scholarly journals Molecular characterization of HEXOKINASE1 in plant innate immunity

2020 ◽  
Vol 63 (1) ◽  
Author(s):  
Wu Jing ◽  
Shahab Uddin ◽  
Rupak Chakraborty ◽  
Duong Thu Van Anh ◽  
Donah Mary Macoy ◽  
...  
Keyword(s):  
Immune Responses ◽  
Pseudomonas Syringae ◽  
Glucose Sensor ◽  
Plant Immunity ◽  
Interacting Protein ◽  
Bacterial Populations ◽  
Effector Triggered Immunity ◽  
Callose Formation ◽  
Molecular Patterns

AbstractHexokinase1 (HXK1) is an Arabidopsis glucose sensor that has a variety of roles during plant growth and devlopment, including during germination, flowering, and senescence. HXK1 also acts as a positive regulator of plant immune responses. Previous research suggested that HXK1 might influence plant immune responses via responses to glucose. Plant immune responses are governed by two main pathways: PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI). PTI involves the recognition of Pathogen-Associated Molecular Patterns (PAMPs) and leads to increased callose formation and accumulation of pathogenesis response (PR) proteins. ETI acts in response to effectors secreted by Gram-negative bacteria. During ETI, the membrane-localized protein RPM1-interacting protein 4 (RIN4) becomes phosphorylated in reponse to interactions with effectors and mediates the downstream response. In this study, the effects of glucose on plant immune responses against infection with Pseudomonas syringae pv. tomato DC3000 and other P. syringae strains were investigated in the presence and absence of HXK1. Infiltration of leaves with glucose prior to infection led to decreases in bacterial populations and reductions in disease symptoms in wild-type Arabidopsis plants, indicating that glucose plays a role in plant immunity. Both PTI and ETI responses were affected. However, these effects were not observed in a hxk1 mutant, indicating that the effects of glucose on plant immune responses were mediated by HXK1-related pathways.

scholarly journals Plant immunity triggered by engineered in vivo release of oligogalacturonides, damage-associated molecular patterns

2015 ◽  
Vol 112 (17) ◽  
pp. 5533-5538 ◽  
Author(s):  
Manuel Benedetti ◽  
Daniela Pontiggia ◽  
Sara Raggi ◽  
Zhenyu Cheng ◽  
Flavio Scaloni ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Immunity ◽  
Inducible Promoter ◽  
Spectrometric Analysis ◽  
In Planta ◽  
Gene Encoding ◽  
Polygalacturonase Inhibiting Protein ◽  
Molecular Patterns ◽  
Damage Associated Molecular Patterns

Oligogalacturonides (OGs) are fragments of pectin that activate plant innate immunity by functioning as damage-associated molecular patterns (DAMPs). We set out to test the hypothesis that OGs are generated in planta by partial inhibition of pathogen-encoded polygalacturonases (PGs). A gene encoding a fungal PG was fused with a gene encoding a plant polygalacturonase-inhibiting protein (PGIP) and expressed in transgenic Arabidopsis plants. We show that expression of the PGIP–PG chimera results in the in vivo production of OGs that can be detected by mass spectrometric analysis. Transgenic plants expressing the chimera under control of a pathogen-inducible promoter are more resistant to the phytopathogens Botrytis cinerea, Pectobacterium carotovorum, and Pseudomonas syringae. These data provide strong evidence for the hypothesis that OGs released in vivo act as a DAMP signal to trigger plant immunity and suggest that controlled release of these molecules upon infection may be a valuable tool to protect plants against infectious diseases. On the other hand, elevated levels of expression of the chimera cause the accumulation of salicylic acid, reduced growth, and eventually lead to plant death, consistent with the current notion that trade-off occurs between growth and defense.

scholarly journals Broad-Spectrum Disease Resistance Conferred by the Overexpression of Rice RLCK BSR1 Results from an Enhanced Immune Response to Multiple MAMPs

2019 ◽  
Vol 20 (22) ◽  
pp. 5523 ◽  
Author(s):  
Yasukazu Kanda ◽  
Hitoshi Nakagawa ◽  
Yoko Nishizawa ◽  
Takashi Kamakura ◽  
Masaki Mori
Keyword(s):  
Disease Resistance ◽  
Immune Responses ◽  
Broad Spectrum ◽  
Transcriptional Activation ◽  
Intracellular Signaling ◽  
Cultured Cells ◽  
Plant Immunity ◽  
Production Of Hydrogen ◽  
Defense Related Gene ◽  
Molecular Patterns

Plants activate their immune system through intracellular signaling pathways after perceiving microbe-associated molecular patterns (MAMPs). Receptor-like cytoplasmic kinases mediate the intracellular signaling downstream of pattern-recognition receptors. BROAD-SPECTRUM RESISTANCE 1 (BSR1), a rice (Oryza sativa) receptor-like cytoplasmic kinase subfamily-VII protein, contributes to chitin-triggered immune responses. It is valuable for agriculture because its overexpression confers strong disease resistance to fungal and bacterial pathogens. However, it remains unclear how overexpressed BSR1 reinforces plant immunity. Here we analyzed immune responses using rice suspension-cultured cells and sliced leaf blades overexpressing BSR1. BSR1 overexpression enhances MAMP-triggered production of hydrogen peroxide (H2O2) and transcriptional activation of the defense-related gene in cultured cells and leaf strips. Furthermore, the co-cultivation of leaves with conidia of the blast fungus revealed that BSR1 overexpression allowed host plants to produce detectable oxidative bursts against compatible pathogens. BSR1 was also involved in the immune responses triggered by peptidoglycan and lipopolysaccharide. Thus, we concluded that the hyperactivation of MAMP-triggered immune responses confers BSR1-mediated robust resistance to broad-spectrum pathogens.

scholarly journals Phosphatase PP2C6 negatively regulates phosphorylation status of Pti1b kinase, a regulator of flagellin-triggered immunity in tomato

2019 ◽  
Author(s):  
Fabian Giska ◽  
Gregory B. Martin
Keyword(s):  
Immune Responses ◽  
Plant Immunity ◽  
Active Form ◽  
Control Plant ◽  
Negative Regulator ◽  
Response To Treatment ◽  
Positive Regulators ◽  
Molecular Patterns

AbstractPlant immune responses, including the production of reactive oxygen species (ROS), are triggered when pattern recognition receptors (PRR) become activated upon detection of microbe-associated molecular patterns (MAMPs). Receptor-like cytoplasmic kinases are key components of PRR-dependent signaling pathways. In tomato two such kinases, Pti1a and Pti1b, are important positive regulators of the plant immune response. However, it is unknown how these kinases control plant immunity at the molecular level, and how their activity is regulated. To investigate these issues, we used mass spectrometry to search for interactors of Pti1b in Nicotiana benthamiana leaves and identified a protein phosphatase, PP2C6. An in vitro pull-down assay and in vivo split luciferase complementation assay verified this interaction. Pti1b was found to autophosphorylate on threonine-233 and this phosphorylation was abolished in the presence of PP2C6. An arginine-to-cysteine substitution at position 240 in the Arabidopsis MARIS kinase was previously reported to convert it into a constitutive-active form. The analogous substitution in Pti1b made it resistant to PP2C6 phosphatase activity, although it still interacted with PP2C6. Treatment of N. benthamiana leaves with the MAMP flg22 induced threonine phosphorylation of Pti1b. Expression of PP2C6, but not a phosphatase-inactive variant of this protein, in N. benthamiana leaves greatly reduced ROS production in response to treatment with MAMPs flg22 or csp22. The results indicate that PP2C6 acts as a negative regulator by dephosphorylating the Pti1b kinase, thereby interfering with its ability to activate plant immune responses.

scholarly journals molecular link from PAMP perception to a MAPK cascade associated with tomato disease resistance

2012 ◽  
Author(s):  
Guido Sessa ◽  
Gregory B. Martin
Keyword(s):  
Cell Death ◽  
Disease Resistance ◽  
Immune Responses ◽  
Map Kinase ◽  
Pseudomonas Syringae ◽  
Molecular Mechanisms ◽  
Plant Immunity ◽  
Defense Responses ◽  
Research Activities ◽  
Mapk Cascades

The research problem: The detection of pathogen-associated molecular patterns (PAMPs) by plant pattern recognition receptors (PRRs) is a key mechanism by which plants activate an effective immune response against pathogen attack. MAPK cascades are important signaling components downstream of PRRs that transduce the PAMP signal to activate various defense responses. Preliminary experiments suggested that the receptor-like cytoplasmickinase (RLCK) Mai5 plays a positive role in pattern-triggered immunity (PTI) and interacts with the MAPKKK M3Kε. We thus hypothesized that Mai5, as other RLCKs, functions as a component PRR complexes and acts as a molecular link between PAMP perception and activation of MAPK cascades. Original goals: The central goal of this research was to investigate the molecular mechanisms by which Mai5 and M3Kε regulate plant immunity. Specific objectives were to: 1. Determine the spectrum of PAMPs whose perception is transmitted by M3Kε; 2. Identify plant proteins that act downstream of M3Kε to mediate PTI; 3. Investigate how and where Mai5 interacts with M3Kε in the plant cell; 4. Examine the mechanism by which Mai5 contributes to PTI. Changes in research directions: We did not find convincing evidence for the involvement of M3Kε in PTI signaling and substituted objectives 1 and 3 with research activities aimed at the analysis of transcriptomic profiles of tomato plants during the onset of plant immunity, isolation of the novel tomato PRR FLS3, and investigation of the involvement of the RLCKBSKs in PTI. Main achievements during this research program are in the following major areas: 1. Functional characterization of Mai5. The function of Mai5 in PTI signaling was demonstrated by testing the effect of silencing the Mai5 gene by virus-induced gene silencing (VIGS) experiments and in cell death assays. Domains of Mai5 that interact with MAPKKKs and subcellular localization of Mai5 were analyzed in detail. 2. Analysis of transcriptional profiles during the tomato immune responses to Pseudomonas syringae (Pombo et al., 2014). We identified tomato genes whose expression is induced specifically in PTI or in effector-triggered immunity (ETI). Thirty ETI-specific genes were examined by VIGS for their involvement in immunity and the MAPKKK EPK1, was found to be required for ETI. 3. Dissection of MAP kinase cascades downstream of M3Kε (Oh et al., 2013; Teper et al., 2015). We identified genes that encode positive (SGT and EDS1) and negative (WRKY1 and WRKY2) regulators of the ETI-associated cell death mediated by M3Kε. In addition, the MKK2 MAPKK, which acts downstream of M3Kε, was found to interact with the MPK3 MAPK and specific MPK3 amino acids involved interaction were identified and found to be required for induction of cell death. We also identified 5 type III effectors of the bacterial pathogen Xanthomonaseuvesicatoria that inhibited cell death induced by components of ETI-associated MAP kinase cascades. 4. Isolation of the tomato PRR FLS3 (Hind et al., submitted). FLS3, a novel PRR of the LRR-RLK family that specifically recognizes the flagellinepitope flgII-28 was isolated. FLS3 was shown to bind flgII-28, to require kinase activity for function, to act in concert with BAK1, and to enhance disease resistance to Pseudomonas syringae. 5. Functional analysis of RLCKs of the brassinosteroid signaling kinase (BSK) family.Arabidopsis and tomato BSKs were found to interact with PRRs. In addition, certain ArabidospsisBSK mutants were found to be impaired in PAMP-induced resistance to Pseudomonas syringae. Scientific and agricultural significance: Our research activities discovered and characterized new molecular components of signaling pathways mediating recognition of invading pathogens and activation of immune responses against them. Increased understanding of molecular mechanisms of immunity will allow them to be manipulated by both molecular breeding and genetic engineering to produce plants with enhanced natural defense against disease.

scholarly journals Identification and Analysis of NBS-LRR Genes in Actinidia chinensis Genome

Plants ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1350
Author(s):  
Tao Wang ◽  
Zhan-Hui Jia ◽  
Ji-Yu Zhang ◽  
Min Liu ◽  
Zhong-Ren Guo ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Immunity ◽  
Domain Architecture ◽  
Bacterial Canker ◽  
Actinidia Chinensis ◽  
R Genes ◽  
Leucine Rich Repeat ◽  
Cis Acting ◽  
Important Disease

Nucleotide-binding site and leucine-rich repeat (NBS-LRR) genes represent the most important disease resistance genes in plants. The genome sequence of kiwifruit (Actinidia chinensis) provides resources for the characterization of NBS-LRR genes and identification of new R-genes in kiwifruit. In the present study, we identified 100 NBS-LRR genes in the kiwifruit genome and they were grouped into six distinct classes based on their domain architecture. Of the 100 genes, 79 are truncated non-regular NBS-LRR genes. Except for 37 NBS-LRR genes with no location information, the remaining 63 genes are distributed unevenly across 18 kiwifruit chromosomes and 38.01% of them are present in clusters. Seventeen families of cis-acting elements were identified in the promoters of the NBS-LRR genes, including AP2, NAC, ERF and MYB. Pseudomonas syringae pv. actinidiae (pathogen of the kiwifruit bacterial canker) infection induced differential expressions of 16 detected NBS-LRR genes and three of them are involved in plant immunity responses. Our study provides insight of the NBS-LRR genes in kiwifruit and a resource for the identification of new R-genes in the fruit.

scholarly journals The Majority of the Type III Effector Inventory of Pseudomonas syringae pv. tomato DC3000 Can Suppress Plant Immunity

2009 ◽  
Vol 22 (9) ◽  
pp. 1069-1080 ◽  
Author(s):  
Ming Guo ◽  
Fang Tian ◽  
Yashitola Wamboldt ◽  
James R. Alfano
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Immunity ◽  
In Planta ◽  
Tomato Dc3000 ◽  
Type Iii Effector ◽  
Type Iii Effectors ◽  
Type Iii ◽  
Molecular Pattern ◽  
Effector Triggered Immunity ◽  
Type Iii Protein Secretion

The Pseudomonas syringae type III protein secretion system (T3SS) and the type III effectors it injects into plant cells are required for plant pathogenicity and the ability to elicit a hypersensitive response (HR). The HR is a programmed cell death that is associated with effector-triggered immunity (ETI). A primary function of P. syringae type III effectors appears to be the suppression of ETI and pathogen-associated molecular pattern–triggered immunity (PTI), which is induced by conserved molecules on microorganisms. We reported that seven type III effectors from P. syringae pv. tomato DC3000 were capable of suppressing an HR induced by P. fluorescens(pHIR11) and have now tested 35 DC3000 type III effectors in this assay, finding that the majority of them can suppress the HR induced by HopA1. One newly identified type III effector with particularly strong HR suppression activity was HopS2. We used the pHIR11 derivative pLN1965, which lacks hopA1, in related assays and found that a subset of the type III effectors that suppressed HopA1-induced ETI also suppressed an ETI response induced by AvrRpm1 in Arabidopsis thaliana. A. thaliana plants expressing either HopAO1 or HopF2, two type III effectors that suppressed the HopA1-induced HR, were reduced in the flagellin-induced PTI response as well as PTI induced by other PAMPs and allowed enhanced in planta growth of P. syringae. Collectively, our results suggest that the majority of DC3000 type III effectors can suppress plant immunity. Additionally, the construct pLN1965 will likely be a useful tool in determining whether other type III effectors or effectors from other types of pathogens can suppress either ETI, PTI, or both.

scholarly journals The μ Subunit of Arabidopsis Adaptor Protein-2 Is Involved in Effector-Triggered Immunity Mediated by Membrane-Localized Resistance Proteins

2016 ◽  
Vol 29 (5) ◽  
pp. 345-351 ◽  
Author(s):  
Noriyuki Hatsugai ◽  
Rachel Hillmer ◽  
Shohei Yamaoka ◽  
Ikuko Hara-Nishimura ◽  
Fumiaki Katagiri
Keyword(s):  
Plasma Membrane ◽  
Immune Responses ◽  
Pseudomonas Syringae ◽  
Adaptor Protein ◽  
Floral Organ ◽  
Coated Vesicle ◽  
Defense Gene Expression ◽  
Hypersensitive Cell Death ◽  
Cell Death Response ◽  
Effector Triggered Immunity

Endocytosis has been suggested to be important in the cellular processes of plant immune responses. However, our understanding of its role during effector-triggered immunity (ETI) is still limited. We have previously shown that plant endocytosis, especially clathrin-coated vesicle formation at the plasma membrane, is mediated by the adaptor protein-2 (AP-2) complex and that loss of the μ subunit of AP-2 (AP2M) affects plant growth and floral organ development. Here, we report that AP2M is required for full-strength ETI mediated by the disease resistance (R) genes RPM1 and RPS2 in Arabidopsis. Reduced ETI was observed in an ap2m mutant plant, measured by growth of Pseudomonas syringae pv. tomato DC3000 strains carrying the corresponding effector genes avrRpm1 or avrRpt2 and by hypersensitive cell death response and defense gene expression triggered by these strains. In contrast, RPS4-mediated ETI and its associated immune responses were not affected by the ap2m mutation. While RPM1 and RPS2 are localized to the plasma membrane, RPS4 is localized to the cytoplasm and nucleus. Our results suggest that AP2M is involved in ETI mediated by plasma membrane–localized R proteins, possibly by mediating endocytosis of the immune receptor complex components from the plasma membrane.

scholarly journals PP2C phosphatase Pic1 negatively regulates the phosphorylation status of Pti1b kinase, a regulator of flagellin-triggered immunity in tomato

2019 ◽  
Vol 476 (11) ◽  
pp. 1621-1635 ◽  
Author(s):  
Fabian Giska ◽  
Gregory B. Martin
Keyword(s):  
Immune Responses ◽  
Plant Immunity ◽  
Active Form ◽  
Control Plant ◽  
Negative Regulator ◽  
Response To Treatment ◽  
Positive Regulators ◽  
Molecular Patterns

Abstract Plant immune responses, including the production of reactive oxygen species (ROS), are triggered when pattern recognition receptors (PRRs) become activated upon detection of microbe-associated molecular patterns (MAMPs). Receptor-like cytoplasmic kinases are key components of PRR-dependent signaling pathways. In tomato, two such kinases, Pti1a and Pti1b, are important positive regulators of the plant immune response. However, it is unknown how these kinases control plant immunity at the molecular level and how their activity is regulated. To investigate these issues, we used mass spectrometry to search for interactors of Pti1b in Nicotiana benthamiana leaves and identified a PP2C protein phosphatase, referred to as Pic1. An in vitro pull-down assay and in vivo split-luciferase complementation assay verified this interaction. Pti1b was found to autophosphorylate on threonine-233, and this phosphorylation was abolished in the presence of Pic1. An arginine-to-cysteine substitution at position 240 in the Arabidopsis MARIS kinase was previously reported to convert it into a constitutive-active form. The analogous substitution in Pti1b made it resistant to Pic1 phosphatase activity, although it still interacted with Pic1. Treatment of N. benthamiana leaves with the MAMP flg22 induced threonine phosphorylation of Pti1b. The expression of Pic1, but not a phosphatase-inactive variant of this protein, in N. benthamiana leaves greatly reduced ROS production in response to treatment with MAMPs flg22 or csp22. The results indicate that Pic1 acts as a negative regulator by dephosphorylating the Pti1b kinase, thereby interfering with its ability to activate plant immune responses.

scholarly journals Pseudomonas syringae type III effector HopAF1 suppresses plant immunity by targeting methionine recycling to block ethylene induction

2016 ◽  
Vol 113 (25) ◽  
pp. E3577-E3586 ◽  
Author(s):  
Erica J. Washington ◽  
M. Shahid Mukhtar ◽  
Omri M. Finkel ◽  
Li Wan ◽  
Mark J. Banfield ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Pathogens ◽  
Plant Immunity ◽  
Ethylene Biosynthesis ◽  
Host Protein ◽  
Loss Of Function ◽  
Type Iii Effector ◽  
Type Iii ◽  
Host Defense Response ◽  
Molecular Patterns

HopAF1 is a type III effector protein of unknown function encoded in the genomes of several strains of Pseudomonas syringae and other plant pathogens. Structural modeling predicted that HopAF1 is closely related to deamidase proteins. Deamidation is the irreversible substitution of an amide group with a carboxylate group. Several bacterial virulence factors are deamidases that manipulate the activity of specific host protein substrates. We identified Arabidopsis methylthioadenosine nucleosidase proteins MTN1 and MTN2 as putative targets of HopAF1 deamidation. MTNs are enzymes in the Yang cycle, which is essential for the high levels of ethylene biosynthesis in Arabidopsis. We hypothesized that HopAF1 inhibits the host defense response by manipulating MTN activity and consequently ethylene levels. We determined that bacterially delivered HopAF1 inhibits ethylene biosynthesis induced by pathogen-associated molecular patterns and that Arabidopsis mtn1 mtn2 mutant plants phenocopy the effect of HopAF1. Furthermore, we identified two conserved asparagines in MTN1 and MTN2 from Arabidopsis that confer loss of function phenotypes when deamidated via site-specific mutation. These residues are potential targets of HopAF1 deamidation. HopAF1-mediated manipulation of Yang cycle MTN proteins is likely an evolutionarily conserved mechanism whereby HopAF1 orthologs from multiple plant pathogens contribute to disease in a large variety of plant hosts.

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