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Zhang P, Jiang Y, Schwab F, Monikh FA, Grillo R, White JC, Guo Z, Lynch I. Strategies for Enhancing Plant Immunity and Resilience Using Nanomaterials for Sustainable Agriculture. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:9051-9060. [PMID: 38742946 PMCID: PMC11137868 DOI: 10.1021/acs.est.4c03522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Revised: 05/04/2024] [Accepted: 05/07/2024] [Indexed: 05/16/2024]
Abstract
Research on plant-nanomaterial interactions has greatly advanced over the past decade. One particularly fascinating discovery encompasses the immunomodulatory effects in plants. Due to the low doses needed and the comparatively low toxicity of many nanomaterials, nanoenabled immunomodulation is environmentally and economically promising for agriculture. It may reduce environmental costs associated with excessive use of chemical pesticides and fertilizers, which can lead to soil and water pollution. Furthermore, nanoenabled strategies can enhance plant resilience against various biotic and abiotic stresses, contributing to the sustainability of agricultural ecosystems and the reduction of crop losses due to environmental factors. While nanoparticle immunomodulatory effects are relatively well-known in animals, they are still to be understood in plants. Here, we provide our perspective on the general components of the plant's immune system, including the signaling pathways, networks, and molecules of relevance for plant nanomodulation. We discuss the recent scientific progress in nanoenabled immunomodulation and nanopriming and lay out key avenues to use plant immunomodulation for agriculture. Reactive oxygen species (ROS), the mitogen-activated protein kinase (MAPK) cascade, and the calcium-dependent protein kinase (CDPK or CPK) pathway are of particular interest due to their interconnected function and significance in the response to biotic and abiotic stress. Additionally, we underscore that understanding the plant hormone salicylic acid is vital for nanoenabled applications to induce systemic acquired resistance. It is suggested that a multidisciplinary approach, incorporating environmental impact assessments and focusing on scalability, can expedite the realization of enhanced crop yields through nanotechnology while fostering a healthier environment.
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Affiliation(s)
- Peng Zhang
- Department
of Environmental Science and Engineering, University of Science and Technology of China, Hefei 230026, China
| | - Yaqi Jiang
- Department
of Environmental Science and Engineering, University of Science and Technology of China, Hefei 230026, China
- Beijing
Key Laboratory of Farmland Soil Pollution Prevention and Remediation,
College of Resources and Environmental Sciences, China Agricultural University, Beijing 100093, China
| | - Fabienne Schwab
- Adolphe
Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland
| | - Fazel Abdolahpur Monikh
- Department
of Environmental and Biological Sciences, University of Eastern Finland, Joensuu-Kuopio 80101, Finland
- Department
of Chemical Sciences, University of Padua, Via Marzolo 1, 35131 Padova, Italy
| | - Renato Grillo
- Department
of Physics and Chemistry, School of Engineering, São Paulo State University (UNESP), Ilha Solteira, SP 15385-000, Brazil
| | - Jason C. White
- Department
of Analytical Chemistry, The Connecticut
Agricultural Experiment Station, New Haven, Connecticut 06504, United States
| | - Zhiling Guo
- School
of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
| | - Iseult Lynch
- School
of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, U.K.
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2
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Zhang B, Huang S, Guo Z, Meng Y, Li X, Tian Y, Chen W. Salicylic acid accelerates carbon starvation-induced leaf senescence in Arabidopsis thaliana by inhibiting autophagy through Nonexpressor of pathogenesis-related genes 1. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2023; 336:111859. [PMID: 37673221 DOI: 10.1016/j.plantsci.2023.111859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 08/09/2023] [Accepted: 09/01/2023] [Indexed: 09/08/2023]
Abstract
In plants, leaf senescence is regulated by several factors, including age and carbon starvation. The molecular mechanism of age-regulated developmental leaf senescence differs from that of carbon starvation-induced senescence. Salicylic acid (SA) and Nonexpressor of pathogenesis-related genes 1 (NPR1) play important roles in promoting developmental leaf senescence. However, the relationship between SA signaling and carbon starvation-induced leaf senescence is not currently well understood. Here, we used Arabidopsis thaliana as material and found that carbon starvation-induced leaf senescence was accelerated in the SA dihydroxylase mutants s3hs5h compared to the Columbia ecotype (Col). Exogenous SA treatment significantly promoted carbon starvation-induced leaf senescence, especially in NPR1-GFP. Increasing the endogenous SA and overexpression of NPR1 inhibited carbon starvation-induced autophagy. However, mutation of NPR1 delayed carbon starvation-induced leaf senescence, increased autophagosome production and accelerated autophagic degradation of the Neighbor of BRCA1 gene 1 (NBR1). In conclusion, SA promotes carbon starvation-induced leaf senescence by inhibiting autophagy via NPR1.
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Affiliation(s)
- Baihong Zhang
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China; Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Shuqin Huang
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China; Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Zetian Guo
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China; Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Yixuan Meng
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China; Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Xue Li
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China; Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Yuzhen Tian
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China; Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China
| | - Wenli Chen
- MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China; Guangdong Provincial Key Laboratory of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
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Saeed B, Trujillo M. Analysis of Immunity-Related Oxidative Bursts by a Luminol-Based Assay. Methods Mol Biol 2022; 2494:339-346. [PMID: 35467219 DOI: 10.1007/978-1-0716-2297-1_24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The rapid production of reactive oxygen species (ROS) in response to biotic and abiotic cues is a conserved hallmark of plant responses. The detection and quantification of ROS generation during immune responses is an excellent readout to analyze signaling triggered by the perception of pathogens. The assay described here is easy to employ and versatile, allowing its use in a multitude of variations. For example, ROS production can be analyzed using different tissues including whole seedlings, roots, leaves, protoplasts, and cultured cells, which can originate from different ecotypes or mutants. Samples can be tested in combination with any ROS-inducing elicitors, such as the FLS2-activating peptide flg22, but also lipids or even abiotic stresses. Furthermore, early (PAMP-triggered) and late (effector-triggered) ROS production induced by virulent and avirulent bacteria, respectively, can also be assayed.
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Affiliation(s)
- Bushra Saeed
- Faculty of Biology, Cell Biology, University of Freiburg, Freiburg, Germany
| | - Marco Trujillo
- Faculty of Biology, Cell Biology, University of Freiburg, Freiburg, Germany.
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Schreiber KJ, Chau-Ly IJ, Lewis JD. What the Wild Things Do: Mechanisms of Plant Host Manipulation by Bacterial Type III-Secreted Effector Proteins. Microorganisms 2021; 9:1029. [PMID: 34064647 PMCID: PMC8150971 DOI: 10.3390/microorganisms9051029] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/03/2021] [Accepted: 05/04/2021] [Indexed: 01/05/2023] Open
Abstract
Phytopathogenic bacteria possess an arsenal of effector proteins that enable them to subvert host recognition and manipulate the host to promote pathogen fitness. The type III secretion system (T3SS) delivers type III-secreted effector proteins (T3SEs) from bacterial pathogens such as Pseudomonas syringae, Ralstonia solanacearum, and various Xanthomonas species. These T3SEs interact with and modify a range of intracellular host targets to alter their activity and thereby attenuate host immune signaling. Pathogens have evolved T3SEs with diverse biochemical activities, which can be difficult to predict in the absence of structural data. Interestingly, several T3SEs are activated following injection into the host cell. Here, we review T3SEs with documented enzymatic activities, as well as T3SEs that facilitate virulence-promoting processes either indirectly or through non-enzymatic mechanisms. We discuss the mechanisms by which T3SEs are activated in the cell, as well as how T3SEs modify host targets to promote virulence or trigger immunity. These mechanisms may suggest common enzymatic activities and convergent targets that could be manipulated to protect crop plants from infection.
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Affiliation(s)
- Karl J. Schreiber
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94710, USA; (K.J.S.); (I.J.C.-L.)
| | - Ilea J. Chau-Ly
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94710, USA; (K.J.S.); (I.J.C.-L.)
| | - Jennifer D. Lewis
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94710, USA; (K.J.S.); (I.J.C.-L.)
- Plant Gene Expression Center, United States Department of Agriculture, University of California, Berkeley, CA 94710, USA
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El-Shetehy M, Moradi A, Maceroni M, Reinhardt D, Petri-Fink A, Rothen-Rutishauser B, Mauch F, Schwab F. Silica nanoparticles enhance disease resistance in Arabidopsis plants. NATURE NANOTECHNOLOGY 2021; 16:344-353. [PMID: 33318639 PMCID: PMC7610738 DOI: 10.1038/s41565-020-00812-0] [Citation(s) in RCA: 90] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Accepted: 10/30/2020] [Indexed: 05/18/2023]
Abstract
In plants, pathogen attack can induce an immune response known as systemic acquired resistance that protects against a broad spectrum of pathogens. In the search for safer agrochemicals, silica nanoparticles (SiO2 NPs; food additive E551) have recently been proposed as a new tool. However, initial results are controversial, and the molecular mechanisms of SiO2 NP-induced disease resistance are unknown. Here we show that SiO2 NPs, as well as soluble Si(OH)4, can induce systemic acquired resistance in a dose-dependent manner, which involves the defence hormone salicylic acid. Nanoparticle uptake and action occurred exclusively through the stomata (leaf pores facilitating gas exchange) and involved extracellular adsorption in the air spaces in the spongy mesophyll of the leaf. In contrast to the treatment with SiO2 NPs, the induction of systemic acquired resistance by Si(OH)4 was problematic since high Si(OH)4 concentrations caused stress. We conclude that SiO2 NPs have the potential to serve as an inexpensive, highly efficient, safe and sustainable alternative for plant disease protection.
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Affiliation(s)
- Mohamed El-Shetehy
- Department of Biology, University of Fribourg, Fribourg, Switzerland.
- Department of Botany and Microbiology, Faculty of Science, Tanta University, Tanta, Egypt.
| | - Aboubakr Moradi
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Mattia Maceroni
- Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland
| | - Didier Reinhardt
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Alke Petri-Fink
- Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland
- Department of Chemistry, University of Fribourg, Fribourg, Switzerland
| | | | - Felix Mauch
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Fabienne Schwab
- Adolphe Merkle Institute, University of Fribourg, Fribourg, Switzerland.
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6
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Schröpfer S, Böttcher C, Wöhner T, Richter K, Norelli J, Rikkerink EHA, Hanke MV, Flachowsky H. A Single Effector Protein, AvrRpt2 EA, from Erwinia amylovora Can Cause Fire Blight Disease Symptoms and Induces a Salicylic Acid-Dependent Defense Response. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:1179-1191. [PMID: 30204065 DOI: 10.1094/mpmi-12-17-0300-r] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The AvrRpt2EA effector protein of Erwinia amylovora is important for pathogen recognition in the fire blight-resistant crabapple Malus × robusta 5; however, little is known about its role in susceptible apples. To study its function in planta, we expressed a plant-optimized version of AvrRpt2EA driven by a heat shock-inducible promoter in transgenic plants of the fire blight-susceptible cultivar Pinova. After induced expression of AvrRpt2EA, transgenic lines showed shoot necrosis and browning of older leaves, with symptoms similar to natural fire blight infections. Transgenic expression of this effector protein resulted in an increase in the expression of the salicylic acid (SA)-responsive PR-1 gene but, also, in the levels of SA and its derivatives, with diverse kinetics in leaves of different ages. In contrast, no increase of expression levels of VSP2 paralogs, used as marker genes for the activation of the jasmonic acid (JA)-dependent defense pathway, could be detected, which is in agreement with metabolic profiling of JA and its derivatives. Our work demonstrates that AvrRpt2EA acts as a virulence factor and induces the formation of SA and SA-dependent systemic acquired resistance.
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Affiliation(s)
- Susan Schröpfer
- 1 Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Fruit Crops, Pillnitzer Platz 3a, 01326 Dresden-Pillnitz, Germany
| | - Christoph Böttcher
- 2 Julius Kühn-Institut, Federal Research Centre for Cultivated Plants, Institute for Ecological Chemistry, Plant Analysis and Stored Product Protection, Königin-Luise-Str. 19, 14195 Berlin, Germany
| | - Thomas Wöhner
- 1 Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Fruit Crops, Pillnitzer Platz 3a, 01326 Dresden-Pillnitz, Germany
| | - Klaus Richter
- 3 Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, Institute for Resistance Research and Stress Tolerance, Erwin-Baur-Str. 27, 06484 Quedlinburg, Germany
| | - John Norelli
- 4 USDA-ARS, Appalachian Fruit Research Station, 2217 Wiltshire Road, Kearneysville, WV 25430, U.S.A.; and
| | - Erik H A Rikkerink
- 5 The New Zealand Institute for Plant and Food Research Limited, Auckland, New Zealand
| | - Magda-Viola Hanke
- 1 Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Fruit Crops, Pillnitzer Platz 3a, 01326 Dresden-Pillnitz, Germany
| | - Henryk Flachowsky
- 1 Julius Kühn-Institut (JKI), Federal Research Centre for Cultivated Plants, Institute for Breeding Research on Fruit Crops, Pillnitzer Platz 3a, 01326 Dresden-Pillnitz, Germany
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7
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Kunkel BN, Harper CP. The roles of auxin during interactions between bacterial plant pathogens and their hosts. JOURNAL OF EXPERIMENTAL BOTANY 2018; 69:245-254. [PMID: 29272462 DOI: 10.1093/jxb/erx447] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Plant pathogens have evolved several strategies to manipulate the biology of their hosts to facilitate colonization, growth to high levels in plant tissue, and production of disease. One of the less well known of these strategies is the synthesis of plant hormones and hormone analogs, and there is growing evidence that modulation of host hormone signaling is important during pathogenesis. Several plant pathogens produce the auxin indole-3-acetic acid (IAA) and/or virulence factors that modulate host auxin signaling. Auxin is well known for being involved in many aspects of plant growth and development, but recent findings have revealed that elevated IAA levels or enhanced auxin signaling can also promote disease development in some plant-pathogen interactions. In addition to stimulating plant cell growth during infection by gall-forming bacteria, auxin and auxin signaling can antagonize plant defense responses. Auxin can also act as a microbial signaling molecule to impact the biology of some pathogens directly. In this review, we summarize recent progress towards elucidating the roles that auxin production, modification of host auxin signaling, and direct effects of auxin on pathogens play during pathogenesis, with emphasis on the impacts of auxin on interactions with bacterial pathogens.
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Affiliation(s)
- Barbara N Kunkel
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
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8
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DRPPP: A machine learning based tool for prediction of disease resistance proteins in plants. Comput Biol Med 2016; 78:42-48. [DOI: 10.1016/j.compbiomed.2016.09.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 09/02/2016] [Accepted: 09/13/2016] [Indexed: 11/22/2022]
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9
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García-Sánchez S, Bernales I, Cristobal S. Early response to nanoparticles in the Arabidopsis transcriptome compromises plant defence and root-hair development through salicylic acid signalling. BMC Genomics 2015; 16:341. [PMID: 25903678 PMCID: PMC4417227 DOI: 10.1186/s12864-015-1530-4] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2014] [Accepted: 04/13/2015] [Indexed: 12/01/2022] Open
Abstract
Background The impact of nano-scaled materials on photosynthetic organisms needs to be evaluated. Plants represent the largest interface between the environment and biosphere, so understanding how nanoparticles affect them is especially relevant for environmental assessments. Nanotoxicology studies in plants allude to quantum size effects and other properties specific of the nano-stage to explain increased toxicity respect to bulk compounds. However, gene expression profiles after exposure to nanoparticles and other sources of environmental stress have not been compared and the impact on plant defence has not been analysed. Results Arabidopsis plants were exposed to TiO2-nanoparticles, Ag-nanoparticles, and multi-walled carbon nanotubes as well as different sources of biotic (microbial pathogens) or abiotic (saline, drought, or wounding) stresses. Changes in gene expression profiles and plant phenotypic responses were evaluated. Transcriptome analysis shows similarity of expression patterns for all plants exposed to nanoparticles and a low impact on gene expression compared to other stress inducers. Nanoparticle exposure repressed transcriptional responses to microbial pathogens, resulting in increased bacterial colonization during an experimental infection. Inhibition of root hair development and transcriptional patterns characteristic of phosphate starvation response were also observed. The exogenous addition of salicylic acid prevented some nano-specific transcriptional and phenotypic effects, including the reduction in root hair formation and the colonization of distal leaves by bacteria. Conclusions This study integrates the effect of nanoparticles on gene expression with plant responses to major sources of environmental stress and paves the way to remediate the impact of these potentially damaging compounds through hormonal priming. Electronic supplementary material The online version of this article (doi:10.1186/s12864-015-1530-4) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Susana García-Sánchez
- Department of Physiology, Faculty of Medicine and Dentistry, University of the Basque Country UPV/EHU, Leioa, Spain.
| | - Irantzu Bernales
- Gene Expression Unit, Genomics Facility of General Research Services (SGIker), Faculty of Science and Technology, University of the Basque Country UPV/EHU, Leioa, Spain.
| | - Susana Cristobal
- IKERBASQUE, Basque Country Foundation for Science. Department of Physiology, Faculty of Medicine and Dentistry, University of the Basque Country UPV/EHU, Leioa, Spain. .,Department of Clinical and Experimental Medicine, Health Science Faculty, Linköping University, Linköping, Sweden.
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10
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Zhao T, Rui L, Li J, Nishimura MT, Vogel JP, Liu N, Liu S, Zhao Y, Dangl JL, Tang D. A truncated NLR protein, TIR-NBS2, is required for activated defense responses in the exo70B1 mutant. PLoS Genet 2015; 11:e1004945. [PMID: 25617755 PMCID: PMC4305288 DOI: 10.1371/journal.pgen.1004945] [Citation(s) in RCA: 112] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 12/09/2014] [Indexed: 11/18/2022] Open
Abstract
During exocytosis, the evolutionarily conserved exocyst complex tethers Golgi-derived vesicles to the target plasma membrane, a critical function for secretory pathways. Here we show that exo70B1 loss-of-function mutants express activated defense responses upon infection and express enhanced resistance to fungal, oomycete and bacterial pathogens. In a screen for mutants that suppress exo70B1 resistance, we identified nine alleles of TIR-NBS2 (TN2), suggesting that loss-of-function of EXO70B1 leads to activation of this nucleotide binding domain and leucine-rich repeat-containing (NLR)-like disease resistance protein. This NLR-like protein is atypical because it lacks the LRR domain common in typical NLR receptors. In addition, we show that TN2 interacts with EXO70B1 in yeast and in planta. Our study thus provides a link between the exocyst complex and the function of a 'TIR-NBS only' immune receptor like protein. Our data are consistent with a speculative model wherein pathogen effectors could evolve to target EXO70B1 to manipulate plant secretion machinery. TN2 could monitor EXO70B1 integrity as part of an immune receptor complex.
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Affiliation(s)
- Ting Zhao
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Lu Rui
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Graduate School of Chinese Academy of Sciences, Beijing, China
| | - Juan Li
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Marc T. Nishimura
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, North Carolina, United States of America
| | - John P. Vogel
- Western Regional Research Center, United States Department of Agriculture, Agricultural Research Service, Albany, California, United States of America
| | - Na Liu
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Graduate School of Chinese Academy of Sciences, Beijing, China
| | - Simu Liu
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Graduate School of Chinese Academy of Sciences, Beijing, China
| | - Yaofei Zhao
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- Graduate School of Chinese Academy of Sciences, Beijing, China
| | - Jeffery L. Dangl
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, North Carolina, United States of America
| | - Dingzhong Tang
- The State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- * E-mail:
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11
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Howard BE, Hu Q, Babaoglu AC, Chandra M, Borghi M, Tan X, He L, Winter-Sederoff H, Gassmann W, Veronese P, Heber S. High-throughput RNA sequencing of pseudomonas-infected Arabidopsis reveals hidden transcriptome complexity and novel splice variants. PLoS One 2013; 8:e74183. [PMID: 24098335 PMCID: PMC3788074 DOI: 10.1371/journal.pone.0074183] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Accepted: 07/30/2013] [Indexed: 01/01/2023] Open
Abstract
We report the results of a genome-wide analysis of transcription in Arabidopsis thaliana after treatment with Pseudomonas syringae pathovar tomato. Our time course RNA-Seq experiment uses over 500 million read pairs to provide a detailed characterization of the response to infection in both susceptible and resistant hosts. The set of observed differentially expressed genes is consistent with previous studies, confirming and extending existing findings about genes likely to play an important role in the defense response to Pseudomonas syringae. The high coverage of the Arabidopsis transcriptome resulted in the discovery of a surprisingly large number of alternative splicing (AS) events--more than 44% of multi-exon genes showed evidence for novel AS in at least one of the probed conditions. This demonstrates that the Arabidopsis transcriptome annotation is still highly incomplete, and that AS events are more abundant than expected. To further refine our predictions, we identified genes with statistically significant changes in the ratios of alternative isoforms between treatments. This set includes several genes previously known to be alternatively spliced or expressed during the defense response, and it may serve as a pool of candidate genes for regulated alternative splicing with possible biological relevance for the defense response against invasive pathogens.
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Affiliation(s)
- Brian E. Howard
- Department of Computer Science, North Carolina State University, Raleigh, North Carolina, United States of America
- * E-mail:
| | - Qiwen Hu
- Department of Computer Science, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Ahmet Can Babaoglu
- Department of Computer Science, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Manan Chandra
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Monica Borghi
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Xiaoping Tan
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Luyan He
- Department of Plant Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Heike Winter-Sederoff
- Department of Plant Biology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Walter Gassmann
- Division of Plant Sciences, University of Missouri, Columbia, Missouri, United States of America
| | - Paola Veronese
- Department of Plant Pathology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Steffen Heber
- Department of Computer Science, North Carolina State University, Raleigh, North Carolina, United States of America
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12
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Cui F, Wu S, Sun W, Coaker G, Kunkel B, He P, Shan L. The Pseudomonas syringae type III effector AvrRpt2 promotes pathogen virulence via stimulating Arabidopsis auxin/indole acetic acid protein turnover. PLANT PHYSIOLOGY 2013; 162:1018-29. [PMID: 23632856 PMCID: PMC3668037 DOI: 10.1104/pp.113.219659] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 04/29/2013] [Indexed: 05/19/2023]
Abstract
To accomplish successful infection, pathogens deploy complex strategies to interfere with host defense systems and subvert host physiology to favor pathogen survival and multiplication. Modulation of plant auxin physiology and signaling is emerging as a common virulence strategy for phytobacteria to cause diseases. However, the underlying mechanisms remain largely elusive. We have previously shown that the Pseudomonas syringae type III effector AvrRpt2 alters Arabidopsis (Arabidopsis thaliana) auxin physiology. Here, we report that AvrRpt2 promotes auxin response by stimulating the turnover of auxin/indole acetic acid (Aux/IAA) proteins, the key negative regulators in auxin signaling. AvrRpt2 acts additively with auxin to stimulate Aux/IAA turnover, suggesting distinct, yet proteasome-dependent, mechanisms operated by AvrRpt2 and auxin to control Aux/IAA stability. Cysteine protease activity is required for AvrRpt2-stimulated auxin signaling and Aux/IAA degradation. Importantly, transgenic plants expressing the dominant axr2-1 mutation recalcitrant to AvrRpt2-mediated degradation ameliorated the virulence functions of AvrRpt2 but did not alter the avirulent function mediated by the corresponding RPS2 resistance protein. Thus, promoting auxin response via modulating the stability of the key transcription repressors Aux/IAA is a mechanism used by the bacterial type III effector AvrRpt2 to promote pathogenicity.
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Wide screening of phage-displayed libraries identifies immune targets in planta. PLoS One 2013; 8:e54654. [PMID: 23372747 PMCID: PMC3556032 DOI: 10.1371/journal.pone.0054654] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2012] [Accepted: 12/17/2012] [Indexed: 11/19/2022] Open
Abstract
Microbe-Associated Molecular Patterns and virulence effectors are recognized by plants as a first step to mount a defence response against potential pathogens. This recognition involves a large family of extracellular membrane receptors and other immune proteins located in different sub-cellular compartments. We have used phage-display technology to express and select for Arabidopsis proteins able to bind bacterial pathogens. To rapidly identify microbe-bound phage, we developed a monitoring method based on microarrays. This combined strategy allowed for a genome-wide screening of plant proteins involved in pathogen perception. Two phage libraries for high-throughput selection were constructed from cDNA of plants infected with Pseudomonas aeruginosa PA14, or from combined samples of the virulent isolate DC3000 of Pseudomonas syringae pv. tomato and its avirulent variant avrRpt2. These three pathosystems represent different degrees in the specificity of plant-microbe interactions. Libraries cover up to 2×107 different plant transcripts that can be displayed as functional proteins on the surface of T7 bacteriophage. A number of these were selected in a bio-panning assay for binding to Pseudomonas cells. Among the selected clones we isolated the ethylene response factor ATERF-1, which was able to bind the three bacterial strains in competition assays. ATERF-1 was rapidly exported from the nucleus upon infiltration of either alive or heat-killed Pseudomonas. Moreover, aterf-1 mutants exhibited enhanced susceptibility to infection. These findings suggest that ATERF-1 contains a microbe-recognition domain with a role in plant defence. To identify other putative pathogen-binding proteins on a genome-wide scale, the copy number of selected-vs.-total clones was compared by hybridizing phage cDNAs with Arabidopsis microarrays. Microarray analysis revealed a set of 472 candidates with significant fold change. Within this set defence-related genes, including well-known targets of bacterial effectors, are over-represented. Other genes non-previously related to defence can be associated through this study with general or strain-specific recognition of Pseudomonas.
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14
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Lee J, Teitzel GM, Munkvold K, del Pozo O, Martin GB, Michelmore RW, Greenberg JT. Type III secretion and effectors shape the survival and growth pattern of Pseudomonas syringae on leaf surfaces. PLANT PHYSIOLOGY 2012; 158:1803-18. [PMID: 22319072 PMCID: PMC3320187 DOI: 10.1104/pp.111.190686] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Accepted: 02/07/2012] [Indexed: 05/19/2023]
Abstract
The bacterium Pseudomonas syringae pv syringae B728a (PsyB728a) uses a type III secretion system (T3SS) to inject effector proteins into plant cells, a process that modulates the susceptibility of different plants to infection. Analysis of GREEN FLUORESCENT PROTEIN-expressing PsyB728a after spray inoculation without additives under moderate relative humidity conditions permitted (1) a detailed analysis of this strain's survival and growth pattern on host (Nicotiana benthamiana) and nonhost (tomato [Solanum lycopersicum]) leaf surfaces, (2) an assessment of the role of plant defenses in affecting PsyB728a leaf surface (epiphytic) growth, and (3) the contribution of the T3SS and specific effectors to PsyB728a epiphytic survival and growth. On host leaf surfaces, PsyB728a cells initially persist without growing, and show an increased population only after 48 h, unless plants are pretreated with the defense-inducing chemical benzothiazole. During the persistence period, some PsyB728a cells induce a T3SS reporter, whereas a T3SS-deficient mutant shows reduced survival. By 72 h, rare invasion by PsyB728a to the mesophyll region of host leaves occurs, but endophytic and epiphytic bacterial growths are not correlated. The effectors HopZ3 and HopAA1 delay the onset of epiphytic growth of PsyB728a on N. benthamiana, whereas they promote epiphytic survival/growth on tomato. These effectors localize to distinct sites in plant cells and likely have different mechanisms of action. HopZ3 may enzymatically modify host targets, as it requires residues important for the catalytic activity of other proteins in its family of proteases. Thus, the T3SS, HopAA1, HopZ3, and plant defenses strongly influence epiphytic survival and/or growth of PsyB728a.
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Affiliation(s)
| | | | | | | | | | | | - Jean T. Greenberg
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637 (J.L., G.M.T., J.T.G.); Boyce Thompson Institute for Plant Research, Ithaca, New York 14853 (K.M., O.d.P., G.B.M.); Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York 14853 (G.B.M.); The Genome Center, University of California, Davis, California 95616 (R.W.M.)
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15
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Wang Y, Nishimura MT, Zhao T, Tang D. ATG2, an autophagy-related protein, negatively affects powdery mildew resistance and mildew-induced cell death in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2011; 68:74-87. [PMID: 21645148 DOI: 10.1111/j.1365-313x.2011.04669.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The molecular interactions between Arabidopsis and the pathogenic powdery mildew Golovinomyces cichoracearum were studied by characterizing a disease-resistant Arabidopsis mutant atg2-2. The atg2-2 mutant showed enhanced resistance to powdery mildew and dramatic mildew-induced cell death as well as early senescence phenotypes in the absence of pathogens. Defense-related genes were constitutively activated in atg2-2. In atg2-2 mutants, spontaneous cell death, early senescence and disease resistance required the salicylic acid (SA) pathway, but interestingly, mildew-induced cell death was not fully suppressed by inactivation of SA signaling. Thus, cell death could be uncoupled from disease resistance, suggesting that cell death is not sufficient for resistance to powdery mildew. ATG2 encodes autophagy-related 2, a protein known to be involved in the early steps of autophagosome biogenesis. The atg2-2 mutant exhibited typical autophagy defects in autophagosome formation. Furthermore, mutations in several other ATG genes, including ATG5, ATG7 and ATG10, exhibited similar powdery mildew resistance and mildew-induced cell death phenotypes. Taken together, our findings provide insights into the role of autophagy in cell death and disease resistance, and may indicate general links between autophagy, senescence, programmed cell death and defense responses in plants.
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Affiliation(s)
- Yiping Wang
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
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16
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Champigny MJ, Shearer H, Mohammad A, Haines K, Neumann M, Thilmony R, He SY, Fobert P, Dengler N, Cameron RK. Localization of DIR1 at the tissue, cellular and subcellular levels during Systemic Acquired Resistance in Arabidopsis using DIR1:GUS and DIR1:EGFP reporters. BMC PLANT BIOLOGY 2011; 11:125. [PMID: 21896186 PMCID: PMC3180652 DOI: 10.1186/1471-2229-11-125] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 09/06/2011] [Indexed: 05/05/2023]
Abstract
BACKGROUND Systemic Acquired Resistance (SAR) is an induced resistance response to pathogens, characterized by the translocation of a long-distance signal from induced leaves to distant tissues to prime them for increased resistance to future infection. DEFECTIVE in INDUCED RESISTANCE 1 (DIR1) has been hypothesized to chaperone a small signaling molecule to distant tissues during SAR in Arabidopsis. RESULTS DIR1 promoter:DIR1-GUS/dir1-1 lines were constructed to examine DIR1 expression. DIR1 is expressed in seedlings, flowers and ubiquitously in untreated or mock-inoculated mature leaf cells, including phloem sieve elements and companion cells. Inoculation of leaves with SAR-inducing avirulent or virulent Pseudomonas syringae pv tomato (Pst) resulted in Type III Secretion System-dependent suppression of DIR1 expression in leaf cells. Transient expression of fluorescent fusion proteins in tobacco and intercellular washing fluid experiments indicated that DIR1's ER signal sequence targets it for secretion to the cell wall. However, DIR1 expressed without a signal sequence rescued the dir1-1 SAR defect, suggesting that a cytosolic pool of DIR1 is important for the SAR response. CONCLUSIONS Although expression of DIR1 decreases during SAR induction, the protein localizes to all living cell types of the vasculature, including companion cells and sieve elements, and therefore DIR1 is well situated to participate in long-distance signaling during SAR.
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Affiliation(s)
- Marc J Champigny
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1 Canada
- Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
| | - Heather Shearer
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1 Canada
- Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
| | - Asif Mohammad
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1 Canada
| | - Karen Haines
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1 Canada
| | - Melody Neumann
- Department of Cell and Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
| | - Roger Thilmony
- Department of Plant Biology, Michigan State University, East Lansing MI, 48824 USA
- USDA-ARS, Western Regional Research Center, Crop Improvement and Utilization Research Unit, 800 Buchanan St., Albany, CA, 94710 USA
| | - Sheng Yang He
- Department of Plant Biology, Michigan State University, East Lansing MI, 48824 USA
| | - Pierre Fobert
- Plant Biotechnology Institute, 110 Gymnasium Place, Saskatoon, SK S7N 0W9 Canada
| | - Nancy Dengler
- Department of Cell and Systems Biology, University of Toronto, 25 Willcocks Street, Toronto, ON, M5S 3B2, Canada
| | - Robin K Cameron
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1 Canada
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17
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Hou S, Yang Y, Wu D, Zhang C. Plant immunity: evolutionary insights from PBS1, Pto, and RIN4. PLANT SIGNALING & BEHAVIOR 2011; 6:794-9. [PMID: 21494098 PMCID: PMC3218475 DOI: 10.4161/psb.6.6.15143] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Two layers of plant immune systems are used by plants to defend against phytopathogens. The first layer is pathogen-associate molecular patterns (PAMPs)-triggered immunity (PTI), which is activated by plant cell-surface pattern recognition receptors (PRRs) upon perception of microbe general elicitors. The second layer is effector-triggered immunity (ETI), which is initiated by specific recognition of pathogen type III secreted effectors (T3SEs) with plant intracellular resistance (R) proteins. Current opinions agree that ETI was evolved from PTI, and the impetus for the evolution of plant immunity is pathogen T3SEs, which exhibit virulence functions through blocking PTI, but show avirulence functions for triggering ETI. A Decoy Model was put forward and explained that the avirulence targets of pathogen T3SEs were evolved as decoys to compete with the virulence targets for binding with pathogen T3SEs. However, little direct evidence for the evolutionary mode has been offered. Here, we reviewed the recent progresses about Pto, PBS1, and RIN4 to present our viewpoints about the evolution of plant immunity.
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Affiliation(s)
- Shuguo Hou
- School of Municipal and Environmental Engineering, Shandong Jianzhu University, Jinan, China.
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18
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Macho AP, Guevara CM, Tornero P, Ruiz-Albert J, Beuzón CR. The Pseudomonas syringae effector protein HopZ1a suppresses effector-triggered immunity. THE NEW PHYTOLOGIST 2010; 187:1018-1033. [PMID: 20636323 DOI: 10.1111/j.1469-8137.2010.03381.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
*The Pseudomonas syringae pv syringae type III effector HopZ1a is a member of the HopZ effector family of cysteine-proteases that triggers immunity in Arabidopsis. This immunity is dependent on HopZ1a cysteine-protease activity, and independent of known resistance genes. We have previously shown that HopZ1a-triggered immunity is partially additive to that triggered by AvrRpt2. These partially additive effects could be caused by at least two mechanisms: their signalling pathways share a common element(s), or one effector interferes with the response triggered by the other. *Here, we investigate the molecular basis for the partially additive effect displayed by AvrRpt2- and HopZ1a-triggered immunities, by analysing competitive indices, hypersensitive response and symptom induction, PR-1 accumulation, expression of PR genes, and systemic acquired resistance (SAR) induction. *Partially additive effects between these defence responses require HopZ1a cysteine-protease activity, and also take place between HopZ1a and AvrRps4 or AvrRpm1-triggered responses. We establish that HopZ1a-triggered immunity is independent of salicylic acid (SA), EDS1, jasmonic acid (JA) and ethylene (ET)-dependent pathways, and show that HopZ1a suppresses the induction of PR-1 and PR-5 associated with P. syringae pv tomato (Pto)-triggered effector-triggered immunity (ETI)-like defences, AvrRpt2-triggered immunity, and Pto or Pto (avrRpt2) activation of SAR, and that suppression requires HopZ1a cysteine-protease activity. *Our results indicate that HopZ1a triggers an unusual resistance independent of known pathways and suppresses SA and EDS1-dependent resistance.
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Affiliation(s)
- Alberto P Macho
- Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain
| | - Carlos M Guevara
- Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain
| | - Pablo Tornero
- Instituto de Biología Molecular y Celular de Plantas (Universidad Politécnica de Valencia - CSIC) Avda de los Naranjos s/n. Valencia E-46022, Spain
| | - Javier Ruiz-Albert
- Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain
| | - Carmen R Beuzón
- Instituto de Hortofruticultura Subtropical y Mediterranea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Depto Biología Celular, Genética y Fisiología, Campus de Teatinos, Málaga E-29071, Spain
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19
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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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20
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Uchida N, Tasaka M. Intersections between immune responses and morphological regulation in plants. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:2539-47. [PMID: 20457577 DOI: 10.1093/jxb/erq126] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Successful plant pathogens have developed strategies to interfere with the defence mechanisms of their host plants through evolution. Conversely, host plants have evolved systems to counteract pathogen attack. Some pathogens induce pathogenic symptoms on plants that include morphological changes in addition to interference with plant growth. Recent studies, based on molecular biology and genetics using Arabidopsis thaliana, have revealed that factors derived from pathogens can modulate host systems and/or host factors that play important roles in the morphological regulation of host plants. Other reports, meanwhile, have shown that factors known to have roles in plant morphology also function in plant immune responses. Evolutionary conservation of these factors and systems implies that host-pathogen interactions and the evolution they drive have yielded tight links between morphological processes and immune responses. In this review, recent findings about these topics are introduced and discussed.
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Affiliation(s)
- Naoyuki Uchida
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Japan.
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21
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Munkvold KR, Martin GB. Advances in experimental methods for the elucidation of Pseudomonas syringae effector function with a focus on AvrPtoB. MOLECULAR PLANT PATHOLOGY 2009; 10:777-93. [PMID: 19849784 PMCID: PMC2835503 DOI: 10.1111/j.1364-3703.2009.00586.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Pseudomonas syringae infects a wide range of plant species through the use of a type III secretion system. The effector proteins injected into the plant cell through this molecular syringe serve as promoters of disease by subverting the plant immune response to the benefit of the bacteria in the intercellular space. The targets and activities of a subset of effectors have been elucidated recently. In this article, we focus on the experimental approaches that have proved most successful in probing the molecular basis of effectors, ranging from loss-of-function to gain-of-function analyses utilizing several techniques for effector delivery into plants. In particular, we highlight how these diverse approaches have been applied to the study of one effector--AvrPtoB--a multifunctional protein with the ability to suppress both effector-triggered immunity and pathogen (or microbe)-associated molecular pattern-triggered immunity. Taken together, advances in this field illustrate the need for multiple experimental approaches when elucidating the function of a single effector.
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Affiliation(s)
- Kathy R Munkvold
- Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, USA
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22
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Athinuwat D, Prathuangwong S, Cursino L, Burr T. Xanthomonas axonopodis pv. glycines soybean cultivar virulence specificity is determined by avrBs3 homolog avrXg1. PHYTOPATHOLOGY 2009; 99:996-1004. [PMID: 19594319 DOI: 10.1094/phyto-99-8-0996] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Three races of Xanthomonas axonopodis pv. glycines were identified on pustule disease resistant and susceptible soybean cultivars based on virulence phenotype. For race 3, an avrBs3 homolog, avrXg1 was identified that conferred resistance expressed as a hypersensitive response on resistant cultivar Williams 82. Mutations in two predicted functional domains of avrXg1 resulted in gained virulence on Williams 82 and an increase in bacterial population number on susceptible cultivars. Expression of avrXg1 in race 1, that is predicted to confer a nonspecific HR, led to virulence on susceptible cultivars Spencer and PI 520733. Expression of avrXg1 in race 2, that is predicted of carrying avrBs3-like genes, resulted in gained virulence and fitness of pathogen on both resistant and susceptible cultivars. The results demonstrate multifunctions for avrXg1 dependent on pathogen and plant genetic backgrounds.
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Affiliation(s)
- Dusit Athinuwat
- Kasetsart University, Plant Pathology, Faculty of Agriculture, Bangkok, Thailand
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23
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Venugopal SC, Jeong RD, Mandal MK, Zhu S, Chandra-Shekara AC, Xia Y, Hersh M, Stromberg AJ, Navarre D, Kachroo A, Kachroo P. Enhanced disease susceptibility 1 and salicylic acid act redundantly to regulate resistance gene-mediated signaling. PLoS Genet 2009; 5:e1000545. [PMID: 19578402 PMCID: PMC2695777 DOI: 10.1371/journal.pgen.1000545] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Accepted: 06/01/2009] [Indexed: 11/19/2022] Open
Abstract
Resistance (R) protein-associated pathways are well known to participate in defense against a variety of microbial pathogens. Salicylic acid (SA) and its associated proteinaceous signaling components, including enhanced disease susceptibility 1 (EDS1), non-race-specific disease resistance 1 (NDR1), phytoalexin deficient 4 (PAD4), senescence associated gene 101 (SAG101), and EDS5, have been identified as components of resistance derived from many R proteins. Here, we show that EDS1 and SA fulfill redundant functions in defense signaling mediated by R proteins, which were thought to function independent of EDS1 and/or SA. Simultaneous mutations in EDS1 and the SA-synthesizing enzyme SID2 compromised hypersensitive response and/or resistance mediated by R proteins that contain coiled coil domains at their N-terminal ends. Furthermore, the expression of R genes and the associated defense signaling induced in response to a reduction in the level of oleic acid were also suppressed by compromising SA biosynthesis in the eds1 mutant background. The functional redundancy with SA was specific to EDS1. Results presented here redefine our understanding of the roles of EDS1 and SA in plant defense.
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Affiliation(s)
- Srivathsa C. Venugopal
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Rae-Dong Jeong
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Mihir K. Mandal
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Shifeng Zhu
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
| | - A. C. Chandra-Shekara
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Ye Xia
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Matthew Hersh
- Department of Statistics, University of Kentucky, Lexington, Kentucky, United States of America
| | - Arnold J. Stromberg
- Department of Statistics, University of Kentucky, Lexington, Kentucky, United States of America
| | - DuRoy Navarre
- United States Department of Agriculture–Agricultural Research Service, Washington State University, Prosser, Washington, United States of America
| | - Aardra Kachroo
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
| | - Pradeep Kachroo
- Department of Plant Pathology, University of Kentucky, Lexington, Kentucky, United States of America
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24
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Lewis JD, Guttman DS, Desveaux D. The targeting of plant cellular systems by injected type III effector proteins. Semin Cell Dev Biol 2009; 20:1055-63. [PMID: 19540926 DOI: 10.1016/j.semcdb.2009.06.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2009] [Revised: 06/11/2009] [Accepted: 06/12/2009] [Indexed: 01/05/2023]
Abstract
The battle between phytopathogenic bacteria and their plant hosts has revealed a diverse suite of strategies and mechanisms employed by the pathogen or the host to gain the higher ground. Pathogens continually evolve tactics to acquire host resources and dampen host defences. Hosts must evolve surveillance and defence systems that are sensitive enough to rapidly respond to a diverse range of pathogens, while reducing costly and damaging inappropriate misexpression. The primary virulence mechanism employed by many bacteria is the type III secretion system, which secretes and translocates effector proteins directly into the cells of their plant hosts. Effectors have diverse enzymatic functions and can target specific components of plant systems. While these effectors should favour bacterial fitness, the host may be able to thwart infection by recognizing the activity or presence of these foreign molecules and initiating retaliatory immune measures. We review the diverse host cellular systems exploited by bacterial effectors, with particular focus on plant proteins directly targeted by effectors. Effector-host interactions reveal different stages of the battle between pathogen and host, as well as the diverse molecular strategies employed by bacterial pathogens to hijack eukaryotic cellular systems.
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Affiliation(s)
- Jennifer D Lewis
- Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, ON M5S3B2, Canada
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25
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Sohn KH, Zhang Y, Jones JDG. The Pseudomonas syringae effector protein, AvrRPS4, requires in planta processing and the KRVY domain to function. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 57:1079-91. [PMID: 19054367 DOI: 10.1111/j.1365-313x.2008.03751.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
A Pseudomonas syringae pv. pisi effector protein, AvrRPS4, triggers RPS4-dependent immunity in Arabidopsis. We characterized biochemical and genetic aspects of AvrRPS4 function. Secretion of AvrRPS4 from Pst DC3000 is type III secretion-dependent, and AvrRPS4 is processed into a smaller form in plant cells but not in bacteria or yeast. Agrobacterium-mediated transient expression analysis of N-terminally truncated AvrRPS4 mutants revealed that the C-terminal 88 amino acids are sufficient to trigger the hypersensitive response in turnip. N-terminal sequencing of the processed AvrRPS4 showed that processing occurs between G133 and G134. The processing-deficient mutant, R112L, still triggers RPS4-dependent immunity, suggesting that the processing is not required for the AvrRPS4 avirulence function. AvrRPS4 enhances bacterial growth when delivered by Pta 6606 into Nicotiana benthamiana in which AvrRPS4 is not recognized. Transgenic expression of AvrRPS4 in the Arabidopsis rps4 mutant enhances the growth of Pst DC3000 and suppresses PTI (PAMP-triggered immunity), showing that AvrRPS4 promotes virulence in two distinct host plants. Furthermore, full virulence activity of AvrRPS4 requires both proteolytic processing and the KRVY motif at the N-terminus of processed AvrRPS4. XopO, an Xcv effector, shares the amino acids required for AvrRPS4 processing and the KRVY motif. XopO is also processed into a smaller form in N. benthamiana, similar to AvrRPS4, suggesting that a common mechanism is involved in activation of the virulence activities of both AvrRPS4 and XopO.
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Affiliation(s)
- Kee Hoon Sohn
- Sainsbury Laboratory, John Innes Centre, Colney Lane, Norwich, UK
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Macho AP, Ruiz-Albert J, Tornero P, Beuzón CR. Identification of new type III effectors and analysis of the plant response by competitive index. MOLECULAR PLANT PATHOLOGY 2009; 10:69-80. [PMID: 19161354 PMCID: PMC6640233 DOI: 10.1111/j.1364-3703.2008.00511.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
In recent years, many efforts have been directed towards the identification of new type III-secreted effectors, and the completion of the secretomes of several Pseudomonas syringae pathovars. Several functional and bioinformatic screenings have been used to search for candidates, which have been tested for translocation into the plant cell, an essential criterion for the identification of new type III effector proteins. The most common translocation assay is based on the use of DeltaAvrRpt2 as a reporter. When fused to a type III effector protein, DeltaAvrRpt2 is translocated and elicits a hypersensitive response in leaves of Arabidopsis thaliana expressing the RPS2 resistance protein. This approach has been used widely and has allowed the identification of a considerable number of new effectors in a fast and convenient manner. However, as the hypersensitive response is a semi-quantitative assay, and the conditions do not resemble those occurring in nature, effectors with low expression or translocation efficiency could fail to translocate sufficient DeltaAvrRpt2 to trigger a clear hypersensitive response. In keeping with these limitations, this test has failed to detect some true effectors that have been confirmed as such by other means. In order to increase the sensitivity of this method, we have developed a modification of the DeltaAvrRpt2-based translocation assay using a competitive index in mixed infection to monitor the limitation of growth associated with the induction of the hypersensitive response. We have tested several effector candidates from P. syringae pv. phaseolicola and other P. syringae pathovars, and have compared the results obtained by our competitive index translocation assay with those obtained by standard hypersensitive response assays. We have identified six type III secretion system-translocated proteins using this approach, five of which failed to be identified by hypersensitive response assays. In addition, we have analysed the defence response triggered by one of these effectors using competitive index assays.
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Affiliation(s)
- Alberto P Macho
- Departamento de Biología Celular, Genética y Fisiología, Area de Genética, Universidad de Málaga, Campus de Teatinos, Málaga E-29071, Spain
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Lewis JD, Abada W, Ma W, Guttman DS, Desveaux D. The HopZ family of Pseudomonas syringae type III effectors require myristoylation for virulence and avirulence functions in Arabidopsis thaliana. J Bacteriol 2008; 190:2880-91. [PMID: 18263728 PMCID: PMC2293245 DOI: 10.1128/jb.01702-07] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2007] [Accepted: 01/28/2008] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas syringae utilizes the type III secretion system to translocate effector proteins into plant cells, where they can contribute to the pathogen's ability to infect and cause disease. Recognition of these effectors by resistance proteins induces defense responses that typically include a programmed cell death reaction called the hypersensitive response. The YopJ/HopZ family of type III effector proteins is a common family of effector proteins found in animal- and plant-pathogenic bacteria. The HopZ family in P. syringae includes HopZ1a(PsyA2), HopZ1b(PgyUnB647), HopZ1c(PmaE54326), HopZ2(Ppi895A) and HopZ3(PsyB728a). HopZ1a is predicted to be most similar to the ancestral hopZ allele and causes a hypersensitive response in multiple plant species, including Arabidopsis thaliana. Therefore, it has been proposed that host defense responses have driven the diversification of this effector family. In this study, we further characterized the hypersensitive response induced by HopZ1a and demonstrated that it is not dependent on known resistance genes. Further, we identified a novel virulence function for HopZ2 that requires the catalytic cysteine demonstrated to be required for protease activity. Sequence analysis of the HopZ family revealed the presence of a predicted myristoylation sequence in all members except HopZ3. We demonstrated that the myristoylation site is required for membrane localization of this effector family and contributes to the virulence and avirulence activities of HopZ2 and HopZ1a, respectively. This paper provides insight into the selective pressures driving virulence protein evolution by describing a detailed functional characterization of the diverse HopZ family of type III effectors with the model plant Arabidopsis.
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Affiliation(s)
- Jennifer D Lewis
- Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario M5S 3B2, Canada
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28
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Pseudomonas syringae type III effector AvrRpt2 alters Arabidopsis thaliana auxin physiology. Proc Natl Acad Sci U S A 2007; 104:20131-6. [PMID: 18056646 DOI: 10.1073/pnas.0704901104] [Citation(s) in RCA: 223] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The Pseudomonas syringae type III effector AvrRpt2 promotes bacterial virulence on Arabidopsis thaliana plants lacking a functional RPS2 gene (rps2 mutant plants). To investigate the mechanisms underlying the virulence activity of AvrRpt2, we examined the phenotypes of transgenic A. thaliana rps2 seedlings constitutively expressing AvrRpt2. These seedlings exhibited phenotypes reminiscent of A. thaliana mutants with altered auxin physiology, including longer primary roots, increased number of lateral roots, and increased sensitivity to exogenous auxin. They also had increased levels of free indole acetic acid (IAA). The presence of AvrRpt2 also was correlated with a further increase in free IAA levels during infection with P. syringae pv. tomato strain DC3000 (PstDC3000). These results indicate that AvrRpt2 alters A. thaliana auxin physiology. Application of the auxin analog 1-naphthaleneacetic acid promoted disease symptom development in PstDC3000-infected plants, suggesting that elevated auxin levels within host tissue promote PstDC3000 virulence. Thus, AvrRpt2 may be among the virulence factors of P. syringae that modulate host auxin physiology to promote disease.
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Macho AP, Zumaquero A, Ortiz-Martín I, Beuzón CR. Competitive index in mixed infections: a sensitive and accurate assay for the genetic analysis of Pseudomonas syringae-plant interactions. MOLECULAR PLANT PATHOLOGY 2007; 8:437-50. [PMID: 20507512 DOI: 10.1111/j.1364-3703.2007.00404.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Mixed infections have been broadly applied to the study of bacterial pathogens in animals. However, the application of mixed infection-based methods in plant pathogens has been very limited. An important factor for this limitation is the different dynamics that mixed infections have been reported to show in the different types of models. Reports in systemic animal infections have shown that any bacterium has the same probability of multiplying within a mixed infection than in a single infection. However, in plant pathogens, bacterial growth in a mixed infection does not seem to reflect growth in a single infection, as growth interference takes place between the co-inoculated strains. Here we show that growth interference in mixed infection between different Pseudomonas syringae strains is not intrinsic to growth within a plant host, but dependent on the dose of inoculation. We also show that the minimal inoculation dose required to avoid interference depends on the aggressiveness of the pathogen as well as the type of virulence factor that differentiates the co-inoculated strains. This study establishes the basis for the use of mixed infection-based applications to the study of phytopathogenic bacteria. Analysis of the virulence of a type III effector mutant and an hrp regulatory mutant illustrate the increased accuracy and sensitivity of competitive index assays vs. regular growth assays. Several applications of this assay are addressed, and potential implications for this and other mixed infection-based methods are discussed.
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Affiliation(s)
- Alberto P Macho
- Departamento de Biología Celular, Genética y Fisiología, Area de Genética, Universidad de Málaga, Campus de Teatinos, Málaga E-29071, Spain
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Sugio A, Yang B, Zhu T, White FF. Two type III effector genes of Xanthomonas oryzae pv. oryzae control the induction of the host genes OsTFIIAgamma1 and OsTFX1 during bacterial blight of rice. Proc Natl Acad Sci U S A 2007; 104:10720-5. [PMID: 17563377 PMCID: PMC1965579 DOI: 10.1073/pnas.0701742104] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Xanthomonas oryzae pv. oryzae strain PXO99(A) induces the expression of the host gene Os8N3, which results in increased host susceptibility to bacterial blight of rice. Here, we show that PXO99(A) affects the expression of two additional genes in a type III secretion system-dependent manner, one encoding a bZIP transcription factor (OsTFX1) and the other the small subunit of the transcription factor IIA located on chromosome 1 (OsTFIIAgamma1). Induction of OsTFX1 and OsTFIIAgamma1 depended on the type III effector genes pthXo6 and pthXo7, respectively, both encoding two previously undescribed members of the transcription activator-like (TAL) effector family. pthXo7 is strain-specific and may reflect adaptation to the resistance mediated by xa5, an allele of OsTFIIAgamma5 encoding a second form of the TFIIA small subunit on chromosome 5 of rice. The loss of pthXo6 resulted in reduced pathogen virulence, and ectopic expression of OsTFX1 abrogated the requirement for pthXo6 for full virulence. X. oryzae pv. oryzae therefore modulates the expression of multiple host genes using multiple TAL effectors from a single strain, and evidence supports the hypothesis that expression of the associated host genes contributes to host susceptibility to disease.
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Affiliation(s)
- Akiko Sugio
- *Department of Plant Pathology, Kansas State University, Manhattan, KS 66506
- Department of Disease and Stress Biology, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, United Kingdom; and
| | - Bing Yang
- *Department of Plant Pathology, Kansas State University, Manhattan, KS 66506
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011
| | - Tong Zhu
- Syngenta Biotechnology, Inc., 3054 Cornwallis Road, Research Triangle Park, NC 27709
| | - Frank F. White
- *Department of Plant Pathology, Kansas State University, Manhattan, KS 66506
- To whom correspondence should be addressed. E-mail:
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Grant SR, Fisher EJ, Chang JH, Mole BM, Dangl JL. Subterfuge and manipulation: type III effector proteins of phytopathogenic bacteria. Annu Rev Microbiol 2006; 60:425-49. [PMID: 16753033 DOI: 10.1146/annurev.micro.60.080805.142251] [Citation(s) in RCA: 282] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Diverse gram-negative bacteria deliver effector proteins into the cells of their eukaryotic hosts using the type III secretion system. Collectively, these type III effector proteins function to optimize the host cell environment for bacterial growth. Type III effector proteins are essential for the virulence of Pseudomonas syringae, Xanthomonas spp., Ralstonia solanacearum and Erwinia species. Type III secretion systems are also found in nonpathogenic pseudomonads and in species of symbiotic nitrogen-fixing Rhizobium. We discuss the functions of type III effector proteins of plant-associated bacteria, with an emphasis on pathogens. Plant pathogens tend to carry diverse collections of type III effectors that likely share overlapping functions. Several effectors inhibit host defense responses. The eukaryotic host targets of only a few type III effector proteins are currently known. We also discuss possible mechanisms for diversification of the suite of type III effector proteins carried by a given bacterial strain.
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Affiliation(s)
- Sarah R Grant
- Department of Biology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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Koch M, Vorwerk S, Masur C, Sharifi-Sirchi G, Olivieri N, Schlaich NL. A role for a flavin-containing mono-oxygenase in resistance against microbial pathogens in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2006; 47:629-39. [PMID: 16856982 DOI: 10.1111/j.1365-313x.2006.02813.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Using activation tagging in the Arabidopsis Col-0 rps2-101C background, we identified a mutant (FMO1-3D) that showed virtually no symptoms after inoculation with virulent Pseudomonas syringae pv. tomato DC3000 bacteria. The dominant, gain-of-function phenotype of the FMO1-3D mutant is due to over-expression of a class 3 flavin-containing mono-oxygenase (FMO). We recapitulated the FMO1-3D mutant phenotype in independent transgenic Col-0 lines over-expressing the FMO1 cDNA under the control of the 35S CaMV promoter. The increased basal resistance observed in the FMO1-3D mutant was also effective against the taxonomically unrelated downy mildew-causing pathogen Hyaloperonospora parasitica. By investigating the progeny from crosses of the FMO1-3D mutant with the NahG transgenic line, we showed that the enhanced basal resistance phenotype was dependent on the accumulation of salicylic acid. FMO1-3D plants showed wild-type resistant reactions after inoculation with avirulent bacteria, indicating that the R-gene-mediated defence physiology was not compromised by FMO1 over-expression. Transcripts of the class 3 FMO1 gene accumulated within 6 h after inoculation of wild-type Col-0 plants with avirulent Pst + avrRpt2 cells. Moreover, a T-DNA insertion into the FMO1 gene resulted in enhanced susceptibility to virulent Pseudomonas and Hyaloperonospora parasitica, suggesting that expression of the FMO1 gene is a hitherto undescribed component of the plant's resistance repertoire. We discuss the possibility that the FMO may participate in the detoxification of virulence factors produced by pathogens.
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Affiliation(s)
- Martina Koch
- RWTH Aachen University, Institut Bio III Pflanzenphysiologie, 52056 Aachen, Germany
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Zhao Y, He SY, Sundin GW. The Erwinia amylovora avrRpt2EA gene contributes to virulence on pear and AvrRpt2EA is recognized by Arabidopsis RPS2 when expressed in pseudomonas syringae. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:644-54. [PMID: 16776298 DOI: 10.1094/mpmi-19-0644] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The enterobacterium Erwinia amylovora is a devastating plant pathogen causing necrotrophic fire blight disease of apple, pear, and other rosaceous plants. In an attempt to identify genes induced during infection of host plants, we identified and cloned a putative effector gene, avrRpt2EA. The deduced amino-acid sequence of the translated AvrRpt2EA protein is homologous to the effector protein AvrRpt2 previously reported in Pseudomonas syringae pv. tomato. These two proteins share 58% identity (70% similarity) in the functional domain; however, the secretion and translocation signal domain varied. The avrRpt2EA promoter region contains a typical 'hrp box,' which suggests that avrRpt2EA is regulated by the alternative sigma factor, HrpL. avrRpt2EA was detected in all E. amylovora strains tested but not in other closely related Erwinia species. An avrRpt2EA deletion mutant was reduced in its ability to cause systemic infection on immature pear fruits as compared with the wild-type strain, indicating that avrRpt2EA acts as a virulence factor on its native host. Growth of P. syringae pv. tomato DC3000 expressing avrRpt2EA was 10-fold higher than that of P. syringae pv. tomato DC3000 in an Arabidopsis rps2 mutant, indicating that avrRpt2EA promotes virulence of P. syringae pv. tomato DC3000 on Arabidopsis similar to P. syringae pv. tomato avrRpt2. When avrRpt2EA was expressed in P. syringae pv. tomato DC3000 in its native form, a weak hypersensitive response (HR) was induced in Arabidopsis; however, a hybrid protein containing the P. syringae pv. tomato avrRpt2 signal sequence, when expressed from the P syringae pv. tomato avrRpt2 promoter, caused a strong HR. Thus, the signal sequence and promoter of avrRpt2EA may affect its expression, secretion, or translocation, singly or in combination, in P. syringae pv. tomato DC3000. These results indicated that avrRpt2EA is genetically recognized by the RPS2 disease resistance gene in Arabidopsis when expressed in P. syringae pv. tomato DC3000. The results also suggested that although distinct pathogens such as E. amylovora and P. syringae may contain similar effector genes, expression and secretion of these effectors can be under specific regulation by the native pathogen.
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Affiliation(s)
- Youfu Zhao
- Department of Plant Pathology, 103 Center for Integrated Plant Systems, Michigan State University, East Lansing, MI 48824, USA
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Vernick KD, Oduol F, Lazzaro BP, Glazebrook J, Xu J, Riehle M, Li J. Molecular genetics of mosquito resistance to malaria parasites. Curr Top Microbiol Immunol 2006; 295:383-415. [PMID: 16265899 DOI: 10.1007/3-540-29088-5_15] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Malaria parasites are transmitted by the bite of an infected mosquito, but even efficient vector species possess multiple mechanisms that together destroy most of the parasites present in an infection. Variation between individual mosquitoes has allowed genetic analysis and mapping of loci controlling several resistance traits, and the underlying mechanisms of mosquito response to infection are being described using genomic tools such as transcriptional and proteomic analysis. Malaria infection imposes fitness costs on the vector, but various forms of resistance inflict their own costs, likely leading to an evolutionary tradeoff between infection and resistance. Plasmodium development can be successfully completed onlyin compatible mosquito-parasite species combinations, and resistance also appears to have parasite specificity. Studies of Drosophila, where genetic variation in immunocompetence is pervasive in wild populations, offer a comparative context for understanding coevolution of the mosquito-malaria relationship. More broadly, plants also possess systems of pathogen resistance with features that are structurally conserved in animal innate immunity, including insects, and genomic datasets now permit useful comparisons of resistance models even between such diverse organisms.
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Affiliation(s)
- K D Vernick
- Department of Microbiology, Center for Microbial and Plant Genomics, University of Minnesota, 1500 Gortner Avenue, St. Paul, MN 55108, USA.
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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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Gürlebeck D, Thieme F, Bonas U. Type III effector proteins from the plant pathogen Xanthomonas and their role in the interaction with the host plant. JOURNAL OF PLANT PHYSIOLOGY 2006; 163:233-55. [PMID: 16386329 DOI: 10.1016/j.jplph.2005.11.011] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2005] [Accepted: 11/15/2005] [Indexed: 05/05/2023]
Abstract
Pathogenicity of Xanthomonas campestris pathovar (pv.) vesicatoria and most other Gram-negative bacterial plant pathogens largely depends on a type III secretion (TTS) system which is encoded by hypersensitive response and pathogenicity (hrp) genes. These genes are induced in the plant and are essential for the bacterium to be virulent in susceptible hosts and for the induction of the hypersensitive response (HR) in resistant host and non-host plants. The TTS machinery secretes proteins into the extracellular milieu and effector proteins into the plant cell cytosol. In the plant, the effectors presumably interfere with cellular processes to the benefit of the pathogen or have an avirulence activity that betrays the bacterium to the plant surveillance system. Type III effectors were identified by their avirulence activity, co-regulation with the TTS system and homology to known effectors. A number of effector proteins are members of families, e.g., the AvrBs3 family in Xanthomonas. AvrBs3 localizes to the nucleus of the plant cell where it modulates plant gene expression. Another family that is also present in Xanthomonas is the YopJ/AvrRxv family. The latter proteins appear to act as SUMO cysteine proteases in the host. Here, we will present an overview about the regulation of the TTS system and its substrates and discuss the function of the AvrRxv and AvrBs3 family members in more detail.
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Affiliation(s)
- Doreen Gürlebeck
- Institute of Genetics, Martin-Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle, Germany.
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Meng X, Bonasera JM, Kim JF, Nissinen RM, Beer SV. Apple proteins that interact with DspA/E, a pathogenicity effector of Erwinia amylovora, the fire blight pathogen. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:53-61. [PMID: 16404953 DOI: 10.1094/mpmi-19-0053] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The disease-specific (dsp) gene dspA/E of Erwinia amylovora encodes an essential pathogenicity effector of 198 kDa, which is critical to the development of the devastating plant disease fire blight. A yeast two-hybrid assay and in vitro protein pull-down assay demonstrated that DspA/E interacts physically and specifically with four similar putative leucine-rich repeat (LRR) receptor-like serine/threonine kinases (RLK) from apple, an important host of E. amylovora. The genes encoding these four DspA/E-interacting proteins of Malus xdomestica (DIPM1 to 4) are conserved in all genera of hosts of E. amylovora tested. They also are conserved in all cultivars of apple tested that range in susceptibility to fire blight from highly susceptible to highly resistant. The four DIPMs have been characterized, and they are expressed constitutively in host plants. In silico analysis indicated that the DIPMs have similar sequence structure and resemble LRR RLKs from other organisms. Evidence is presented for direct physical interaction between DspA/E and the apple proteins encoded by the four identified clones, which may act as susceptibility factors and be essential to disease development. Knowledge of DIPMs and the interaction with DspA/E thus may facilitate understanding of fire blight development and lead to new approaches to control of disease.
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Affiliation(s)
- Xiangdong Meng
- Department of Plant Pathology, Cornell University, Ithaca, NY 14853, USA
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Schornack S, Peter K, Bonas U, Lahaye T. Expression levels of avrBs3-like genes affect recognition specificity in tomato Bs4- but not in pepper Bs3-mediated perception. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:1215-25. [PMID: 16353556 DOI: 10.1094/mpmi-18-1215] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The tomato Bs4 disease resistance gene mediates recognition of avrBs4-expressing strains of the bacterial spot pathogen Xanthomonas campestris pv. vesicatoria to give a hypersensitive response (HR). Here, we present the characterization of the Bs4 promoter and its application for low-level expression of bacterial type III effector proteins in planta. Real-time polymerase chain reaction showed that Bs4 is constitutively expressed at low levels and that transcript abundance does not change significantly upon infection with avrBs4-containing xanthomonads. A 302-bp promoter fragment was found to be sufficient to promote Bs4 gene function. Previous studies have shown that high, constitutive in planta expression of avrBs3 (AvrBs3 and AvrBs4 proteins are 96.6% identical) via the Cauliflower mosaic virus 35S (35S) promoter triggers a Bs4-dependent HR whereas X. campestris pv. vesicatoria-mediated delivery of AvrBs3 into the plant cytoplasm does not. Here, we demonstrate that, when expressed under control of the weak Bs4 promoter, avrBs3 does not trigger a Bs4-dependent HR whereas avrBs4 does. In contrast, the pepper Bs3 gene, which mediates recognition of AvrBs3- but not AvrBs4-delivering xanthomonads, retains its recognition specificity even if avrBs4 was expressed in planta from the strong 35S promoter. Importantly, Bs4 promoter-driven expression of hax3, hax4 (two recently isolated avrBs3-like genes), avrBs3, and avrBs4 resulted in identical reactions as observed upon infection with X. campestris pv. vesicatoria strains that express the respective avr gene, suggesting that the protein levels expressed under control of the Bs4 promoter are similar to those that are translocated by the bacterial type III secretion system.
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Li X, Lin H, Zhang W, Zou Y, Zhang J, Tang X, Zhou JM. Flagellin induces innate immunity in nonhost interactions that is suppressed by Pseudomonas syringae effectors. Proc Natl Acad Sci U S A 2005; 102:12990-5. [PMID: 16123135 PMCID: PMC1200263 DOI: 10.1073/pnas.0502425102] [Citation(s) in RCA: 197] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Arabidopsis NONHOST1 (NHO1) is required for limiting the in planta growth of nonhost Pseudomonas bacteria but completely ineffective against the virulent bacterium Pseudomonas syringae pv. tomato DC3000. However, the molecular basis underlying this observation remains unknown. Here we show that NHO1 is transcriptionally activated by flagellin. The nonhost bacterium P. syringae pv. tabaci lacking flagellin is unable to induce NHO1, multiplies much better than does the wild-type bacterium, and causes disease symptoms on Arabidopsis. DC3000 also possesses flagellin that is potent in NHO1 induction, but this induction is rapidly suppressed by DC3000 in a type III secretion system-dependent manner. Direct expression of DC3000 effectors in protoplasts indicated that at least nine effectors, HopS1, HopAI1, HopAF1, HopT1-1, HopT1-2, HopAA1-1, HopF2, HopC1, and AvrPto, are capable of suppressing the flagellin-induced NHO1 expression. One of the effectors, HopAI1, is conserved in both animal and plant bacteria. When expressed in transgenic Arabidopsis plants, HopAI1 promotes growth of the nonpathogenic hrpL- mutant bacteria. In addition, the purified phytotoxin coronatine, a known virulence factor of P. syringae, suppresses the flagellin-induced NHO1 transcription. These results demonstrate that flagellin-induced defenses play an important role in nonhost resistance. A remarkable number of DC3000 virulence factors act in the plant cell by suppressing the species level defenses, and that contributes to the specialization of DC3000 on Arabidopsis.
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Affiliation(s)
- Xinyan Li
- National Institute of Biological Sciences, Beijing 102206, China
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Kover PX, Wolf JB, Kunkel BN, Cheverud JM. Genetic architecture of Arabidopsis thaliana response to infection by Pseudomonas syringae. Heredity (Edinb) 2005; 94:507-17. [PMID: 15770233 DOI: 10.1038/sj.hdy.6800651] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Plant pathogens can severely reduce host yield and fitness. Thus, investigating the genetic basis of plant response to pathogens is important to further understand plant-pathogen coevolution and to improve crop production. The interaction between Arabidopsis thaliana and Pseudomonas syringae is an important model for studying the genetic basis of plant-pathogen interactions. Studies in this model have led to the discovery of many genes that differentiate a resistant from a susceptible plant. However, little is known about the genetic basis of quantitative variation in response to P. syringae. In this study, we investigate the genetic basis of three aspects of A. thaliana's response to P. syringae: symptom severity, bacterial population size and fruit production using a quantitative trait loci (QTL) analysis. We found two QTL for symptom severity and two for fruit production (possible candidate genes for observed QTL are discussed). We also found significant two-locus epistatic effect on symptom severity and fruit production. Although bacterial population size and symptom severity were strongly phenotypically correlated, we did not detect any QTL for bacterial population size. Despite the detected genetic variation observed for susceptibility, we found only a weak overall relationship between susceptibility traits and fitness, suggesting that these traits may not respond to selection.
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Affiliation(s)
- P X Kover
- School of Biological Sciences, University of Manchester, Stopford Building 3.614, Oxford Road, Manchester M13 9PT, UK.
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Lim MTS, Kunkel BN. The Pseudomonas syringae avrRpt2 gene contributes to virulence on tomato. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2005; 18:626-33. [PMID: 16042008 DOI: 10.1094/mpmi-18-0626] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In order to cause disease on plants, gram-negative phytopathogenic bacteria introduce numerous virulence factors into the host cell in order to render host tissue more hospitable for pathogen proliferation. The mode of action of such bacterial virulence factors and their interaction with host defense pathways remain poorly understood. avrRpt2, a gene from Pseudomonas syringae pv. tomato JL1065, has been shown to promote the virulence of heterologous P. syringae strains on Arabidopsis thaliana. However, the contribution of avrRpt2 to the virulence of JL1065 has not been examined previously. We show that a mutant derivative of JL1065 that carries a disruption in avrRpt2 is impaired in its ability to cause disease on tomato (Lycopersicon esculentum), indicating that avrRpt2 also acts as a virulence gene in its native strain on a natural host. The virulence activity of avrRpt2 was detectable on tomato lines that are defective in either ethylene perception or the accumulation of salicylic acid, but could not be detected on a tomato mutant insensitive to jasmonic acid. The enhanced virulence conferred by the expression of avrRpt2 in JL1065 was not associated with the suppression of several defense-related genes induced during the infection of tomato.
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Affiliation(s)
- Melisa T S Lim
- Department of Biology, Washington University, St Louis, MO 63130, USA
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Kim MG, da Cunha L, McFall AJ, Belkhadir Y, DebRoy S, Dangl JL, Mackey D. Two Pseudomonas syringae Type III Effectors Inhibit RIN4-Regulated Basal Defense in Arabidopsis. Cell 2005; 121:749-59. [PMID: 15935761 DOI: 10.1016/j.cell.2005.03.025] [Citation(s) in RCA: 321] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2004] [Revised: 09/09/2004] [Accepted: 03/18/2005] [Indexed: 12/30/2022]
Abstract
Plant cells have two defense systems that detect bacterial pathogens. One is a basal defense system that recognizes complex pathogen-associated molecular patterns (PAMPs). A second system uses disease-resistance (R) proteins to recognize type lll effector proteins that are delivered into the plant cell by the pathogen's type III secretion system. Here we show that these two pathways are linked. We find that two Pseudomonas syringae type III effectors, AvrRpt2 and AvrRpm1, inhibit PAMP-induced signaling and thus compromise the host's basal defense system. RIN4 is an Arabidopsis protein targeted by AvrRpt2 and AvrRpm1 for degradation and phosphorylation, respectively. We find that RIN4 is itself a regulator of PAMP signaling. The R proteins, RPS2 and RPM1, sense type III effector-induced perturbations of RIN4. Thus, R proteins guard the plant against type III effectors that inhibit PAMP signaling and provide a mechanistic link between the two plant defense systems.
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Affiliation(s)
- Min Gab Kim
- Department of Plant Cellular and Molecular Biology, Program in Molecular Cellular and Developmental Biology, The Ohio State University, Columbus, Ohio 43210, USA
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Singer AU, Desveaux D, Betts L, Chang JH, Nimchuk Z, Grant SR, Dangl JL, Sondek J. Crystal structures of the type III effector protein AvrPphF and its chaperone reveal residues required for plant pathogenesis. Structure 2005; 12:1669-81. [PMID: 15341731 DOI: 10.1016/j.str.2004.06.023] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2004] [Revised: 06/17/2004] [Accepted: 06/24/2004] [Indexed: 12/31/2022]
Abstract
The avrPphF locus from Pseudomonas syringae pv. phaseolicola, the causative agent of bean halo-blight disease, encodes proteins which either enhance virulence on susceptible hosts or elicit defense responses on hosts carrying the R1 resistance gene. Here we present the crystal structures of the two proteins from the avrPphF operon. The structure of AvrPphF ORF1 is strikingly reminiscent of type III chaperones from bacterial pathogens of animals, indicating structural conservation of these specialized chaperones, despite high sequence divergence. The AvrPphF ORF2 effector adopts a novel "mushroom"-like structure containing "head" and "stalk" subdomains. The head subdomain possesses limited structural homology to the catalytic domain of bacterial ADP-ribosyltransferases (ADP-RTs), though no ADP-RT activity was detected for AvrPphF ORF2 in standard assays. Nonetheless, this structural similarity identified two clusters of conserved surface-exposed residues important for both virulence mediated by AvrPphF ORF2 and recognition of this effector by bean plants expressing the R1 resistance gene.
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Affiliation(s)
- Alex U Singer
- Department of Pharmacology, University of North Carolina at Chapel Hill, 27599, USA
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Oguiza JA, Asensio AC. The VirPphA/AvrPtoB family of type III effectors in Pseudomonas syringae. Res Microbiol 2005; 156:298-303. [PMID: 15808932 DOI: 10.1016/j.resmic.2004.10.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Accepted: 10/26/2004] [Indexed: 01/22/2023]
Abstract
The VirPphA/AvrPtoB family of type III effector proteins from the phytopathogenic bacterium Pseudomonas syringae is one of the models providing insights into the molecular mechanisms conferring plant disease resistance and pathogenesis. In this review we summarize recent advances concerning the VirPphA/AvrPtoB family of effectors involved in the elicitation and suppression of plant defense responses.
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Affiliation(s)
- José A Oguiza
- Departamento de Producción Agraria, Universidad Pública de Navarra, 31006 Pamplona, Spain.
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Metz M, Dahlbeck D, Morales CQ, Al Sady B, Clark ET, Staskawicz BJ. The conserved Xanthomonas campestris pv. vesicatoria effector protein XopX is a virulence factor and suppresses host defense in Nicotiana benthamiana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2005; 41:801-14. [PMID: 15743446 DOI: 10.1111/j.1365-313x.2005.02338.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Nicotiana benthamiana leaves display a visible plant cell death response when infiltrated with a high titer inoculum of the non-host pathogen, Xanthomonas campestris pv. vesicatoria (Xcv). This visual phenotype was used to identify overlapping cosmid clones from a genomic cosmid library constructed from the Xcv strain, GM98-38. Individual cosmid clones from the Xcv library were conjugated into X. campestris pv. campestris (Xcc) and exconjugants were scored for an altered visual high titer inoculation response in N. benthamiana. The molecular characterization of the cosmid clones revealed that they contained a novel gene, xopX, that encodes a 74-kDa type III secretion system (TTSS) effector protein. Agrobacterium-mediated transient expression of XopX in N. benthamiana did not elicit the plant cell death response although detectable XopX protein was produced. Interestingly, the plant cell death response occurred when the xopX Agrobacterium-mediated transient expression construct was co-inoculated with strains of either XcvDeltaxopX or Xcc, both lacking xopX. The co-inoculation complementation of the plant cell death response also depends on whether the Xanthomonas strains contain an active TTSS. Transgenic 35S-xopX-expressing N. benthamiana plants also have the visible plant cell death response when inoculated with the non-xopX-expressing strains XcvDeltaxopX and Xcc. Unexpectedly, transgenic 35S-xopX N. benthamiana plants displayed enhanced susceptibility to bacterial growth of Xcc as well as other non-xopX-expressing Xanthomonas and Pseudomonas strains. This result is also consistent with the increase in bacterial growth on wild type N. benthamiana plants observed for Xcc when XopX is expressed in trans. Furthermore, XopX contributes to the virulence of Xcv on host pepper (Capsicum annuum) and tomato (Lycopersicum esculentum) plants. We propose that the XopX bacterial effector protein targets basic innate immunity in plants, resulting in enhanced plant disease susceptibility.
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Affiliation(s)
- Matthew Metz
- Department of Plant and Microbial Biology, 111 Koshland Hall, University of California, Berkeley, CA 94720-3102, USA
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Chisholm ST, Dahlbeck D, Krishnamurthy N, Day B, Sjolander K, Staskawicz BJ. Molecular characterization of proteolytic cleavage sites of the Pseudomonas syringae effector AvrRpt2. Proc Natl Acad Sci U S A 2005; 102:2087-92. [PMID: 15684089 PMCID: PMC548309 DOI: 10.1073/pnas.0409468102] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
During infection of Arabidopsis thaliana, the bacterium Pseudomonas syringae pv tomato delivers the effector protein AvrRpt2 into the plant cell cytosol. Within the plant cell, AvrRpt2 undergoes N-terminal processing and causes elimination of Arabidopsis RIN4. Previous work established that AvrRpt2 is a putative cysteine protease, and AvrRpt2 processing and RIN4 elimination require an intact predicted catalytic triad in that AvrRpt2. In this work, proteolytic events that depend on AvrRpt2 activity were characterized. The amino acid sequence surrounding the processing site of AvrRpt2 and two related sequences from RIN4 triggered Avr-Rpt2-dependent proteolytic cleavage of a synthetic substrate, demonstrating that these sequences are cleavage recognition sites for AvrRpt2 activity. Processing-deficient AvrRpt2 mutants were identified and shown to retain their ability to eliminate wild-type RIN4. Single amino acid substitutions were made in each of the two RIN4 cleavage sites, and mutation of both sites resulted in cleavage-resistant RIN4. Growth of Pseudomonas expressing AvrRpt2 was significantly higher than catalytically inactive mutants on Arabidopsis rin4/rps2 mutant plants, suggesting there are additional protein targets of AvrRpt2 that account for the virulence activity of this effector. Bioinformatics analysis identified putative Arabidopsis proteins containing sequences similar to the proteolytic cleavage sites conserved in AvrRpt2 and RIN4. Several of these proteins were eliminated in an AvrRpt2-dependent manner in a transient in planta expression system. These results identify amino acids important for AvrRpt2 substrate recognition and cleavage as well as demonstrate AvrRpt2 protease activity eliminates multiple Arabidopsis proteins in a transient expression system.
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Affiliation(s)
- Stephen T Chisholm
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA
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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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Lim MTS, Kunkel BN. The Pseudomonas syringae type III effector AvrRpt2 promotes virulence independently of RIN4, a predicted virulence target in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2004; 40:790-798. [PMID: 15546361 DOI: 10.1111/j.1365-313x.2004.02251.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
AvrRpt2, an effector protein from Pseudomonas syringae pv. tomato (Pst), behaves as an avirulence factor that activates resistance in Arabidopsis thaliana lines expressing the resistance gene RPS2. AvrRpt2 can also enhance pathogen fitness by promoting the ability of the bacteria to grow and to cause disease on susceptible lines of A. thaliana that lack functional RPS2. The activation of RPS2 is coupled to the AvrRpt2-induced disappearance of the A. thaliana RIN4 protein. However, the significance of this RIN4 elimination to AvrRpt2 virulence function is unresolved. To clarify our understanding of the contribution of RIN4 disappearance to AvrRpt2 virulence function, we generated new avrRpt2 alleles by random mutagenesis. We show that the ability of six novel AvrRpt2 mutants to induce RIN4 disappearance correlated well with their avirulence activities but not with their virulence activities. Moreover, the virulence activity of wild-type AvrRpt2 was detectable in an A. thaliana line lacking RIN4. Collectively, these results indicate that the virulence activity of AvrRpt2 in A. thaliana is likely to rely on the modification of host susceptibility factors other than, or in addition to, RIN4.
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Affiliation(s)
- Melisa T S Lim
- Department of Biology, Washington University, 1 Brookings Drive, St Louis, MO 63130, USA
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Abstract
Plant pathogens deliver a variety of virulence factors to host cells to suppress basal defence responses and create suitable environments for their propagation. Plants have in turn evolved disease resistance genes whose products detect the virulence factors as a signal of invasion and activate effective defence responses. Understanding how a virulence effector contributes to virulence on susceptible hosts but becomes an avirulence factor that triggers defence responses on resistance hosts has been a major focus in plant research. Recent studies have shown that a growing list of pathogen-encoded effectors functions as proteases that are secreted into plant cells to modify host proteins. In addition, several plant proteases have been found to function in activation of the defence mechanism. These findings reveal that post-translational modification of host proteins through proteolytic processing is a widely used mechanism in regulating the plant defence response.
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Affiliation(s)
- Yiji Xia
- Donald Danforth Plant Science Center, 975 N Warson Road, St. Louis, MO 63132, USA.
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