanGermany
| | - Ursula Schombel
- Research Center Borstel, Leibniz Lung CenterDivision of Bioanalytical Chemistry, Priority Area InfectionsParkallee 1‐4023845BorstelGermany
| | - Michelle Wröbel
- Research Center Borstel, Leibniz Lung CenterDivision of Bioanalytical Chemistry, Priority Area InfectionsParkallee 1‐4023845BorstelGermany
| | - Nicolas Gisch
- Research Center Borstel, Leibniz Lung CenterDivision of Bioanalytical Chemistry, Priority Area InfectionsParkallee 1‐4023845BorstelGermany
| | - Stefanie Ranf
- Technical University of MunichPhytopathology, TUM School of Life Sciences Weihenstephan85354Freising‐WeihenstephanGermany
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Carella P, Evangelisti E, Schornack S. Sticking to it: phytopathogen effector molecules may converge on evolutionarily conserved host targets in green plants. CURRENT OPINION IN PLANT BIOLOGY 2018; 44:175-180. [PMID: 30071474 PMCID: PMC6119762 DOI: 10.1016/j.pbi.2018.04.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/06/2018] [Accepted: 04/28/2018] [Indexed: 05/26/2023]
Abstract
•Phytopathogen effectors converge on similar sets of host proteins in angiosperms. •Effectors may target host proteins and processes present across the green plant lineage. •Bryophyte model plants are promising systems to investigate effector–target relationships. Plant-associated microbes secrete effector proteins that subvert host cellular machinery to facilitate the colonization of plant tissues and cells. Accumulating data suggests that independently evolved effectors from bacterial, fungal, and oomycete pathogens may converge on a similar set of host proteins in certain angiosperm models, however, whether this concept is relevant throughout the green plant lineage is unknown. Here, we explore the idea that pathogen effector molecules target host proteins present across evolutionarily distant land plant lineages to promote disease. We discuss that host proteins targeted by phytopathogens or integrated into angiosperm immune receptors are likely found across green plant genomes, from early diverging non-vascular lineages (bryophytes) to flowering plants (angiosperms). This would suggest that independently evolved pathogens might manipulate their hosts by targeting `vulnerability’ hubs that are present across land plants. Future work focusing on accessible early divergent land plant model systems may therefore provide an insightful evolutionary backdrop for effector–target research.
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Affiliation(s)
- Philip Carella
- University of Cambridge, Sainsbury Laboratory, Cambridge, United Kingdom
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