scholarly journals The BIR2/BIR3-interacting Phospholipase D gamma 1 negatively regulates immunity in Arabidopsis

2019 ◽  
Author(s):  
Maria A. Schlöffel ◽  
Andrea Salzer ◽  
Wei-Lin Wan ◽  
Ringo van Wijk ◽  
Maja Šemanjski ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Pseudomonas Syringae ◽  
Phospholipase D ◽  
Plant Immunity ◽  
Negative Regulator ◽  
Regulatory Function ◽  
Membrane Phospholipids ◽  
Effective Strategies ◽  
Pathogen Invasion ◽  
Molecular Patterns

ABSTRACTPlants have evolved effective strategies to defend themselves against pathogen invasion. Starting from the plasma membrane with the recognition of microbe-associated molecular patterns (MAMPs) via pattern recognition receptors, internal cellular signaling pathways are induced to ultimately fend off the attack. Phospholipase D (PLD) hydrolyzes membrane phospholipids to produce phosphatidic acid (PA), which has been proposed to play a second messenger role in immunity. The Arabidopsis PLD family consists of 12 members and for some a specific function in resistance towards a subset of pathogens has been shown. We demonstrate here that Arabidopsis PLDγ1, but not its close homologs PLDγ2 and PLDγ3, is specifically involved in plant immunity. Genetic inactivation of PLDγ1 resulted in increased resistance towards the virulent bacterium Pseudomonas syringae pv. tomato DC3000 and the necrotrophic fungus Botrytis cinerea. As pldγ1 mutant plants responded with elevated levels of reactive oxygen species to MAMP-treatment, a negative regulatory function for this PLD isoform is proposed. Importantly, PA levels in pldγ1 mutants were not affected compared to stressed wild-type plants, suggesting that alterations in PA levels are unlikely the cause for the enhanced immunity in the pldγ1 line. Instead, the plasma-membrane-attached PLDγ1 protein colocalized and associated with the receptor-like kinases BIR2 and BIR3, which are known negative regulators of pattern-triggered immunity. Moreover, complex formation of PLDγ1 and BIR2 was further promoted upon MAMP-treatment. Hence, we propose that PLDγ1 acts as a negative regulator of plant immune responses in complex with immunity-related proteins BIR2 and BIR3.One-sentence summaryA phospholipase D is a novel negative regulator of plant immunity and forms complexes with regulatory receptor-like kinases.

scholarly journals Evolutionary Plasticity of AmrZ Regulation in Pseudomonas

mSphere ◽  
2018 ◽  
Vol 3 (2) ◽  
pp. e00132-18 ◽  
Author(s):  
David A. Baltrus ◽  
Kevin Dougherty ◽  
Beatriz Diaz ◽  
Rachel Murillo
Keyword(s):  
Pseudomonas Syringae ◽  
Negative Regulator ◽  
Regulatory Function ◽  
Dual Function ◽  
Genomic Context ◽  
Master Regulator ◽  
Content Type ◽  
Swimming Motility ◽  
Positive Regulator ◽  
Mode Of Regulation

ABSTRACT amrZ encodes a master regulator protein conserved across pseudomonads, which can be either a positive or negative regulator of swimming motility depending on the species examined. To better understand plasticity in the regulatory function of AmrZ, we characterized the mode of regulation for this protein for two different motility-related phenotypes in Pseudomonas stutzeri. As in Pseudomonas syringae, AmrZ functions as a positive regulator of swimming motility within P. stutzeri, which suggests that the functions of this protein with regard to swimming motility have switched at least twice across pseudomonads. Shifts in mode of regulation cannot be explained by changes in AmrZ sequence alone. We further show that AmrZ acts as a positive regulator of colony spreading within this strain and that this regulation is at least partially independent of swimming motility. Closer investigation of mechanistic shifts in dual-function regulators like AmrZ could provide unique insights into how transcriptional pathways are rewired between closely related species. IMPORTANCE Microbes often display finely tuned patterns of gene regulation across different environments, with major regulatory changes controlled by a small group of “master” regulators within each cell. AmrZ is a master regulator of gene expression across pseudomonads and can be either a positive or negative regulator for a variety of pathways depending on the strain and genomic context. Here, we demonstrate that the phenotypic outcomes of regulation of swimming motility by AmrZ have switched at least twice independently in pseudomonads, so that AmrZ promotes increased swimming motility in P. stutzeri and P. syringae but represses this phenotype in Pseudomonas fluorescens and Pseudomonas aeruginosa. Since examples of switches in regulatory mode are relatively rare, further investigation into the mechanisms underlying shifts in regulator function for AmrZ could provide unique insights into the evolution of bacterial regulatory proteins.

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 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 Characterization of a Novel, Defense-Related Arabidopsis Mutant, cir1, Isolated By Luciferase Imaging

2002 ◽  
Vol 15 (6) ◽  
pp. 557-566 ◽  
Author(s):  
Shane L. Murray ◽  
Catherine Thomson ◽  
Andrea Chini ◽  
Nick D. Read ◽  
Gary J. Loake
Keyword(s):  
Signaling Pathways ◽  
Pseudomonas Syringae ◽  
Constitutive Expression ◽  
Bacterial Pathogen ◽  
Negative Regulator ◽  
Reactive Oxygen Intermediate ◽  
Peronospora Parasitica ◽  
Tomato Dc3000 ◽  
Pathogen Invasion ◽  
Arabidopsis Mutant

In order to identify components of the defense signaling network engaged following attempted pathogen invasion, we generated a novel PR-1∷luciferase (LUC) transgenic line that was deployed in an imaging-based screen to uncover defense-related mutants. The recessive mutant designated cir1 exhibited constitutive expression of salicylic acid (SA), jasmonic acid (JA)/ethylene, and reactive oxygen intermediate-dependent genes. Moreover, this mutation conferred resistance against the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 and a virulent oomycete pathogen Peronospora parasitica Noco2. Epistasis analyses were undertaken between cir1 and mutants that disrupt the SA (npr1, nahG), JA (jar1), and ethylene (ET) (ein2) signaling pathways. While resistance against both P. syringae pv. tomato DC3000 and Peronospora parasitica Noco2 was partially reduced by npr1, resistance against both of these pathogens was lost in an nahG genetic background. Hence, cir1-mediated resistance is established via NPR1-dependent and -independent signaling pathways and SA accumulation is essential for the function of both pathways. While jar1 and ein2 reduced resistance against P. syringae pv. tomato DC3000, these mutations appeared not to impact cir1-mediated resistance against Peronospora parasitica Noco2. Thus, JA and ET sensitivity are required for cir1-mediated resistance against P. syringae pv. tomato DC3000 but not Peronospora parasitica Noco2. Therefore, the cir1 mutation may define a negative regulator of disease resistance that operates upstream of SA, JA, and ET accumulation.

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.

scholarly journals Bacterial Effector HopF2 Suppresses Arabidopsis Innate Immunity at the Plasma Membrane

2011 ◽  
Vol 24 (5) ◽  
pp. 585-593 ◽  
Author(s):  
Shujing Wu ◽  
Dongping Lu ◽  
Mehdi Kabbage ◽  
Hai-Lei Wei ◽  
Bryan Swingle ◽  
...  
Keyword(s):  
Innate Immunity ◽  
Plasma Membrane ◽  
Pseudomonas Syringae ◽  
Plant Immunity ◽  
Mapk Signaling ◽  
Effector Proteins ◽  
Host Cells ◽  
Mitogen Activated Protein Kinase ◽  
Immune Response Gene ◽  
Secretion Systems

Many bacterial pathogens inject a cocktail of effector proteins into host cells through type III secretion systems. These effectors act in concert to modulate host physiology and immune signaling, thereby promoting pathogenicity. In a search for additional Pseudomonas syringae effectors in suppressing plant innate immunity triggered by pathogen or microbe-associated molecular patterns (PAMPs or MAMPs), we identified P. syringae tomato DC3000 effector HopF2 as a potent suppressor of early immune-response gene transcription and mitogen-activated protein kinase (MAPK) signaling activated by multiple MAMPs, including bacterial flagellin, elongation factor Tu, peptidoglycan, lipopolysaccharide and HrpZ1 harpin, and fungal chitin. The conserved surface-exposed residues of HopF2 are essential for its MAMP suppression activity. HopF2 is targeted to the plant plasma membrane through a putative myristoylation site, and the membrane association appears to be required for its MAMP-suppression function. Expression of HopF2 in plants potently diminished the flagellin-induced phosphorylation of BIK1, a plasma membrane–associated cytoplasmic kinase that is rapidly phosphorylated within one minute upon flagellin perception. Thus, HopF2 likely intercepts MAMP signaling at the plasma membrane immediately of signal perception. Consistent with the potent suppression function of multiple MAMP signaling, expression of HopF2 in transgenic plants compromised plant nonhost immunity to bacteria P. syringae pv. Phaseolicola and plant immunity to the necrotrophic fungal pathogen Botrytis cinerea.

The relationship between calcium and the metabolism of plasma membrane phospholipids in hemolysis induced by brown spider venom phospholipase-D toxin

2011 ◽  
Vol 112 (9) ◽  
pp. 2529-2540 ◽  
Author(s):  
Daniele Chaves-Moreira ◽  
Fernanda N. Souza ◽  
Rosalvo T.H. Fogaça ◽  
Oldemir C. Mangili ◽  
Waldemiro Gremski ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Phospholipase D ◽  
Spider Venom ◽  
Membrane Phospholipids ◽  
Brown Spider ◽  
The Relationship

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 NbSOBIR1 Partitions Into Plasma Membrane Microdomains and Binds ER-Localized NbRLP1

2021 ◽  
Vol 12 ◽  
Author(s):  
Yi-Hua Li ◽  
Tai-Yu Ke ◽  
Wei-Che Shih ◽  
Ruey-Fen Liou ◽  
Chao-Wen Wang
Keyword(s):  
Plasma Membrane ◽  
Nicotiana Benthamiana ◽  
Affinity Purification ◽  
Bimolecular Fluorescence Complementation ◽  
Membrane Microdomains ◽  
Lateral Movement ◽  
Pathogen Invasion ◽  
Receptor Like Kinase ◽  
Molecular Patterns ◽  
Plasma Membrane Microdomains

The receptor-like kinase Suppressor of BIR1 (SOBIR1) binds various receptor-like proteins (RLPs) that perceive microbe-associated molecular patterns (MAMPs) at the plasma membrane, which is thought to activate plant pattern-triggered immunity (PTI) against pathogen invasion. Despite its potentially crucial role, how SOBIR1 transmits immune signaling to ultimately elicit PTI remains largely unresolved. Herein, we report that a Nicotiana benthamiana gene NbRLP1, like NbSOBIR1, was highly induced upon Phytophthora parasitica infection. Intriguingly, NbRLP1 is characterized as a receptor-like protein localizing to the endoplasmic reticulum (ER) membrane rather than the plasma membrane. Using bimolecular fluorescence complementation and affinity purification assays, we established that NbRLP1 is likely to associate with NbSOBIR1 through the contact between the ER and plasma membrane. We further found that NbSOBIR1 at the plasma membrane partitions into mobile microdomains that undergo frequent lateral movement and internalization. Remarkably, the dynamics of NbSOBIR1 microdomain is coupled to the remodeling of the cortical ER network. When NbSOBIR1 microdomains were induced by the P. parasitica MAMP ParA1, tobacco cells overexpressing NbRLP1 accelerated NbSOBIR1 internalization. Overexpressing NbRLP1 in tobacco further exaggerated the ParA1-induced necrosis. Together, these findings have prompted us to propose that ER and the ER-localized NbRLP1 may play a role in transmitting plant immune signals by regulating NbSOBIR1 internalization.

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