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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: 2] [Impact Index Per Article: 2.0] [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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2
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Reinar WB, Lalun VO, Reitan T, Jakobsen KS, Butenko MA. Length variation in short tandem repeats affects gene expression in natural populations of Arabidopsis thaliana. THE PLANT CELL 2021; 33:2221-2234. [PMID: 33848350 PMCID: PMC8364236 DOI: 10.1093/plcell/koab107] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 04/07/2021] [Indexed: 06/12/2023]
Abstract
The genetic basis for the fine-tuned regulation of gene expression is complex and ultimately influences the phenotype and thus the local adaptation of natural populations. Short tandem repeats (STRs) consisting of repetitive DNA motifs have been shown to regulate gene expression. STRs are variable in length within a population and serve as a heritable, but semi-reversible, reservoir of standing genetic variation. For sessile organisms, such as plants, STRs could be of major importance in fine-tuning gene expression as a response to a shifting local environment. Here, we used a transcriptome dataset from natural accessions of Arabidopsis thaliana to investigate population-wide gene expression patterns in light of genome-wide STR variation. We empirically modeled gene expression as a response to the STR length within and around the gene and demonstrated that an association between gene expression and STR length variation is unequivocally present in the sampled population. To support our model, we explored the promoter activity in a transcriptional regulator involved in root hair formation and provided experimentally determined causality between coding sequence length variation and promoter activity. Our results support a general link between gene expression variation and STR length variation in A. thaliana.
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Affiliation(s)
- William B. Reinar
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, 0316 Oslo, Norway
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, 0316 Oslo, Norway
| | - Vilde O. Lalun
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, 0316 Oslo, Norway
| | - Trond Reitan
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, 0316 Oslo, Norway
| | - Kjetill S. Jakobsen
- Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, 0316 Oslo, Norway
| | - Melinka A. Butenko
- Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, 0316 Oslo, Norway
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3
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Jayaraman J, Chatterjee A, Hunter S, Chen R, Stroud EA, Saei H, Hoyte S, Deroles S, Tahir J, Templeton MD, Brendolise C. Rapid Methodologies for Assessing Pseudomonas syringae pv. actinidiae Colonization and Effector-Mediated Hypersensitive Response in Kiwifruit. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2021; 34:880-890. [PMID: 33834857 DOI: 10.1094/mpmi-02-21-0043-r] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The infection of Pseudomonas syringae pv. actinidiae in kiwifruit is currently assessed by numerous methodologies, each with their own limitations. Most studies are based on either a laborious method of growth quantification of the pathogen or qualitative assessments by visual scoring following stem or cutting inoculation. Additionally, when assessing for resistance against specific pathogen effectors, confounding interactions between multiple genes in the pathogen can make mapping resistance phenotypes nearly impossible. Here, we present robust alternative methods to quantify pathogen load based on rapid bacterial DNA quantification by PCR, the use of Pseudomonas fluorescens, and a transient reporter eclipse assay for assessing resistance conferred by isolated bacterial avirulence genes. These assays compare well with bacterial plate counts to assess bacterial colonization as a result of plant resistance activation. The DNA-based quantification, when coupled with the P. fluorescens and reporter eclipse assays to independently identify bacterial avirulence genes, is rapid, highly reproducible, and scalable for high-throughput screens of multiple cultivars or genotypes. Application of these methodologies will allow rapid and high-throughput identification of resistant cultivars and the bacterial avirulence genes they recognize, facilitating resistance gene discovery for plant breeding programs.[Formula: see text] Copyright © 2021 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)
- Jay Jayaraman
- The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand
- Bio-Protection Research Centre, Lincoln, New Zealand
| | - Abhishek Chatterjee
- The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand
| | - Shannon Hunter
- The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand
| | - Ronan Chen
- The New Zealand Institute for Plant and Food Research Limited, Palmerston North, New Zealand
| | - Erin A Stroud
- The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Hassan Saei
- The New Zealand Institute for Plant and Food Research Limited, Palmerston North, New Zealand
| | - Stephen Hoyte
- The New Zealand Institute for Plant and Food Research Limited, Ruakura Research Centre, Hamilton, New Zealand
| | - Simon Deroles
- The New Zealand Institute for Plant and Food Research Limited, Palmerston North, New Zealand
| | - Jibran Tahir
- The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand
| | - Matthew D Templeton
- The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand
- Bio-Protection Research Centre, Lincoln, New Zealand
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Cyril Brendolise
- The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand
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Biotic and Abiotic Elicitors of Stilbenes Production in Vitis vinifera L. Cell Culture. PLANTS 2021; 10:plants10030490. [PMID: 33807609 PMCID: PMC8001344 DOI: 10.3390/plants10030490] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2021] [Revised: 02/27/2021] [Accepted: 02/28/2021] [Indexed: 11/17/2022]
Abstract
The in vitro cell cultures derived from the grapevine (Vitis vinifera L.) have been used for the production of stilbenes treated with different biotic and abiotic elicitors. The red-grape cultivar Váh has been elicited by natural cellulose from Trichoderma viride, the cell wall homogenate from Fusarium oxysporum and synthetic jasmonates. The sodium-orthovanadate, known as an inhibitor of hypersensitive necrotic response in treated plant cells able to enhance production and release of secondary metabolite into the cultivation medium, was used as an abiotic elicitor. Growth of cells and the content of phenolic compounds trans-resveratrol, trans-piceid, δ-viniferin, and ɛ-viniferin, were analyzed in grapevine cells treated by individual elicitors. The highest accumulation of analyzed individual stilbenes, except of trans-piceid has been observed after treatment with the cell wall homogenate from F. oxysporum. Maximum production of trans-resveratrol, δ- and ɛ-viniferins was triggered by treatment with cellulase from T. viride. The accumulation of trans-piceid in cell cultures elicited by this cellulase revealed exactly the opposite effect, with almost three times higher production of trans-resveratrol than that of trans-piceid. This study suggested that both used fungal elicitors can enhance production more effectively than commonly used jasmonates.
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McMillan HM, Zebell SG, Ristaino JB, Dong X, Kuehn MJ. Protective plant immune responses are elicited by bacterial outer membrane vesicles. Cell Rep 2021; 34:108645. [PMID: 33472073 PMCID: PMC8158063 DOI: 10.1016/j.celrep.2020.108645] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 10/26/2020] [Accepted: 12/21/2020] [Indexed: 12/22/2022] Open
Abstract
Bacterial outer membrane vesicles (OMVs) perform a variety of functions in bacterial survival and virulence. In mammalian systems, OMVs activate immune responses and are exploited as vaccines. However, little work has focused on the interactions of OMVs with plant hosts. Here, we report that OMVs from Pseudomonas syringae and P. fluorescens activate plant immune responses that protect against bacterial and oomycete pathogens. OMV-mediated immunomodulatory activity from these species displayed different sensitivity to biochemical stressors, reflecting differences in OMV content. Importantly, OMV-mediated plant responses are distinct from those triggered by conserved bacterial epitopes or effector molecules alone. Our study shows that OMV-induced protective immune responses are independent of the T3SS and protein, but that OMV-mediated seedling growth inhibition largely depends on proteinaceous components. OMVs provide a unique opportunity to understand the interplay between virulence and host response strategies and add a new dimension to consider in host-microbe interactions. The role that bacterial outer membrane vesicles (OMVs) play in plant-microbe interactions is poorly characterized. McMillan et al. show that OMVs elicit plant immune responses that protect against pathogens. This study also reveals a use for OMVs as tools to probe the plant immune system.
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Affiliation(s)
- Hannah M McMillan
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC 27710, USA
| | - Sophia G Zebell
- Howard Hughes Medical Institute, Department of Biology, Duke University, Durham, NC 27708, USA
| | - Jean B Ristaino
- Department of Entomology and Plant Pathology, North Carolina State University, Raleigh, NC 27695, USA
| | - Xinnian Dong
- Howard Hughes Medical Institute, Department of Biology, Duke University, Durham, NC 27708, USA
| | - Meta J Kuehn
- Department of Molecular Genetics and Microbiology, Duke University, Durham, NC 27710, USA; Department of Biochemistry, Duke University, Durham, NC 27710, USA.
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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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Bulman S, Richter F, Marschollek S, Benade F, Jülke S, Ludwig-Müller J. Arabidopsis thaliana expressing PbBSMT, a gene encoding a SABATH-type methyltransferase from the plant pathogenic protist Plasmodiophora brassicae, show leaf chlorosis and altered host susceptibility. PLANT BIOLOGY (STUTTGART, GERMANY) 2019; 21 Suppl 1:120-130. [PMID: 29607585 DOI: 10.1111/plb.12728] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/24/2018] [Indexed: 06/08/2023]
Abstract
The plant pathogenic protist Plasmodiophora brassicae causes clubroot disease of Brassicaceae. This biotrophic organism can down-regulate plant defence responses. The previously characterised P. brassicae PbBSMT methyltransferase has substrate specificity for salicylic, benzoic and anthranilic acids. We therefore propose a role for the methylation of SA in attenuating plant defence response in infected roots as a novel strategy for intracellular parasitism. We overexpressed PbBSMT under the control of an inducible promoter in Arabidopsis thaliana and performed physiological, molecular and phytopathological analyses with the transgenic plants under control and induced conditions in comparison to the wild type. Upon induction, transcription of PbBSMT was associated with: (1) strong leaf phenotypes from anthocyanin accumulation and chlorosis followed by browning; (2) increased plant susceptibility after infection with P. brassicae that was manifested as more yellow leaves and reduced growth of upper plant parts; and (3) induced transgenic plants were not able to support large galls and had a brownish appearance of some clubs. Microarray data indicated that chlorophyll loss was accompanied by reduced transcription of genes involved in photosynthesis, while genes encoding glucose metabolism, mitochondrial functions and cell wall synthesis were up-regulated. Our results indicate a role for PbBSMT in attenuation of host defence responses in the roots by metabolising a plant defence signal.
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Affiliation(s)
- S Bulman
- New Zealand Institute for Plant & Food Research Ltd, Christchurch, New Zealand
| | - F Richter
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
| | - S Marschollek
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
| | - F Benade
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
| | - S Jülke
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
| | - J Ludwig-Müller
- Institute of Botany, Technische Universität Dresden, Dresden, Germany
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8
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Jiang N, Cui J, Meng J, Luan Y. A Tomato Nucleotide Binding Sites-Leucine-Rich Repeat Gene Is Positively Involved in Plant Resistance to Phytophthora infestans. PHYTOPATHOLOGY 2018; 108:980-987. [PMID: 29595084 DOI: 10.1094/phyto-12-17-0389-r] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The nucleotide binding sites-leucine-rich repeat (NBS-LRR) genes are key regulatory components of plant to pathogens. Phytophthora infestans-inducible coding sequence encoding an NBS-LRR (SpNBS-LRR) protein in tomato (Solanum pimpinellifolium L3708) was cloned and characterized based on our RNA-Seq data and tomato genome. After sequence analysis, SpNBS-LRR was identified as a hydrophilic protein with no transmembrane topological structure and no signal peptide. SpNBS-LRR had a close genetic relationship to RPS2 of Arabidopsis thaliana by phylogenetic analysis. In addition, SpNBS-LRR gene was mainly expressed in root, with low expression observed in leaf and stem. To further investigate the role of SpNBS-LRR in tomato-P. infestans interaction, SpNBS-LRR was introduced in susceptible tomatoes and three transgenic lines with higher expression level of SpNBS-LRR were selected. These transgenic tomato plants that overexpressed SpNBS-LRR displayed greater resistance than wild-type tomato plants after infection with P. infestans, as shown by decreased disease index, lesion diameters, number of necrotic cells, P. infestans abundance, and higher expression levels of the defense-related genes. This information provides insight into SpNBS-LRR involved in the resistance of tomato to P. infestans infection and candidate for breeding to enhance biotic stress-resistance in tomato.
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Affiliation(s)
- Ning Jiang
- First, second, and fourth authors: School of Life Science and Biotechnology, Dalian University of Technology, Dalian, 116024, China; and third author: School of Computer Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Jun Cui
- First, second, and fourth authors: School of Life Science and Biotechnology, Dalian University of Technology, Dalian, 116024, China; and third author: School of Computer Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Jun Meng
- First, second, and fourth authors: School of Life Science and Biotechnology, Dalian University of Technology, Dalian, 116024, China; and third author: School of Computer Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Yushi Luan
- First, second, and fourth authors: School of Life Science and Biotechnology, Dalian University of Technology, Dalian, 116024, China; and third author: School of Computer Science and Technology, Dalian University of Technology, Dalian 116024, China
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9
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Mugford ST, Barclay E, Drurey C, Findlay KC, Hogenhout SA. An Immuno-Suppressive Aphid Saliva Protein Is Delivered into the Cytosol of Plant Mesophyll Cells During Feeding. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2016; 29:854-861. [PMID: 27831211 DOI: 10.1094/mpmi-08-16-0168-r] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Herbivore selection of plant hosts and plant responses to insect colonization have been subjects of intense investigations. A growing body of evidence suggests that, for successful colonization to occur, (effector/virulence) proteins in insect saliva must modulate plant defense responses to the benefit of the insect. A range of insect saliva proteins that modulate plant defense responses have been identified, but there is no direct evidence that these proteins are delivered into specific plant tissues and enter plant cells. Aphids and other sap-sucking insects of the order Hemiptera use their specialized mouthparts (stylets) to probe plant mesophyll cells until they reach the phloem cells for long-term feeding. Here, we show, by immunogold-labeling of ultrathin sections of aphid feeding sites, that an immuno-suppressive aphid effector localizes in the cytoplasm of mesophyll cells near aphid stylets but not in cells further away from aphid feeding sites. In contrast, another aphid effector protein localizes in the sheaths composed of gelling saliva that surround the aphid stylets. Thus, insects deliver effectors directly into plant tissue. Moreover, different aphid effectors locate extracellularly in the sheath saliva or are introduced into the cytoplasm of plant cells. [Formula: see text] Copyright © 2016 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)
- Sam T Mugford
- Cell and Developmental Biology, John Innes Centre, Norwich, NR4 7UH, U.K
| | - Elaine Barclay
- Cell and Developmental Biology, John Innes Centre, Norwich, NR4 7UH, U.K
| | - Claire Drurey
- Cell and Developmental Biology, John Innes Centre, Norwich, NR4 7UH, U.K
| | - Kim C Findlay
- Cell and Developmental Biology, John Innes Centre, Norwich, NR4 7UH, U.K
| | - Saskia A Hogenhout
- Cell and Developmental Biology, John Innes Centre, Norwich, NR4 7UH, U.K
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10
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Whitham SA, Qi M, Innes RW, Ma W, Lopes-Caitar V, Hewezi T. Molecular Soybean-Pathogen Interactions. ANNUAL REVIEW OF PHYTOPATHOLOGY 2016; 54:443-68. [PMID: 27359370 DOI: 10.1146/annurev-phyto-080615-100156] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Soybean hosts a wide variety of pathogens that cause significant yield losses. The importance of soybean as a major oilseed crop has led to research focused on its interactions with pathogens, such as Soybean mosaic virus, Pseudomonas syringae, Phytophthora sojae, Phakopsora pachyrhizi, and Heterodera glycines. Pioneering work on soybean's interactions with these organisms, which represent the five major pathogen groups (viruses, bacteria, oomycetes, fungi, and nematodes), has contributed to our understanding of the molecular mechanisms underlying virulence and immunity. These mechanisms involve conserved and unique features that validate the need for research in both soybean and homologous model systems. In this review, we discuss identification of effectors and their functions as well as resistance gene-mediated recognition and signaling. We also point out areas in which model systems and recent advances in resources and tools have provided opportunities to gain deeper insights into soybean-pathogen interactions.
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Affiliation(s)
- Steven A Whitham
- Department of Plant Pathology and Microbiology, Iowa State University, Ames, Iowa 50011; ,
| | - Mingsheng Qi
- Department of Plant Pathology and Microbiology, Iowa State University, Ames, Iowa 50011; ,
| | - Roger W Innes
- Department of Biology, Indiana University, Bloomington, Indiana 47405;
| | - Wenbo Ma
- Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521;
| | - Valéria Lopes-Caitar
- Department of Plant Sciences, University of Tennessee, Knoxville, Tennessee 37996; ,
| | - Tarek Hewezi
- Department of Plant Sciences, University of Tennessee, Knoxville, Tennessee 37996; ,
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11
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Bao Y, Song WM, Pan J, Jiang CM, Srivastava R, Li B, Zhu LY, Su HY, Gao XS, Liu H, Yu X, Yang L, Cheng XH, Zhang HX. Overexpression of the NDR1/HIN1-Like Gene NHL6 Modifies Seed Germination in Response to Abscisic Acid and Abiotic Stresses in Arabidopsis. PLoS One 2016; 11:e0148572. [PMID: 26849212 PMCID: PMC4744021 DOI: 10.1371/journal.pone.0148572] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2015] [Accepted: 01/19/2016] [Indexed: 01/29/2023] Open
Abstract
NHL (NDR1/HIN1-like) genes play crucial roles in pathogen induced plant responses to biotic stress. Here, we report the possible function of NHL6 in plant response to abscisic acid (ABA) and abiotic stress. NHL6 was highly expressed in non-germinated seeds, and its expression was strongly induced by ABA and multiple abiotic stress signals. Loss-of-function of NHL6 decreased sensitivity to ABA in the early developmental stages including seed germination and post-germination seedling growth of the nhl6 mutants. However, overexpression of NHL6 increased sensitivity to ABA, salt and osmotic stress of the transgenic plants. Further studies indicated that the increased sensitivity in the 35S::NHL6 overexpressing plants could be a result of both ABA hypersensitivity and increased endogenous ABA accumulation under the stress conditions. It was also seen that the ABA-responsive element binding factors AREB1, AREB2 and ABF3 could regulate NHL6 expression at transcriptional level. Our results indicate that NHL6 plays an important role in the abiotic stresses-induced ABA signaling and biosynthesis, particularly during seed germination and early seedling development in Arabidopsis.
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Affiliation(s)
- Yan Bao
- College of Agriculture, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
- Plant Sciences Institute and the Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, United States of America
| | - Wei-Meng Song
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
| | - Jing Pan
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
| | - Chun-Mei Jiang
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
| | - Renu Srivastava
- Plant Sciences Institute and the Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, United States of America
| | - Bei Li
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
| | - Lu-Ying Zhu
- College of Agriculture, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
| | - Hong-Yan Su
- College of Agriculture, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
| | - Xiao-Shu Gao
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
| | - Hua Liu
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
| | - Xiang Yu
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
| | - Lei Yang
- College of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing, 210093, China
| | - Xian-Hao Cheng
- College of Agriculture, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
- * E-mail: (X-HC); (H-XZ)
| | - Hong-Xia Zhang
- College of Agriculture, Ludong University, 186 Hongqizhong Road, Yantai, 264025, China
- National Key Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai, 200032, China
- * E-mail: (X-HC); (H-XZ)
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12
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Provart NJ, Alonso J, Assmann SM, Bergmann D, Brady SM, Brkljacic J, Browse J, Chapple C, Colot V, Cutler S, Dangl J, Ehrhardt D, Friesner JD, Frommer WB, Grotewold E, Meyerowitz E, Nemhauser J, Nordborg M, Pikaard C, Shanklin J, Somerville C, Stitt M, Torii KU, Waese J, Wagner D, McCourt P. 50 years of Arabidopsis research: highlights and future directions. THE NEW PHYTOLOGIST 2016; 209:921-44. [PMID: 26465351 DOI: 10.1111/nph.13687] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 08/24/2015] [Indexed: 05/14/2023]
Abstract
922 I. 922 II. 922 III. 925 IV. 925 V. 926 VI. 927 VII. 928 VIII. 929 IX. 930 X. 931 XI. 932 XII. 933 XIII. Natural variation and genome-wide association studies 934 XIV. 934 XV. 935 XVI. 936 XVII. 937 937 References 937 SUMMARY: The year 2014 marked the 25(th) International Conference on Arabidopsis Research. In the 50 yr since the first International Conference on Arabidopsis Research, held in 1965 in Göttingen, Germany, > 54 000 papers that mention Arabidopsis thaliana in the title, abstract or keywords have been published. We present herein a citational network analysis of these papers, and touch on some of the important discoveries in plant biology that have been made in this powerful model system, and highlight how these discoveries have then had an impact in crop species. We also look to the future, highlighting some outstanding questions that can be readily addressed in Arabidopsis. Topics that are discussed include Arabidopsis reverse genetic resources, stock centers, databases and online tools, cell biology, development, hormones, plant immunity, signaling in response to abiotic stress, transporters, biosynthesis of cells walls and macromolecules such as starch and lipids, epigenetics and epigenomics, genome-wide association studies and natural variation, gene regulatory networks, modeling and systems biology, and synthetic biology.
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Affiliation(s)
- Nicholas J Provart
- Department of Cell & Systems Biology/CAGEF, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Jose Alonso
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA
| | - Sarah M Assmann
- Department of Biology, Pennsylvania State University, University Park, PA, 16802, USA
| | | | - Siobhan M Brady
- Department of Plant Biology, University of California, Davis, CA, 95616, USA
| | - Jelena Brkljacic
- Arabidopsis Biological Resource Center, The Ohio State University, Columbus, OH, 43210, USA
| | - John Browse
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
| | - Clint Chapple
- Department of Biochemistry, Purdue University, West Lafayette, IN, 47907, USA
| | - Vincent Colot
- Departement de Biologie École Normale Supérieure, Biologie Moleculaire des Organismes Photosynthetiques, F-75230, Paris, France
| | - Sean Cutler
- Department of Botany and Plant Sciences, University of California, Riverside, CA, 92507, USA
| | - Jeff Dangl
- Department of Biology and Howard Hughes Medical Institute, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC, 27599, USA
| | - David Ehrhardt
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
| | - Joanna D Friesner
- Department of Plant Biology, Agricultural Sustainability Institute, University of California, Davis, CA, 95616, USA
| | - Wolf B Frommer
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
| | - Erich Grotewold
- Center for Applied Plant Science, The Ohio State University, Columbus, OH, 43210, USA
| | - Elliot Meyerowitz
- Division of Biology and Biological Engineering and Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA, 91125, USA
| | - Jennifer Nemhauser
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | - Magnus Nordborg
- Gregor Mendel Institute of Molecular Plant Biology, A-1030, Vienna, Austria
| | - Craig Pikaard
- Department of Biology, Indiana University, Bloomington, IN, 47405, USA
| | - John Shanklin
- Biology Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Chris Somerville
- Energy Biosciences Institute, University of California, Berkeley, CA, 94704, USA
| | - Mark Stitt
- Metabolic Networks Department, Max Planck Institute for Molecular Plant Physiology, D-14476, Potsdam, Germany
| | - Keiko U Torii
- Department of Biology, University of Washington, Seattle, WA, 98195, USA
| | - Jamie Waese
- Department of Cell & Systems Biology/CAGEF, University of Toronto, Toronto, ON, M5S 3B2, Canada
| | - Doris Wagner
- Department of Biology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Peter McCourt
- Department of Cell & Systems Biology/CAGEF, University of Toronto, Toronto, ON, M5S 3B2, Canada
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13
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Catanzariti AM, Lim GTT, Jones DA. The tomato I-3 gene: a novel gene for resistance to Fusarium wilt disease. THE NEW PHYTOLOGIST 2015; 207:106-118. [PMID: 25740416 DOI: 10.1111/nph.13348] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2014] [Accepted: 01/29/2015] [Indexed: 05/22/2023]
Abstract
Plant resistance proteins provide race-specific immunity through the recognition of pathogen effectors. The resistance genes I, I-2 and I-3 have been incorporated into cultivated tomato (Solanum lycopersicum) from wild tomato species to confer resistance against Fusarium oxysporum f. sp. lycopersici (Fol) races 1, 2 and 3, respectively. Although the Fol effectors corresponding to these resistance genes have all been identified, only the I-2 resistance gene has been isolated from tomato. To isolate the I-3 resistance gene, we employed a map-based cloning approach and used transgenic complementation to test candidate genes for resistance to Fol race 3. Here, we describe the fine mapping and sequencing of genes at the I-3 locus, which revealed a family of S-receptor-like kinase (SRLK) genes. Transgenic tomato lines were generated with three of these SRLK genes and one was found to confer Avr3-dependent resistance to Fol race 3, confirming it to be I-3. The finding that I-3 encodes an SRLK reveals a new pathway for Fol resistance and a new class of resistance genes, of which Pi-d2 from rice is also a member. The identification of I-3 also allows the investigation of the complex effector-resistance protein interaction involving Avr1-mediated suppression of I-2- and I-3-dependent resistance in tomato.
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Affiliation(s)
- Ann-Maree Catanzariti
- Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT, 2601, Australia
| | - Ginny T T Lim
- Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT, 2601, Australia
| | - David A Jones
- Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT, 2601, Australia
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14
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Detection and function of nitric oxide during the hypersensitive response in Arabidopsis thaliana: Where there’s a will there’s a way. Nitric Oxide 2014; 43:81-8. [DOI: 10.1016/j.niox.2014.06.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 06/20/2014] [Accepted: 06/26/2014] [Indexed: 12/19/2022]
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15
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Abstract
Fungal and oomycete plant parasites are among the most devastating pathogens of food crops. These microbes secrete effector proteins inside plant cells to manipulate host processes and facilitate colonization. How these effectors reach the host cytoplasm remains an unclear and debated area of plant research. In this article, we examine recent conflicting findings that have generated discussion in the field. We also highlight promising approaches based on studies of both parasite and host during infection. Ultimately, this knowledge may inform future broad spectrum strategies for protecting crops from such pathogens.
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Affiliation(s)
- Benjamin Petre
- The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom
- INRA, Interactions Arbres/Microorganismes, UMR 1136, Champenoux, France
| | - Sophien Kamoun
- The Sainsbury Laboratory, Norwich Research Park, Norwich, United Kingdom
- * E-mail:
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16
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Xiong M, Long D, He H, Li Y, Li Y, Wang X. Phosphatidylcholine synthesis is essential for HrpZ harpin secretion in plant pathogenic Pseudomonas syringae and non-pathogenic Pseudomonas sp. 593. Microbiol Res 2014; 169:196-204. [PMID: 23886927 DOI: 10.1016/j.micres.2013.06.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 06/21/2013] [Accepted: 06/22/2013] [Indexed: 10/26/2022]
Abstract
Pseudomonas syringae pv. syringae van Hall is important phytopathogenic bacterium of stone fruit trees, and able to elicit hypersensitive response (HR) in nonhost plants. The HrpZ, secreted via type III secretion system (T3SS) to the extracellular space of the plant, is a T3SS-dependent protein and a sole T3SS effector able to induce the host defense response outside host cells. We deleted the phosphatidylcholine synthase gene (pcs) of P. syringae pv. syringae van Hall CFCC 1336, and found that the 1336 pcs(-) mutant was unable to synthesize phosphatidylcholine and elicit a typical HR in soybean. Further studies showed that the 1336 pcs(-) mutant was unable to secrete HrpZ harpin but could express HrpZ protein in cytoplasm as effectively as the wild type. To confirm if phosphatidylcholine affects HrpZ harpin secretion, we introduced the hrpZ gene into the soil-dwelling bacterium Pseudomonas sp. 593 and the 593 pcs(-) mutant, which were unable to express HrpZ harpin and elicit HR in tobacco or soybean. Western blotting and HR assay showed that the 593H not only secreted HrpZ harpin but also caused a strong HR in tobacco and soybean. In contrast, the 593 pcs(-)H only expressed HrpZ protein in its cytoplasm at the wild type level, but did not secrete HrpZ harpin or elicit HR reaction. Our results demonstrate that phosphatidylcholine is essential for the secretion of HrpZ harpin in P. syringae pv. syringae van Hall and other Pseudomonas strains.
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Affiliation(s)
- Min Xiong
- The Faculty of Life Science, Hubei University, China
| | - Deliang Long
- The Faculty of Life Science, Hubei University, China
| | - Huoguang He
- The Faculty of Life Science, Hubei University, China
| | - Yang Li
- The Faculty of Life Science, Hubei University, China
| | - Yadong Li
- The Faculty of Life Science, Hubei University, China
| | - Xingguo Wang
- The Faculty of Life Science, Hubei University, China.
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17
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Ho YP, Tan CM, Li MY, Lin H, Deng WL, Yang JY. The AvrB_AvrC domain of AvrXccC of Xanthomonas campestris pv. campestris is required to elicit plant defense responses and manipulate ABA homeostasis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:419-30. [PMID: 23252460 DOI: 10.1094/mpmi-06-12-0164-r] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Plant disease induced by Xanthomonas campestris pv. campestris depends on type III effectors but the molecular basis is poorly understood. Here, AvrXccC8004 was characterized, and it was found that the AvrB_AvrC domain was essential and sufficient to elicit defense responses in an Arabidopsis-resistant ecotype (Col-0). An upregulation of genes in responding to the AvrB_AvrC domain of AvrXccC8004 was shown in a profile of host gene expression. The molecular changes were correlated with morphological changes observed in phenotypic and ultrastructural characterizations. Interestingly, the abscisic acid (ABA)-signaling pathway was also a prominent target for the AvrB_AvrC domain of AvrXccC8004. The highly elicited NCED5, encoding a key enzyme of ABA biosynthesis, was increased in parallel with ABA levels in AvrXccC8004 transgenic plants. Consistently, the X. campestris pv. campestris 8004 ΔavrXccC mutant was severely impaired in the ability to manipulate the accumulation of ABA and induction of ABA-related genes in challenged leaves. Moreover, exogenous application of ABA also enhanced the susceptibility of Arabidopsis to the X. campestris pv. campestris strains. These results indicate that the AvrB_AvrC domain of AvrXccC8004 alone has the activity to manipulate ABA homeostasis, which plays an important role in regulating the interactions of X. campestris pv. campestris and Arabidopsis.
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Affiliation(s)
- Yi-Ping Ho
- Institute of Biochemistry, National ChungHsing University, Taichung, Taiwan
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18
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Pick T, Jaskiewicz M, Peterhänsel C, Conrath U. Heat shock factor HsfB1 primes gene transcription and systemic acquired resistance in Arabidopsis. PLANT PHYSIOLOGY 2012; 159:52-5. [PMID: 22427343 PMCID: PMC3375984 DOI: 10.1104/pp.111.191841] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Accepted: 03/15/2012] [Indexed: 05/19/2023]
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19
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Unifying themes in microbial associations with animal and plant hosts described using the gene ontology. Microbiol Mol Biol Rev 2011; 74:479-503. [PMID: 21119014 DOI: 10.1128/mmbr.00017-10] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Microbes form intimate relationships with hosts (symbioses) that range from mutualism to parasitism. Common microbial mechanisms involved in a successful host association include adhesion, entry of the microbe or its effector proteins into the host cell, mitigation of host defenses, and nutrient acquisition. Genes associated with these microbial mechanisms are known for a broad range of symbioses, revealing both divergent and convergent strategies. Effective comparisons among these symbioses, however, are hampered by inconsistent descriptive terms in the literature for functionally similar genes. Bioinformatic approaches that use homology-based tools are limited to identifying functionally similar genes based on similarities in their sequences. An effective solution to these limitations is provided by the Gene Ontology (GO), which provides a standardized language to describe gene products from all organisms. The GO comprises three ontologies that enable one to describe the molecular function(s) of gene products, the biological processes to which they contribute, and their cellular locations. Beginning in 2004, the Plant-Associated Microbe Gene Ontology (PAMGO) interest group collaborated with the GO consortium to extend the GO to accommodate terms for describing gene products associated with microbe-host interactions. Currently, over 900 terms that describe biological processes common to diverse plant- and animal-associated microbes are incorporated into the GO database. Here we review some unifying themes common to diverse host-microbe associations and illustrate how the new GO terms facilitate a standardized description of the gene products involved. We also highlight areas where new terms need to be developed, an ongoing process that should involve the whole community.
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20
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Wilton M, Desveaux D. Lessons learned from type III effector transgenic plants. PLANT SIGNALING & BEHAVIOR 2010; 5:746-8. [PMID: 20505348 PMCID: PMC3001578 DOI: 10.4161/psb.5.6.11703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The Gram negative bacterial phytopathogen Pseudomonas syringae employs a molecular syringe termed the Type III secretion system (TTSS) to deliver an array of Type III secreted effector (TTSE) proteins into plant cells. The major function ascribed to type III effectors of P. syringae is their ability to suppress plant immunity. Because individual pathovars of P. syringae can possess over 30 TTSEs, functional redundancy can provide a hurdle to ascribing functions by TTSE-deletion or -overexpression in such TTSE-rich backgrounds. Approaches to overcome functional redundancy have included the deletion of multiple TTSEs from individual pathovars as well as engineering the plant commensal P. fluorescens strain to express the P. syringae TTSS and deliver P. syringae TTSEs. As we describe here, transgenic Arabidopsis plants expressing individual TTSEs have also be used to overcome problems of functional redundancy and provide invaluable insights into TTSE virulence functions.
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Affiliation(s)
- Mike Wilton
- Department of Cell and Systems Biology; University of Toronto; Toronta Canada
| | - Darrell Desveaux
- Department of Cell and Systems Biology; University of Toronto; Toronta Canada
- Centre for the Analysis of Genome Evolution and Function; University of Toronto; Toronta Canada
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21
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Oh HS, Park DH, Collmer A. Components of the Pseudomonas syringae type III secretion system can suppress and may elicit plant innate immunity. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2010; 23:727-39. [PMID: 20459312 DOI: 10.1094/mpmi-23-6-0727] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The type III secretion system (T3SS) of Pseudomonas syringae translocates into plant cells multiple effectors that suppress pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI). P. syringae pv. tomato DC3000 no longer delivers the T3SS translocation reporter AvrPto-Cya in Nicotiana benthamiana leaf tissue in which PTI was induced by prior inoculation with P. fluorescens(pLN18). Cosmid pLN18 expresses the T3SS system of P. syringae pv. syringae 61 but lacks the hopA1(Psy61) effector gene. P. fluorescens(pLN18) expressing HrpH(PtoDC3000) or HopP1(PtoDC3000), two T3SS-associated putative lytic transglycosylases, suppresses PTI, based on multiple assays involving DC3000 challenge inoculum (AvrPto-Cya translocation, hypersensitive response elicitation, and colony development in planta) or on plant responses (vascular dye uptake or callose deposition). Analysis of additional mutations in pHIR11 derivatives revealed that the pLN18-encoded T3SS elicits a higher level of reactive oxygen species (ROS) than does P. fluorescens without a T3SS, that enhanced ROS production is dependent on the HrpK1 translocator, and that HopA1(Psy61) suppresses ROS elicitation attributable to both the P. fluorescens PAMPs and the presence of a functional T3SS.
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Affiliation(s)
- Hye-Sook Oh
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, USA
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22
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Cui H, Wang Y, Xue L, Chu J, Yan C, Fu J, Chen M, Innes RW, Zhou JM. Pseudomonas syringae effector protein AvrB perturbs Arabidopsis hormone signaling by activating MAP kinase 4. Cell Host Microbe 2010; 7:164-75. [PMID: 20159621 DOI: 10.1016/j.chom.2010.01.009] [Citation(s) in RCA: 155] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2009] [Revised: 12/21/2009] [Accepted: 01/27/2010] [Indexed: 12/24/2022]
Abstract
Pathogenic microbes often modulate phytohormone physiology in the host to their advantage. We previously showed that the Pseudomonas syringae effector protein AvrB perturbs hormone signaling, as exemplified by upregulated expression of jasmonic acid response genes, and enhances plant susceptibility. Here we show that these effects of AvrB require the Arabidopsis mitogen-activated protein kinase MAP kinase 4 (MPK4), HSP90 chaperone components, and the AvrB-interacting protein, RIN4. AvrB interacts with MPK4 and the HSP90 chaperone, and AvrB induces MPK4 activation in a manner promoted by HSP90; RIN4 likely acts downstream of MPK4. These findings link Arabidopsis proteins MPK4, HSP90, and RIN4 into a pathway that P. syringae AvrB activates for the benefit of the bacterium, perturbing hormone signaling and enhancing plant susceptibility.
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Affiliation(s)
- Haitao Cui
- Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
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23
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Nishimura MT, Dangl JL. Arabidopsis and the plant immune system. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2010; 61:1053-66. [PMID: 20409278 PMCID: PMC2859471 DOI: 10.1111/j.1365-313x.2010.04131.x] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Understanding the fundamental mechanisms of plant disease resistance is of central importance to sustainable agriculture and human health. Use of the model plant Arabidopsis thaliana has resulted in an explosion of information regarding both disease resistance and susceptibility to pathogens. The last 20 years of research have demonstrated the commonalities between Arabidopsis and crop species. In this review, commemorating the 10th anniversary of the sequencing of the Arabidopsis genome, we will address some of the insights derived from the use of Arabidopsis as a model plant pathology system.
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Affiliation(s)
- Marc T Nishimura
- Department of Biology, University of North Carolina, Chapel Hill, NC 27599, USA
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24
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Tampakaki AP, Skandalis N, Gazi AD, Bastaki MN, Sarris PF, Charova SN, Kokkinidis M, Panopoulos NJ. Playing the "Harp": evolution of our understanding of hrp/hrc genes. ANNUAL REVIEW OF PHYTOPATHOLOGY 2010; 48:347-370. [PMID: 20455697 DOI: 10.1146/annurev-phyto-073009-114407] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
With the advent of recombinant DNA techniques, the field of molecular plant pathology witnessed dramatic shifts in the 1970s and 1980s. The new and conventional methodologies of bacterial molecular genetics put bacteria center stage. The discovery in the mid-1980s of the hrp/hrc gene cluster and the subsequent demonstration that it encodes a type III secretion system (T3SS) common to Gram negative bacterial phytopathogens, animal pathogens, and plant symbionts was a landmark in molecular plant pathology. Today, T3SS has earned a central role in our understanding of many fundamental aspects of bacterium-plant interactions and has contributed the important concept of interkingdom transfer of effector proteins determining race-cultivar specificity in plant-bacterium pathosystems. Recent developments in genomics, proteomics, and structural biology enable detailed and comprehensive insights into the functional architecture, evolutionary origin, and distribution of T3SS among bacterial pathogens and support current research efforts to discover novel antivirulence drugs.
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25
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Mansfield JW. From bacterial avirulence genes to effector functions via the hrp delivery system: an overview of 25 years of progress in our understanding of plant innate immunity. MOLECULAR PLANT PATHOLOGY 2009; 10:721-34. [PMID: 19849780 PMCID: PMC6640528 DOI: 10.1111/j.1364-3703.2009.00576.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Cloning the first avirulence (avr) gene has led not only to a deeper understanding of gene-for-gene interactions in plant disease, but also to fundamental insights into the suppression of basal defences against microbial attack. This article (focusing on Pseudomonas syringae) charts the development of ideas and research progress over the 25 years following the breakthrough achieved by Staskawicz and coworkers. Advances in gene cloning technology underpinned the identification of both avr and hrp genes, the latter being required for the activation of the defensive hypersensitive reaction (HR) and pathogenicity. The delivery of Avr proteins through the type III secretion machinery encoded by hrp gene clusters was demonstrated, and the activity of the proteins inside plant cells as elicitors of the HR was confirmed. Key roles for avr genes in pathogenic fitness have now been established. The rebranding of Avr proteins as effectors, proteins that suppress the HR and cell wall-based defences, has led to the ongoing search for their targets, and is generating new insights into the co-ordination of plant resistance against diverse microbes. Bioinformatics-led analysis of effector gene distribution in genomes has provided a remarkable view of the interchange of effectors and also their functional domains, as the arms race of attack and defence drives the evolution of microbial pathogenicity. The application of our accrued knowledge for the development of disease control strategies is considered.
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26
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McLellan H, Gilroy EM, Yun BW, Birch PRJ, Loake GJ. Functional redundancy in the Arabidopsis Cathepsin B gene family contributes to basal defence, the hypersensitive response and senescence. THE NEW PHYTOLOGIST 2009; 183:408-418. [PMID: 19453434 DOI: 10.1111/j.1469-8137.2009.02865.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Cysteine proteases are required for programmed cell death (PCD) in animals. Recent work in Nicotiana benthamiana has implicated cathepsin B-like cysteine proteases in the hypersensitive response (HR) in plants, a form of PCD involved in disease resistance. Here, we investigate the function and regulation of Cathepsin B (CathB) genes in plant defence, and in both pathogen-inducible and developmental forms of PCD. Single, double and triple knockout mutants were isolated for the three Arabidopsis thaliana AtCathB genes. AtCathB genes were redundantly required for full basal resistance against the virulent bacterial pathogen Pseudomonas syringae pv. tomato (Pst) DC3000. By contrast, AtCathB genes were not required for R gene-mediated resistance to Pst DC3000 expressing AvrB or AvrRps4. Neither did they contribute to PCD triggered by AvrRps4, although they were crucial for the full development of PCD during HR triggered by AvrB. Cathepsin B has also been proposed to play a positive regulatory role in senescence. Atcathb triple mutants showed a delay in senescence and a seven-fold decrease in accumulation of senescence marker gene SAG12. Our results demonstrate a redundant function for AtCathB genes in basal defence as well as a potential regulatory role in distinct forms of plant PCD.
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Affiliation(s)
- Hazel McLellan
- Institute of Molecular Plant Sciences, University of Edinburgh, King's Buildings, Edinburgh EH9 3JR, UK
- Plant Pathology Programme, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Eleanor M Gilroy
- Plant Pathology Programme, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
| | - Byung-Wook Yun
- Institute of Molecular Plant Sciences, University of Edinburgh, King's Buildings, Edinburgh EH9 3JR, UK
| | - Paul R J Birch
- Plant Pathology Programme, Scottish Crop Research Institute, Invergowrie, Dundee DD2 5DA, UK
- Division of Plant Science, College of Life Sciences, University of Dundee (at SCRI), Invergowrie, Dundee DD2 5DA, UK
| | - Gary J Loake
- Institute of Molecular Plant Sciences, University of Edinburgh, King's Buildings, Edinburgh EH9 3JR, UK
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27
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Kim MG, Geng X, Lee SY, Mackey D. The Pseudomonas syringae type III effector AvrRpm1 induces significant defenses by activating the Arabidopsis nucleotide-binding leucine-rich repeat protein RPS2. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 57:645-653. [PMID: 18980653 DOI: 10.1111/j.1365-313x.2008.03716.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Plant disease resistance (R) proteins recognize potential pathogens expressing corresponding avirulence (Avr) proteins through 'gene-for-gene' interactions. RPM1 is an Arabidopsis R-protein that triggers a robust defense response upon recognizing the Pseudomonas syringae effector AvrRpm1. Avr-proteins of phytopathogenic bacteria include type III effector proteins that are often capable of enhancing virulence when not recognized by an R-protein. In rpm1 plants, AvrRpm1 suppresses basal defenses induced by microbe-associated molecular patterns. Here, we show that expression of AvrRpm1 in rpm1 plants induced PR-1, a classical defense marker, and symptoms including chlorosis and necrosis. PR-1 expression and symptoms were reduced in plants with mutations in defense signaling genes (pad4, sid2, npr1, rar1, and ndr1) and were strongly reduced in rpm1 rps2 plants, indicating that AvrRpm1 elicits defense signaling through the Arabidopsis R-protein, RPS2. Bacteria expressing AvrRpm1 grew more on rpm1 rps2 than on rpm1 plants. Thus, independent of its classical 'gene-for-gene' activation of RPM1, AvrRpm1 also induces functionally relevant defenses that are dependent on RPS2. Finally, AvrRpm1 suppressed host defenses and promoted the growth of type III secretion mutant bacteria equally well in rps2 and RPS2 plants, indicating that virulence activity of over-expressed AvrRpm1 predominates over defenses induced by weak activation of RPS2.
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Affiliation(s)
- Min Gab Kim
- Department of Horticulture and Crop Science, Rm. 306C Kottman Hall, The Ohio State University, Columbus, OH 43210, USA
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28
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Engelhardt S, Lee J, Gäbler Y, Kemmerling B, Haapalainen ML, Li CM, Wei Z, Keller H, Joosten M, Taira S, Nürnberger T. Separable roles of the Pseudomonas syringae pv. phaseolicola accessory protein HrpZ1 in ion-conducting pore formation and activation of plant immunity. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 57:706-717. [PMID: 18980650 DOI: 10.1111/j.1365-313x.2008.03723.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The HrpZ1 gene product from phytopathogenic Pseudomonas syringae is secreted in a type-III secretion system-dependent manner during plant infection. The ability of HrpZ1 to form ion-conducting pores is proposed to contribute to bacterial effector delivery into host cells, or may facilitate the nutrition of bacteria in the apoplast. Furthermore, HrpZ1 is reminiscent of a pathogen-associated molecular pattern (PAMP) that triggers immunity-associated responses in a variety of plants. Here, we provide evidence that the ion pore formation and immune activation activities of HrpZ1 have different structure requirements. All HrpZ1 orthologous proteins tested possess pore formation activities, but some of these proteins fail to trigger plant defense-associated responses. In addition, a C-terminal fragment of HrpZ1 retains the ability to activate plant immunity, whereas ion pore formation requires intact HrpZ1. Random insertion mutagenesis of HrpZ1 further revealed the C terminus to be important for the PAMP activity of the protein. HrpZ1 binds to plant membranes with high affinity and specificity, suggesting that the activation of plant immunity-associated responses by HrpZ1 is receptor-mediated. Our data are consistent with dual roles of HrpZ1 as a virulence factor affecting host membrane integrity, and as a microbial pattern governing the activation of plant immunity during infection.
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Affiliation(s)
- Stefan Engelhardt
- Center for Plant Molecular Biology-Plant Biochemistry, University of Tübingen, Tübingen, Germany
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Gopalan S, Ausubel FM. A metasystem of framework model organisms to study emergence of new host-microbe adaptations. PLoS One 2008; 3:e3891. [PMID: 19066631 PMCID: PMC2588659 DOI: 10.1371/journal.pone.0003891] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Accepted: 11/13/2008] [Indexed: 11/24/2022] Open
Abstract
An unintended consequence of global industrialization and associated societal rearrangements is new interactions of microbes and potential hosts (especially mammals and plants), providing an opportunity for the rapid emergence of host-microbe adaptation and eventual establishment of new microbe-related diseases. We describe a new model system comprising the model plant Arabidopsis thaliana and several microbes, each representing different modes of interaction, to study such “maladaptations”. The model microbes include human and agricultural pathogens and microbes that are commonly considered innocuous. The system has a large knowledge base corresponding to each component organism and is amenable to high-throughput automation assisted perturbation screens for identifying components that modulate host-pathogen interactions. This would aid in the study of emergence and progression of host-microbe maladaptations in a controlled environment.
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Affiliation(s)
- Suresh Gopalan
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, USA.
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Lin SS, Martin R, Mongrand S, Vandenabeele S, Chen KC, Jang IC, Chua NH. RING1 E3 ligase localizes to plasma membrane lipid rafts to trigger FB1-induced programmed cell death in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2008; 56:550-61. [PMID: 18643987 DOI: 10.1111/j.1365-313x.2008.03625.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Ubiquitination plays important roles in plant development, including programmed cell death. Here, we characterize a novel membrane-bound RING motif protein, encoded by RING1, that is expressed at a low level in all Arabidopsis tissues but can be upregulated by fumonisin B1 (FB1) treatment and pathogen infection. RING1 displays E3 ubiquitin ligase activity in vitro, which is dependent on the integrity of the RING motif. GFP fusion protein localization and cell fractionation experiments show that this E3 ligase is associated with the lipid rafts of plasma membranes. Knock-down of RING1 transcripts using artificial microRNA (amiR-R1(159)) leads to FB1 hyposensitivity, but overexpression of RING1 confers hypersensitivity. Additionally, expression of the pathogenesis-related 1 (PR-1) gene is lower and delayed in amiR-R1(159) plants compared with wild-type and RING1-overexpressing plants. The FB1 hyposensitivity of amiR-R1(159) plants can be rescued by expression of cleavage-resistant RING1mut transcripts. Our results suggest that RING1 acts as a signal from the plasma membrane lipid rafts to trigger the FB1-induced plant programmed cell death pathway.
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Affiliation(s)
- Shih-Shun Lin
- Laboratory of Plant Molecular Biology, Rockefeller University, 1230 York Avenue, New York, NY 10065, USA
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31
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Bent AF, Mackey D. Elicitors, effectors, and R genes: the new paradigm and a lifetime supply of questions. ANNUAL REVIEW OF PHYTOPATHOLOGY 2007; 45:399-436. [PMID: 17506648 DOI: 10.1146/annurev.phyto.45.062806.094427] [Citation(s) in RCA: 460] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The plant basal immune system can detect broadly present microbe-associated molecular patterns (MAMPs, also called PAMPs) and induce defenses, but adapted microbes express a suite of effector proteins that often act to suppress these defenses. Plants have evolved other receptors (R proteins) that detect these pathogen effectors and activate strong defenses. Pathogens can subsequently alter or delete their recognized effectors to avoid defense elicitation, at risk of a fitness cost associated with loss of those effectors. Significant research progress is revealing, among other things, mechanisms of MAMP perception, the host defense processes and specific host proteins that pathogen effectors target, the mechanisms of R protein activation, and the ways in which pathogen effector suites and R genes evolve. These findings carry practical ramifications for resistance durability and for future resistance engineering. The present review uses numerous questions to help clarify what we know and to identify areas that are ripe for further investigation.
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Affiliation(s)
- Andrew F Bent
- Department of Plant Pathology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
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32
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Shang Y, Li X, Cui H, He P, Thilmony R, Chintamanani S, Zwiesler-Vollick J, Gopalan S, Tang X, Zhou JM. RAR1, a central player in plant immunity, is targeted by Pseudomonas syringae effector AvrB. Proc Natl Acad Sci U S A 2006; 103:19200-5. [PMID: 17148606 PMCID: PMC1748199 DOI: 10.1073/pnas.0607279103] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2006] [Indexed: 11/18/2022] Open
Abstract
Pathogenic bacterial effectors suppress pathogen-associated molecular pattern (PAMP)-triggered host immunity, thereby promoting parasitism. In the presence of cognate resistance genes, it is proposed that plants detect the virulence activity of bacterial effectors and trigger a defense response, referred to here as effector-triggered immunity (ETI). However, the link between effector virulence and ETI at the molecular level is unknown. Here, we show that the Pseudomonas syringae effector AvrB suppresses PAMP-triggered immunity (PTI) through RAR1, a co-chaperone of HSP90 required for ETI. AvrB expressed in plants lacking the cognate resistance gene RPM1 suppresses cell wall defense induced by the flagellar peptide flg22, a well known PAMP, and promotes the growth of nonpathogenic bacteria in a RAR1-dependent manner. rar1 mutants display enhanced cell wall defense in response to flg22, indicating that RAR1 negatively regulates PTI. Furthermore, coimmunoprecipitation experiments indicated that RAR1 and AvrB interact in the plant. The results demonstrate that RAR1 molecularly links PTI, effector virulence, and ETI. The study supports that both pathogen virulence and plant disease resistance have evolved around PTI.
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Affiliation(s)
- Yulei Shang
- *National Institute of Biological Sciences, Beijing 102206, China
| | - Xinyan Li
- *National Institute of Biological Sciences, Beijing 102206, China
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506; and
| | - Haitao Cui
- *National Institute of Biological Sciences, Beijing 102206, China
| | - Ping He
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506; and
| | - Roger Thilmony
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - Satya Chintamanani
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506; and
| | - Julie Zwiesler-Vollick
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - Suresh Gopalan
- Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824
| | - Xiaoyan Tang
- Department of Plant Pathology, Kansas State University, Manhattan, KS 66506; and
| | - Jian-Min Zhou
- *National Institute of Biological Sciences, Beijing 102206, China
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33
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Fu ZQ, Guo M, Alfano JR. Pseudomonas syringae HrpJ is a type III secreted protein that is required for plant pathogenesis, injection of effectors, and secretion of the HrpZ1 Harpin. J Bacteriol 2006; 188:6060-9. [PMID: 16923873 PMCID: PMC1595357 DOI: 10.1128/jb.00718-06] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The bacterial plant pathogen Pseudomonas syringae requires a type III protein secretion system (TTSS) to cause disease. The P. syringae TTSS is encoded by the hrp-hrc gene cluster. One of the genes within this cluster, hrpJ, encodes a protein with weak similarity to YopN, a type III secreted protein from the animal pathogenic Yersinia species. Here, we show that HrpJ is secreted in culture and translocated into plant cells by the P. syringae pv. tomato DC3000 TTSS. A DC3000 hrpJ mutant, UNL140, was greatly reduced in its ability to cause disease symptoms and multiply in Arabidopsis thaliana. UNL140 exhibited a reduced ability to elicit a hypersensitive response (HR) in nonhost tobacco plants. UNL140 was unable to elicit an AvrRpt2- or AvrB1-dependent HR in A. thaliana but maintained its ability to secrete AvrB1 in culture via the TTSS. Additionally, UNL140 was defective in its ability to translocate the effectors AvrPto1, HopB1, and AvrPtoB. Type III secretion assays showed that UNL140 secreted HrpA1 and AvrPto1 but was unable to secrete HrpZ1, a protein that is normally secreted in culture in relatively large amounts, into culture supernatants. Taken together, our data indicate that HrpJ is a type III secreted protein that is important for pathogenicity and the translocation of effectors into plant cells. Based on the failure of UNL140 to secrete HrpZ1, HrpJ may play a role in controlling type III secretion, and in its absence, specific accessory proteins, like HrpZ1, may not be extracellularly localized, resulting in disabled translocation of effectors into plant cells.
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Affiliation(s)
- Zheng Qing Fu
- Plant Science Initiative, The Beadle Center for Genetic Research, University of Nebraska, 1901 Vine St., Lincoln, NE 68588-0660, USA
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34
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Abstract
SUMMARY Plants are under strong evolutionary pressure to maintain surveillance against pathogens. Resistance (R) gene-dependent recognition of pathogen avirulence (Avr) determinants plays a major role in plant defence. Here we highlight recent insights into the molecular mechanisms and selective forces that drive the evolution of NB-LRR (nucleotide binding-leucine-rich repeat) resistance genes. New implications for models of R gene evolution have been raised by demonstrations that R proteins can detect cognate Avr proteins indirectly by 'guarding' virulence targets, and by evidence that R protein signalling is regulated by intramolecular interactions between different R functional domains. Comparative genomic surveys of NB-LRR diversity in different species have revealed ancient NB-LRR lineages that are unequally represented among plant taxa, consistent with a Birth and Death Model of evolution. The physical distribution of NB-LRRs in plant genomes indicates that tandem and segmental duplication are important factors in R gene proliferation. The majority of R genes reside in clusters, and the frequency of recombination between clustered genes can vary strikingly, even within a single cluster. Biotic and abiotic factors have been shown to increase the frequency of recombination in reporter transgene-based assays, suggesting that external stressors can affect genome stability. Fitness penalties have been associated with some R genes, and population studies have provided evidence for maintenance of ancient R allelic diversity by balancing selection. The available data suggest that different R genes can follow strikingly distinct evolutionary trajectories, indicating that it will be difficult to formulate universally applicable models of R gene evolution.
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Affiliation(s)
- John M McDowell
- Department of Plant Pathology, Physiology, and Weed Science, and Fralin Biotechnology Center, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0346, USA
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35
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Abstract
The Pseudomonas syringae pv. glycinea effector protein AvrB induces resistance responses in soybean varieties that contain the resistance gene Rpg1-b and Arabidopsis varieties that carry RPM1. In addition to this avirulence activity, AvrB also enhances bacterial virulence on soybean plants that lack Rpg1-b and induces a chlorotic phenotype on Arabidopsis plants that lack RPM1. We screened a library of avrB mutants for loss of avirulence on soybean and Arabidopsis, and assayed selected avirulence mutants for loss of virulence on both plants. All mutants screened were recognized similarly on both plant species. Nine single-site avrB mutations that affected avirulence localized to a solvent-accessible pocket in the protein structure. Seven of these mutated residues are absolutely conserved between AvrB and its nine homologues. Avirulence mutants generally lost virulence enhancement on susceptible soybean varieties and lost the ability to induce a chlorotic response on the rpm1 null Arabidopsis variety Mt-0. Three of four avirulence mutants tested failed to interact with RIN4, an Arabidopsis protein previously shown to be required for RPM1 function. Our results suggest that soybean and Arabidopsis recognize AvrB in the same manner, and that AvrB enzymatic activity is required for its function as an avirulence and virulence effector on two different plant species.
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Affiliation(s)
- Laura E Ong
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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36
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Badel JL, Shimizu R, Oh HS, Collmer A. A Pseudomonas syringae pv. tomato avrE1/hopM1 mutant is severely reduced in growth and lesion formation in tomato. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:99-111. [PMID: 16529372 DOI: 10.1094/mpmi-19-0099] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The model plant pathogen Pseudomonas syringae pv. tomato DC3000 grows and produces necrotic lesions in the leaves of its host, tomato. Both abilities are dependent upon the hypersensitive response and pathogenicity (Hrp) type III secretion system (TTSS), which translocates multiple effector proteins into plant cells. A previously constructed DC3000 mutant with a 9.3-kb deletion in the Hrp pathogenicity island conserved effector locus (CEL) was strongly reduced in growth and lesion formation in tomato leaves. The ACEL mutation affects three putative or known effector genes: avrE1, hopM1, and hopAA1-1. Comparison of genomic sequences of DC3000, P. syringae pv. phaseolicola 1448A, and P. syringae pv. syringae B728a revealed that these are the only effector genes present in the CEL of all three strains. AvrEl was shown to carry functional TTSS translocation signals based on the performance of a fusion of the first 315 amino acids of AvrE1 to the Cya translocation reporter. A DC3000 delta avrE1 mutant was reduced in its ability to produce lesions but not in its ability to grow in host tomato leaves. AvrE1 expressed from the 35S promoter elicited cell death in nonhost Nicotiana tabacum leaves and host tomato leaves in Agrobacterium-mediated transient expression experiments. Mutations involving combinations of avrE1, hopM1, and hopAA1-1 revealed that deletion of both avrE1 and hopM1 reproduced the strongly reduced growth and lesion phenotype of the delta CEL mutant. Furthermore, quantitative assays involving different levels of inoculum and electrolyte leakage revealed that the avrE1/hopM1 and deltaCEL mutants both were partially impaired in their ability to elicit the hypersensitive response in nonhost N. benthamiana leaves. However, the avrE1/hopM1 mutant was not impaired in its ability to deliver AvrPto1(1-100)-Cya to nonhost N. benthamiana or host tomato leaves during the first 9 h after inoculation. These data suggest that AvrE1 acts within plant cells and promotes lesion formation and that the combined action of AvrE1 and HopM1 is particularly important in promoting bacterial growth in planta.
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Affiliation(s)
- Jorge L Badel
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA
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37
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Bronstein PA, Marrichi M, Cartinhour S, Schneider DJ, DeLisa MP. Identification of a twin-arginine translocation system in Pseudomonas syringae pv. tomato DC3000 and its contribution to pathogenicity and fitness. J Bacteriol 2005; 187:8450-61. [PMID: 16321949 PMCID: PMC1317023 DOI: 10.1128/jb.187.24.8450-8461.2005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 09/30/2005] [Indexed: 01/06/2023] Open
Abstract
The bacterial plant pathogen Pseudomonas syringae pv. tomato DC3000 (DC3000) causes disease in Arabidopsis thaliana and tomato plants, and it elicits the hypersensitive response in nonhost plants such as Nicotiana tabacum and Nicotiana benthamiana. While these events chiefly depend upon the type III protein secretion system and the effector proteins that this system translocates into plant cells, additional factors have been shown to contribute to DC3000 virulence and still many others are likely to exist. Therefore, we explored the contribution of the twin-arginine translocation (Tat) system to the physiology of DC3000. We found that a tatC mutant strain of DC3000 displayed a number of phenotypes, including loss of motility on soft agar plates, deficiency in siderophore synthesis and iron acquisition, sensitivity to copper, loss of extracellular phospholipase activity, and attenuated virulence in host plant leaves. In the latter case, we provide evidence that decreased virulence of tatC mutants likely arises from a synergistic combination of (i) compromised fitness of bacteria in planta; (ii) decreased efficiency of type III translocation; and (iii) cytoplasmically retained virulence factors. Finally, we demonstrate a novel broad-host-range genetic reporter based on the green fluorescent protein for the identification of Tat-targeted secreted virulence factors that should be generally applicable to any gram-negative bacterium. Collectively, our evidence supports the notion that virulence of DC3000 is a multifactorial process and that the Tat system is an important virulence determinant of this phytopathogenic bacterium.
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Affiliation(s)
- Philip A Bronstein
- U.S. Plant, Soil, and Nutrition Laboratory, U.S. Department of Agriculture, Agricultural Research Service, USA
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38
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Pandey AK, Ger MJ, Huang HE, Yip MK, Zeng J, Feng TY. Expression of the hypersensitive response-assisting protein in Arabidopsis results in harpin-dependent hypersensitive cell death in response to Erwinia carotovora. PLANT MOLECULAR BIOLOGY 2005; 59:771-80. [PMID: 16270229 DOI: 10.1007/s11103-005-1002-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2004] [Accepted: 07/15/2005] [Indexed: 05/05/2023]
Abstract
Active defense mechanisms of plants against pathogens often include a rapid plant cell death known as the hypersensitive cell death (HCD). Hypersensitive response-assisting protein (HRAP) isolated from sweet pepper intensifies the harpin(Pss)-mediated HCD. Here we demonstrate that constitutive expression of the hrap gene in Arabidopsis results in an enhanced disease resistance towards soft rot pathogen, E. carotovora subsp. carotovora. This resistance was due to the induction of HCD since different HCD markers viz. Athsr3, Athsr4, ion leakage, H(2)O(2) and protein kinase were induced. One of the elicitor harpin proteins, HrpN, from Erwinia carotovora subsp. carotovora was able to induce a stronger HCD in hrap-Arabidopsis than non-transgenic controls. To elucidate the role of HrpN, we used E. carotovora subsp. carotovora defective in HrpN production. The hrpN(-) mutant did not induce disease resistance or HCD markers in hrap-Arabidopsis. These results imply that the disease resistance of hrap-Arabidopsis against a virulent pathogen is harpin dependent.
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Affiliation(s)
- Ajay-Kumar Pandey
- Institute of Plant and Microbial Biology, Academia Sinica 115, Taipei, Taiwan
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39
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Gassmann W. Natural variation in the Arabidopsis response to the avirulence gene hopPsyA uncouples the hypersensitive response from disease resistance. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:1054-60. [PMID: 16255244 DOI: 10.1094/mpmi-18-1054] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The plant hypersensitive response (HR) is tightly associated with gene-for-gene resistance and has been proposed to function in containing pathogens at the invasion site. This tight association has made it difficult to unequivocally evaluate the importance of HR for plant disease resistance. Here, hopPsyA from Pseudomonas syringae pv. syringae 61 is identified as a new avirulence gene for Arabidopsis that triggers resistance in the absence of macroscopic HR. Resistance to P. syringae pv. tomato DC3000 expressing hopPsyA was EDS1-dependent and NDR1-independent. Intriguingly, several Arabidopsis accessions were resistant to DC3000(hopPsyA) in the absence of HR. This is comparable to the Arabidopsis response to avrRps4, but it is shown that hopPsyA does not signal through RPS4. In a cross between two hopPsyA-resistant accessions that differ in their HR response, the HR segregated as a recessive phenotype regulated by a single locus. This locus, HED1 (HR regulator in EDS1 pathway), is proposed to encode a protein whose activity can cause suppression of the EDS1-dependent HR signaling pathway. HED1-regulated symptomless gene-for-gene resistance responses may explain some cases of Arabidopsis resistance to bacteria that are classified as nonhost resistance.
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Affiliation(s)
- Walter Gassmann
- Division of Plant Sciences, University of Missouri-Columbia, MO 65211-7310, USA.
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40
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Type III protein secretion mechanism in mammalian and plant pathogens. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1694:181-206. [PMID: 15546666 DOI: 10.1016/j.bbamcr.2004.03.011] [Citation(s) in RCA: 205] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2003] [Revised: 03/26/2004] [Accepted: 03/26/2004] [Indexed: 01/12/2023]
Abstract
The type III protein secretion system (TTSS) is a complex organelle in the envelope of many Gram-negative bacteria; it delivers potentially hundreds of structurally diverse bacterial virulence proteins into plant and animal cells to modulate host cellular functions. Recent studies have revealed several basic features of this secretion system, including assembly of needle/pilus-like secretion structures, formation of putative translocation pores in the host membrane, recognition of N-terminal/5' mRNA-based secretion signals, and requirement of small chaperone proteins for optimal delivery and/or expression of effector proteins. Although most of our knowledge about the TTSS is derived from studies of mammalian pathogenic bacteria, similar and unique features are learned from studies of plant pathogenic bacteria. Here, we summarize the most salient aspects of the TTSS, with special emphasis on recent findings.
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41
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Mudgett MB. New insights to the function of phytopathogenic bacterial type III effectors in plants. ANNUAL REVIEW OF PLANT BIOLOGY 2005; 56:509-31. [PMID: 15862106 DOI: 10.1146/annurev.arplant.56.032604.144218] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Phytopathogenic bacteria use the type III secretion system (TTSS) to inject effector proteins into plant cells. This system is essential for bacteria to multiply in plant tissue and to promote the development of disease symptoms. Until recently, little was known about the function of TTSS effectors in bacterial-plant interactions. New studies dissecting the molecular and biochemical action of TTSS effectors show that these proteins contribute to bacterial pathogenicity by interfering with plant defense signal transduction. These investigations provide us with a fresh view of how bacteria manipulate plant physiology to colonize their hosts.
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Affiliation(s)
- Mary Beth Mudgett
- Department of Biological Sciences, Stanford University, Stanford, California 94305-5020, USA.
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42
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López-Solanilla E, Bronstein PA, Schneider AR, Collmer A. HopPtoN is a Pseudomonas syringae Hrp (type III secretion system) cysteine protease effector that suppresses pathogen-induced necrosis associated with both compatible and incompatible plant interactions. Mol Microbiol 2004; 54:353-65. [PMID: 15469508 DOI: 10.1111/j.1365-2958.2004.04285.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Pseudomonas syringae pv. tomato DC3000 causes bacterial speck disease in tomato, and it elicits the hypersensitive response (HR) in non-host plants such as Nicotiana tabacum and Nicotiana benthamiana. The compatible and incompatible interactions of DC3000 with tomato and Nicotiana spp., respectively, result in plant cell death, but the HR cell death occurs more rapidly and is associated with effective plant defense. Both interactions require the Hrp (HR and pathogenicity) type III secretion system (TTSS), which injects Hop (Hrp outer protein) effectors into plant cells. Here, we demonstrate that HopPtoN is translocated into tomato cells via the Hrp TTSS. A hopPtoN mutant produced eightfold more necrotic 'speck' lesions on tomato leaves than did DC3000, but the mutant and the wild-type strain grew to the same level in infected leaves. In non-host N. tabacum leaves, the hopPtoN mutant produced more cell death, whereas a DC3000 strain overexpressing HopPtoN produced less cell death and associated electrolyte leakage in comparison with wild-type DC3000. Transient expression of HopPtoN via infection with a PVX viral vector enabled tomato and N. benthamiana plants to tolerate, with reduced disease lesions, challenge infections with DC3000 and P. syringae pv. tabaci 11528, respectively. HopPtoN showed cysteine protease activity in vitro, and hopPtoN mutants altered in the predicted cysteine protease catalytic triad (C172S, H283A and D299A) lost HR suppression activity. These observations reveal that HopPtoN is a TTSS effector that can suppress plant cell death events in both compatible and incompatible interactions.
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43
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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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44
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Zhao B, Ardales EY, Raymundo A, Bai J, Trick HN, Leach JE, Hulbert SH. The avrRxo1 gene from the rice pathogen Xanthomonas oryzae pv. oryzicola confers a nonhost defense reaction on maize with resistance gene Rxo1. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:771-9. [PMID: 15242171 DOI: 10.1094/mpmi.2004.17.7.771] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Maize lines that contain the single dominant gene Rxo1 exhibit a rapid hypersensitive response (HR) after infiltration with the rice bacterial streak pathogen Xanthomonas oryzae pv. oryzicola, but not with the rice bacterial blight pathogen X. oryzae pv. oryzae. The avirulence effector gene that corresponds to Rxo1, designated avrRxo1, was identified in an X. oryzae pv. oryzicola genomic library. When introduced into X. oryzae pv. oryzae, clones containing avrRxo1 induced an HR on maize with Rxo1, but not on maize without Rxo1. The avrRxo1 gene is 1,266 bp long and shows no significant homology to any database sequences. When expressed in an X. oryzae pv. oryzae hrpC mutant that is deficient in the type III secretion system, avrRxo1 did not elicit the HR, indicating that the avrRxo1-Rxo1 interaction is dependent on type III secretion. Transient expression of avrRxo1 in onion cells after biolistic delivery revealed that the protein product was associated with the plasma membrane. Transient expression in maize lines carrying Rxo1 resulted in cell death, suggesting that AvrRxo1 functions from inside maize cells to elicit Rxo1-dependent pathogen recognition.
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Affiliation(s)
- Bingyu Zhao
- Department of Plant Pathology, 4024 Throckmorton Plant Sciences Center, Kansas State University, Manhattan 66506-5502, USA
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45
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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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Zhang C, Gutsche AT, Shapiro AD. Feedback control of the Arabidopsis hypersensitive response. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2004; 17:357-365. [PMID: 15077668 DOI: 10.1094/mpmi.2004.17.4.357] [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 plant hypersensitive response (HR) to avirulent bacterial pathogens results from programmed cell death of plant cells in the infected region. Ion leakage and changes in signaling components associated with HR progression were measured. These studies compared Arabidopsis mutants affecting feedback loops with wild-type plants, with timepoints taken hourly. In response to Pseudomonas syringae pv. tomato DC3000 x avrB, npr1-2 mutant plants showed increased ion leakage relative to wild-type plants. Hydrogen peroxide accumulation was similar to that in wild type, but salicylic acid accumulation was reduced at some timepoints. With DC3000 x avrRpt2, similar trends were seen. In response to DC3000 x avrB, ndr1-1 mutant plants showed more ion leakage than wild-type or npr1-2 plants. Hydrogen peroxide accumulation was delayed by approximately 1 h and reached half the level seen with wild-type plants. Salicylic acid accumulation was similar to npr1-2 mutant plants. With DC3000 x avrRpt2, ndr1-1 mutant plants showed no ion leakage, no hydrogen peroxide accumulation, and minimal salicylic acid accumulation. Results with a ndr1-1 and npr1-2 double mutant were similar to ndr1-1. A model consistent with these data is presented, in which one positive and two negative regulatory circuits control HR progression. Understanding this circuitry will facilitate HR manipulation for enhanced disease resistance.
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Affiliation(s)
- Chu Zhang
- Department of Plant and Soil Sciences, Delaware Agricultural Experiment Station, College of Agriculture and Natural Resources, University of Delaware, Newark, DE 19716-2170, USA
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Ezra D, Barash I, Weinthal DM, Gaba V, Manulis S. pthG from Pantoea agglomerans pv. gypsophilae encodes an avirulence effector that determines incompatibility in multiple beet species. MOLECULAR PLANT PATHOLOGY 2004; 5:105-113. [PMID: 20565587 DOI: 10.1111/j.1364-3703.2004.00211.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
SUMMARY Pantoea agglomerans pv. gypsophilae (Pag) causes root and crown gall disease on gypsophila, whereas P. agglomerans pv. betae (Pab) induces the disease on beet as well as gypsophila. Both pathovars harbour a pathogenicity plasmid (pPATH(Pag) or pPATH(Pab)) that determines disease development. We have previously isolated and partially characterized a pleiotropic gene from the pPATH(Pag), designated as pthG, that encodes a virulence factor in gypsophila and an elicitor of a hypersensitive-like response in beet roots. The present study was undertaken to characterize pthG further as an avr gene. The infiltration of beet leaves with strains expressing PthG (i.e. Pag or Pab containing pthG in trans) caused an hypersensitive reaction (HR) response within 48 h, whereas strains lacking intact pthG (i.e. Pab or Pag mutated in pthG) resulted in gall formation after 5 days. A hypersensitive reaction was elicited by PthG on multiple beet species, whereas a marker exchange mutant of Pag in pthG extended its host range on these beet species. A marker exchange mutant of Pag in hrpJ, encoding a component of the Type III secretion system, prevented HR elicitation. Mutations in each of the hrp regulatory genes (hrpY, hrpS and hrpL) substantially reduced the transcriptional activity of pthG in gypsophila cuttings. PthG could only be detected inside Pag cells during over-expression of hrpS or hrpL. Particle bombardment of GFP-PthG fusion caused cell death in beet, but not in non-host (melon) leaves. Present and previous results have established pthG as a broad-host-range avr gene that functions in multiple host plant species and the first functional avr gene in Pantoea spp.
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Affiliation(s)
- David Ezra
- Department of Plant Pathology, ARO, The Volcani Center, Bet Dagan, 50250 Israel
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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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Dodds PN, Lawrence GJ, Catanzariti AM, Ayliffe MA, Ellis JG. The Melampsora lini AvrL567 avirulence genes are expressed in haustoria and their products are recognized inside plant cells. THE PLANT CELL 2004; 16:755-68. [PMID: 14973158 PMCID: PMC385286 DOI: 10.1105/tpc.020040] [Citation(s) in RCA: 187] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2003] [Accepted: 01/13/2004] [Indexed: 05/18/2023]
Abstract
The Linum usitatissimum (flax) L gene alleles, which encode nucleotide binding site-Leu rich repeat class intracellular receptor proteins, confer resistance against the Melampsora lini (flax rust) fungus. At least 11 different L resistance specificities are known, and the corresponding avirulence genes in M. lini map to eight independent loci, some of which are complex and encode multiple specificities. We identified an M. lini cDNA marker that cosegregates in an F2 rust family with a complex locus determining avirulence on the L5, L6, and L7 resistance genes. Two related avirulence gene candidates, designated AvrL567-A and AvrL567-B, were identified in a genomic DNA contig from the avirulence allele, whereas the corresponding virulence allele contained a single copy of a related gene, AvrL567-C. Agrobacterium tumefaciens-mediated transient expression of the mature AvrL567-A or AvrL567-B (but not AvrL567-C) proteins as intracellular products in L. usitatissimum and Nicotiana tabacum (tobacco) induced a hypersensitive response-like necrosis that was dependent on coexpression of the L5, L6, or L7 resistance gene. An F1 seedling lethal or stunted growth phenotype also was observed when transgenic L. usitatissimum plants expressing AvrL567-A or AvrL567-B (but not AvrL567-C) were crossed to resistant lines containing L5, L6, or L7. The AvrL567 genes are expressed in rust haustoria and encode 127 amino acid secreted proteins. Intracellular recognition of these rust avirulence proteins implies that they are delivered into host cells across the plant membrane. Differences in the three AvrL567 protein sequences result from diversifying selection, which is consistent with a coevolutionary arms race.
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Affiliation(s)
- Peter N Dodds
- Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, Canberra, ACT 2601, Australia
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Jamir Y, Guo M, Oh HS, Petnicki-Ocwieja T, Chen S, Tang X, Dickman MB, Collmer A, Alfano JR. Identification of Pseudomonas syringae type III effectors that can suppress programmed cell death in plants and yeast. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 37:554-65. [PMID: 14756767 DOI: 10.1046/j.1365-313x.2003.01982.x] [Citation(s) in RCA: 213] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The Pseudomonas syringae pv. tomato DC3000 type III secretion system (TTSS) is required for bacterial pathogenicity on plants and elicitation of the hypersensitive response (HR), a programmed cell death (PCD) that occurs on resistant plants. Cosmid pHIR11 enables non-pathogens to elicit an HR dependent upon the TTSS and the effector HopPsyA. We used pHIR11 to determine that effectors HopPtoE, avirulence AvrPphEPto, AvrPpiB1Pto, AvrPtoB, and HopPtoF could suppress a HopPsyA-dependent HR on tobacco and Arabidopsis. Mixed inoculum and Agrobacterium-mediated transient expression experiments confirmed that suppressor action occurred within plant cells. These suppressors, with the exception of AvrPpiB1Pto, inhibited the expression of the tobacco pathogenesis-related (PR) gene PR1a. DC3000 suppressor mutants elicited an enhanced HR consistent with these mutants lacking an HR suppressor. Additionally, HopPtoG was identified as a suppressor on the basis of an enhanced HR produced by a hopPtoG mutant. Remarkably, these proteins functioned to inhibit the ability of the pro-apoptotic protein, Bax to induce PCD in plants and yeast, indicating that these effectors function as anti-PCD proteins in a trans-kingdom manner. The high proportion of effectors that suppress PCD suggests that suppressing plant immunity is one of the primary roles for DC3000 effectors and a central requirement for P. syringae pathogenesis.
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Affiliation(s)
- Yashitola Jamir
- Plant Science Initiative and Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588-0660, USA
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