51
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Pitino M, Armstrong CM, Cano LM, Duan Y. Transient Expression of Candidatus Liberibacter Asiaticus Effector Induces Cell Death in Nicotiana benthamiana. FRONTIERS IN PLANT SCIENCE 2016; 7:982. [PMID: 27458468 PMCID: PMC4933711 DOI: 10.3389/fpls.2016.00982] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 06/21/2016] [Indexed: 05/19/2023]
Abstract
Candidatus Liberibacter asiaticus "Las" is a phloem-limited bacterial plant pathogen, and the most prevalent species of Liberibacter associated with citrus huanglongbing (HLB), a devastating disease of citrus worldwide. Although, the complete sequence of the Las genome provides the basis for studying functional genomics of Las and molecular mechanisms of Las-plant interactions, the functional characterization of Las effectors remains a slow process since remains to be cultured. Like other plant pathogens, Las may deliver effector proteins into host cells and modulate a variety of host cellular functions for their infection progression. In this study, we identified 16 putative Las effectors via bioinformatics, and transiently expressed them in Nicotiana benthamiana. Diverse subcellular localization with different shapes and aggregation patterns of the effector candidates were revealed by UV- microscopy after transient expression in leaf tissue. Intriguingly, one of the 16 candidates, Las5315mp (mature protein), was localized in the chloroplast and induced cell death at 3 days post inoculation (dpi) in N. benthamiana. Moreover, Las5315mp induced strong callose deposition in plant cells. This study provides new insights into the localizations and potential roles of these Las effectors in planta.
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Affiliation(s)
- Marco Pitino
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of AgricultureFort Pierce, FL, USA
| | - Cheryl M. Armstrong
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of AgricultureFort Pierce, FL, USA
| | - Liliana M. Cano
- Institute of Food and Agricultural Sciences, Department of Plant Pathology, Indian River Research and Education Center, University of FloridaFort Pierce, FL, USA
| | - Yongping Duan
- U.S. Horticultural Research Laboratory, Agricultural Research Service, United States Department of AgricultureFort Pierce, FL, USA
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52
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Mukhtar M, McCormack M, Argueso C, Pajerowska-Mukhtar K. Pathogen Tactics to Manipulate Plant Cell Death. Curr Biol 2016; 26:R608-R619. [DOI: 10.1016/j.cub.2016.02.051] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
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53
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Serrano I, Audran C, Rivas S. Chloroplasts at work during plant innate immunity. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:3845-54. [PMID: 26994477 DOI: 10.1093/jxb/erw088] [Citation(s) in RCA: 128] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The major role played by chloroplasts during light harvesting, energy production, redox homeostasis, and retrograde signalling processes has been extensively characterized. Beyond the obvious link between chloroplast functions in primary metabolism and as providers of photosynthesis-derived carbon sources and energy, a growing body of evidence supports a central role for chloroplasts as integrators of environmental signals and, more particularly, as key defence organelles. Here, we review the importance of these organelles as primary sites for the biosynthesis and transmission of pro-defence signals during plant immune responses. In addition, we highlight interorganellar communication as a crucial process for amplification of the immune response. Finally, molecular strategies used by microbes to manipulate, directly or indirectly, the production/function of defence-related signalling molecules and subvert chloroplast-based defences are also discussed.
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Affiliation(s)
- Irene Serrano
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Corinne Audran
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
| | - Susana Rivas
- LIPM, Université de Toulouse, INRA, CNRS, Castanet-Tolosan, France
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54
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Camejo D, Guzmán-Cedeño Á, Moreno A. Reactive oxygen species, essential molecules, during plant-pathogen interactions. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2016; 103:10-23. [PMID: 26950921 DOI: 10.1016/j.plaphy.2016.02.035] [Citation(s) in RCA: 186] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Revised: 02/24/2016] [Accepted: 02/25/2016] [Indexed: 05/18/2023]
Abstract
Reactive oxygen species (ROS) are continually generated as a consequence of the normal metabolism in aerobic organisms. Accumulation and release of ROS into cell take place in response to a wide variety of adverse environmental conditions including salt, temperature, cold stresses and pathogen attack, among others. In plants, peroxidases class III, NADPH oxidase (NOX) locates in cell wall and plasma membrane, respectively, may be mainly enzymatic systems involving ROS generation. It is well documented that ROS play a dual role into cells, acting as important signal transduction molecules and as toxic molecules with strong oxidant power, however some aspects related to its function during plant-pathogen interactions remain unclear. This review focuses on the principal enzymatic systems involving ROS generation addressing the role of ROS as signal molecules during plant-pathogen interactions. We described how the chloroplasts, mitochondria and peroxisomes perceive the external stimuli as pathogen invasion, and trigger resistance response using ROS as signal molecule.
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Affiliation(s)
- Daymi Camejo
- CEBAS-CSIC, Centro de Edafología y Biología Aplicada del Segura, Department of Stress Biology and Plant Pathology, E-30100, Murcia, Spain; ESPAM-MES, Escuela Superior Politécnica Agropecuaria de Manabí, Manuel Félix López, Agricultural School, Manabí, Ecuador.
| | - Ángel Guzmán-Cedeño
- ESPAM-MES, Escuela Superior Politécnica Agropecuaria de Manabí, Manuel Félix López, Agricultural School, Manabí, Ecuador; ULEAM-MES, "Eloy Alfaro" University, Agropecuary School, Manabí, Ecuador.
| | - Alexander Moreno
- UTMachala-MES, Universidad Técnica de Machala, Botany Laboratory, Machala, Ecuador.
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55
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Macho AP. Subversion of plant cellular functions by bacterial type-III effectors: beyond suppression of immunity. THE NEW PHYTOLOGIST 2016; 210:51-7. [PMID: 26306858 DOI: 10.1111/nph.13605] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 07/10/2015] [Indexed: 05/20/2023]
Abstract
Most bacterial plant pathogens employ a type-III secretion system to inject type-III effector (T3E) proteins directly inside plant cells. These T3Es manipulate host cellular processes in order to create a permissive niche for bacterial proliferation, allowing development of the disease. An important role of T3Es in plant pathogenic bacteria is the suppression of plant immune responses. However, in recent years, research has uncovered T3E functions different from direct immune suppression, including the modulation of plant hormone signaling, metabolism or organelle function. This insight article discusses T3E functions other than suppression of immunity, which may contribute to the modulation of plant cells in order to promote bacterial survival, nutrient release, and bacterial replication and dissemination.
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Affiliation(s)
- Alberto P Macho
- Shanghai Center for Plant Stress Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, 201602, China
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56
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Teper D, Burstein D, Salomon D, Gershovitz M, Pupko T, Sessa G. Identification of novel Xanthomonas euvesicatoria type III effector proteins by a machine-learning approach. MOLECULAR PLANT PATHOLOGY 2016; 17:398-411. [PMID: 26104875 PMCID: PMC6638362 DOI: 10.1111/mpp.12288] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The Gram-negative bacterium Xanthomonas euvesicatoria (Xcv) is the causal agent of bacterial spot disease in pepper and tomato. Xcv pathogenicity depends on a type III secretion (T3S) system that delivers effector proteins into host cells to suppress plant immunity and promote disease. The pool of known Xcv effectors includes approximately 30 proteins, most identified in the 85-10 strain by various experimental and computational techniques. To identify additional Xcv 85-10 effectors, we applied a genome-wide machine-learning approach, in which all open reading frames (ORFs) were scored according to their propensity to encode effectors. Scoring was based on a large set of features, including genomic organization, taxonomic dispersion, hypersensitive response and pathogenicity (hrp)-dependent expression, 5' regulatory sequences, amino acid composition bias and GC content. Thirty-six predicted effectors were tested for translocation into plant cells using the hypersensitive response (HR)-inducing domain of AvrBs2 as a reporter. Seven proteins (XopAU, XopAV, XopAW, XopAP, XopAX, XopAK and XopAD) harboured a functional translocation signal and their translocation relied on the HrpF translocon, indicating that they are bona fide T3S effectors. Remarkably, four belong to novel effector families. Inactivation of the xopAP gene reduced the severity of disease symptoms in infected plants. A decrease in cell death and chlorophyll content was observed in pepper leaves inoculated with the xopAP mutant when compared with the wild-type strain. However, populations of the xopAP mutant in infected leaves were similar in size to those of wild-type bacteria, suggesting that the reduction in virulence was not caused by impaired bacterial growth.
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Affiliation(s)
- Doron Teper
- Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, 69978, Israel
| | - David Burstein
- Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Dor Salomon
- Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Michael Gershovitz
- Department of Cell Research and Immunology, Tel Aviv University, Tel Aviv, 69978, Israel
| | - Tal Pupko
- Department of Earth and Planetary Science, UC Berkeley, Berkeley, CA, 94720, USA
| | - Guido Sessa
- Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv, 69978, Israel
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57
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Durian G, Rahikainen M, Alegre S, Brosché M, Kangasjärvi S. Protein Phosphatase 2A in the Regulatory Network Underlying Biotic Stress Resistance in Plants. FRONTIERS IN PLANT SCIENCE 2016; 7:812. [PMID: 27375664 PMCID: PMC4901049 DOI: 10.3389/fpls.2016.00812] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 05/25/2016] [Indexed: 05/20/2023]
Abstract
Biotic stress factors pose a major threat to plant health and can significantly deteriorate plant productivity by impairing the physiological functions of the plant. To combat the wide range of pathogens and insect herbivores, plants deploy converging signaling pathways, where counteracting activities of protein kinases and phosphatases form a basic mechanism for determining appropriate defensive measures. Recent studies have identified Protein Phosphatase 2A (PP2A) as a crucial component that controls pathogenesis responses in various plant species. Genetic, proteomic and metabolomic approaches have underscored the versatile nature of PP2A, which contributes to the regulation of receptor signaling, organellar signaling, gene expression, metabolic pathways, and cell death, all of which essentially impact plant immunity. Associated with this, various PP2A subunits mediate post-translational regulation of metabolic enzymes and signaling components. Here we provide an overview of protein kinase/phosphatase functions in plant immunity signaling, and position the multifaceted functions of PP2A in the tightly inter-connected regulatory network that controls the perception, signaling and responding to biotic stress agents in plants.
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Affiliation(s)
- Guido Durian
- Department of Biochemistry, Molecular Plant Biology, University of TurkuTurku, Finland
| | - Moona Rahikainen
- Department of Biochemistry, Molecular Plant Biology, University of TurkuTurku, Finland
| | - Sara Alegre
- Department of Biochemistry, Molecular Plant Biology, University of TurkuTurku, Finland
| | - Mikael Brosché
- Department of Biochemistry, Molecular Plant Biology, University of TurkuTurku, Finland
| | - Saijaliisa Kangasjärvi
- Department of Biochemistry, Molecular Plant Biology, University of TurkuTurku, Finland
- *Correspondence: Saijaliisa Kangasjärvi,
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58
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Durian G, Rahikainen M, Alegre S, Brosché M, Kangasjärvi S. Protein Phosphatase 2A in the Regulatory Network Underlying Biotic Stress Resistance in Plants. FRONTIERS IN PLANT SCIENCE 2016. [PMID: 27375664 DOI: 10.3389/fpls.2016.00812/abstract] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Biotic stress factors pose a major threat to plant health and can significantly deteriorate plant productivity by impairing the physiological functions of the plant. To combat the wide range of pathogens and insect herbivores, plants deploy converging signaling pathways, where counteracting activities of protein kinases and phosphatases form a basic mechanism for determining appropriate defensive measures. Recent studies have identified Protein Phosphatase 2A (PP2A) as a crucial component that controls pathogenesis responses in various plant species. Genetic, proteomic and metabolomic approaches have underscored the versatile nature of PP2A, which contributes to the regulation of receptor signaling, organellar signaling, gene expression, metabolic pathways, and cell death, all of which essentially impact plant immunity. Associated with this, various PP2A subunits mediate post-translational regulation of metabolic enzymes and signaling components. Here we provide an overview of protein kinase/phosphatase functions in plant immunity signaling, and position the multifaceted functions of PP2A in the tightly inter-connected regulatory network that controls the perception, signaling and responding to biotic stress agents in plants.
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Affiliation(s)
- Guido Durian
- Department of Biochemistry, Molecular Plant Biology, University of Turku Turku, Finland
| | - Moona Rahikainen
- Department of Biochemistry, Molecular Plant Biology, University of Turku Turku, Finland
| | - Sara Alegre
- Department of Biochemistry, Molecular Plant Biology, University of Turku Turku, Finland
| | - Mikael Brosché
- Department of Biochemistry, Molecular Plant Biology, University of Turku Turku, Finland
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59
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Petre B, Lorrain C, Saunders DG, Win J, Sklenar J, Duplessis S, Kamoun S. Rust fungal effectors mimic host transit peptides to translocate into chloroplasts. Cell Microbiol 2015; 18:453-65. [DOI: 10.1111/cmi.12530] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Revised: 09/22/2015] [Accepted: 09/29/2015] [Indexed: 02/06/2023]
Affiliation(s)
- Benjamin Petre
- The Sainsbury Laboratory; Norwich Research Park; Norwich NR4 7UH UK
- INRA, UMR 1136 Interactions Arbres/Microorganismes; Centre INRA Nancy Lorraine; Champenoux 54280 France
- Université de Lorraine; UMR 1136 Interactions Arbres/Microorganismes, Faculté des Sciences et Technologies; Vandoeuvre-lès-Nancy 54506 France
| | - Cécile Lorrain
- The Sainsbury Laboratory; Norwich Research Park; Norwich NR4 7UH UK
- INRA, UMR 1136 Interactions Arbres/Microorganismes; Centre INRA Nancy Lorraine; Champenoux 54280 France
- Université de Lorraine; UMR 1136 Interactions Arbres/Microorganismes, Faculté des Sciences et Technologies; Vandoeuvre-lès-Nancy 54506 France
| | - Diane G.O. Saunders
- The Sainsbury Laboratory; Norwich Research Park; Norwich NR4 7UH UK
- The Genome Analysis Centre; Norwich Research Park; Norwich NR4 7UH UK
- The John Innes Centre; Norwich Research Park; Norwich NR4 7UH UK
| | - Joe Win
- The Sainsbury Laboratory; Norwich Research Park; Norwich NR4 7UH UK
| | - Jan Sklenar
- The Sainsbury Laboratory; Norwich Research Park; Norwich NR4 7UH UK
| | - Sébastien Duplessis
- INRA, UMR 1136 Interactions Arbres/Microorganismes; Centre INRA Nancy Lorraine; Champenoux 54280 France
- Université de Lorraine; UMR 1136 Interactions Arbres/Microorganismes, Faculté des Sciences et Technologies; Vandoeuvre-lès-Nancy 54506 France
| | - Sophien Kamoun
- The Sainsbury Laboratory; Norwich Research Park; Norwich NR4 7UH UK
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60
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Van Aken O, Van Breusegem F. Licensed to Kill: Mitochondria, Chloroplasts, and Cell Death. TRENDS IN PLANT SCIENCE 2015; 20:754-766. [PMID: 26442680 DOI: 10.1016/j.tplants.2015.08.002] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2015] [Revised: 08/03/2015] [Accepted: 08/10/2015] [Indexed: 05/18/2023]
Abstract
Programmed cell death (PCD) is crucial in plant organogenesis and survival. In this review the involvement of mitochondria and chloroplasts in PCD execution is critically assessed. Recent findings support a central role for mitochondria in PCD, with newly identified components of the mitochondrial electron transport chain (mETC), FOF1 ATP synthase, cardiolipins, and ATPase AtOM66. While chloroplasts received less attention, their contribution to PCD is well supported, suggesting that they possibly contribute by producing reactive oxygen species (ROS) in the presence of light or even contribute through cytochrome f release. Finally we discuss two working models where mitochondria and chloroplasts could cooperatively execute PCD: mitochondria initiate the commitment steps and recruit chloroplasts for swift execution or, alternatively, mitochondria and chloroplasts could operate in parallel.
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Affiliation(s)
- Olivier Van Aken
- ARC Centre of Excellence in Plant Energy Biology, University of Western Australia, Crawley, Australia.
| | - Frank Van Breusegem
- Department of Plant Systems Biology, VIB, Ghent University, B-9052 Gent, Belgium; Department of Plant Biotechnology and Bioinformatics, Ghent University, B-9052 Gent, Belgium
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61
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Petre B, Saunders DGO, Sklenar J, Lorrain C, Win J, Duplessis S, Kamoun S. Candidate Effector Proteins of the Rust Pathogen Melampsora larici-populina Target Diverse Plant Cell Compartments. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:689-700. [PMID: 25650830 DOI: 10.1094/mpmi-01-15-0003-r] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Rust fungi are devastating crop pathogens that deliver effector proteins into infected tissues to modulate plant functions and promote parasitic growth. The genome of the poplar leaf rust fungus Melampsora larici-populina revealed a large catalog of secreted proteins, some of which have been considered candidate effectors. Unraveling how these proteins function in host cells is a key to understanding pathogenicity mechanisms and developing resistant plants. In this study, we used an effectoromics pipeline to select, clone, and express 20 candidate effectors in Nicotiana benthamiana leaf cells to determine their subcellular localization and identify the plant proteins they interact with. Confocal microscopy revealed that six candidate effectors target the nucleus, nucleoli, chloroplasts, mitochondria, and discrete cellular bodies. We also used coimmunoprecipitation (coIP) and mass spectrometry to identify 606 N. benthamiana proteins that associate with the candidate effectors. Five candidate effectors specifically associated with a small set of plant proteins that may represent biologically relevant interactors. We confirmed the interaction between the candidate effector MLP124017 and TOPLESS-related protein 4 from poplar by in planta coIP. Altogether, our data enable us to validate effector proteins from M. larici-populina and reveal that these proteins may target multiple compartments and processes in plant cells. It also shows that N. benthamiana can be a powerful heterologous system to study effectors of obligate biotrophic pathogens.
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Affiliation(s)
- Benjamin Petre
- 1 The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, U.K
- 2 INRA, UMR 1136 Interactions Arbres/Microorganismes, Centre INRA Nancy Lorraine, 54280 Champenoux, France
- 3 Université de Lorraine, UMR 1136 Interactions Arbres/Microorganismes, Faculté des Sciences et Technologies, 54506 Vandoeuvre-lès-Nancy, France
| | - Diane G O Saunders
- 1 The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, U.K
- 4 The Genome Analysis Centre, Norwich Research Park, NR4 7UH Norwich, U.K
- 5 The John Innes Centre, Norwich Research Park, NR4 7UH Norwich, U.K
| | - Jan Sklenar
- 1 The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, U.K
| | - Cécile Lorrain
- 1 The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, U.K
- 2 INRA, UMR 1136 Interactions Arbres/Microorganismes, Centre INRA Nancy Lorraine, 54280 Champenoux, France
- 3 Université de Lorraine, UMR 1136 Interactions Arbres/Microorganismes, Faculté des Sciences et Technologies, 54506 Vandoeuvre-lès-Nancy, France
| | - Joe Win
- 1 The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, U.K
| | - Sébastien Duplessis
- 2 INRA, UMR 1136 Interactions Arbres/Microorganismes, Centre INRA Nancy Lorraine, 54280 Champenoux, France
- 3 Université de Lorraine, UMR 1136 Interactions Arbres/Microorganismes, Faculté des Sciences et Technologies, 54506 Vandoeuvre-lès-Nancy, France
| | - Sophien Kamoun
- 1 The Sainsbury Laboratory, Norwich Research Park, NR4 7UH Norwich, U.K
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de Torres Zabala M, Littlejohn G, Jayaraman S, Studholme D, Bailey T, Lawson T, Tillich M, Licht D, Bölter B, Delfino L, Truman W, Mansfield J, Smirnoff N, Grant M. Chloroplasts play a central role in plant defence and are targeted by pathogen effectors. NATURE PLANTS 2015; 1:15074. [PMID: 27250009 DOI: 10.1038/nplants.2015.74] [Citation(s) in RCA: 178] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 04/24/2015] [Indexed: 05/19/2023]
Abstract
Microbe associated molecular pattern (MAMP) receptors in plants recognize MAMPs and activate basal defences; however a complete understanding of the molecular and physiological mechanisms conferring immunity remains elusive. Pathogens suppress active defence in plants through the combined action of effector proteins. Here we show that the chloroplast is a key component of early immune responses. MAMP perception triggers the rapid, large-scale suppression of nuclear encoded chloroplast-targeted genes (NECGs). Virulent Pseudomonas syringae effectors reprogramme NECG expression in Arabidopsis, target the chloroplast and inhibit photosynthetic CO2 assimilation through disruption of photosystem II. This activity prevents a chloroplastic reactive oxygen burst. These physiological changes precede bacterial multiplication and coincide with pathogen-induced abscisic acid (ABA) accumulation. MAMP pretreatment protects chloroplasts from effector manipulation, whereas application of ABA or the inhibitor of photosynthetic electron transport, DCMU, abolishes the MAMP-induced chloroplastic reactive oxygen burst, and enhances growth of a P. syringae hrpA mutant that fails to secrete effectors.
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Affiliation(s)
- Marta de Torres Zabala
- Biosciences, College of Life and Environment Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - George Littlejohn
- Biosciences, College of Life and Environment Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Siddharth Jayaraman
- Biosciences, College of Life and Environment Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - David Studholme
- Biosciences, College of Life and Environment Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Trevor Bailey
- Biosciences, College of Life and Environment Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Tracy Lawson
- School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK
| | - Michael Tillich
- Max Planck Institute of Molecular Plant Physiology, Am Müehlenberg 1, Potsdam-Golm D-14476, Germany
| | - Dirk Licht
- Max Planck Institute of Molecular Plant Physiology, Am Müehlenberg 1, Potsdam-Golm D-14476, Germany
| | - Bettina Bölter
- Department of Biology I, Botany, Ludwig-Maximilians-Universität München, Groβhaderner Strase 2-4, Planegg-Martinsried D-82152, Germany
| | - Laura Delfino
- Department of Biology I, Botany, Ludwig-Maximilians-Universität München, Groβhaderner Strase 2-4, Planegg-Martinsried D-82152, Germany
| | - William Truman
- Department of Plant Biology, University of Minnesota, USA
| | - John Mansfield
- Department of Life Sciences, Imperial College, London SW7 2AZ, UK
| | - Nicholas Smirnoff
- Biosciences, College of Life and Environment Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Murray Grant
- Biosciences, College of Life and Environment Sciences, University of Exeter, Exeter EX4 4QD, UK
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63
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Mitchell K, Brown I, Knox P, Mansfield J. The role of cell wall-based defences in the early restriction of non-pathogenic hrp mutant bacteria in Arabidopsis. PHYTOCHEMISTRY 2015; 112:139-150. [PMID: 25108744 DOI: 10.1016/j.phytochem.2014.07.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 06/23/2014] [Accepted: 07/10/2014] [Indexed: 06/03/2023]
Abstract
We have investigated the cause of the restricted multiplication of hrp mutant bacteria in leaves of Arabidopsis. Our focus was on early interactions leading to differentiation between virulent wild-type and non-pathogenic hrpA mutant strains of Pseudomonas syringae pv. tomato. An initial drop in recoverable bacteria detected 0-4 h after inoculation with either strain was dependent on a functional FLS2 receptor and H2O2 accumulation in challenged leaves. Wild-type bacteria subsequently multiplied rapidly whereas the hrpA mutant was restricted within 6 h. Despite the early restriction, the hrpA mutant was still viable several days after inoculation. Analysis of intercellular washing fluids (IWFs), showed that high levels of nutrients were readily available to bacteria in the apoplast and that no diffusible inhibitors were produced in response to bacterial challenge. Histochemical and immunocytochemical methods were used to detect changes in polysaccharides (callose, two forms of cellulose, and pectin), arabinogalactan proteins (AGPs), H2O2 and peroxidase. Quantitative analysis showed very similar changes in localisation of AGPs, cellulose epitopes and callose 2 and 4 h after inoculation with either strain. However from 6 to 12 h after inoculation papillae expanded only next to the hrp mutant. In contrast to the similar patterns of secretory activity recorded from mesophyll cells, accumulation of H2O2 and peroxidase was significantly greater around the hrpA mutant within the first 4h after inoculation. A striking differential accumulation of H2O2 was also found in chloroplasts in cells next to the mutant. Ascorbate levels were lower in the IWFs recovered from sites inoculated with the hrp mutant than with wild-type bacteria. The critical response, observed at the right time and place to explain the observed differential behaviour of wild-type and hrpA mutant bacteria was the accumulation of H2O2, probably generated through Type III peroxidase activity and in chloroplasts. It is proposed that H2O2 and apoplastic peroxidase cross-link secreted glycoproteins and polysaccharides to agglutinate the hrp mutant. Generation of H2O2 has been identified as a likely target for effector proteins injected into plant cells by the wild-type bacteria.
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Affiliation(s)
- Kathy Mitchell
- Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
| | - Ian Brown
- School of Biological Sciences, University of Kent, Canterbury CT127NZ, UK
| | - Paul Knox
- Centre for Plant Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - John Mansfield
- Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK.
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64
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Targeting of plant pattern recognition receptor-triggered immunity by bacterial type-III secretion system effectors. Curr Opin Microbiol 2015; 23:14-22. [DOI: 10.1016/j.mib.2014.10.009] [Citation(s) in RCA: 190] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2014] [Revised: 10/16/2014] [Accepted: 10/24/2014] [Indexed: 01/08/2023]
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Bobik K, Burch-Smith TM. Chloroplast signaling within, between and beyond cells. FRONTIERS IN PLANT SCIENCE 2015; 6:781. [PMID: 26500659 PMCID: PMC4593955 DOI: 10.3389/fpls.2015.00781] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 09/10/2015] [Indexed: 05/18/2023]
Abstract
The most conspicuous function of plastids is the oxygenic photosynthesis of chloroplasts, yet plastids are super-factories that produce a plethora of compounds that are indispensable for proper plant physiology and development. Given their origins as free-living prokaryotes, it is not surprising that plastids possess their own genomes whose expression is essential to plastid function. This semi-autonomous character of plastids requires the existence of sophisticated regulatory mechanisms that provide reliable communication between them and other cellular compartments. Such intracellular signaling is necessary for coordinating whole-cell responses to constantly varying environmental cues and cellular metabolic needs. This is achieved by plastids acting as receivers and transmitters of specific signals that coordinate expression of the nuclear and plastid genomes according to particular needs. In this review we will consider the so-called retrograde signaling occurring between plastids and nuclei, and between plastids and other organelles. Another important role of the plastid we will discuss is the involvement of plastid signaling in biotic and abiotic stress that, in addition to influencing retrograde signaling, has direct effects on several cellular compartments including the cell wall. We will also review recent evidence pointing to an intriguing function of chloroplasts in regulating intercellular symplasmic transport. Finally, we consider an intriguing yet less widely known aspect of plant biology, chloroplast signaling from the perspective of the entire plant. Thus, accumulating evidence highlights that chloroplasts, with their complex signaling pathways, provide a mechanism for exquisite regulation of plant development, metabolism and responses to the environment. As chloroplast processes are targeted for engineering for improved productivity the effect of such modifications on chloroplast signaling will have to be carefully considered in order to avoid unintended consequences on plant growth and development.
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Affiliation(s)
| | - Tessa M. Burch-Smith
- *Correspondence: Tessa M. Burch-Smith, Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, 1414 Cumberland Avenue, M407 Walters Life Science, Knoxville, TN 37932, USA,
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Peters JE, Fricker AD, Kapili BJ, Petassi MT. Heteromeric transposase elements: generators of genomic islands across diverse bacteria. Mol Microbiol 2014; 93:1084-92. [PMID: 25091064 DOI: 10.1111/mmi.12740] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/31/2014] [Indexed: 11/30/2022]
Abstract
Horizontally acquired genetic information in bacterial chromosomes accumulates in blocks termed genomic islands. Tn7-like transposons form genomic islands at a programmed insertion site in bacterial chromosomes, attTn7. Transposition involves five transposon-encoded genes (tnsABCDE) including an atypical heteromeric transposase. One transposase subunit, TnsB, is from the large family of bacterial transposases, the second, TnsA, is related to endonucleases. A regulator protein, TnsC, functions with different target site selecting proteins to recognize different targets. TnsD directs transposition into attTn7, while TnsE encourages horizontal transmission by targeting mobile plasmids. Recent work suggests that distantly related elements with heteromeric transposases exist with alternate targeting pathways that also facilitate the formation of genomic islands. Tn6230 and related elements can be found at a single position in a gene of unknown function (yhiN) in various bacteria as well as in mobile plasmids. Another group we term Tn6022-like elements form pathogenicity islands in the Acinetobacter baumannii comM gene. We find that Tn6022-like elements also appear to have an uncharacterized mechanism for provoking internal transposition and deletion events that serve as a conduit for evolving new elements. As a group, heteromeric transposase elements utilize diverse target site selection mechanisms adapted to the spread and rearrangement of genomic islands.
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Affiliation(s)
- Joseph E Peters
- Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA
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The Evolution of Ethylene Signaling in Plant Chemical Ecology. J Chem Ecol 2014; 40:700-16. [DOI: 10.1007/s10886-014-0474-5] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2014] [Revised: 06/19/2014] [Accepted: 06/26/2014] [Indexed: 01/10/2023]
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