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Zhang Y, Li D, Zhang H, Hong Y, Huang L, Liu S, Li X, Ouyang Z, Song F. Tomato histone H2B monoubiquitination enzymes SlHUB1 and SlHUB2 contribute to disease resistance against Botrytis cinerea through modulating the balance between SA- and JA/ET-mediated signaling pathways. BMC PLANT BIOLOGY 2015; 15:252. [PMID: 26490733 PMCID: PMC4618151 DOI: 10.1186/s12870-015-0614-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2015] [Accepted: 09/13/2015] [Indexed: 05/17/2023]
Abstract
BACKGROUND Histone H2B monoubiquitination pathway has been shown to play critical roles in regulating growth/development and stress response in Arabidopsis. In the present study, we explored the involvement of the tomato histone H2B monoubiquitination pathway in defense response against Botrytis cinerea by functional analysis of SlHUB1 and SlHUB2, orthologues of the Arabidopsis AtHUB1/AtHUB2. METHODS We used the TRV-based gene silencing system to knockdown the expression levels of SlHUB1 or SlHUB2 in tomato plants and compared the phenotype between the silenced and the control plants after infection with B. cinerea and Pseudomonas syringae pv. tomato (Pst) DC3000. Biochemical and interaction properties of proteins were examined using in vitro histone monoubiquitination and yeast two-hybrid assays, respectively. The transcript levels of genes were analyzed by quantitative real time PCR (qRT-PCR). RESULTS The tomato SlHUB1 and SlHUB2 had H2B monoubiquitination E3 ligases activity in vitro and expression of SlHUB1 and SlHUB2 was induced by infection of B. cinerea and Pst DC3000 and by treatment with salicylic acid (SA) and 1-amino cyclopropane-1-carboxylic acid (ACC). Silencing of either SlHUB1 or SlHUB2 in tomato plants showed increased susceptibility to B. cinerea, whereas silencing of SlHUB1 resulted in increased resistance against Pst DC3000. SlMED21, a Mediator complex subunit, interacted with SlHUB1 but silencing of SlMED21 did not affect the disease resistance to B. cinerea and Pst DC3000. The SlHUB1- and SlHUB2-silenced plants had thinner cell wall but increased accumulation of reactive oxygen species (ROS), increased callose deposition and exhibited altered expression of the genes involved in phenylpropanoid pathway and in ROS generation and scavenging system. Expression of genes in the SA-mediated signaling pathway was significantly upregulated, whereas expression of genes in the jasmonic acid (JA)/ethylene (ET)-mediated signaling pathway were markedly decreased in SlHUB1- and SlHUB2-silenced plants after infection of B. cinerea. CONCLUSION VIGS-based functional analyses demonstrate that both SlHUB1 and SlHUB2 contribute to resistance against B. cinerea most likely through modulating the balance between the SA- and JA/ET-mediated signaling pathways.
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Affiliation(s)
- Yafen Zhang
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
| | - Dayong Li
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
| | - Huijuan Zhang
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
| | - Yongbo Hong
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
| | - Lei Huang
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
| | - Shixia Liu
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
| | - Xiaohui Li
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
| | - Zhigang Ouyang
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
| | - Fengming Song
- National Key Laboratory for Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, 310058, China.
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Anderson RG, Deb D, Fedkenheuer K, McDowell JM. Recent Progress in RXLR Effector Research. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:1063-72. [PMID: 26125490 DOI: 10.1094/mpmi-01-15-0022-cr] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Some of the most devastating oomycete pathogens deploy effector proteins, with the signature amino acid motif RXLR, that enter plant cells to promote virulence. Research on the function and evolution of RXLR effectors has been very active over the decade that has transpired since their discovery. Comparative genomics indicate that RXLR genes play a major role in virulence for Phytophthora and downy mildew species. Importantly, gene-for-gene resistance against these oomycete lineages is based on recognition of RXLR proteins. Comparative genomics have revealed several mechanisms through which this resistance can be broken, most notably involving epigenetic control of RXLR gene expression. Structural studies have revealed a core fold that is present in the majority of RXLR proteins, providing a foundation for detailed mechanistic understanding of virulence and avirulence functions. Finally, functional studies have demonstrated that suppression of host immunity is a major function for RXLR proteins. Host protein targets are being identified in a variety of plant cell compartments. Some targets comprise hubs that are also manipulated by bacteria and fungi, thereby revealing key points of vulnerability in the plant immune network.
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Affiliation(s)
- Ryan G Anderson
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Blacksburg, VA, U.S.A
| | - Devdutta Deb
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Blacksburg, VA, U.S.A
| | - Kevin Fedkenheuer
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Blacksburg, VA, U.S.A
| | - John M McDowell
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Blacksburg, VA, U.S.A
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103
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The Decoy Substrate of a Pathogen Effector and a Pseudokinase Specify Pathogen-Induced Modified-Self Recognition and Immunity in Plants. Cell Host Microbe 2015; 18:285-95. [DOI: 10.1016/j.chom.2015.08.004] [Citation(s) in RCA: 160] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 07/31/2015] [Accepted: 08/12/2015] [Indexed: 01/09/2023]
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104
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Christopoulou M, McHale LK, Kozik A, Reyes-Chin Wo S, Wroblewski T, Michelmore RW. Dissection of Two Complex Clusters of Resistance Genes in Lettuce (Lactuca sativa). MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:751-65. [PMID: 25650829 DOI: 10.1094/mpmi-06-14-0175-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Of the over 50 phenotypic resistance genes mapped in lettuce, 25 colocalize to three major resistance clusters (MRC) on chromosomes 1, 2, and 4. Similarly, the majority of candidate resistance genes encoding nucleotide binding-leucine rich repeat (NLR) proteins genetically colocalize with phenotypic resistance loci. MRC1 and MRC4 span over 66 and 63 Mb containing 84 and 21 NLR-encoding genes, respectively, as well as 765 and 627 genes that are not related to NLR genes. Forward and reverse genetic approaches were applied to dissect MRC1 and MRC4. Transgenic lines exhibiting silencing were selected using silencing of β-glucuronidase as a reporter. Silencing of two of five NLR-encoding gene families resulted in abrogation of nine of 14 tested resistance phenotypes mapping to these two regions. At MRC1, members of the coiled coil-NLR-encoding RGC1 gene family were implicated in host and nonhost resistance through requirement for Dm5/8- and Dm45-mediated resistance to downy mildew caused by Bremia lactucae as well as the hypersensitive response to effectors AvrB, AvrRpm1, and AvrRpt2 of the nonpathogen Pseudomonas syringae. At MRC4, RGC12 family members, which encode toll interleukin receptor-NLR proteins, were implicated in Dm4-, Dm7-, Dm11-, and Dm44-mediated resistance to B. lactucae. Lesions were identified in the sequence of a candidate gene within dm7 loss-of-resistance mutant lines, confirming that RGC12G confers Dm7.
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Affiliation(s)
- Marilena Christopoulou
- Genome Center and Department of Plant Sciences, University of California-Davis, CA 95616, U.S.A
| | - Leah K McHale
- Genome Center and Department of Plant Sciences, University of California-Davis, CA 95616, U.S.A
| | - Alex Kozik
- Genome Center and Department of Plant Sciences, University of California-Davis, CA 95616, U.S.A
| | - Sebastian Reyes-Chin Wo
- Genome Center and Department of Plant Sciences, University of California-Davis, CA 95616, U.S.A
| | - Tadeusz Wroblewski
- Genome Center and Department of Plant Sciences, University of California-Davis, CA 95616, U.S.A
| | - Richard W Michelmore
- Genome Center and Department of Plant Sciences, University of California-Davis, CA 95616, U.S.A
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105
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Wang S, Sun Z, Wang H, Liu L, Lu F, Yang J, Zhang M, Zhang S, Guo Z, Bent AF, Sun W. Rice OsFLS2-Mediated Perception of Bacterial Flagellins Is Evaded by Xanthomonas oryzae pvs. oryzae and oryzicola. MOLECULAR PLANT 2015; 8:1024-37. [PMID: 25617720 DOI: 10.1016/j.molp.2015.01.012] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 01/10/2015] [Accepted: 01/11/2015] [Indexed: 05/26/2023]
Abstract
Bacterial flagellins are often recognized by the receptor kinase FLAGELLIN SENSITIVE2 (FLS2) and activate MAMP-triggered immunity in dicotyledonous plants. However, the capacity of monocotyledonous rice to recognize flagellins of key rice pathogens and its biological relevance remain poorly understood. We demonstrate that ectopically expressed OsFLS2 in Arabidopsis senses the eliciting flg22 peptide and in vitro purified Acidovorax avenae (Aa) flagellin in an expression level-dependent manner, but does not recognize purified flagellins or derivative flg22(Xo) peptides of Xanthomonas oryzae pvs. oryzae (Xoo) and oryzicola (Xoc). Consistently, the flg22 peptide and purified Aa flagellin, but not Xoo/Xoc flagellins, induce various immune responses such as defense gene induction and MAPK activation in rice. Perception of flagellin by rice does induce strong resistance to Xoo infection, as shown after pre-treatment of rice leaves with Aa flagellin. OsFLS2 was found to differ from AtFLS2 in its perception specificities or sensitivities to different flg22 sequences. In addition, post-translational modification of Xoc flagellin was altered by deletion of glycosyltransferase-encoding rbfC, but this had little effect on Xoc motility and rpfC mutation did not detectably reduce Xoc virulence on rice. Deletion of flagellin-encoding fliC from Xoo/Xoc blocked swimming motility but also did not significantly alter Xoo/Xoc virulence. These results suggest that Xoo/Xoc carry flg22-region amino acid changes that allow motility while evading the ancient flagellin detection system in rice, which retains recognition capacity for other bacterial pathogens.
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Affiliation(s)
- Shanzhi Wang
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Zhe Sun
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Huiqin Wang
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Lijuan Liu
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Fen Lu
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Jun Yang
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Rice Research Institute, Shandong Academy of Agricultural Science, Jinan 250100, Shandong Province, China
| | - Min Zhang
- College of Bioscience and Biotechnology, Hunan Agricultural University, Changsha 410128, Hunan Province, China
| | - Shiyong Zhang
- Rice Research Institute, Shandong Academy of Agricultural Science, Jinan 250100, Shandong Province, China
| | - Zejian Guo
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China
| | - Andrew F Bent
- Department of Plant Pathology, University of Wisconsin, Madison, WI 53706, USA
| | - Wenxian Sun
- Department of Plant Pathology, China Agricultural University, 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China; Key Laboratory of Plant Pathology, Ministry of Agriculture, China Agricultural University, Beijing 100193, China.
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106
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Weßling R, Epple P, Altmann S, He Y, Yang L, Henz SR, McDonald N, Wiley K, Bader KC, Gläßer C, Mukhtar MS, Haigis S, Ghamsari L, Stephens AE, Ecker JR, Vidal M, Jones JDG, Mayer KFX, Ver Loren van Themaat E, Weigel D, Schulze-Lefert P, Dangl JL, Panstruga R, Braun P. Convergent targeting of a common host protein-network by pathogen effectors from three kingdoms of life. Cell Host Microbe 2015; 16:364-75. [PMID: 25211078 DOI: 10.1016/j.chom.2014.08.004] [Citation(s) in RCA: 269] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2014] [Revised: 06/27/2014] [Accepted: 08/14/2014] [Indexed: 01/31/2023]
Abstract
While conceptual principles governing plant immunity are becoming clear, its systems-level organization and the evolutionary dynamic of the host-pathogen interface are still obscure. We generated a systematic protein-protein interaction network of virulence effectors from the ascomycete pathogen Golovinomyces orontii and Arabidopsis thaliana host proteins. We combined this data set with corresponding data for the eubacterial pathogen Pseudomonas syringae and the oomycete pathogen Hyaloperonospora arabidopsidis. The resulting network identifies host proteins onto which intraspecies and interspecies pathogen effectors converge. Phenotyping of 124 Arabidopsis effector-interactor mutants revealed a correlation between intraspecies and interspecies convergence and several altered immune response phenotypes. Several effectors and the most heavily targeted host protein colocalized in subnuclear foci. Products of adaptively selected Arabidopsis genes are enriched for interactions with effector targets. Our data suggest the existence of a molecular host-pathogen interface that is conserved across Arabidopsis accessions, while evolutionary adaptation occurs in the immediate network neighborhood of effector targets.
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Affiliation(s)
- Ralf Weßling
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, D-50829, Germany
| | - Petra Epple
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Stefan Altmann
- Technische Universität München (TUM), Center for Life and Food Sciences Weihenstephan, Department for Plant Systems Biology, D-85354 Freising, Germany
| | - Yijian He
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Li Yang
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Stefan R Henz
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, D-72076 Tübingen, Germany
| | - Nathan McDonald
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kristin Wiley
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Kai Christian Bader
- Plant Genome and Systems Biology, Helmholtz Zentrum München, D-85764 Neuherberg, Germany
| | - Christine Gläßer
- Plant Genome and Systems Biology, Helmholtz Zentrum München, D-85764 Neuherberg, Germany
| | - M Shahid Mukhtar
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Biology, University of Alabama Birmingham, Birmingham, AL 35294, USA
| | - Sabine Haigis
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, D-50829, Germany
| | - Lila Ghamsari
- Center for Cancer Systems Biology (CCSB) and Department of Cancer Biology, Dana Farber Cancer Institute, and Harvard Medical School, Department of Genetics, Boston, MA 02215, USA
| | - Amber E Stephens
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, D-50829, Germany
| | - Joseph R Ecker
- Howard Hughes Medical Institute and Salk Institute for Biological Studies, Plant Biology Lab, La Jolla, CA 92037, USA
| | - Marc Vidal
- Center for Cancer Systems Biology (CCSB) and Department of Cancer Biology, Dana Farber Cancer Institute, and Harvard Medical School, Department of Genetics, Boston, MA 02215, USA
| | - Jonathan D G Jones
- The Sainsbury Laboratory, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK
| | - Klaus F X Mayer
- Plant Genome and Systems Biology, Helmholtz Zentrum München, D-85764 Neuherberg, Germany
| | - Emiel Ver Loren van Themaat
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, D-50829, Germany
| | - Detlef Weigel
- Department of Molecular Biology, Max Planck Institute for Developmental Biology, D-72076 Tübingen, Germany
| | - Paul Schulze-Lefert
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, D-50829, Germany
| | - Jeffery L Dangl
- Howard Hughes Medical Institute and Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Carolina Center for Genome Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA; Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Ralph Panstruga
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Cologne, D-50829, Germany; Rheinisch Westfälische Technische Hochschule (RWTH) Aachen University, Institute for Biology I, Unit of Plant Molecular Cell Biology, D-52074 Aachen, Germany.
| | - Pascal Braun
- Technische Universität München (TUM), Center for Life and Food Sciences Weihenstephan, Department for Plant Systems Biology, D-85354 Freising, Germany.
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107
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Zhang M, Ahmed Rajput N, Shen D, Sun P, Zeng W, Liu T, Juma Mafurah J, Dou D. A Phytophthora sojae cytoplasmic effector mediates disease resistance and abiotic stress tolerance in Nicotiana benthamiana. Sci Rep 2015; 5:10837. [PMID: 26039925 PMCID: PMC4454142 DOI: 10.1038/srep10837] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 05/05/2015] [Indexed: 11/29/2022] Open
Abstract
Each oomycete pathogen encodes a large number of effectors. Some effectors can be used in crop disease resistance breeding, such as to accelerate R gene cloning and utilisation. Since cytoplasmic effectors may cause acute physiological changes in host cells at very low concentrations, we assume that some of these effectors can serve as functional genes for transgenic plants. Here, we generated transgenic Nicotiana benthamiana plants that express a Phytophthora sojae CRN (crinkling and necrosis) effector, PsCRN115. We showed that its expression did not significantly affect the growth and development of N. benthamiana, but significantly improved disease resistance and tolerance to salt and drought stresses. Furthermore, we found that expression of heat-shock-protein and cytochrome-P450 encoding genes were unregulated in PsCRN115-transgenic N. benthamiana based on digital gene expression profiling analyses, suggesting the increased plant defence may be achieved by upregulation of these stress-related genes in transgenic plants. Thus, PsCRN115 may be used to improve plant tolerance to biotic and abiotic stresses.
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Affiliation(s)
- Meixiang Zhang
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China
| | - Nasir Ahmed Rajput
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China
- Department of Plant Pathology, Sindh Agriculture University, Tandojam, Pakistan
| | - Danyu Shen
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China
| | - Peng Sun
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China
| | - Wentao Zeng
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China
| | - Tingli Liu
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China
| | - Joseph Juma Mafurah
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China
| | - Daolong Dou
- Department of Plant Pathology, Nanjing Agricultural University, Nanjing, China
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108
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Zhou J, Peng Z, Long J, Sosso D, Liu B, Eom JS, Huang S, Liu S, Vera Cruz C, Frommer WB, White FF, Yang B. Gene targeting by the TAL effector PthXo2 reveals cryptic resistance gene for bacterial blight of rice. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 82:632-43. [PMID: 25824104 DOI: 10.1111/tpj.12838] [Citation(s) in RCA: 240] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Revised: 03/22/2015] [Accepted: 03/23/2015] [Indexed: 05/19/2023]
Abstract
Bacterial blight of rice is caused by the γ-proteobacterium Xanthomonas oryzae pv. oryzae, which utilizes a group of type III TAL (transcription activator-like) effectors to induce host gene expression and condition host susceptibility. Five SWEET genes are functionally redundant to support bacterial disease, but only two were experimentally proven targets of natural TAL effectors. Here, we report the identification of the sucrose transporter gene OsSWEET13 as the disease-susceptibility gene for PthXo2 and the existence of cryptic recessive resistance to PthXo2-dependent X. oryzae pv. oryzae due to promoter variations of OsSWEET13 in japonica rice. PthXo2-containing strains induce OsSWEET13 in indica rice IR24 due to the presence of an unpredicted and undescribed effector binding site not present in the alleles in japonica rice Nipponbare and Kitaake. The specificity of effector-associated gene induction and disease susceptibility is attributable to a single nucleotide polymorphism (SNP), which is also found in a polymorphic allele of OsSWEET13 known as the recessive resistance gene xa25 from the rice cultivar Minghui 63. The mutation of OsSWEET13 with CRISPR/Cas9 technology further corroborates the requirement of OsSWEET13 expression for the state of PthXo2-dependent disease susceptibility to X. oryzae pv. oryzae. Gene profiling of a collection of 104 strains revealed OsSWEET13 induction by 42 isolates of X. oryzae pv. oryzae. Heterologous expression of OsSWEET13 in Nicotiana benthamiana leaf cells elevates sucrose concentrations in the apoplasm. The results corroborate a model whereby X. oryzae pv. oryzae enhances the release of sucrose from host cells in order to exploit the host resources.
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Affiliation(s)
- Junhui Zhou
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
| | - Zhao Peng
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506, USA
| | - Juying Long
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
- Key Laboratory of Integrated Pest Management in Crops in Eastern China, Nanjing Agricultural University, Ministry of Agriculture, Nanjing, 210095, China
| | - Davide Sosso
- Carnegie Institute for Science, 260 Panama Street, Stanford, CA, 94305, USA
| | - Bo Liu
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
| | - Joon-Seob Eom
- Carnegie Institute for Science, 260 Panama Street, Stanford, CA, 94305, USA
| | - Sheng Huang
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
| | - Sanzhen Liu
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506, USA
| | - Casiana Vera Cruz
- International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines
| | - Wolf B Frommer
- Carnegie Institute for Science, 260 Panama Street, Stanford, CA, 94305, USA
| | - Frank F White
- Department of Plant Pathology, Kansas State University, Manhattan, KS, 66506, USA
| | - Bing Yang
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA
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109
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Tsuda K, Somssich IE. Transcriptional networks in plant immunity. THE NEW PHYTOLOGIST 2015; 206:932-947. [PMID: 25623163 DOI: 10.1111/nph.13286] [Citation(s) in RCA: 287] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 12/09/2014] [Indexed: 05/18/2023]
Abstract
Next to numerous abiotic stresses, plants are constantly exposed to a variety of pathogens within their environment. Thus, their ability to survive and prosper during the course of evolution was strongly dependent on adapting efficient strategies to perceive and to respond to such potential threats. It is therefore not surprising that modern plants have a highly sophisticated immune repertoire consisting of diverse signal perception and intracellular signaling pathways. This signaling network is intricate and deeply interconnected, probably reflecting the diverse lifestyles and infection strategies used by the multitude of invading phytopathogens. Moreover it allows signal communication between developmental and defense programs thereby ensuring that plant growth and fitness are not significantly retarded. How plants integrate and prioritize the incoming signals and how this information is transduced to enable appropriate immune responses is currently a major research area. An important finding has been that pathogen-triggered cellular responses involve massive transcriptional reprogramming within the host. Additional key observations emerging from such studies are that transcription factors (TFs) are often sites of signal convergence and that signal-regulated TFs act in concert with other context-specific TFs and transcriptional co-regulators to establish sensory transcription regulatory networks required for plant immunity.
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Affiliation(s)
- Kenichi Tsuda
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, Cologne, 50829, Germany
| | - Imre E Somssich
- Department of Plant Microbe Interactions, Max Planck Institute for Plant Breeding Research, Carl-von-Linne Weg 10, Cologne, 50829, Germany
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110
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Bigeard J, Colcombet J, Hirt H. Signaling mechanisms in pattern-triggered immunity (PTI). MOLECULAR PLANT 2015; 8:521-39. [PMID: 25744358 DOI: 10.1016/j.molp.2014.12.022] [Citation(s) in RCA: 533] [Impact Index Per Article: 59.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Revised: 12/17/2014] [Accepted: 12/30/2014] [Indexed: 05/20/2023]
Abstract
In nature, plants constantly have to face pathogen attacks. However, plant disease rarely occurs due to efficient immune systems possessed by the host plants. Pathogens are perceived by two different recognition systems that initiate the so-called pattern-triggered immunity (PTI) and effector-triggered immunity (ETI), both of which are accompanied by a set of induced defenses that usually repel pathogen attacks. Here we discuss the complex network of signaling pathways occurring during PTI, focusing on the involvement of mitogen-activated protein kinases.
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Affiliation(s)
- Jean Bigeard
- Unité de Recherche en Génomique Végétale (URGV), UMR INRA/CNRS/Université d'Evry Val d'Essonne/Saclay Plant Sciences, 2 rue Gaston Crémieux, 91057 Evry, France
| | - Jean Colcombet
- Unité de Recherche en Génomique Végétale (URGV), UMR INRA/CNRS/Université d'Evry Val d'Essonne/Saclay Plant Sciences, 2 rue Gaston Crémieux, 91057 Evry, France
| | - Heribert Hirt
- Center for Desert Agriculture, 4700 King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Kingdom of Saudi Arabia.
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Boyle PC, Martin GB. Greasy tactics in the plant-pathogen molecular arms race. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66:1607-16. [PMID: 25725095 DOI: 10.1093/jxb/erv059] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The modification of proteins by the attachment of fatty acids is a targeting tactic involved in mechanisms of both plant immunity and bacterial pathogenesis. The plant plasma membrane (PM) is a key battleground in the war against disease-causing microbes. This membrane is armed with an array of sensor proteins that function as a surveillance system to detect invading pathogens. Several of these sensor proteins are directed to the plasma membrane through the covalent addition of fatty acids, a process termed fatty acylation. Phytopathogens secrete effector proteins into the plant cell to subvert these surveillance mechanisms, rendering the host susceptible to infection. The targeting of effectors to specific locales within plant cells, particularly the internal face of the host PM, is critical for their virulence function. Several bacterial effectors hijack the host fatty acylation machinery to be modified and directed to this contested locale. To find and fight these fatty acylated effectors the plant leverages lipid-modified intracellular sensors. This review provides examples featuring how fatty acylation is a battle tactic used by both combatants in the molecular arms race between plants and pathogens. Also highlighted is the exploitation of a specific form of host-mediated fatty acid modification, which appears to be exclusively employed by phytopathogenic effector proteins.
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Affiliation(s)
- Patrick C Boyle
- Boyce Thompson Institute for Plant Research, Ithaca, NY 14853, USA
| | - Gregory B Martin
- Boyce Thompson Institute for Plant Research, Ithaca, NY 14853, USA Section of Plant Pathology and Plant-Microbe Biology, School of Integrative Plant Science, Cornell University, Ithaca, NY 14853, USA
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Recognition and activation domains contribute to allele-specific responses of an Arabidopsis NLR receptor to an oomycete effector protein. PLoS Pathog 2015; 11:e1004665. [PMID: 25671309 PMCID: PMC4335498 DOI: 10.1371/journal.ppat.1004665] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Accepted: 01/06/2015] [Indexed: 11/19/2022] Open
Abstract
In plants, specific recognition of pathogen effector proteins by nucleotide-binding leucine-rich repeat (NLR) receptors leads to activation of immune responses. RPP1, an NLR from Arabidopsis thaliana, recognizes the effector ATR1, from the oomycete pathogen Hyaloperonospora arabidopsidis, by direct association via C-terminal leucine-rich repeats (LRRs). Two RPP1 alleles, RPP1-NdA and RPP1-WsB, have narrow and broad recognition spectra, respectively, with RPP1-NdA recognizing a subset of the ATR1 variants recognized by RPP1-WsB. In this work, we further characterized direct effector recognition through random mutagenesis of an unrecognized ATR1 allele, ATR1-Cala2, screening for gain-of-recognition phenotypes in a tobacco hypersensitive response assay. We identified ATR1 mutants that a) confirm surface-exposed residues contribute to recognition by RPP1, and b) are recognized by and activate the narrow-spectrum allele RPP1-NdA, but not RPP1-WsB, in co-immunoprecipitation and bacterial growth inhibition assays. Thus, RPP1 alleles have distinct recognition specificities, rather than simply different sensitivity to activation. Using chimeric RPP1 constructs, we showed that RPP1-NdA LRRs were sufficient for allele-specific recognition (association with ATR1), but insufficient for receptor activation in the form of HR. Additional inclusion of the RPP1-NdA ARC2 subdomain, from the central NB-ARC domain, was required for a full range of activation specificity. Thus, cooperation between recognition and activation domains seems to be essential for NLR function.
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Zhou X, Hu X, Li J, Wang N. A Novel Periplasmic Protein, VrpA, Contributes to Efficient Protein Secretion by the Type III Secretion System in Xanthomonas spp. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:143-153. [PMID: 25338144 DOI: 10.1094/mpmi-10-14-0309-r] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Efficient secretion of type III effector proteins from the bacterial cytoplasm to host cell cytosol via a type III secretion system (T3SS) is crucial for virulence of plant-pathogenic bacterium. Our previous study revealed a conserved hypothetical protein, virulence-related periplasm protein A (VrpA), which was identified as a critical virulence factor for Xanthomonas citri subsp. citri. In this study, we demonstrate that mutation of vrpA compromises X. citri subsp. citri virulence and hypersensitive response induction. This deficiency is also observed in the X. campestris pv. campestris strain, suggesting a functional conservation of VrpA in Xanthomonas spp. Our study indicates that VrpA is required for efficient protein secretion via T3SS, which is supported by multiple lines of evidence. A CyaA reporter assay shows that VrpA is involved in type III effector secretion; quantitative reverse-transcription polymerase chain reaction analysis suggests that the vrpA mutant fails to activate citrus-canker-susceptible gene CsLOB1, which is transcriptionally activated by transcription activator-like effector PthA4; in vitro secretion study reveals that VrpA plays an important role in secretion of T3SS pilus, translocon, and effector proteins. Our data also indicate that VrpA in X. citri subsp. citri localizes to bacterial periplasmic space and the periplasmic localization is required for full function of VrpA and X. citri subsp. citri virulence. Protein-protein interaction studies show that VrpA physically interacts with periplasmic T3SS components HrcJ and HrcC. However, the mutation of VrpA does not affect T3SS gene expression. Additionally, VrpA is involved in X. citri subsp. citri tolerance of oxidative stress. Our data contribute to the mechanical understanding of an important periplasmic protein VrpA in Xanthomonas spp.
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Ma L, Borhan MH. The receptor-like kinase SOBIR1 interacts with Brassica napus LepR3 and is required for Leptosphaeria maculans AvrLm1-triggered immunity. FRONTIERS IN PLANT SCIENCE 2015; 6:933. [PMID: 26579176 PMCID: PMC4625043 DOI: 10.3389/fpls.2015.00933] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2015] [Accepted: 10/15/2015] [Indexed: 05/07/2023]
Abstract
The fungus Leptosphaeria maculans (L. maculans) is the causal agent of blackleg disease of canola/oilseed rape (Brassica napus) worldwide. We previously reported cloning of the B. napus blackleg resistance gene, LepR3, which encodes a receptor-like protein. LepR3 triggers localized cell death upon recognition of its cognate Avr protein, AvrLm1. Here, we exploited the Nicotiana benthamiana model plant to investigate the recognition mechanism of AvrLm1 by LepR3. Co-expression of the LepR3/AvrLm1 gene pair in N. benthamiana resulted in development of a hypersensitive response (HR). However, a truncated AvrLm1 lacking its indigenous signal peptide was compromised in its ability to induce LepR3-mediated HR, indicating that AvrLm1 is perceived by LepR3 extracellularly. Structure-function analysis of the AvrLm1 protein revealed that the C-terminal region of AvrLm1 was required for LepR3-mediated HR in N. benthamiana and for resistance to L. maculans in B. napus. LepR3 was shown to be physically interacting with the B. napus receptor like kinase, SOBIR1 (BnSOBIR1). Silencing of NbSOBIR1 or NbSERK3 (BAK1) compromised LepR3-AvrLm1-dependent HR in N. benthamiana, suggesting that LepR3-mediated resistance to L. maculans in B. napus requires SOBIR1 and BAK1/SERK3. Using this model system, we determined that BnSOBIR1 and SERK3/BAK1 are essential partners in the LepR3 signaling complex and were able to define the AvrLm1 effector domain.
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Andersson MX, Nilsson AK, Johansson ON, Boztaş G, Adolfsson LE, Pinosa F, Petit CG, Aronsson H, Mackey D, Tör M, Hamberg M, Ellerström M. Involvement of the electrophilic isothiocyanate sulforaphane in Arabidopsis local defense responses. PLANT PHYSIOLOGY 2015; 167:251-61. [PMID: 25371552 PMCID: PMC4281013 DOI: 10.1104/pp.114.251892] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2014] [Accepted: 11/03/2014] [Indexed: 05/18/2023]
Abstract
Plants defend themselves against microbial pathogens through a range of highly sophisticated and integrated molecular systems. Recognition of pathogen-secreted effector proteins often triggers the hypersensitive response (HR), a complex multicellular defense reaction where programmed cell death of cells surrounding the primary site of infection is a prominent feature. Even though the HR was described almost a century ago, cell-to-cell factors acting at the local level generating the full defense reaction have remained obscure. In this study, we sought to identify diffusible molecules produced during the HR that could induce cell death in naive tissue. We found that 4-methylsulfinylbutyl isothiocyanate (sulforaphane) is released by Arabidopsis (Arabidopsis thaliana) leaf tissue undergoing the HR and that this compound induces cell death as well as primes defense in naive tissue. Two different mutants impaired in the pathogen-induced accumulation of sulforaphane displayed attenuated programmed cell death upon bacterial and oomycete effector recognition as well as decreased resistance to several isolates of the plant pathogen Hyaloperonospora arabidopsidis. Treatment with sulforaphane provided protection against a virulent H. arabidopsidis isolate. Glucosinolate breakdown products are recognized as antifeeding compounds toward insects and recently also as intracellular signaling and bacteriostatic molecules in Arabidopsis. The data presented here indicate that these compounds also trigger local defense responses in Arabidopsis tissue.
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Affiliation(s)
- Mats X Andersson
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Anders K Nilsson
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Oskar N Johansson
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Gülin Boztaş
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Lisa E Adolfsson
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Francesco Pinosa
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Christel Garcia Petit
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Henrik Aronsson
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - David Mackey
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Mahmut Tör
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Mats Hamberg
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
| | - Mats Ellerström
- Department of Biological and Environmental Sciences, University of Gothenburg, SE-405 30 Gothenburg, Sweden (M.X.A., A.K.N., O.N.J., L.E.A., F.P., C.G.P., H.A., M.E.);National Pollen and Aerobiology Research Unit, Institute of Science and the Environment, University of Worcester, Worcester WR2 6AJ, United Kingdom (G.B., M.T.);Departments of Horticulture and Crop Science and Molecular Genetics, Ohio State University, Columbus, Ohio 43210 (D.M.); andDivision of Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden (M.H.)
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Lewis JD, Wilton M, Mott G.A, Lu W, Hassan JA, Guttman DS, Desveaux D. Immunomodulation by the Pseudomonas syringae HopZ type III effector family in Arabidopsis. PLoS One 2014; 9:e116152. [PMID: 25546415 PMCID: PMC4278861 DOI: 10.1371/journal.pone.0116152] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 12/04/2014] [Indexed: 11/19/2022] Open
Abstract
Pseudomonas syringae employs a type III secretion system to inject 20-30 different type III effector (T3SE) proteins into plant host cells. A major role of T3SEs is to suppress plant immune responses and promote bacterial infection. The YopJ/HopZ acetyltransferases are a superfamily of T3SEs found in both plant and animal pathogenic bacteria. In P. syringae, this superfamily includes the evolutionarily diverse HopZ1, HopZ2 and HopZ3 alleles. To investigate the roles of the HopZ family in immunomodulation, we generated dexamethasone-inducible T3SE transgenic lines of Arabidopsis for HopZ family members and characterized them for immune suppression phenotypes. We show that all of the HopZ family members can actively suppress various facets of Arabidopsis immunity in a catalytic residue-dependent manner. HopZ family members can differentially suppress the activation of mitogen-activated protein (MAP) kinase cascades or the production of reactive oxygen species, whereas all members can promote the growth of non-virulent P. syringae. Localization studies show that four of the HopZ family members containing predicted myristoylation sites are localized to the vicinity of the plasma membrane while HopZ3 which lacks the myristoylation site is at least partially nuclear localized, suggesting diversification of immunosuppressive mechanisms. Overall, we demonstrate that despite significant evolutionary diversification, all HopZ family members can suppress immunity in Arabidopsis.
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Affiliation(s)
- Jennifer D. Lewis
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Plant Gene Expression Center, United States Department of Agriculture, Albany, California, United States of America
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
| | - Mike Wilton
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - G . Adam Mott
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Wenwan Lu
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Jana A. Hassan
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
| | - David S. Guttman
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
| | - Darrell Desveaux
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
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117
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Liang Y, Tóth K, Cao Y, Tanaka K, Espinoza C, Stacey G. Lipochitooligosaccharide recognition: an ancient story. THE NEW PHYTOLOGIST 2014; 204:289-96. [PMID: 25453133 DOI: 10.1111/nph.12898] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Chitin is the second most abundant polysaccharide in nature, found in crustacean shells, insect exoskeletons and fungal cell walls. The action of chitin and chitin derivatives on plants has become a very interesting story of late. Chitin is a b1-4-linked polymer of N-acetyl-Dglucosamine(GlcNAc). In this unmodified form, chitooligosaccharides (degree of polymerization(dp) = 6–8)) are strong inducers of plant innate immunity. By contrast, when these chitooligosaccharides are acylated (so-called lipochitooligosaccharides, LCOs) and further modified, they can act as Nod factors, the key signaling molecules that play an important role in the initiation of the legume–rhizobium symbiosis. In a similar form, these molecules can also act as Myc factors, the key signaling molecules involved in the arbuscular mycorrhizal (AM)symbiosis. It has been proposed that Nod factor perception might have evolved from the more ancient AM symbiosis. Increasing evidence now suggests that LCO perception might have evolved from plant innate immunity signaling. In this review, we will discuss the evolutionary origin of symbiotic LCO recognition.
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Affiliation(s)
- Yan Liang
- Divisions of Plant Science and Biochemistry, National Center for Soybean Biotechnology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, MO 65211, USA
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Chung EH, El-Kasmi F, He Y, Loehr A, Dangl J. A Plant Phosphoswitch Platform Repeatedly Targeted by Type III Effector Proteins Regulates the Output of Both Tiers of Plant Immune Receptors. Cell Host Microbe 2014; 16:484-94. [DOI: 10.1016/j.chom.2014.09.004] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 08/07/2014] [Accepted: 08/29/2014] [Indexed: 10/24/2022]
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119
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Clarke CR, Hayes BW, Runde BJ, Wicker E, Vinatzer BA. Eggplant and related species are promising genetic resources to dissect the plant immune response to Pseudomonas syringae and Xanthomonas euvesicatoria and to identify new resistance determinants. MOLECULAR PLANT PATHOLOGY 2014; 15:814-822. [PMID: 24684604 PMCID: PMC6638909 DOI: 10.1111/mpp.12140] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The apparent lack of durability of many resistance (R) genes highlights the need for the constant identification of new genetic sources of resistance for the breeding of new disease-resistant crop cultivars. To this end, we screened a collection of accessions of eggplant and close relatives for resistance against Pseudomonas syringae pv. tomato (Pto) and Xanthomonas euvesicatoria (Xeu), foliar plant pathogens of many solanaceous crops. Both pathogens caused substantial disease on most genotypes of eggplant and its relatives. Promisingly, however, some of the genotypes were fully or partially resistant to either of the pathogens, suggesting the presence of effective resistance determinants in these genotypes. Segregation of resistance to the growth of Xeu following infiltration in F2 progeny from a cross of a resistant and susceptible genotype suggests that resistance to Xeu is inherited as a multigenic trait. With regard to Pto, a mutant strain lacking all 28 functional type III secreted effectors, and a Pseudomonas fluorescens strain expressing a P. syringae type III secretion system (T3SS), both elicit a strong cell death response on most eggplant lines. Several genotypes thus appear to harbour a mechanism for the direct recognition of a component of the T3SS. Therefore, eggplant and its close relatives are promising resources to unravel novel aspects of plant immunity and to identify new candidate R genes that could be employed in other Solanaceae in which Xeu and Pto cause agriculturally relevant diseases.
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Affiliation(s)
- Christopher R Clarke
- Department of Plant Pathology, Physiology, and Weed Sciences, Virginia Tech, 537 Latham Hall, West Campus Drive, Blacksburg, VA, 24061, USA
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Lam HN, Chakravarthy S, Wei HL, BuiNguyen H, Stodghill PV, Collmer A, Swingle BM, Cartinhour SW. Global analysis of the HrpL regulon in the plant pathogen Pseudomonas syringae pv. tomato DC3000 reveals new regulon members with diverse functions. PLoS One 2014; 9:e106115. [PMID: 25170934 PMCID: PMC4149516 DOI: 10.1371/journal.pone.0106115] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2014] [Accepted: 07/28/2014] [Indexed: 11/18/2022] Open
Abstract
The type III secretion system (T3SS) is required for virulence in the gram-negative plant pathogen Pseudomonas syringae pv. tomato DC3000. The alternative sigma factor HrpL directly regulates expression of T3SS genes via a promoter sequence, often designated as the "hrp promoter." Although the HrpL regulon has been extensively investigated in DC3000, it is not known whether additional regulon members remain to be found. To systematically search for HrpL-regulated genes, we used chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-Seq) and bulk mRNA sequencing (RNA-Seq) to identify HrpL-binding sites and likely hrp promoters. The analysis recovered 73 sites of interest, including 20 sites that represent new hrp promoters. The new promoters lie upstream of a diverse set of genes encoding potential regulators, enzymes and hypothetical proteins. PSPTO_5633 is the only new HrpL regulon member that is potentially an effector and is now designated HopBM1. Deletions in several other new regulon members, including PSPTO_5633, PSPTO_0371, PSPTO_2130, PSPTO_2691, PSPTO_2696, PSPTO_3331, and PSPTO_5240, in either DC3000 or ΔhopQ1-1 backgrounds, do not affect the hypersensitive response or in planta growth of the resulting strains. Many new HrpL regulon members appear to be unrelated to the T3SS, and orthologs for some of these can be identified in numerous non-pathogenic bacteria. With the identification of 20 new hrp promoters, the list of HrpL regulon members is approaching saturation and most likely includes all DC3000 effectors.
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Affiliation(s)
- Hanh N. Lam
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
| | - Suma Chakravarthy
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
| | - Hai-Lei Wei
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
| | - HoangChuong BuiNguyen
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
| | - Paul V. Stodghill
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
- United States Department of Agriculture-Agricultural Research Service, Ithaca, New York, United States of America
| | - Alan Collmer
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
| | - Bryan M. Swingle
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
- United States Department of Agriculture-Agricultural Research Service, Ithaca, New York, United States of America
| | - Samuel W. Cartinhour
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York, United States of America
- United States Department of Agriculture-Agricultural Research Service, Ithaca, New York, United States of America
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Pto kinase binds two domains of AvrPtoB and its proximity to the effector E3 ligase determines if it evades degradation and activates plant immunity. PLoS Pathog 2014; 10:e1004227. [PMID: 25058029 PMCID: PMC4110037 DOI: 10.1371/journal.ppat.1004227] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 05/16/2014] [Indexed: 11/19/2022] Open
Abstract
The tomato--Pseudomonas syringae pv. tomato (Pst)--pathosystem is one of the best understood models for plant-pathogen interactions. Certain wild relatives of tomato express two closely related members of the same kinase family, Pto and Fen, which recognize the Pst virulence protein AvrPtoB and activate effector-triggered immunity (ETI). AvrPtoB, however, contains an E3 ubiquitin ligase domain in its carboxyl terminus which causes degradation of Fen and undermines its ability to activate ETI. In contrast, Pto evades AvrPtoB-mediated degradation and triggers ETI in response to the effector. It has been reported recently that Pto has higher kinase activity than Fen and that this difference allows Pto to inactivate the E3 ligase through phosphorylation of threonine-450 (T450) in AvrPtoB. Here we show that, in contrast to Fen which can only interact with a single domain proximal to the E3 ligase of AvrPtoB, Pto binds two distinct domains of the effector, the same site as Fen and another N-terminal domain. In the absence of E3 ligase activity Pto binds to either domain of AvrPtoB to activate ETI. However, the presence of an active E3 ligase domain causes ubiquitination of Pto that interacts with the domain proximal to the E3 ligase, identical to ubiquitination of Fen. Only when Pto binds its unique distal domain can it resist AvrPtoB-mediated degradation and activate ETI. We show that phosphorylation of T450 is not required for Pto-mediated resistance in vivo and that a kinase-inactive version of Pto is still capable of activating ETI in response to AvrPtoB. Our results demonstrate that the ability of Pto to interact with a second site distal to the E3 ligase domain in AvrPtoB, and not a higher kinase activity or T450 phosphorylation, allows Pto to evade ubiquitination and to confer immunity to Pst.
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122
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Fraiture M, Brunner F. Killing two birds with one stone: trans-kingdom suppression of PAMP/MAMP-induced immunity by T3E from enteropathogenic bacteria. Front Microbiol 2014; 5:320. [PMID: 25101059 PMCID: PMC4105635 DOI: 10.3389/fmicb.2014.00320] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 06/11/2014] [Indexed: 01/07/2023] Open
Abstract
Within the past decade, remarkable similarities between the molecular organization of animal and plant systems for non-self discrimination were revealed. Obvious parallels exist between the molecular structures of the receptors mediating the recognition of pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs) with plant pattern recognition receptors strikingly resembling mammalian Toll-like receptors. Mitogen-activated protein kinase cascades, leading to the transcriptional activation of immunity-associated genes, illustrate the conservation of whole molecular building blocks of PAMP/MAMP-induced signaling. Enteropathogenic Salmonella and Escherichia coli use a type three secretion system (T3SS) to inject effector proteins into the mammalian host cell to subvert defense mechanisms and promote gut infection. Lately, disease occurrence was increasingly associated with bacteria-contaminated fruits and vegetables and common themes have emerged with regard to whether and how effectors target innate immune responses in a trans-kingdom manner. We propose that numerous Salmonella or E. coli effectors may be active in planta and tend to target central components (hubs) of immune signaling pathways.
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Affiliation(s)
- Malou Fraiture
- Plant Biochemistry, Centre for Plant Molecular Biology, Eberhard Karls University Tübingen Tübingen, Germany
| | - Frédéric Brunner
- Plant Biochemistry, Centre for Plant Molecular Biology, Eberhard Karls University Tübingen Tübingen, Germany
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123
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Chen CW, Panzeri D, Yeh YH, Kadota Y, Huang PY, Tao CN, Roux M, Chien SC, Chin TC, Chu PW, Zipfel C, Zimmerli L. The Arabidopsis malectin-like leucine-rich repeat receptor-like kinase IOS1 associates with the pattern recognition receptors FLS2 and EFR and is critical for priming of pattern-triggered immunity. THE PLANT CELL 2014; 26:3201-19. [PMID: 25070640 PMCID: PMC4145141 DOI: 10.1105/tpc.114.125682] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 06/25/2014] [Accepted: 07/13/2014] [Indexed: 05/19/2023]
Abstract
Plasma membrane-localized pattern recognition receptors such as FLAGELLIN SENSING2 (FLS2) and EF-TU RECEPTOR (EFR) recognize microbe-associated molecular patterns (MAMPs) to activate the first layer of plant immunity termed pattern-triggered immunity (PTI). A reverse genetics approach with genes responsive to the priming agent β-aminobutyric acid (BABA) revealed IMPAIRED OOMYCETE SUSCEPTIBILITY1 (IOS1) as a critical PTI player. Arabidopsis thaliana ios1 mutants were hypersusceptible to Pseudomonas syringae bacteria. Accordingly, ios1 mutants demonstrated defective PTI responses, notably delayed upregulation of PTI marker genes, lower callose deposition, and mitogen-activated protein kinase activities upon bacterial infection or MAMP treatment. Moreover, Arabidopsis lines overexpressing IOS1 were more resistant to P. syringae and demonstrated a primed PTI response. In vitro pull-down, bimolecular fluorescence complementation, coimmunoprecipitation, and mass spectrometry analyses supported the existence of complexes between the membrane-localized IOS1 and FLS2 and EFR. IOS1 also associated with BRASSINOSTEROID INSENSITIVE1-ASSOCIATED KINASE1 (BAK1) in a ligand-independent manner and positively regulated FLS2/BAK1 complex formation upon MAMP treatment. Finally, ios1 mutants were defective in BABA-induced resistance and priming. This work reveals IOS1 as a regulatory protein of FLS2- and EFR-mediated signaling that primes PTI activation upon bacterial elicitation.
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Affiliation(s)
- Ching-Wei Chen
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
| | - Dario Panzeri
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
| | - Yu-Hung Yeh
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
| | | | - Pin-Yao Huang
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
| | - Chia-Nan Tao
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
| | - Milena Roux
- Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom
| | - Shiao-Chiao Chien
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
| | - Tzu-Chuan Chin
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
| | - Po-Wei Chu
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
| | - Cyril Zipfel
- Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom
| | - Laurent Zimmerli
- Department of Life Science and Institute of Plant Biology, National Taiwan University, Taipei 106, Taiwan
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Huang PY, Yeh YH, Liu AC, Cheng CP, Zimmerli L. The Arabidopsis LecRK-VI.2 associates with the pattern-recognition receptor FLS2 and primes Nicotiana benthamiana pattern-triggered immunity. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 79:243-55. [PMID: 24844677 DOI: 10.1111/tpj.12557] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 04/24/2014] [Accepted: 05/06/2014] [Indexed: 05/27/2023]
Abstract
Pattern-triggered immunity (PTI) is broad spectrum and manipulation of PTI is believed to represent an attractive way to engineer plants with broad-spectrum disease resistance. PTI is activated upon perception of microbe-associated molecular patterns (MAMPs) by pattern-recognition receptors (PRRs). We have recently demonstrated that the L-type lectin receptor kinase-VI.2 (LecRK-VI.2) positively regulates Arabidopsis thaliana PTI. Here we show through in vitro pull-down, bimolecular fluorescence complementation and co-immunoprecipitation analyses that LecRK-VI.2 associates with the PRR FLS2. We also demonstrated that LecRK-VI.2 from the cruciferous plant Arabidopsis remains functional after interfamily transfer to the Solanaceous plant Nicotiana benthamiana. Wild tobacco plants ectopically expressing LecRK-VI.2 were indeed more resistant to virulent hemi-biotrophic and necrotrophic bacteria, but not to the fungal pathogen Botrytis cinerea suggesting that, as with Arabidopsis, the LecRK-VI.2 protective effect in N. benthamiana is bacteria specific. Ectopic expression of LecRK-VI.2 in N. benthamiana primed PTI-mediated reactive oxygen species production, mitogen-activated protein kinase (MAPK) activity, callose deposition and gene expression upon treatment with the MAMP flagellin. Our findings identified LecRK-VI.2 as a member of the FLS2 receptor complex and suggest that heterologous expression of components of PRR complexes can be used as tools to engineer plant disease resistance to bacteria.
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Affiliation(s)
- Pin-Yao Huang
- Institute of Plant Biology, College of Life Science, National Taiwan University, Taipei, Taiwan
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125
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Functionally redundant RXLR effectors from Phytophthora infestans act at different steps to suppress early flg22-triggered immunity. PLoS Pathog 2014; 10:e1004057. [PMID: 24763622 PMCID: PMC3999189 DOI: 10.1371/journal.ppat.1004057] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 02/18/2014] [Indexed: 12/25/2022] Open
Abstract
Genome sequences of several economically important phytopathogenic oomycetes have revealed the presence of large families of so-called RXLR effectors. Functional screens have identified RXLR effector repertoires that either compromise or induce plant defense responses. However, limited information is available about the molecular mechanisms underlying the modes of action of these effectors in planta. The perception of highly conserved pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs), such as flg22, triggers converging signaling pathways recruiting MAP kinase cascades and inducing transcriptional re-programming, yielding a generic anti-microbial response. We used a highly synchronizable, pathogen-free protoplast-based assay to identify a set of RXLR effectors from Phytophthora infestans (PiRXLRs), the causal agent of potato and tomato light blight that manipulate early stages of flg22-triggered signaling. Of thirty-three tested PiRXLR effector candidates, eight, called Suppressor of early Flg22-induced Immune response (SFI), significantly suppressed flg22-dependent activation of a reporter gene under control of a typical MAMP-inducible promoter (pFRK1-Luc) in tomato protoplasts. We extended our analysis to Arabidopsis thaliana, a non-host plant species of P. infestans. From the aforementioned eight SFI effectors, three appeared to share similar functions in both Arabidopsis and tomato by suppressing transcriptional activation of flg22-induced marker genes downstream of post-translational MAP kinase activation. A further three effectors interfere with MAMP signaling at, or upstream of, the MAP kinase cascade in tomato, but not in Arabidopsis. Transient expression of the SFI effectors in Nicotiana benthamiana enhances susceptibility to P. infestans and, for the most potent effector, SFI1, nuclear localization is required for both suppression of MAMP signaling and virulence function. The present study provides a framework to decipher the molecular mechanisms underlying the manipulation of host MAMP-triggered immunity (MTI) by P. infestans and to understand the basis of host versus non-host resistance in plants towards P. infestans. Phytophthora species are among the most devastating crop pathogens worldwide. P. infestans is a pathogen of tomato and potato plants. The genome of P. infestans has been sequenced, revealing the presence of a large number of host-targeting RXLR effector proteins that are thought to manipulate cellular activities to the benefit of the pathogen. One step toward disease management comprises understanding the molecular basis of host susceptibility. In this paper, we used a protoplast-based system to analyze a subset of P. infestans RXLR (PiRXLR) effectors that interfere with plant immunity initiated by the recognition of microbial patterns (MAMP-triggered immunity - MTI). We identified PiRXLR effectors that suppress different stages early in the signaling cascade leading to MTI in tomato. By conducting a comparative functional analysis, we found that some of these effectors attenuate early MTI signaling in Arabidopsis, a plant that is not colonized by P. infestans. The PiRXLR effectors localize to different sub-cellular compartments, consistent with their ability to suppress different steps of the MTI signaling pathway. We conclude that the effector complement of P. infestans contains functional redundancy in the context of suppressing early signal transduction and gene activation associated with plant immunity.
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126
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Cheng C, Gao X, Feng B, Sheen J, Shan L, He P. Plant immune response to pathogens differs with changing temperatures. Nat Commun 2014; 4:2530. [PMID: 24067909 DOI: 10.1038/ncomms3530] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Accepted: 09/02/2013] [Indexed: 01/19/2023] Open
Abstract
Temperature fluctuation is a key determinant for microbial invasion and host evasion. In contrast to mammals that maintain constant body temperature, plant temperature oscillates on a daily basis. It remains elusive how plants operate inducible defenses in response to temperature fluctuation. Here we report that ambient temperature changes lead to pronounced shifts of the following two distinct plant immune responses: pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). Plants preferentially activate ETI signaling at relatively low temperatures (10-23 °C), whereas they switch to PTI signaling at moderately elevated temperatures (23-32 °C). The Arabidopsis arp6 and hta9hta11 mutants, phenocopying plants grown at elevated temperatures, exhibit enhanced PTI and yet reduced ETI responses. As the secretion of bacterial effectors favours low temperatures, whereas bacteria multiply vigorously at elevated temperatures accompanied with increased microbe-associated molecular pattern production, our findings suggest that temperature oscillation might have driven dynamic co-evolution of distinct plant immune signaling responding to pathogen physiological changes.
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Affiliation(s)
- Cheng Cheng
- 1] Department of Biochemistry and Biophysics, Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, Texas 77843, USA [2]
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Macho AP, Schwessinger B, Ntoukakis V, Brutus A, Segonzac C, Roy S, Kadota Y, Oh MH, Sklenar J, Derbyshire P, Lozano-Duran R, Malinovsky FG, Monaghan J, Menke FL, Huber SC, He SY, Zipfel C. A Bacterial Tyrosine Phosphatase Inhibits Plant Pattern Recognition Receptor Activation. Science 2014; 343:1509-12. [DOI: 10.1126/science.1248849] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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128
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Block A, Toruño TY, Elowsky CG, Zhang C, Steinbrenner J, Beynon J, Alfano JR. The Pseudomonas syringae type III effector HopD1 suppresses effector-triggered immunity, localizes to the endoplasmic reticulum, and targets the Arabidopsis transcription factor NTL9. THE NEW PHYTOLOGIST 2014; 201:1358-1370. [PMID: 24329768 DOI: 10.1111/nph.12626] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2013] [Accepted: 10/30/2013] [Indexed: 05/23/2023]
Abstract
• Pseudomonas syringae type III effectors are known to suppress plant immunity to promote bacterial virulence. However, the activities and targets of these effectors are not well understood. • We used genetic, molecular, and cell biology methods to characterize the activities, localization, and target of the HopD1 type III effector in Arabidopsis. • HopD1 contributes to P. syringae virulence in Arabidopsis and reduces effector-triggered immunity (ETI) responses but not pathogen-associated molecular pattern-triggered immunity (PTI) responses. Plants expressing HopD1 supported increased growth of ETI-inducing P. syringae strains compared with wild-type Arabidopsis. We show that HopD1 interacts with the membrane-tethered Arabidopsis transcription factor NTL9 and demonstrate that this interaction occurs at the endoplasmic reticulum (ER). A P. syringae hopD1 mutant and ETI-inducing P. syringae strains exhibited enhanced growth on Arabidopsis ntl9 mutant plants. Conversely, growth of P. syringae strains was reduced in plants expressing a constitutively active NTL9 derivative, indicating that NTL9 is a positive regulator of plant immunity. Furthermore, HopD1 inhibited the induction of NTL9-regulated genes during ETI but not PTI. • HopD1 contributes to P. syringae virulence in part by targeting NTL9, resulting in the suppression of ETI responses but not PTI responses and the promotion of plant pathogenicity.
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Affiliation(s)
- Anna Block
- Center for Plant Science Innovation, University of Nebraska, Lincoln, NE, 68588-0660, USA
- Department of Plant Pathology, University of Nebraska, Lincoln, NE, 68588-0722, USA
| | - Tania Y Toruño
- Center for Plant Science Innovation, University of Nebraska, Lincoln, NE, 68588-0660, USA
- Department of Plant Pathology, University of Nebraska, Lincoln, NE, 68588-0722, USA
| | - Christian G Elowsky
- Center for Biotechnology, University of Nebraska, Lincoln, NE, 68588-0665, USA
| | - Chi Zhang
- Center for Plant Science Innovation, University of Nebraska, Lincoln, NE, 68588-0660, USA
- School of Biological Sciences, University of Nebraska, Lincoln, NE, 68588-0118, USA
| | - Jens Steinbrenner
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Jim Beynon
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - James R Alfano
- Center for Plant Science Innovation, University of Nebraska, Lincoln, NE, 68588-0660, USA
- Department of Plant Pathology, University of Nebraska, Lincoln, NE, 68588-0722, USA
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129
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Teper D, Salomon D, Sunitha S, Kim JG, Mudgett MB, Sessa G. Xanthomonas euvesicatoria type III effector XopQ interacts with tomato and pepper 14-3-3 isoforms to suppress effector-triggered immunity. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 77:297-309. [PMID: 24279912 DOI: 10.1111/tpj.12391] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 11/12/2013] [Accepted: 11/15/2013] [Indexed: 05/09/2023]
Abstract
Effector-triggered immunity (ETI) to host-adapted pathogens is associated with rapid cell death at the infection site. The plant-pathogenic bacterium Xanthomonas euvesicatoria (Xcv) interferes with plant cellular processes by injecting effector proteins into host cells through the type III secretion system. Here, we show that the Xcv effector XopQ suppresses cell death induced by components of the ETI-associated MAP kinase cascade MAPKKKα MEK2/SIPK and by several R/avr gene pairs. Inactivation of xopQ by insertional mutagenesis revealed that this effector inhibits ETI-associated cell death induced by avirulent Xcv in resistant pepper (Capsicum annuum), and enhances bacterial growth in resistant pepper and tomato (Solanum lycopersicum). Using protein-protein interaction studies in yeast (Saccharomyces cerevisiae) and in planta, we identified the tomato 14-3-3 isoform SlTFT4 and homologs from other plant species as XopQ interactors. A mutation in the putative 14-3-3 binding site of XopQ impaired interaction of the effector with CaTFT4 in yeast and its virulence function in planta. Consistent with a role in ETI, TFT4 mRNA abundance increased during the incompatible interaction of tomato and pepper with Xcv. Silencing of NbTFT4 in Nicotiana benthamiana significantly reduced cell death induced by MAPKKKα. In addition, silencing of CaTFT4 in pepper delayed the appearance of ETI-associated cell death and enhanced growth of virulent and avirulent Xcv, demonstrating the requirement of TFT4 for plant immunity to Xcv. Our results suggest that the XopQ virulence function is to suppress ETI and immunity-associated cell death by interacting with TFT4, which is an important component of ETI and a bona fide target of XopQ.
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Affiliation(s)
- Doron Teper
- Department of Molecular Biology and Ecology of Plants, Tel Aviv University, 69978, Tel Aviv, Israel
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130
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Li G, Froehlich JE, Elowsky C, Msanne J, Ostosh AC, Zhang C, Awada T, Alfano JR. Distinct Pseudomonas type-III effectors use a cleavable transit peptide to target chloroplasts. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 77:310-21. [PMID: 24299018 DOI: 10.1111/tpj.12396] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 11/13/2013] [Accepted: 11/19/2013] [Indexed: 05/24/2023]
Abstract
The pathogen Pseudomonas syringae requires a type-III protein secretion system and the effector proteins it injects into plant cells for pathogenesis. The primary role for P. syringae type-III effectors is the suppression of plant immunity. The P. syringae pv. tomato DC3000 HopK1 type-III effector was known to suppress the hypersensitive response (HR), a programmed cell death response associated with effector-triggered immunity. Here we show that DC3000 hopK1 mutants are reduced in their ability to grow in Arabidopsis, and produce reduced disease symptoms. Arabidopsis transgenically expressing HopK1 are reduced in PAMP-triggered immune responses compared with wild-type plants. An N-terminal region of HopK1 shares similarity with the corresponding region in the well-studied type-III effector AvrRps4; however, their C-terminal regions are dissimilar, indicating that they have different effector activities. HopK1 is processed in planta at the same processing site found in AvrRps4. The processed forms of HopK1 and AvrRps4 are chloroplast localized, indicating that the shared N-terminal regions of these type-III effectors represent a chloroplast transit peptide. The HopK1 contribution to virulence and the ability of HopK1 and AvrRps4 to suppress immunity required their respective transit peptides, but the AvrRps4-induced HR did not. Our results suggest that a primary virulence target of these type-III effectors resides in chloroplasts, and that the recognition of AvrRps4 by the plant immune system occurs elsewhere. Moreover, our results reveal that distinct type-III effectors use a cleavable transit peptide to localize to chloroplasts, and that targets within this organelle are important for immunity.
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Affiliation(s)
- Guangyong Li
- Center for Plant Science Innovation, University of Nebraska, Lincoln, NE, 68588-0660, USA; Department of Plant Pathology, University of Nebraska, Lincoln, NE, 68583-0722, USA
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131
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Hann DR, Domínguez-Ferreras A, Motyka V, Dobrev PI, Schornack S, Jehle A, Felix G, Chinchilla D, Rathjen JP, Boller T. The Pseudomonas type III effector HopQ1 activates cytokinin signaling and interferes with plant innate immunity. THE NEW PHYTOLOGIST 2014; 201:585-598. [PMID: 24124900 DOI: 10.1111/nph.12544] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 09/02/2013] [Indexed: 05/26/2023]
Abstract
We characterized the molecular function of the Pseudomonas syringae pv. tomato DC3000 (Pto) effector HopQ1. In silico studies suggest that HopQ1 might possess nucleoside hydrolase activity based on the presence of a characteristic aspartate motif. Transgenic Arabidopsis lines expressing HopQ1 or HopQ1 aspartate mutant variants were characterized with respect to flagellin triggered immunity, phenotype and changes in phytohormone content by high-performance liquid chromatography-MS (HPLC-MS). We found that HopQ1, but not its aspartate mutants, suppressed all tested immunity marker assays. Suppression of immunity was the result of a lack of the flagellin receptor FLS2, whose gene expression was abolished by HopQ1 in a promoter-dependent manner. Furthermore, HopQ1 induced cytokinin signaling in Arabidopsis and the elevation in cytokinin signaling appears to be responsible for the attenuation of FLS2 expression. We conclude that HopQ1 can activate cytokinin signaling and that moderate activation of cytokinin signaling leads to suppression of FLS2 accumulation and thus defense signaling.
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Affiliation(s)
- Dagmar R Hann
- Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland
| | - Ana Domínguez-Ferreras
- Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland
| | - Vaclav Motyka
- Institute of Experimental Botany AS CR, Rozvojová 263, 165 02, Praha 6 - Lysolaje, Czech Republic
| | - Petre I Dobrev
- Institute of Experimental Botany AS CR, Rozvojová 263, 165 02, Praha 6 - Lysolaje, Czech Republic
| | | | - Anna Jehle
- Forschungsgruppe Pflanzenbiochemie, ZMBP - Zentrum für Molekularbiologie der Pflanzen, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 5, 72076, Tübingen, Germany
| | - Georg Felix
- Forschungsgruppe Pflanzenbiochemie, ZMBP - Zentrum für Molekularbiologie der Pflanzen, Eberhard-Karls-Universität Tübingen, Auf der Morgenstelle 5, 72076, Tübingen, Germany
| | - Delphine Chinchilla
- Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland
| | - John P Rathjen
- The Australian National University, The Linnaeus Building, Building 134, Linnaeus Way, Canberra, ACT, 0200, Australia
| | - Thomas Boller
- Section of Plant Physiology, Botanical Institute, Hebelstrasse 1, CH-4056, Basel, Switzerland
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132
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Vinatzer BA, Monteil CL, Clarke CR. Harnessing population genomics to understand how bacterial pathogens emerge, adapt to crop hosts, and disseminate. ANNUAL REVIEW OF PHYTOPATHOLOGY 2014; 52:19-43. [PMID: 24820995 DOI: 10.1146/annurev-phyto-102313-045907] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Crop diseases emerge without warning. In many cases, diseases cross borders, or even oceans, before plant pathologists have time to identify and characterize the causative agents. Genome sequencing, in combination with intensive sampling of pathogen populations and application of population genetic tools, is now providing the means to unravel how bacterial crop pathogens emerge from environmental reservoirs, how they evolve and adapt to crops, and what international and intercontinental routes they follow during dissemination. Here, we introduce the field of population genomics and review the population genomics research of bacterial plant pathogens over the past 10 years. We highlight the potential of population genomics for investigating plant pathogens, using examples of population genomics studies of human pathogens. We also describe the complementary nature of the fields of population genomics and molecular plant-microbe interactions and propose how to translate new insights into improved disease prevention and control.
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Affiliation(s)
- Boris A Vinatzer
- Department of Plant Pathology, Physiology, and Weed Science, Virginia Tech, Blacksburg, Virginia 24061; ,
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133
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Chang JH, Desveaux D, Creason AL. The ABCs and 123s of bacterial secretion systems in plant pathogenesis. ANNUAL REVIEW OF PHYTOPATHOLOGY 2014; 52:317-45. [PMID: 24906130 DOI: 10.1146/annurev-phyto-011014-015624] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Bacteria have many export and secretion systems that translocate cargo into and across biological membranes. Seven secretion systems contribute to pathogenicity by translocating proteinaceous cargos that can be released into the extracellular milieu or directly into recipient cells. In this review, we describe these secretion systems and how their complexities and functions reflect differences in the destinations, states, functions, and sizes of the translocated cargos as well as the architecture of the bacterial cell envelope. We examine the secretion systems from the perspective of pathogenic bacteria that proliferate within plant tissues and highlight examples of translocated proteins that contribute to the infection and disease of plant hosts.
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Affiliation(s)
- Jeff H Chang
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97331; ,
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Abstract
Plants are invaded by an array of pathogens of which only a few succeed in causing disease. The attack by others is countered by a sophisticated immune system possessed by the plants. The plant immune system is broadly divided into two, viz. microbial-associated molecular-patterns-triggered immunity (MTI) and effector-triggered immunity (ETI). MTI confers basal resistance, while ETI confers durable resistance, often resulting in hypersensitive response. Plants also possess systemic acquired resistance (SAR), which provides long-term defense against a broad-spectrum of pathogens. Salicylic-acid-mediated systemic acquired immunity provokes the defense response throughout the plant system during pathogen infection at a particular site. Trans-generational immune priming allows the plant to heritably shield their progeny towards pathogens previously encountered. Plants circumvent the viral infection through RNA interference phenomena by utilizing small RNAs. This review summarizes the molecular mechanisms of plant immune system, and the latest breakthroughs reported in plant defense. We discuss the plant–pathogen interactions and integrated defense responses in the context of presenting an integral understanding in plant molecular immunity.
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135
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Lin W, Ma X, Shan L, He P. Big roles of small kinases: the complex functions of receptor-like cytoplasmic kinases in plant immunity and development. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2013; 55:1188-97. [PMID: 23710768 PMCID: PMC4391744 DOI: 10.1111/jipb.12071] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Accepted: 05/21/2013] [Indexed: 05/19/2023]
Abstract
Plants have evolved a large number of receptor-like cytoplasmic kinases (RLCKs) that often functionally and physically associate with receptor-like kinases (RLKs) to modulate plant growth, development and immune responses. Without any apparent extracellular domain, RLCKs relay intracellular signaling often via RLK complex-mediated transphosphorylation events. Recent advances have suggested essential roles of diverse RLCKs in concert with RLKs in regulating various cellular and physiological responses. We summarize here the complex roles of RLCKs in mediating plant immune responses and growth regulation, and discuss specific and overlapping functions of RLCKs in transducing diverse signaling pathways. [Figure: see text] Ping He (Corresponding author).
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Affiliation(s)
- Wenwei Lin
- Department of Plant Pathology and Microbiology, and Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, Texas 77843, USA
| | - Xiyu Ma
- Department of Biochemistry and Biophysics, and Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, Texas 77843, USA
| | - Libo Shan
- Department of Plant Pathology and Microbiology, and Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, Texas 77843, USA
| | - Ping He
- Department of Biochemistry and Biophysics, and Institute for Plant Genomics and Biotechnology, Texas A&M University, College Station, Texas 77843, USA
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136
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Wu Y, Zhou JM. Receptor-like kinases in plant innate immunity. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2013; 55:1271-86. [PMID: 24308571 DOI: 10.1111/jipb.12123] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Accepted: 10/23/2013] [Indexed: 05/20/2023]
Abstract
Plants employ a highly effective surveillance system to detect potential pathogens, which is critical for the success of land plants in an environment surrounded by numerous microbes. Recent efforts have led to the identification of a number of immune receptors and components of immune receptor complexes. It is now clear that receptor-like kinases (RLKs) and receptor-like proteins (RLPs) are key pattern-recognition receptors (PRRs) for microbe- and plant-derived molecular patterns that are associated with pathogen invasion. RLKs and RLPs involved in immune signaling belong to large gene families in plants and have undergone lineage specific expansion. Molecular evolution and population studies on phytopathogenic molecular signatures and their receptors have provided crucial insight into the co-evolution between plants and pathogens. [Figure: see text] Jian-Min Zhou (Corresponding author).
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Affiliation(s)
- Ying Wu
- State Key Laboratory of Plant Genomics and National Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
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137
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Dudler R. The role of bacterial phytotoxins in inhibiting the eukaryotic proteasome. Trends Microbiol 2013; 22:28-35. [PMID: 24284310 DOI: 10.1016/j.tim.2013.10.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 10/25/2013] [Accepted: 10/30/2013] [Indexed: 11/19/2022]
Abstract
The ubiquitin-26S proteasome degradation system (UPS) plays a pivotal role in almost all aspects of plant life, including defending against pathogens. Although the proteasome is important for plant immunity, it has been found to be also exploited by pathogens using effectors to increase their virulence. Recent work on the XopJ effector and syringolin A/syrbactins has highlighted host proteasome inhibition as a virulence strategy of pathogens. This review will focus on these recent developments.
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Affiliation(s)
- Robert Dudler
- Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, CH-8008 Zurich, Switzerland.
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138
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Lohou D, Lonjon F, Genin S, Vailleau F. Type III chaperones & Co in bacterial plant pathogens: a set of specialized bodyguards mediating effector delivery. FRONTIERS IN PLANT SCIENCE 2013; 4:435. [PMID: 24319448 PMCID: PMC3837300 DOI: 10.3389/fpls.2013.00435] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 10/12/2013] [Indexed: 05/19/2023]
Abstract
Gram-negative plant pathogenic bacteria possess a type III secretion system (T3SS) to inject bacterial proteins, called type III effectors (T3Es), into host cells through a specialized syringe structure. T3Es are virulence factors that can suppress plant immunity but they can also conversely be recognized by the plant and trigger specific resistance mechanisms. The T3SS and injected T3Es play a central role in determining the outcome of a host-pathogen interaction. Still little is known in plant pathogens on the assembly of the T3SS and the regulatory mechanisms involved in the temporal control of its biosynthesis and T3E translocation. However, recent insights point out the role of several proteins as prime candidates in the role of regulators of the type III secretion (T3S) process. In this review we report on the most recent advances on the regulation of the T3S by focusing on protein players involved in secretion/translocation regulations, including type III chaperones (T3Cs), type III secretion substrate specificity switch (T3S4) proteins and other T3S orchestrators.
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Affiliation(s)
- David Lohou
- Institut National de la Recherche Agronomique, UMR441, Laboratoire des Interactions Plantes-MicroorganismesCastanet-Tolosan, France
- Centre National de la Recherche Scientifique, UMR2594, Laboratoire des Interactions Plantes-MicroorganismesCastanet-Tolosan, France
| | - Fabien Lonjon
- Institut National de la Recherche Agronomique, UMR441, Laboratoire des Interactions Plantes-MicroorganismesCastanet-Tolosan, France
- Centre National de la Recherche Scientifique, UMR2594, Laboratoire des Interactions Plantes-MicroorganismesCastanet-Tolosan, France
| | - Stéphane Genin
- Institut National de la Recherche Agronomique, UMR441, Laboratoire des Interactions Plantes-MicroorganismesCastanet-Tolosan, France
- Centre National de la Recherche Scientifique, UMR2594, Laboratoire des Interactions Plantes-MicroorganismesCastanet-Tolosan, France
| | - Fabienne Vailleau
- Institut National de la Recherche Agronomique, UMR441, Laboratoire des Interactions Plantes-MicroorganismesCastanet-Tolosan, France
- Centre National de la Recherche Scientifique, UMR2594, Laboratoire des Interactions Plantes-MicroorganismesCastanet-Tolosan, France
- Institut National Polytechnique, École Nationale Supérieure Agronomique de Toulouse, Université de ToulouseCastanet-Tolosan, France
- *Correspondence: Fabienne Vailleau, Institut National de la Recherche Agronomique, UMR441, Laboratoire des Interactions Plantes-Microorganismes, CS 52627, 24 Chemin de Borde Rouge-Auzeville, Castanet-Tolosan cedex 31326, France e-mail:
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139
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Gaucher M, Dugé de Bernonville T, Guyot S, Dat JF, Brisset MN. Same ammo, different weapons: enzymatic extracts from two apple genotypes with contrasted susceptibilities to fire blight (Erwinia amylovora) differentially convert phloridzin and phloretin in vitro. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2013; 72:178-89. [PMID: 23561298 DOI: 10.1016/j.plaphy.2013.03.012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 03/13/2013] [Indexed: 05/14/2023]
Abstract
The necrogenic bacterium Erwinia amylovora responsible for the fire blight disease causes cell death in apple tissues to enrich intercellular spaces with nutrients. Apple leaves contain large amounts of dihydrochalcones (DHCs), including phloridzin and its aglycone phloretin. Previous work showed an important decrease in the constitutive DHCs stock in infected leaves, probably caused by transformation reactions during the infection process. At least two flavonoid transformation pathways have been described so far: deglucosylation and oxidation. The aim of the present study was to determine whether DHCs are differentially converted in two apple genotypes displaying contrasted susceptibilities to the disease. Different analyses were performed: i) enzymatic activity assays in infected leaves, ii) identification/quantification of end-products obtained after in vitro enzymatic reactions with DHCs, iii) evaluation of the bactericidal activity of end-products. The results of the enzymatic assays showed that deglucosylation was dominant over oxidation in the susceptible genotype MM106 while the opposite was observed in the resistant genotype Evereste. These data were confirmed by LC-UV/Vis-MS analysis of in vitro reaction mixtures, especially because higher levels of o-quinoid oxidation products of phloretin were measured by using the enzymatic extracts of Evereste infected leaves. Their presence correlated well with a strong bactericidal activity of the reaction mixtures. Thus, our results suggest that a differential transformation of DHCs occur in apple genotypes with a potential involvement in the establishment of the susceptibility or the resistance to fire blight, through the release of glucose or of highly bactericidal compounds respectively.
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Affiliation(s)
- Matthieu Gaucher
- INRA, UMR1345 Institut de Recherche en Horticulture et Semences, F-49071 Angers, France; Université d'Angers, UMR1345 Institut de Recherche en Horticulture et Semences, F-49071 Angers, France; Agrocampus-Ouest, UMR1345 Institut de Recherche en Horticulture et Semences, F-49071 Angers, France
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140
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Jacob F, Vernaldi S, Maekawa T. Evolution and Conservation of Plant NLR Functions. Front Immunol 2013; 4:297. [PMID: 24093022 PMCID: PMC3782705 DOI: 10.3389/fimmu.2013.00297] [Citation(s) in RCA: 182] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 09/09/2013] [Indexed: 12/21/2022] Open
Abstract
In plants and animals, nucleotide-binding domain and leucine-rich repeats (NLR)-containing proteins play pivotal roles in innate immunity. Despite their similar biological functions and protein architecture, comparative genome-wide analyses of NLRs and genes encoding NLR-like proteins suggest that plant and animal NLRs have independently arisen in evolution. Furthermore, the demonstration of interfamily transfer of plant NLR functions from their original species to phylogenetically distant species implies evolutionary conservation of the underlying immune principle across plant taxonomy. In this review we discuss plant NLR evolution and summarize recent insights into plant NLR-signaling mechanisms, which might constitute evolutionarily conserved NLR-mediated immune mechanisms.
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Affiliation(s)
- Florence Jacob
- Department of Plant-Microbe Interactions, Max Planck Institute for Plant Breeding Research , Cologne , Germany ; Unité de Recherche en Génomique Végétale, Institut National de la Recherche Agronomique, Centre National de la Recherche Scientifique, Université Evry Val d'Essone , Evry , France
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141
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A receptor-like cytoplasmic kinase targeted by a plant pathogen effector is directly phosphorylated by the chitin receptor and mediates rice immunity. Cell Host Microbe 2013; 13:347-57. [PMID: 23498959 DOI: 10.1016/j.chom.2013.02.007] [Citation(s) in RCA: 166] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Revised: 01/10/2013] [Accepted: 02/20/2013] [Indexed: 01/14/2023]
Abstract
CERK1 is a lysine motif-containing plant pattern recognition receptor for chitin and peptidoglycan. Chitin recognition by OsCERK1 triggers rapid engagement of a rice MAP kinase cascade, which leads to defense response activation. How the MAP kinase cascades are engaged downstream of OsCERK1 remains obscure. Searching for host proteins that interact with Xoo1488, an effector of the rice pathogen Xanthomonas oryzae, we identified the rice receptor-like cytoplasmic kinase, OsRLCK185. Silencing OsRLCK185 suppressed peptidoglycan- and chitin-induced immune responses, including MAP kinase activation and defense-gene expression. In response to chitin, OsRLCK185 associates with, and is directly phosphorylated by, OsCERK1 at the plasma membrane. Xoo1488 inhibits peptidoglycan- and chitin-induced immunity and pathogen resistance. Additionally, OsCERK1-mediated phosphorylation of OsRLCK185 is suppressed by Xoo1488, resulting in the inhibition of chitin-induced MAP kinase activation. These data support a role for OsRLCK185 as an essential immediate downstream signaling partner of OsCERK1 in mediating chitin- and peptidoglycan-induced plant immunity.
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142
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Mitchum MG, Hussey RS, Baum TJ, Wang X, Elling AA, Wubben M, Davis EL. Nematode effector proteins: an emerging paradigm of parasitism. THE NEW PHYTOLOGIST 2013; 199:879-894. [PMID: 23691972 DOI: 10.1111/nph.12323] [Citation(s) in RCA: 184] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 04/05/2013] [Indexed: 05/18/2023]
Abstract
Phytonematodes use a stylet and secreted effectors to modify host cells and ingest nutrients to support their growth and development. The molecular function of nematode effectors is currently the subject of intense investigation. In this review, we summarize our current understanding of nematode effectors, with a particular focus on proteinaceous stylet-secreted effectors of sedentary endoparasitic phytonematodes, for which a wealth of information has surfaced in the past 10 yr. We provide an update on the effector repertoires of several of the most economically important genera of phytonematodes and discuss current approaches to dissecting their function. Lastly, we highlight the latest breakthroughs in effector discovery that promise to shed new light on effector diversity and function across the phylum Nematoda.
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Affiliation(s)
- Melissa G Mitchum
- Division of Plant Sciences and Bond Life Sciences Center, University of Missouri, Columbia, MO, 65211, USA
| | - Richard S Hussey
- Department of Plant Pathology, University of Georgia, Athens, GA, 30602, USA
| | - Thomas J Baum
- Department of Plant Pathology and Microbiology, Iowa State University, Ames, IA, 50011, USA
| | - Xiaohong Wang
- USDA-ARS, Robert W. Holley Center for Agriculture and Health and Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Axel A Elling
- Department of Plant Pathology, Washington State University, Pullman, WA, 99164, USA
| | - Martin Wubben
- USDA-ARS, Crop Science Research Laboratory, Genetics and Precision Agriculture Research Unit and Department of Biochemistry and Molecular Biology, Mississippi State University, Mississippi State, MS, 39762, USA
| | - Eric L Davis
- Department of Plant Pathology, North Carolina State University, Raleigh, NC, 27695, USA
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143
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Üstün S, Bartetzko V, Börnke F. The Xanthomonas campestris type III effector XopJ targets the host cell proteasome to suppress salicylic-acid mediated plant defence. PLoS Pathog 2013; 9:e1003427. [PMID: 23785289 PMCID: PMC3681735 DOI: 10.1371/journal.ppat.1003427] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 05/01/2013] [Indexed: 01/15/2023] Open
Abstract
The phytopathogenic bacterium Xanthomonas campestris pv. vesicatoria (Xcv) requires type III effector proteins (T3Es) for virulence. After translocation into the host cell, T3Es are thought to interact with components of host immunity to suppress defence responses. XopJ is a T3E protein from Xcv that interferes with plant immune responses; however, its host cellular target is unknown. Here we show that XopJ interacts with the proteasomal subunit RPT6 in yeast and in planta to inhibit proteasome activity. A C235A mutation within the catalytic triad of XopJ as well as a G2A exchange within the N-terminal myristoylation motif abolishes the ability of XopJ to inhibit the proteasome. Xcv ΔxopJ mutants are impaired in growth and display accelerated symptom development including tissue necrosis on susceptible pepper leaves. Application of the proteasome inhibitor MG132 restored the ability of the Xcv ΔxopJ to attenuate the development of leaf necrosis. The XopJ dependent delay of tissue degeneration correlates with reduced levels of salicylic acid (SA) and changes in defence- and senescence-associated gene expression. Necrosis upon infection with Xcv ΔxopJ was greatly reduced in pepper plants with reduced expression of NPR1, a central regulator of SA responses, demonstrating the involvement of SA-signalling in the development of XopJ dependent phenotypes. Our results suggest that XopJ-mediated inhibition of the proteasome interferes with SA-dependent defence response to attenuate onset of necrosis and to alter host transcription. A central role of the proteasome in plant defence is discussed.
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Affiliation(s)
- Suayib Üstün
- Friedrich-Alexander-University Erlangen-Nuremberg, Department of Biology, Division of Biochemistry, Erlangen, Germany
| | - Verena Bartetzko
- Friedrich-Alexander-University Erlangen-Nuremberg, Department of Biology, Division of Biochemistry, Erlangen, Germany
| | - Frederik Börnke
- Friedrich-Alexander-University Erlangen-Nuremberg, Department of Biology, Division of Biochemistry, Erlangen, Germany
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144
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Exploitation of eukaryotic subcellular targeting mechanisms by bacterial effectors. Nat Rev Microbiol 2013; 11:316-26. [PMID: 23588250 DOI: 10.1038/nrmicro3009] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Several bacterial species have evolved specialized secretion systems to deliver bacterial effector proteins into eukaryotic cells. These effectors have the capacity to modulate host cell pathways in order to promote bacterial survival and replication. The spatial and temporal context in which the effectors exert their biochemical activities is crucial for their function. To fully understand effector function in the context of infection, we need to understand the mechanisms that lead to the precise subcellular localization of effectors following their delivery into host cells. Recent studies have shown that bacterial effectors exploit host cell machinery to accurately target their biochemical activities within the host cell.
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145
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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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146
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Speak, friend, and enter: signalling systems that promote beneficial symbiotic associations in plants. Nat Rev Microbiol 2013; 11:252-63. [PMID: 23493145 DOI: 10.1038/nrmicro2990] [Citation(s) in RCA: 818] [Impact Index Per Article: 74.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Plants associate with a wide range of microorganisms, with both detrimental and beneficial outcomes. Central to plant survival is the ability to recognize invading microorganisms and either limit their intrusion, in the case of pathogens, or promote the association, in the case of symbionts. To aid in this recognition process, elaborate communication and counter-communication systems have been established that determine the degree of ingress of the microorganism into the host plant. In this Review, I describe the common signalling processes used by plants during mutualistic interactions with microorganisms as diverse as arbuscular mycorrhizal fungi and rhizobial bacteria.
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147
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Dou D, Zhou JM. Phytopathogen effectors subverting host immunity: different foes, similar battleground. Cell Host Microbe 2013; 12:484-95. [PMID: 23084917 DOI: 10.1016/j.chom.2012.09.003] [Citation(s) in RCA: 293] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Phytopathogenic bacteria, fungi, and oomycetes invade and colonize their host plants through distinct routes. These pathogens secrete diverse groups of effector proteins that aid infection and establishment of different parasitic lifestyles. Despite this diversity, a comparison of different plant-pathogen systems has revealed remarkable similarities in the host immune pathways targeted by effectors from distinct pathogen groups. Immune signaling pathways mediated by pattern recognition receptors, phytohormone homeostasis or signaling, defenses associated with host secretory pathways and pathogen penetrations, and plant cell death represent some of the key processes controlling disease resistance against diverse pathogens. These immune pathways are targeted by effectors that carry a wide range of biochemical functions and are secreted by completely different pathogen groups, suggesting that these pathways are a common battleground encountered by many plant pathogens.
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Affiliation(s)
- Daolong Dou
- College of Plant Protection, Nanjing Agricultural University, Nanjing, 210095, China
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148
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Wang Y, Sun M, Bao H, White AP. T3_MM: a Markov model effectively classifies bacterial type III secretion signals. PLoS One 2013; 8:e58173. [PMID: 23472154 PMCID: PMC3589343 DOI: 10.1371/journal.pone.0058173] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 01/31/2013] [Indexed: 11/18/2022] Open
Abstract
MOTIVATION Type III Secretion Systems (T3SSs) play important roles in the interaction between gram-negative bacteria and their hosts. T3SSs function by translocating a group of bacterial effector proteins into the host cytoplasm. The details of specific type III secretion process are yet to be clarified. This research focused on comparing the amino acid composition within the N-terminal 100 amino acids from type III secretion (T3S) signal sequences or non-T3S proteins, specifically whether each residue exerts a constraint on residues found in adjacent positions. We used these comparisons to set up a statistic model to quantitatively model and effectively distinguish T3S effectors. RESULTS In this study, the amino acid composition (Aac) probability profiles conditional on its sequentially preceding position and corresponding amino acids were compared between N-terminal sequences of T3S and non-T3S proteins. The profiles are generally different. A Markov model, namely T3_MM, was consequently designed to calculate the total Aac conditional probability difference, i.e., the likelihood ratio of a sequence being a T3S or a non-T3S protein. With T3_MM, known T3S and non-T3S proteins were found to well approximate two distinct normal distributions. The model could distinguish validated T3S and non-T3S proteins with a 5-fold cross-validation sensitivity of 83.9% at a specificity of 90.3%. T3_MM was also shown to be more robust, accurate, simple, and statistically quantitative, when compared with other T3S protein prediction models. The high effectiveness of T3_MM also indicated the overall Aac difference between N-termini of T3S and non-T3S proteins, and the constraint of Aac exerted by its preceding position and corresponding Aac. AVAILABILITY An R package for T3_MM is freely downloadable from: http://biocomputer.bio.cuhk.edu.hk/softwares/T3_MM. T3_MM web server: http://biocomputer.bio.cuhk.edu.hk/T3DB/T3_MM.php.
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Affiliation(s)
- Yejun Wang
- Genomics Research Center, Haerbin Medical University, Harbin, China
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Ming'an Sun
- School of Life Science, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong
| | - Hongxia Bao
- Genomics Research Center, Haerbin Medical University, Harbin, China
| | - Aaron P. White
- Vaccine and Infectious Disease Organization, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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149
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Shi H, Shen Q, Qi Y, Yan H, Nie H, Chen Y, Zhao T, Katagiri F, Tang D. BR-SIGNALING KINASE1 physically associates with FLAGELLIN SENSING2 and regulates plant innate immunity in Arabidopsis. THE PLANT CELL 2013; 25:1143-57. [PMID: 23532072 PMCID: PMC3634682 DOI: 10.1105/tpc.112.107904] [Citation(s) in RCA: 190] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 03/07/2013] [Accepted: 03/12/2013] [Indexed: 05/19/2023]
Abstract
Pathogen-associated molecular pattern (PAMP)-trigged immunity (PTI) is the first defensive line of plant innate immunity and is mediated by pattern recognition receptors. Here, we show that a mutation in BR-SIGNALING KINASE1 (BSK1), a substrate of the brassinosteroid (BR) receptor BRASSINOSTEROID INSENSITIVE1, suppressed the powdery mildew resistance caused by a mutation in ENHANCED DISEASE RESISTANCE2, which negatively regulates powdery mildew resistance and programmed cell death, in Arabidopsis thaliana. A loss-of-function bsk1 mutant displayed enhanced susceptibility to virulent and avirulent pathogens, including Golovinomyces cichoracearum, Pseudomonas syringae, and Hyaloperonospora arabidopsidis. The bsk1 mutant also accumulated lower levels of salicylic acid upon infection with G. cichoracearum and P. syringae. BSK1 belongs to a receptor-like cytoplasmic kinase family and displays kinase activity in vitro; this kinase activity is required for its function. BSK1 physically associates with the PAMP receptor FLAGELLIN SENSING2 and is required for a subset of flg22-induced responses, including the reactive oxygen burst, but not for mitogen-activated protein kinase activation. Our data demonstrate that BSK1 is involved in positive regulation of PTI. Together with previous findings, our work indicates that BSK1 represents a key component directly involved in both BR signaling and plant immunity.
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Affiliation(s)
- Hua Shi
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qiujing Shen
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yiping Qi
- Department of Plant Biology, Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, Minnesota 55108
| | - Haojie Yan
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Haozhen Nie
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yongfang Chen
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Ting Zhao
- State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Fumiaki Katagiri
- Department of Plant Biology, Microbial and Plant Genomics Institute, University of Minnesota, St. Paul, Minnesota 55108
| | - Dingzhong Tang
- 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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Grant MR, Kazan K, Manners JM. Exploiting pathogens' tricks of the trade for engineering of plant disease resistance: challenges and opportunities. Microb Biotechnol 2013; 6:212-22. [PMID: 23279915 PMCID: PMC3815916 DOI: 10.1111/1751-7915.12017] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Accepted: 11/17/2012] [Indexed: 12/01/2022] Open
Abstract
With expansion of our understanding of pathogen effector strategies and the multiplicity of their host targets, it is becoming evident that novel approaches to engineering broad-spectrum resistance need to be deployed. The increasing availability of high temporal gene expression data of a range of plant–microbe interactions enables the judicious choices of promoters to fine-tune timing and magnitude of expression under specified stress conditions. We can therefore contemplate engineering a range of transgenic lines designed to interfere with pathogen virulence strategies that target plant hormone signalling or deploy specific disease resistance genes. An advantage of such an approach is that hormonal signalling is generic so if this strategy is effective, it can be easily implemented in a range of crop species. Additionally, multiple re-wired lines can be crossed to develop more effective responses to pathogens.
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Affiliation(s)
- Murray R Grant
- College of Life and Environmental Sciences, University of Exeter, Exeter, Stocker Road, Exeter, EX4 4QD, UK.
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