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Volkov M, van Schie KA, van der Woude D. Autoantibodies and B Cells: The ABC of rheumatoid arthritis pathophysiology. Immunol Rev 2019; 294:148-163. [PMID: 31845355 PMCID: PMC7065213 DOI: 10.1111/imr.12829] [Citation(s) in RCA: 77] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 11/07/2019] [Indexed: 12/16/2022]
Abstract
Rheumatoid arthritis (RA) is an autoimmune disease characterized by joint inflammation. In the last few decades, new insights into RA‐specific autoantibodies and B cells have greatly expanded our understanding of the disease. The best‐known autoantibodies in RA—rheumatoid factor (RF) and anti‐citrullinated protein antibodies (ACPA)—are present long before disease onset, and both responses show signs of maturation around the time of the first manifestation of arthritis. A very intriguing characteristic of ACPA is their remarkably high abundance of variable domain glycans. Since these glycans may convey an important selection advantage of citrulline‐reactive B cells, they may be the key to understanding the evolution of the autoimmune response. Recently discovered autoantibodies targeting other posttranslational modifications, such as anti‐carbamylated and anti‐acetylated protein antibodies, appear to be closely related to ACPA, which makes it possible to unite them under the term of anti‐modified protein antibodies (AMPA). Despite the many insights gained about these autoantibodies, it is unclear whether they are pathogenic or play a causal role in disease development. Autoreactive B cells from which the autoantibodies originate have also received attention as perhaps more likely disease culprits. The development of autoreactive B cells in RA largely depends on the interaction with T cells in which HLA “shared epitope” and HLA DERAA may play an important role. Recent technological advances made it possible to identify and characterize citrulline‐reactive B cells and acquire ACPA monoclonal antibodies, which are providing valuable insights and help to understand the nature of the autoimmune response underlying RA. In this review, we summarize what is currently known about the role of autoantibodies and autoreactive B cells in RA and we discuss the most prominent hypotheses aiming to explain the origins and the evolution of autoimmunity in RA.
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Affiliation(s)
- Mikhail Volkov
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Karin Anna van Schie
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
| | - Diane van der Woude
- Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands
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Tan X, Qiu H, Li F, Cheng D, Zheng X, Wang B, Huang M, Li W, Li Y, Sang K, Song B, Du J, Chen H, Xie C. Complete Genome Sequence of Sequevar 14M Ralstonia solanacearum Strain HA4-1 Reveals Novel Type III Effectors Acquired Through Horizontal Gene Transfer. Front Microbiol 2019; 10:1893. [PMID: 31474968 PMCID: PMC6703095 DOI: 10.3389/fmicb.2019.01893] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2019] [Accepted: 07/31/2019] [Indexed: 01/08/2023] Open
Abstract
Ralstonia solanacearum, which causes bacterial wilt in a broad range of plants, is considered a "species complex" due to its significant genetic diversity. Recently, we have isolated a new R. solanacearum strain HA4-1 from Hong'an county in Hubei province of China and identified it being phylotype I, sequevar 14M (phylotype I-14M). Interestingly, we found that it can cause various disease symptoms among different potato genotypes and display different pathogenic behavior compared to a phylogenetically related strain, GMI1000. To dissect the pathogenic mechanisms of HA4-1, we sequenced its whole genome by combined sequencing technologies including Illumina HiSeq2000, PacBio RS II, and BAC-end sequencing. Genome assembly results revealed the presence of a conventional chromosome, a megaplasmid as well as a 143 kb plasmid in HA4-1. Comparative genome analysis between HA4-1 and GMI1000 shows high conservation of the general virulence factors such as secretion systems, motility, exopolysaccharides (EPS), and key regulatory factors, but significant variation in the repertoire and structure of type III effectors, which could be the determinants of their differential pathogenesis in certain potato species or genotypes. We have identified two novel type III effectors that were probably acquired through horizontal gene transfer (HGT). These novel R. solanacearum effectors display homology to several YopJ and XopAC family members. We named them as RipBR and RipBS. Notably, the copy of RipBR on the plasmid is a pseudogene, while the other on the megaplasmid is normal. For RipBS, there are three copies located in the megaplasmid and plasmid, respectively. Our results have not only enriched the genome information on R. solanacearum species complex by sequencing the first sequevar 14M strain and the largest plasmid reported in R. solanacearum to date but also revealed the variation in the repertoire of type III effectors. This will greatly contribute to the future studies on the pathogenic evolution, host adaptation, and interaction between R. solanacearum and potato.
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Affiliation(s)
- Xiaodan Tan
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Huishan Qiu
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Feng Li
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Dong Cheng
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Xueao Zheng
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Bingsen Wang
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Mengshu Huang
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Wenhao Li
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Yanping Li
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Kangqi Sang
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
| | - Botao Song
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Juan Du
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Huilan Chen
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- Key Laboratory of Horticultural Plant Biology, Ministry of Education, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
| | - Conghua Xie
- Key Laboratory of Potato Biology and Biotechnology, Ministry of Agriculture and Rural Affairs, Huazhong Agricultural University, Wuhan, China
- National Center for Vegetable Improvement (Central China), Wuhan, China
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53
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Christensen DG, Xie X, Basisty N, Byrnes J, McSweeney S, Schilling B, Wolfe AJ. Post-translational Protein Acetylation: An Elegant Mechanism for Bacteria to Dynamically Regulate Metabolic Functions. Front Microbiol 2019; 10:1604. [PMID: 31354686 PMCID: PMC6640162 DOI: 10.3389/fmicb.2019.01604] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 06/26/2019] [Indexed: 12/15/2022] Open
Abstract
Post-translational modifications (PTM) decorate proteins to provide functional heterogeneity to an existing proteome. The large number of known PTMs highlights the many ways that cells can modify their proteins to respond to diverse stimuli. Recently, PTMs have begun to receive increased interest because new sensitive proteomics workflows and structural methodologies now allow researchers to obtain large-scale, in-depth and unbiased information concerning PTM type and site localization. However, few PTMs have been extensively assessed for functional consequences, leaving a large knowledge gap concerning the inner workings of the cell. Here, we review understanding of N-𝜀-lysine acetylation in bacteria, a PTM that was largely ignored in bacteria until a decade ago. Acetylation is a modification that can dramatically change the function of a protein through alteration of its properties, including hydrophobicity, solubility, and surface properties, all of which may influence protein conformation and interactions with substrates, cofactors and other macromolecules. Most bacteria carry genes predicted to encode the lysine acetyltransferases and lysine deacetylases that add and remove acetylations, respectively. Many bacteria also exhibit acetylation activities that do not depend on an enzyme, but instead on direct transfer of acetyl groups from the central metabolites acetyl coenzyme A or acetyl phosphate. Regardless of mechanism, most central metabolic enzymes possess lysines that are acetylated in a regulated fashion and many of these regulated sites are conserved across the spectrum of bacterial phylogeny. The interconnectedness of acetylation and central metabolism suggests that acetylation may be a response to nutrient availability or the energy status of the cell. However, this and other hypotheses related to acetylation remain untested.
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Affiliation(s)
- David G. Christensen
- Health Sciences Division, Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, United States
| | - Xueshu Xie
- Buck Institute for Research on Aging, Novato, CA, United States
| | - Nathan Basisty
- Buck Institute for Research on Aging, Novato, CA, United States
| | - James Byrnes
- Energy & Photon Sciences Directorate, National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, United States
| | - Sean McSweeney
- Energy & Photon Sciences Directorate, National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, United States
| | | | - Alan J. Wolfe
- Health Sciences Division, Department of Microbiology and Immunology, Stritch School of Medicine, Loyola University Chicago, Maywood, IL, United States
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Bastedo DP, Khan M, Martel A, Seto D, Kireeva I, Zhang J, Masud W, Millar D, Lee JY, Lee AHY, Gong Y, Santos-Severino A, Guttman DS, Desveaux D. Perturbations of the ZED1 pseudokinase activate plant immunity. PLoS Pathog 2019; 15:e1007900. [PMID: 31269090 PMCID: PMC6634424 DOI: 10.1371/journal.ppat.1007900] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Revised: 07/16/2019] [Accepted: 06/08/2019] [Indexed: 11/19/2022] Open
Abstract
The Pseudomonas syringae acetyltransferase HopZ1a is delivered into host cells by the type III secretion system to promote bacterial growth. However, in the model plant host Arabidopsis thaliana, HopZ1a activity results in an effector-triggered immune response (ETI) that limits bacterial proliferation. HopZ1a-triggered immunity requires the nucleotide-binding, leucine-rich repeat domain (NLR) protein, ZAR1, and the pseudokinase, ZED1. Here we demonstrate that HopZ1a can acetylate members of a family of ‘receptor-like cytoplasmic kinases’ (RLCK family VII; also known as PBS1-like kinases, or PBLs) and promote their interaction with ZED1 and ZAR1 to form a ZAR1-ZED1-PBL ternary complex. Interactions between ZED1 and PBL kinases are determined by the pseudokinase features of ZED1, and mutants designed to restore ZED1 kinase motifs can (1) bind to PBLs, (2) recruit ZAR1, and (3) trigger ZAR1-dependent immunity in planta, all independently of HopZ1a. A ZED1 mutant that mimics acetylation by HopZ1a also triggers immunity in planta, providing evidence that effector-induced perturbations of ZED1 also activate ZAR1. Overall, our results suggest that interactions between these two RLCK families are promoted by perturbations of structural features that distinguish active from inactive kinase domain conformations. We propose that effector-induced interactions between ZED1/ZRK pseudokinases (RLCK family XII) and PBL kinases (RLCK family VII) provide a sensitive mechanism for detecting perturbations of either kinase family to activate ZAR1-mediated ETI. All plants must ward off potentially infectious microbes, and those grown in large-scale crop operations are especially vulnerable to the rapid spread of disease by successful pathogens. Although many bacteria and fungi can supress plant immune responses by producing specialized virulence proteins called ‘effectors’, these effectors can also trigger immune responses that render plants resistant to infection. We studied the molecular mechanisms underlying one such effector-triggered immune response elicited by the bacterial effector HopZ1a in the model plant host Arabidopsis thaliana. We have shown that HopZ1a promotes binding between a ZED1, a ‘pseudokinase’ required for HopZ1a-triggered immunity, and several ‘true kinases’ (known as PBLs) that are likely targets of HopZ1a activity in planta. HopZ1a-induced ZED1-PBL interactions also recruit ZAR1, an Arabidopsis ‘resistance protein’ previously implicated in HopZ1a-triggered immunity. Importantly, ZED1 mutants that restore degenerate kinase motifs can bridge interactions between PBLs and ZAR1 (independently of HopZ1a) and trigger immunity in planta. Our results suggest that equilibria between active and inactive kinase domain conformations regulate ZED1-PBL interactions and formation of ternary complexes with ZAR1. Improved models describing molecular interactions between immunity determinants, effectors and effector targets will inform efforts to exploit natural diversity for development of crops with enhanced disease resistance.
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Affiliation(s)
- D. Patrick Bastedo
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Madiha Khan
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Alexandre Martel
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Derek Seto
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Inga Kireeva
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
| | - Jianfeng Zhang
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Wardah Masud
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - David Millar
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Jee Yeon Lee
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
| | - Amy Huei-Yi Lee
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
- Department of Pharmaceutical Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yunchen Gong
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
| | - André Santos-Severino
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
| | - David S. Guttman
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
- * E-mail: (DSG); (DD)
| | - Darrell Desveaux
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
- * E-mail: (DSG); (DD)
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55
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Immunoprecipitation Under Non-Denaturing or Denaturing Conditions of Lysine-Acetylated Proteins Expressed in Planta. Methods Mol Biol 2019. [PMID: 31041758 DOI: 10.1007/978-1-4939-9458-8_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Protein lysine acetylation is a highly conserved posttranslational modification that plays key roles in many biological processes such as the regulation of gene expression, chromatin dynamics, and metabolic pathways. Recent studies revealed that various pathogens use lysine acetylation to interfere with host immune responses. Identification of lysine-acetylated host proteins resulting from virulence activities of pathogen effectors is therefore essential for understanding their biological functions. Here we provide a method for immunoprecipitating lysine-acetylated proteins transiently expressed in planta under non-denaturing or denaturing conditions and detecting them by immunoblotting. To illustrate this rapid and simple procedure, immunoprecipitation of the lysine-acetylated WRKY domain of the RRS1-R immune receptor, a substrate of the Ralstonia solanacearum PopP2 effector, is presented as a typical example.
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56
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Christensen DG, Baumgartner JT, Xie X, Jew KM, Basisty N, Schilling B, Kuhn ML, Wolfe AJ. Mechanisms, Detection, and Relevance of Protein Acetylation in Prokaryotes. mBio 2019; 10:e02708-18. [PMID: 30967470 PMCID: PMC6456759 DOI: 10.1128/mbio.02708-18] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Posttranslational modification of a protein, either alone or in combination with other modifications, can control properties of that protein, such as enzymatic activity, localization, stability, or interactions with other molecules. N-ε-Lysine acetylation is one such modification that has gained attention in recent years, with a prevalence and significance that rival those of phosphorylation. This review will discuss the current state of the field in bacteria and some of the work in archaea, focusing on both mechanisms of N-ε-lysine acetylation and methods to identify, quantify, and characterize specific acetyllysines. Bacterial N-ε-lysine acetylation depends on both enzymatic and nonenzymatic mechanisms of acetylation, and recent work has shed light into the regulation of both mechanisms. Technological advances in mass spectrometry have allowed researchers to gain insight with greater biological context by both (i) analyzing samples either with stable isotope labeling workflows or using label-free protocols and (ii) determining the true extent of acetylation on a protein population through stoichiometry measurements. Identification of acetylated lysines through these methods has led to studies that probe the biological significance of acetylation. General and diverse approaches used to determine the effect of acetylation on a specific lysine will be covered.
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Affiliation(s)
- D G Christensen
- Department of Microbiology and Immunology, Loyola University Chicago, Health Sciences Division, Stritch School of Medicine, Maywood, Illinois, USA
| | - J T Baumgartner
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California, USA
| | - X Xie
- Buck Institute for Research on Aging, Novato, California, USA
| | - K M Jew
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California, USA
| | - N Basisty
- Buck Institute for Research on Aging, Novato, California, USA
| | - B Schilling
- Buck Institute for Research on Aging, Novato, California, USA
| | - M L Kuhn
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California, USA
| | - A J Wolfe
- Department of Microbiology and Immunology, Loyola University Chicago, Health Sciences Division, Stritch School of Medicine, Maywood, Illinois, USA
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Bastedo DP, Lo T, Laflamme B, Desveaux D, Guttman DS. Diversity and Evolution of Type III Secreted Effectors: A Case Study of Three Families. Curr Top Microbiol Immunol 2019; 427:201-230. [DOI: 10.1007/82_2019_165] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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58
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Schultink A, Qi T, Bally J, Staskawicz B. Using forward genetics in Nicotiana benthamiana to uncover the immune signaling pathway mediating recognition of the Xanthomonas perforans effector XopJ4. THE NEW PHYTOLOGIST 2019; 221:1001-1009. [PMID: 30156705 DOI: 10.1111/nph.15411] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Accepted: 07/23/2018] [Indexed: 05/22/2023]
Abstract
The immune pathway responsible for perception of the Xanthomonas perforans effector XopJ4 was identified in the plant Nicotiana benthamiana. This pathogen causes significant yield loss in commercial tomato cultivation. Genetic mapping and viral-induced gene silencing were used to identify immune signaling components of the XopJ4 perception pathway in N. benthamiana. Transient complementation assays were performed to determine the functionality of gene variants and co-immunoprecipitation assays were used to gain insight into the molecular mechanism of the pathway. Two N. benthamiana ethyl methanesulfonate (EMS) mutants deficient for XopJ4 perception were identified as having loss-of-function mutations in the gene encoding the nucleotide binding, leucine-rich repeat (NLR) protein NbZAR1. Silencing of a receptor-like cytoplasmic kinase family XII gene, subsequently named XOPJ4 IMMUNITY 2 (JIM2), blocks perception of XopJ4. This study demonstrates the feasibility of conducting mutant screens in N. benthamiana to investigate the genetic basis of the plant immune system and other processes. The identification of NbZAR1 and JIM2 as mediating XopJ4 perception in N. benthamiana supports the model of ZAR1 being involved in the perception of many different pathogen effector proteins with specificity dictated by associated receptor-like cytoplasmic kinases.
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Affiliation(s)
- Alex Schultink
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Tiancong Qi
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Julia Bally
- Centre for Tropical Crops and Biocommodities, Queensland University of Technology, Brisbane, Qld, 4001, Australia
| | - Brian Staskawicz
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
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59
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Bürger M, Chory J. Structural and chemical biology of deacetylases for carbohydrates, proteins, small molecules and histones. Commun Biol 2018; 1:217. [PMID: 30534609 PMCID: PMC6281622 DOI: 10.1038/s42003-018-0214-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2018] [Accepted: 10/31/2018] [Indexed: 01/02/2023] Open
Abstract
Deacetylation is the removal of an acetyl group and occurs on a plethora of targets and for a wide range of biological reasons. Several pathogens deacetylate their surface carbohydrates to evade immune response or to support biofilm formation. Furthermore, dynamic acetylation/deacetylation cycles govern processes from chromatin remodeling to posttranslational modifications that compete with phosphorylation. Acetylation usually occurs on nitrogen and oxygen atoms and are referred to as N- and O-acetylation, respectively. This review discusses the structural prerequisites that enzymes must have to catalyze the deacetylation reaction, and how they adapted by formation of specific substrate and metal binding sites.
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Affiliation(s)
- Marco Bürger
- Plant Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037 USA
| | - Joanne Chory
- Plant Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037 USA
- Howard Hughes Medical Institute, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037 USA
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60
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Abrahamian P, Timilsina S, Minsavage GV, Kc S, Goss EM, Jones JB, Vallad GE. The Type III Effector AvrBsT Enhances Xanthomonas perforans Fitness in Field-Grown Tomato. PHYTOPATHOLOGY 2018; 108:1355-1362. [PMID: 29905507 DOI: 10.1094/phyto-02-18-0052-r] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Type III secretion system effectors contribute to pathogenicity through various mechanisms. Recent surveys showed an increasing prevalence of the type III secretion effector avrBsT among Xanthomonas perforans strains. We hypothesized that the acquisition of avrBsT has a fitness advantage for the pathogen. The contribution of avrBsT to fitness on tomato was evaluated based on disease severity, in planta growth, competition, and recovery rates of wild-type (WT) and avrBsT mutant strains in greenhouse and field plants. GEV872 and GEV1001, representative strains of two phylogenomic groups of X. perforans, were selected for generating avrBsT mutants. Disease severity was higher for WT strains compared with the avrBsT mutant strains. X. perforans WT and avrBsT mutant strains did not differ following leaf infiltration of greenhouse plants in direct competition and in planta growth assays. The effect of avrBsT on pathogen fitness was noticeable under field conditions. Differences in strain recovery were significant, with WT being recovered two to eight times more than avrBsT mutant strains in the case of both strains GEV872 and GEV1001. WT strains were capable of spreading longer distances across field plots compared with avrBsT mutant strains. Findings suggest that the functional AvrBsT affects the fitness of X. perforans under field conditions, making it an ideal candidate for bacterial spot resistance breeding efforts in tomato.
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Affiliation(s)
- Peter Abrahamian
- First, second, fourth, and seventh authors; Gulf Coast and Research Education Center, Wimauma, FL; first, second, third, fifth, sixth, and seventh authors: Department of Plant Pathology, University of Florida, Gainesville; and fifth author: Emerging Pathogens Institute, University of Florida, Gainesville
| | - Sujan Timilsina
- First, second, fourth, and seventh authors; Gulf Coast and Research Education Center, Wimauma, FL; first, second, third, fifth, sixth, and seventh authors: Department of Plant Pathology, University of Florida, Gainesville; and fifth author: Emerging Pathogens Institute, University of Florida, Gainesville
| | - Gerald V Minsavage
- First, second, fourth, and seventh authors; Gulf Coast and Research Education Center, Wimauma, FL; first, second, third, fifth, sixth, and seventh authors: Department of Plant Pathology, University of Florida, Gainesville; and fifth author: Emerging Pathogens Institute, University of Florida, Gainesville
| | - Sushmita Kc
- First, second, fourth, and seventh authors; Gulf Coast and Research Education Center, Wimauma, FL; first, second, third, fifth, sixth, and seventh authors: Department of Plant Pathology, University of Florida, Gainesville; and fifth author: Emerging Pathogens Institute, University of Florida, Gainesville
| | - Erica M Goss
- First, second, fourth, and seventh authors; Gulf Coast and Research Education Center, Wimauma, FL; first, second, third, fifth, sixth, and seventh authors: Department of Plant Pathology, University of Florida, Gainesville; and fifth author: Emerging Pathogens Institute, University of Florida, Gainesville
| | - Jeffrey B Jones
- First, second, fourth, and seventh authors; Gulf Coast and Research Education Center, Wimauma, FL; first, second, third, fifth, sixth, and seventh authors: Department of Plant Pathology, University of Florida, Gainesville; and fifth author: Emerging Pathogens Institute, University of Florida, Gainesville
| | - Gary E Vallad
- First, second, fourth, and seventh authors; Gulf Coast and Research Education Center, Wimauma, FL; first, second, third, fifth, sixth, and seventh authors: Department of Plant Pathology, University of Florida, Gainesville; and fifth author: Emerging Pathogens Institute, University of Florida, Gainesville
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Labriola JM, Zhou Y, Nagar B. Structural Analysis of the Bacterial Effector AvrA Identifies a Critical Helix Involved in Substrate Recognition. Biochemistry 2018; 57:4985-4996. [PMID: 30025209 DOI: 10.1021/acs.biochem.8b00512] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Bacterial effector proteins are essential for the infection and proliferation of pathogenic bacteria through manipulation of host immune response pathways. AvrA is a Salmonella effector that belongs to the YopJ family of acetyltransferases, which suppresses c-JUN N-terminal kinase (JNK) signaling in mammals through acetylation of mitogen-activated receptor kinase kinases 4 and 7 (MKK4/7). Interestingly, there are two paralogues of AvrA that differ by only a single internal leucine residue, which when absent (AvrAΔL140) abrogates the ability to suppress JNK signaling. Here, we present the first crystal structure of a bacterial effector from an animal pathogen, AvrAΔL140, accompanied by a thorough biophysical characterization of both AvrA variants. The structure in complex with inositol hexaphosphate and coenzyme A reveals two closely associated domains consisting of a catalytic core that resembles the CE clan peptidases and a wedge-shaped regulatory region that mediates cofactor and substrate binding. The loss of the putative function of AvrAΔL140 is due to its inability to interact with MKK4/7, which ultimately arises from an altered conformation of a critical helix adjacent to the active site that harbors L140. These results provide general insights into substrate recognition across the YopJ family of acetyltransferases.
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Affiliation(s)
- Jonathan M Labriola
- Department of Biochemistry and Groupe de Recherche Axé sur la Structure des Protéines , McGill University , Montreal , QC H3G 0B1 , Canada
| | - Yifan Zhou
- Department of Biochemistry and Groupe de Recherche Axé sur la Structure des Protéines , McGill University , Montreal , QC H3G 0B1 , Canada
| | - Bhushan Nagar
- Department of Biochemistry and Groupe de Recherche Axé sur la Structure des Protéines , McGill University , Montreal , QC H3G 0B1 , Canada
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62
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Choi S, Jayaraman J, Sohn KH. Arabidopsis thaliana SOBER1 (SUPPRESSOR OF AVRBST-ELICITED RESISTANCE 1) suppresses plant immunity triggered by multiple bacterial acetyltransferase effectors. THE NEW PHYTOLOGIST 2018; 219:324-335. [PMID: 29577317 DOI: 10.1111/nph.15125] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 02/19/2018] [Indexed: 05/21/2023]
Abstract
Plants evolved disease resistance (R) proteins that recognize corresponding pathogen effectors and activate effector-triggered immunity (ETI). However, it is largely unknown why, in some cases, a suppressor of ETI exists in plants. Arabidopsis SOBER1 (Suppressor of AvrBsT-elicited Resistance 1) was identified previously as a suppressor of Xanthomonas acetyltransferase effector AvrBsT-triggered immunity. Nevertheless, the extent to which SOBER1 suppresses ETI is unclear. Here, we identified SOBER1 as a suppressor of Pseudomonas acetyltransferase effector HopZ5-triggered immunity in Arabidopsis using recombinant inbred lines. Further analysis showed that SOBER1 suppresses immunity triggered by multiple bacterial acetyltransferases. Interestingly, SOBER1 interferes with the immunity signalling activated by some but not all tested acetyltransferase effectors, indicating that SOBER1 might target components that are shared between several ETI pathways.
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Affiliation(s)
- Sera Choi
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Korea
- Bioprotection Research Centre, Institute of Agriculture and Environment, Massey University, Palmerston North, 4474, New Zealand
| | - Jay Jayaraman
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Korea
- Bioprotection Research Centre, Institute of Agriculture and Environment, Massey University, Palmerston North, 4474, New Zealand
- New Zealand Institute for Plant & Food Research Limited (PFR), Mt Albert, Auckland, 1025, New Zealand
| | - Kee Hoon Sohn
- Department of Life Sciences, Pohang University of Science and Technology, Pohang, 37673, Korea
- Bioprotection Research Centre, Institute of Agriculture and Environment, Massey University, Palmerston North, 4474, New Zealand
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang, 37673, Korea
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63
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Heine W, Beckstette M, Heroven AK, Thiemann S, Heise U, Nuss AM, Pisano F, Strowig T, Dersch P. Loss of CNFY toxin-induced inflammation drives Yersinia pseudotuberculosis into persistency. PLoS Pathog 2018; 14:e1006858. [PMID: 29390040 PMCID: PMC5811047 DOI: 10.1371/journal.ppat.1006858] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 02/13/2018] [Accepted: 01/05/2018] [Indexed: 12/16/2022] Open
Abstract
Gastrointestinal infections caused by enteric yersiniae can become persistent and complicated by relapsing enteritis and severe autoimmune disorders. To establish a persistent infection, the bacteria have to cope with hostile surroundings when they transmigrate through the intestinal epithelium and colonize underlying gut-associated lymphatic tissues. How the bacteria gain a foothold in the face of host immune responses is poorly understood. Here, we show that the CNFY toxin, which enhances translocation of the antiphagocytic Yop effectors, induces inflammatory responses. This results in extensive tissue destruction, alteration of the intestinal microbiota and bacterial clearance. Suppression of CNFY function, however, increases interferon-γ-mediated responses, comprising non-inflammatory antimicrobial activities and tolerogenesis. This process is accompanied by a preterm reprogramming of the pathogen's transcriptional response towards persistence, which gives the bacteria a fitness edge against host responses and facilitates establishment of a commensal-type life style.
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Affiliation(s)
- Wiebke Heine
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Michael Beckstette
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Ann Kathrin Heroven
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Sophie Thiemann
- Group Microbial Immune Regulation, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Ulrike Heise
- Group Mouse Pathology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Aaron Mischa Nuss
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Fabio Pisano
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Till Strowig
- Group Microbial Immune Regulation, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | - Petra Dersch
- Department of Molecular Infection Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany
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64
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El Qaidi S, Wu M, Zhu C, Hardwidge PR. Salmonella, E. coli, and Citrobacter Type III Secretion System Effector Proteins that Alter Host Innate Immunity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1111:205-218. [PMID: 30411307 DOI: 10.1007/5584_2018_289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Bacteria deliver virulence proteins termed 'effectors' to counteract host innate immunity. Protein-protein interactions within the host cell ultimately subvert the generation of an inflammatory response to the infecting pathogen. Here we briefly describe a subset of T3SS effectors produced by enterohemorrhagic Escherichia coli (EHEC), enteropathogenic E. coli (EPEC), Citrobacter rodentium, and Salmonella enterica that inhibit innate immune pathways. These effectors are interesting for structural and mechanistic reasons, as well as for their potential utility in being engineered to treat human autoimmune disorders associated with perturbations in NF-κB signaling.
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Affiliation(s)
- Samir El Qaidi
- College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Miaomiao Wu
- College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Congrui Zhu
- College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA
| | - Philip R Hardwidge
- College of Veterinary Medicine, Kansas State University, Manhattan, KS, USA.
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65
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Abstract
Lysine acetylation is a key posttranslational modification that regulates diverse proteins involved in a range of biological processes. The role of histone acetylation in plant defense is well established, and it is known that pathogen effector proteins encoding acetyltransferases can directly acetylate host proteins to alter immunity. However, it is unclear whether endogenous plant enzymes can modulate protein acetylation during an immune response. Here, we investigate how the effector molecule HC-toxin (HCT), a histone deacetylase inhibitor produced by the fungal pathogen Cochliobolus carbonum race 1, promotes virulence in maize through altering protein acetylation. Using mass spectrometry, we globally quantified the abundance of 3,636 proteins and the levels of acetylation at 2,791 sites in maize plants treated with HCT as well as HCT-deficient or HCT-producing strains of C. carbonum Analyses of these data demonstrate that acetylation is a widespread posttranslational modification impacting proteins encoded by many intensively studied maize genes. Furthermore, the application of exogenous HCT enabled us to show that the activity of plant-encoded enzymes (histone deacetylases) can be modulated to alter acetylation of nonhistone proteins during an immune response. Collectively, these results provide a resource for further mechanistic studies examining the regulation of protein function by reversible acetylation and offer insight into the complex immune response triggered by virulent C. carbonum.
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66
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Scott NE, Hartland EL. Post-translational Mechanisms of Host Subversion by Bacterial Effectors. Trends Mol Med 2017; 23:1088-1102. [PMID: 29150361 DOI: 10.1016/j.molmed.2017.10.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Revised: 10/19/2017] [Accepted: 10/19/2017] [Indexed: 12/19/2022]
Abstract
Bacterial effector proteins are a specialized class of secreted proteins that are translocated directly into the host cytoplasm by bacterial pathogens. Effector proteins have diverse activities and targets, and many mediate post-translational modifications of host proteins. Effector proteins offer potential in novel biotechnological and medical applications as enzymes that may modify human proteins. Here, we discuss the mechanisms used by effectors to subvert the human host through blocking, blunting, or subverting immune mechanisms. This capacity allows bacteria to control host cell function to support pathogen survival, replication and dissemination to other hosts. In addition, we highlight that knowledge of effector protein activity may be used to develop chemical inhibitors as a new approach to treat bacterial infections.
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Affiliation(s)
- Nichollas E Scott
- Department of Microbiology and Immunology, University of Melbourne at the Peter Doherty Institute for Infection and Immunity, Melbourne 3000, Australia
| | - Elizabeth L Hartland
- Centre for Innate Immunity and Infectious Diseases, Hudson Institute of Medical Research, Clayton 3168, Australia; Department of Molecular and Translational Science, Monash University, Clayton 3168, Australia.
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Abstract
In 2007, we reported that a phytopathogen effector directly inhibits a MAP kinase cascade. In the decade since, many more effectors have been found to inhibit MAP kinase cascades, providing not only a mechanistic understanding of pathogenesis and immunity in plants, but also the identification of previously unknown enzymes.
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Affiliation(s)
- Guozhi Bi
- The State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Jian-Min Zhou
- The State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
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68
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Varden FA, De la Concepcion JC, Maidment JH, Banfield MJ. Taking the stage: effectors in the spotlight. CURRENT OPINION IN PLANT BIOLOGY 2017; 38:25-33. [PMID: 28460241 DOI: 10.1016/j.pbi.2017.04.013] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Revised: 04/10/2017] [Accepted: 04/11/2017] [Indexed: 06/07/2023]
Abstract
Plant pathogens are a serious threat to agriculture and to global food security, causing diverse crop diseases which lead to extensive annual yield losses. Production of effector proteins by pathogens, to manipulate host cellular processes, is central to their success. An understanding of fundamental effector biology is key to addressing the threat posed by these pathogens. Recent advances in 'omics' technologies have facilitated high-throughput identification of putative effector proteins, while evolving cellular, structural and biochemical approaches have assisted in characterising their function. Furthermore, structures of effectors in complex with host factors now provide opportunities for applying our knowledge of effector biology to influence disease outcomes. In this review, we highlight recent advances in the field and suggest avenues for future research.
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Affiliation(s)
- Freya A Varden
- Dept. of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | | | - Josephine Hr Maidment
- Dept. of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom
| | - Mark J Banfield
- Dept. of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom.
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69
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Baudin M, Hassan JA, Schreiber KJ, Lewis JD. Analysis of the ZAR1 Immune Complex Reveals Determinants for Immunity and Molecular Interactions. PLANT PHYSIOLOGY 2017; 174:2038-2053. [PMID: 28652264 PMCID: PMC5543953 DOI: 10.1104/pp.17.00441] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 06/22/2017] [Indexed: 05/06/2023]
Abstract
Plants depend on innate immunity to prevent disease. Plant pathogenic bacteria, like Pseudomonas syringae and Xanthomonas campestris, use the type III secretion system as a molecular syringe to inject type III secreted effector (T3SE) proteins in plants. The primary function of most T3SEs is to suppress immunity; however, the plant can evolve nucleotide-binding domain-leucine-rich repeat domain-containing proteins to recognize specific T3SEs. The AtZAR1 NLR induces strong defense responses against P. syringae and X. campestris The P. syringae T3SE HopZ1a is an acetyltransferase that acetylates the pseudokinase AtZED1 and triggers recognition by AtZAR1. However, little is known about the molecular mechanisms that lead to AtZAR1-induced immunity in response to HopZ1a. We established a transient expression system in Nicotiana benthamiana to study detailed interactions among HopZ1a, AtZED1, and AtZAR1. We show that the AtZAR1 immune pathway is conserved in N. benthamiana and identify AtZAR1 domains, and residues in AtZAR1 and AtZED1, that are important for immunity and protein-protein interactions in planta and in yeast (Saccharomyces cerevisiae). We show that the coiled-coil domain of AtZAR1 oligomerizes, and this domain acts as a signal to induce immunity. This detailed analysis of the AtZAR1-AtZED1 protein complex provides a better understanding of the immune signaling hub controlled by AtZAR1.
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Affiliation(s)
- Maël Baudin
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720
| | - Jana A Hassan
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720
| | - Karl J Schreiber
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720
| | - Jennifer D Lewis
- Department of Plant and Microbial Biology, University of California Berkeley, Berkeley, California 94720
- Plant Gene Expression Center, U.S. Department of Agriculture, Albany, California 94710
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70
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Zhang ZM, Ma KW, Gao L, Hu Z, Schwizer S, Ma W, Song J. Mechanism of host substrate acetylation by a YopJ family effector. NATURE PLANTS 2017; 3:17115. [PMID: 28737762 PMCID: PMC5546152 DOI: 10.1038/nplants.2017.115] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 06/26/2017] [Indexed: 05/22/2023]
Abstract
The Yersinia outer protein J (YopJ) family of bacterial effectors depends on a novel acetyltransferase domain to acetylate signalling proteins from plant and animal hosts. However, the underlying mechanism is unclear. Here, we report the crystal structures of PopP2, a YopJ effector produced by the plant pathogen Ralstonia solanacearum, in complex with inositol hexaphosphate (InsP6), acetyl-coenzyme A (AcCoA) and/or substrate Resistance to Ralstonia solanacearum 1 (RRS1-R)WRKY. PopP2 recognizes the WRKYGQK motif of RRS1-RWRKY to position a targeted lysine in the active site for acetylation. Importantly, the PopP2-RRS1-RWRKY association is allosterically regulated by InsP6 binding, suggesting a previously unidentified role of the eukaryote-specific cofactor in substrate interaction. Furthermore, we provide evidence for the reaction intermediate of PopP2-mediated acetylation, an acetyl-cysteine covalent adduct, lending direct support to the 'ping-pong'-like catalytic mechanism proposed for YopJ effectors. Our study provides critical mechanistic insights into the virulence activity of YopJ class of acetyltransferases.
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Affiliation(s)
- Zhi-Min Zhang
- Department of Biochemistry, University of California, Riverside, California 92521, USA
| | - Ka-Wai Ma
- Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA
| | - Linfeng Gao
- Environmental Toxicology Program, University of California, Riverside, California 92521, USA
| | - Zhenquan Hu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Anhui 230031, China
| | - Simon Schwizer
- Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA
| | - Wenbo Ma
- Department of Plant Pathology and Microbiology, University of California, Riverside, California 92521, USA
- Center for Plant Cell Biology, University of California, Riverside, California 92521, USA
- Institute of Integrative Genome Biology, University of California, Riverside, California 92521, USA
| | - Jikui Song
- Department of Biochemistry, University of California, Riverside, California 92521, USA
- Environmental Toxicology Program, University of California, Riverside, California 92521, USA
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71
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Segonzac C, Newman TE, Choi S, Jayaraman J, Choi DS, Jung GY, Cho H, Lee YK, Sohn KH. A Conserved EAR Motif Is Required for Avirulence and Stability of the Ralstonia solanacearum Effector PopP2 In Planta. FRONTIERS IN PLANT SCIENCE 2017; 8:1330. [PMID: 28824668 PMCID: PMC5539180 DOI: 10.3389/fpls.2017.01330] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 07/17/2017] [Indexed: 05/20/2023]
Abstract
Ralstonia solanacearum is the causal agent of the devastating bacterial wilt disease in many high value Solanaceae crops. R. solanacearum secretes around 70 effectors into host cells in order to promote infection. Plants have, however, evolved specialized immune receptors that recognize corresponding effectors and confer qualitative disease resistance. In the model species Arabidopsis thaliana, the paired immune receptors RRS1 (resistance to Ralstonia solanacearum 1) and RPS4 (resistance to Pseudomonas syringae 4) cooperatively recognize the R. solanacearum effector PopP2 in the nuclei of infected cells. PopP2 is an acetyltransferase that binds to and acetylates the RRS1 WRKY DNA-binding domain resulting in reduced RRS1-DNA association thereby activating plant immunity. Here, we surveyed the naturally occurring variation in PopP2 sequence among the R. solanacearum strains isolated from diseased tomato and pepper fields across the Republic of Korea. Our analysis revealed high conservation of popP2 sequence with only three polymorphic alleles present amongst 17 strains. Only one variation (a premature stop codon) caused the loss of RPS4/RRS1-dependent recognition in Arabidopsis. We also found that PopP2 harbors a putative eukaryotic transcriptional repressor motif (ethylene-responsive element binding factor-associated amphiphilic repression or EAR), which is known to be involved in the recruitment of transcriptional co-repressors. Remarkably, mutation of the EAR motif disabled PopP2 avirulence function as measured by the development of hypersensitive response, electrolyte leakage, defense marker gene expression and bacterial growth in Arabidopsis. This lack of recognition was partially but significantly reverted by the C-terminal addition of a synthetic EAR motif. We show that the EAR motif-dependent gain of avirulence correlated with the stability of the PopP2 protein. Furthermore, we demonstrated the requirement of the PopP2 EAR motif for PTI suppression. A yeast two-hybrid screen indicated that PopP2 does not interact with any well-known Arabidopsis transcriptional co-repressors. Overall, this study reveals high conservation of the PopP2 effector in Korean R. solanacearum strains isolated from commercially cultivated tomato and pepper genotypes. Importantly, our data also indicate that the PopP2 conserved repressor motif could contribute to the effector accumulation in plant cells.
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Affiliation(s)
- Cécile Segonzac
- Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
- Plant Science Department, Plant Genomics and Breeding Institute and Research Institute of Agriculture and Life Sciences, College of Agriculture and Life Sciences, Seoul National UniversitySeoul, South Korea
- *Correspondence: Kee Hoon Sohn, Cécile Segonzac,
| | - Toby E. Newman
- Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
- Bioprotection Centre of Research Excellence, Institute of Agriculture and Environment, Massey UniversityPalmerston North, New Zealand
| | - Sera Choi
- Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
- Bioprotection Centre of Research Excellence, Institute of Agriculture and Environment, Massey UniversityPalmerston North, New Zealand
| | - Jay Jayaraman
- Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
- Bioprotection Centre of Research Excellence, Institute of Agriculture and Environment, Massey UniversityPalmerston North, New Zealand
| | - Du Seok Choi
- Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
| | - Ga Young Jung
- Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
| | - Heejung Cho
- National Institute of Agricultural Sciences, Rural Development AdministrationWanju, South Korea
| | - Young Kee Lee
- National Institute of Agricultural Sciences, Rural Development AdministrationWanju, South Korea
| | - Kee Hoon Sohn
- Department of Life Sciences, Pohang University of Science and TechnologyPohang, South Korea
- School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and TechnologyPohang, South Korea
- *Correspondence: Kee Hoon Sohn, Cécile Segonzac,
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