scholarly journals Focus on Activation, Regulation, and Evolution of MTI and ETI

2019 ◽  
Vol 32 (1) ◽  
pp. 5-5
Author(s):  
John M. McDowell
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Disease Resistance ◽  
Protein Complexes ◽  
Plant Cells ◽  
Effector Proteins ◽  
Mitogen Activated Protein Kinase ◽  
Receptor Protein ◽  
Cell Infection ◽  
Mitogen Activated Protein ◽  
Effector Triggered Immunity

Plants perceive a variety of molecules produced by microbes, insects, and nematodes. These pathogen-derived components include so-called microbe-associated molecular patterns, or MAMPs, as well as effector proteins that are secreted to the exterior or interior of plant cells and these molecules can be recognized by receptor protein complexes on the exterior or interior of plant cells, thereby activating MAMP- or effector-triggered immunity (MTI or ETI, respectively). Because these processes are key components of plant disease resistance, they have been studied intensively. We are now in a golden age of ETI and MTI research, in which mechanistic and evolutionary understanding of both processes is emerging rapidly. Accordingly, in this Focus issue , we explore diverse aspects of MTI and ETI, with a unifying theme of integration at multiple levels. Additional content is available on the Focus on Activation, Regulation, and Evolution of MTI and ETI. Mitogen-Activated Protein Kinase Phosphatase 1 (MKP1) Negatively Regulates the Production of Reactive Oxygen Species During Arabidopsis Immune Responses Development of a Pseudomonas syringae–Arabidopsis Suspension Cell Infection System for Investigating Host Metabolite-Dependent Regulation of Type III Secretion and Pattern-Triggered Immunity Direct Regulation of the EFR-Dependent Immune Response by Arabidopsis TCP Transcription Factors Convergent Evolution of Effector Protease Recognition by Arabidopsis and Barley

scholarly journals The bacterial effector HopZ1a acetylates MKK7 to suppress plant immunity

2020 ◽  
Author(s):  
José S. Rufián ◽  
Javier Rueda-Blanco ◽  
Diego López-Márquez ◽  
Alberto P. Macho ◽  
Carmen R. Beuzón ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Immunity ◽  
Inducible Promoter ◽  
Effector Proteins ◽  
Mitogen Activated Protein Kinase ◽  
In Planta ◽  
Systemic Immunity ◽  
Mitogen Activated Protein ◽  
Ros Burst

ABSTRACTThe Pseudomonas syringae type III secretion system translocates effector proteins into the host cell cytosol, suppressing plant basal immunity triggered upon recognition of pathogen-associated molecular patterns (PAMPs), and effector-triggered immunity. Effector HopZ1a suppresses local and systemic immunity triggered by PAMPs and effectors, through target acetylation. HopZ1a has been shown to target several plant proteins, but none fully substantiates HopZ1a-associated immune suppression. Here, we investigate Arabidopsis thaliana mitogen-activated protein kinase kinases (MKKs) as potential targets, focusing on AtMKK7, a positive regulator of local and systemic immunity. We analyse HopZ1a interference with AtMKK7 by translocation of HopZ1a from bacteria inoculated into Arabidopsis expressing MKK7 from an inducible promoter. Reciprocal phenotypes are analysed on plants expressing a construct quenching MKK7 native expression. We analyse HopZ1a-MKK7 interaction by three independent methods, and the relevance of acetylation by in vitro kinase and in planta functional assays. We demonstrate AtMKK7 contribution to immune signalling showing MKK7-dependent flg22-induced ROS burst, MAPK activation, and callose accumulation, plus AvrRpt2-triggered MKK7-dependent signalling. Further, we demonstrate HopZ1a suppression of all MKK7-dependent responses, HopZ1a-MKK7 interaction in planta, and HopZ1a acetylation of MKK7 in a lysine required for full kinase activity. We demonstrate that HopZ1a targets AtMKK7 to suppress local and systemic plant immunity.

scholarly journals Pseudomonas syringae Strains Naturally Lacking the Classical P. syringae hrp/hrc Locus Are Common Leaf Colonizers Equipped with an Atypical Type III Secretion System

2010 ◽  
Vol 23 (2) ◽  
pp. 198-210 ◽  
Author(s):  
Christopher R. Clarke ◽  
Rongman Cai ◽  
David J. Studholme ◽  
David S. Guttman ◽  
Boris A. Vinatzer
Keyword(s):  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Type Iii Secretion System ◽  
Ice Nucleation ◽  
Secretion System ◽  
Effector Proteins ◽  
Population Densities ◽  
Type Iii ◽  
Effector Genes

Pseudomonas syringae is best known as a plant pathogen that causes disease by translocating immune-suppressing effector proteins into plant cells through a type III secretion system (T3SS). However, P. syringae strains belonging to a newly described phylogenetic subgroup (group 2c) are missing the canonical P. syringae hrp/hrc cluster coding for a T3SS, flanking effector loci, and any close orthologue of known P. syringae effectors. Nonetheless, P. syringae group 2c strains are common leaf colonizers and grow on some tested plant species to population densities higher than those obtained by other P. syringae strains on nonhost species. Moreover, group 2c strains have genes necessary for the production of phytotoxins, have an ice nucleation gene, and, most interestingly, contain a novel hrp/hrc cluster, which is only distantly related to the canonical P. syringae hrp/hrc cluster. This hrp/hrc cluster appears to encode a functional T3SS although the genes hrpK and hrpS, present in the classical P. syringae hrp/hrc cluster, are missing. The genome sequence of a representative group 2c strain also revealed distant orthologues of the P. syringae effector genes avrE1 and hopM1 and the P. aeruginosa effector genes exoU and exoY. A putative life cycle for group 2c P. syringae is discussed.

scholarly journals Integrative Proteomic and Phosphoproteomic Analyses of Pattern- and Effector-Triggered Immunity in Tomato

2021 ◽  
Vol 12 ◽  
Author(s):  
Juanjuan Yu ◽  
Juan M. Gonzalez ◽  
Zhiping Dong ◽  
Qianru Shan ◽  
Bowen Tan ◽  
...  
Keyword(s):  
Plant Defense ◽  
Pseudomonas Syringae ◽  
Redox Homeostasis ◽  
Mitogen Activated Protein Kinase ◽  
Regulatory Mechanisms ◽  
Pcr Analysis ◽  
Plant Responses ◽  
Serine Esterase ◽  
Proteomics Data ◽  
Effector Triggered Immunity

Plants have evolved a two-layered immune system consisting of pattern-triggered immunity (PTI) and effector-triggered immunity (ETI). PTI and ETI are functionally linked, but also have distinct characteristics. Unraveling how these immune systems coordinate plant responses against pathogens is crucial for understanding the regulatory mechanisms underlying plant defense. Here we report integrative proteomic and phosphoproteomic analyses of the tomato-Pseudomonas syringae (Pst) pathosystem with different Pst mutants that allow the dissection of PTI and ETI. A total of 225 proteins and 79 phosphopeptides differentially accumulated in tomato leaves during Pst infection. The abundances of many proteins and phosphoproteins changed during PTI or ETI, and some responses were triggered by both PTI and ETI. For most proteins, the ETI response was more robust than the PTI response. The patterns of protein abundance and phosphorylation changes revealed key regulators involved in Ca2+ signaling, mitogen-activated protein kinase cascades, reversible protein phosphorylation, reactive oxygen species (ROS) and redox homeostasis, transcription and protein turnover, transport and trafficking, cell wall remodeling, hormone biosynthesis and signaling, suggesting their common or specific roles in PTI and/or ETI. A NAC (NAM, ATAF, and CUC family) domain protein and lipid particle serine esterase, two PTI-specific genes identified from previous transcriptomic work, were not detected as differentially regulated at the protein level and were not induced by PTI. Based on integrative transcriptomics and proteomics data, as well as qRT-PCR analysis, several potential PTI and ETI-specific markers are proposed. These results provide insights into the regulatory mechanisms underlying PTI and ETI in the tomato-Pst pathosystem, and will promote future validation and application of the disease biomarkers in plant defense.

scholarly journals Receptor Heterodimerization and Co-Receptor Engagement in TLR2 Activation Induced by MIC1 and MIC4 from Toxoplasma gondii

2019 ◽  
Vol 20 (20) ◽  
pp. 5001 ◽  
Author(s):  
Flávia Costa Mendonça-Natividade ◽  
Carla Duque Lopes ◽  
Rafael Ricci-Azevedo ◽  
Aline Sardinha-Silva ◽  
Camila Figueiredo Pinzan ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Transforming Growth Factor Beta ◽  
Cell Activation ◽  
Cytokine Production ◽  
Transforming Growth Factor ◽  
Protein Complexes ◽  
Transmembrane Protein ◽  
Mitogen Activated Protein Kinase ◽  
Mitogen Activated Protein ◽  
Carbohydrate Recognition Domains

The microneme organelles of Toxoplasma gondii tachyzoites release protein complexes (MICs), including one composed of the transmembrane protein MIC6 plus MIC1 and MIC4. In this complex, carbohydrate recognition domains of MIC1 and MIC4 are exposed and interact with terminal sialic acid and galactose residues, respectively, of host cell glycans. Recently, we demonstrated that MIC1 and MIC4 binding to the N-glycans of Toll-like receptor (TLR) 2 and TLR4 on phagocytes triggers cell activation and pro-inflammatory cytokine production. Herein, we investigated the requirement for TLR2 heterodimerization and co-receptors in MIC-induced responses, as well as the signaling molecules involved. We used MICs to stimulate macrophages and HEK293T cells transfected with TLR2 and TLR1 or TLR6, both with or without the co-receptors CD14 and CD36. Then, the cell responses were analyzed, including nuclear factor-kappa B (NF-κB) activation and cytokine production, which showed that (1) only TLR2, among the studied factors, is crucial for MIC-induced cell activation; (2) TLR2 heterodimerization augments, but is not critical for, activation; (3) CD14 and CD36 enhance the response to MIC stimulus; and (4) MICs activate cells through a transforming growth factor beta-activated kinase 1 (TAK1)-, mammalian p38 mitogen-activated protein kinase (p38)-, and NF-κB-dependent pathway. Remarkably, among the studied factors, the interaction of MIC1 and MIC4 with TLR2 N-glycans is sufficient to induce cell activation, which promotes host protection against T. gondii infection.

scholarly journals Pseudomonas syringae HrpP Is a Type III Secretion Substrate Specificity Switch Domain Protein That Is Translocated into Plant Cells but Functions Atypically for a Substrate-Switching Protein

2009 ◽  
Vol 191 (9) ◽  
pp. 3120-3131 ◽  
Author(s):  
Joanne E. Morello ◽  
Alan Collmer
Keyword(s):  
Substrate Specificity ◽  
Pseudomonas Syringae ◽  
Type Iii Secretion ◽  
Fluorescent Protein ◽  
Plant Cells ◽  
Effector Proteins ◽  
Type Iii ◽  
Native Promoter ◽  
C Terminus ◽  
Green Fluorescent

ABSTRACT Pseudomonas syringae delivers virulence effector proteins into plant cells via an Hrp1 type III secretion system (T3SS). P. syringae pv. tomato DC3000 HrpP has a C-terminal, putative T3SS substrate specificity switch domain, like Yersinia YscP. A ΔhrpP DC3000 mutant could not cause disease in tomato or elicit a hypersensitive response (HR) in tobacco, but the HR could be restored by expression of HrpP in trans. Though HrpP is a relatively divergent protein in the T3SS of different P. syringae pathovars, hrpP from P. syringae pv. syringae 61 and P. syringae pv. phaseolicola 1448A restored HR elicitation and pathogenicity to DC3000 ΔhrpP. HrpP was translocated into Nicotiana benthamiana cells via the DC3000 T3SS when expressed from its native promoter, but it was not secreted in culture. N- and C-terminal truncations of HrpP were tested for their ability to be translocated and to restore HR elicitation activity to the ΔhrpP mutant. No N-terminal truncation completely abolished translocation, implying that HrpP has an atypical T3SS translocation signal. Deleting more than 20 amino acids from the C terminus abolished the ability to restore HR elicitation. HrpP fused to green fluorescent protein was no longer translocated but could restore HR elicitation activity to the ΔhrpP mutant, suggesting that translocation is not essential for the function of HrpP. No T3SS substrates were detectably secreted by DC3000 ΔhrpP except the pilin subunit HrpA, which unexpectedly was secreted poorly. HrpP may function somewhat differently than YscP because the P. syringae T3SS pilus likely varies in length due to differing plant cell walls.

scholarly journals Identification of Pseudomonas syringae pv. syringae 61 Type III Secretion System Hrp Proteins That Can Travel the Type III Pathway and Contribute to the Translocation of Effector Proteins into Plant Cells

2007 ◽  
Vol 189 (15) ◽  
pp. 5773-5778 ◽  
Author(s):  
Adela R. Ramos ◽  
Joanne E. Morello ◽  
Sandeep Ravindran ◽  
Wen-Ling Deng ◽  
Hsiou-Chen Huang ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Hypersensitive Response ◽  
Type Iii Secretion ◽  
Plant Cells ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Effector Proteins ◽  
Type Iii

ABSTRACT Pseudomonas syringae translocates effector proteins into plant cells via an Hrp1 type III secretion system (T3SS). T3SS components HrpB, HrpD, HrpF, and HrpP were shown to be pathway substrates and to contribute to elicitation of the plant hypersensitive response and to translocation and secretion of the model effector AvrPto1.

scholarly journals Effects of epidermal growth factor and insulin on the activity of N-acetylglucosaminyltransferase V

1997 ◽  
Vol 324 (2) ◽  
pp. 543-545 ◽  
Author(s):  
Qiaohong WANG ◽  
Dapeng ZHOU ◽  
Dongmin SHAO ◽  
Zhonghou SHEN ◽  
Jianxin GU
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Protein Tyrosine Kinase ◽  
Kinase Activity ◽  
Mitogen Activated Protein Kinase ◽  
Receptor Protein ◽  
Mitogen Activated Protein ◽  
Epidermal Growth

When quiescent rat hepatocellular carcinoma 7919 cells were treated with epidermal growth factor (EGF) or insulin (stimulators of receptor tyrosine kinase activity), the activity of N-acetylglucosaminyltransferase V was increased. The effect of EGF reached a maximum after 10 min and remained high for 30 min, while the effect of insulin reached a maximum after 5 min and decreased after 15 min. Preincubation of the cells with 1-O-octadecyl-2-O-methylglycerophosphocholine (Et18-OH3), which blocked the activation of mitogen-activated protein kinase by EGF, also blocked the activation of N-acetylglucosamyltransferase V by this hormone, whereas the activation of N-acetylglucosamyltransferase V by insulin could not be blocked by Et18-OH3. Our results suggest that N-acetylglucosamyltransferase V may be regulated by different receptor protein tyrosine kinase pathways.

scholarly journals A Pseudomonas syringae ADP-Ribosyltransferase Inhibits Arabidopsis Mitogen-Activated Protein Kinase Kinases

2010 ◽  
Vol 22 (6) ◽  
pp. 2033-2044 ◽  
Author(s):  
Yujing Wang ◽  
Jifeng Li ◽  
Shuguo Hou ◽  
Xingwei Wang ◽  
Yuan Li ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Pseudomonas Syringae ◽  
Mitogen Activated Protein Kinase ◽  
Mitogen Activated Protein ◽  
Adp Ribosyltransferase

scholarly journals Armet, an aphid effector protein, induces pathogen resistance in plants by promoting the accumulation of salicylic acid

2019 ◽  
Vol 374 (1767) ◽  
pp. 20180314 ◽  
Author(s):  
Na Cui ◽  
Hong Lu ◽  
Tianzuo Wang ◽  
Wenhao Zhang ◽  
Le Kang ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Pseudomonas Syringae ◽  
Plant Pathogen ◽  
Bacterial Pathogen ◽  
Pathogen Resistance ◽  
Effector Proteins ◽  
Mitogen Activated Protein Kinase ◽  
Effector Protein ◽  
Plant Interactions ◽  
Fourfold Increase

Effector proteins present in aphid saliva are thought to modulate aphid–plant interactions. Armet, an effector protein, is found in the phloem sap of pea-aphid-infested plants and is indispensable for the survival of aphids on plants. However, its function in plants has not been investigated. Here, we explored the functions of Armet after delivery into plants. Examination of the transcriptomes of Nicotiana benthamiana and Medicago truncatula following transgenic expression of Armet or infiltration of the protein showed that Armet activated pathways associated with plant–pathogen interactions, mitogen-activated protein kinase and salicylic acid (SA). Armet induced a fourfold increase in SA accumulation by regulating the expression of SAMT and SABP2 , two genes associated with SA metabolism, in Armet-infiltrated tobacco. The increase in SA enhanced the plants' resistance to bacterial pathogen Pseudomonas syringae but had no detectable adverse effects on aphid survival or reproduction. Similar molecular responses and a chlorosis phenotype were induced in tobacco by Armet from two aphid species but not by locust Armet, suggesting that the effector function of Armet may be specific for aphids. The results suggest that Armet causes plants to make a pathogen-resistance decision and reflect a novel tripartite insect–plant–pathogen interaction. This article is part of the theme issue ‘Biotic signalling sheds light on smart pest management’.

The small molecule Zaractin activates ZAR1-mediated immunity in Arabidopsis

2021 ◽  
Vol 118 (47) ◽  
pp. e2116570118
Author(s):  
Derek Seto ◽  
Madiha Khan ◽  
D. Patrick Bastedo ◽  
Alexandre Martel ◽  
Trinh Vo ◽  
...  
Keyword(s):  
Immune System ◽  
Pseudomonas Syringae ◽  
Small Molecule ◽  
Nucleotide Binding ◽  
Infection Process ◽  
Effector Proteins ◽  
Cellular Proteins ◽  
Leucine Rich Repeat ◽  
Effector Triggered Immunity ◽  
Immune Pathway

Pathogenic effector proteins use a variety of enzymatic activities to manipulate host cellular proteins and favor the infection process. However, these perturbations can be sensed by nucleotide-binding leucine-rich-repeat (NLR) proteins to activate effector-triggered immunity (ETI). Here we have identified a small molecule (Zaractin) that mimics the immune eliciting activity of the Pseudomonas syringae type III secreted effector (T3SE) HopF1r and show that both HopF1r and Zaractin activate the same NLR-mediated immune pathway in Arabidopsis. Our results demonstrate that the ETI-inducing action of pathogenic effectors can be harnessed to identify synthetic activators of the eukaryotic immune system.

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