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 ◽  
...  

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.

Author(s):  
Tian-Ying Yu ◽  
Meng-Kun Sun ◽  
Li-Kun Liang

Plants adjust amplitude and duration of immune responses via different strategies to maintain growth, development and resistance to pathogens. Pathogen-associated molecular patterns (PAMPs)-triggered immunity (PTI) and effector-triggered immunity (ETI) play vital roles. PRRs (pattern recognition receptors), comprising a large number of receptor-like protein kinases (RLKs) and receptor-like proteins (RLPs), recognize related ligands and trigger immunity. PTI is the first layer of the innate immune system, and it recognizes PAMPs at plasma membrane to prevent infection. However, pathogens exploit effector proteins to bypass or directly inhibit the PTI immune pathway. Consistently, plants have evolved intracellular nucleotide-binding domain and leucine-rich repeat-containing (NLR) proteins to detect pathogenic effectors and trigger a hypersensitive response to activate ETI. PTI and ETI work together to protect plants from infection of virus and other pathogens. Diverse receptors and the corresponding ligands, especially several pairs of well-studied receptors and ligands in PTI immunity, are reviewed to illustrate the dynamic process of PTI response here.


2017 ◽  
Vol 114 (10) ◽  
pp. E2053-E2062 ◽  
Author(s):  
Marc T. Nishimura ◽  
Ryan G. Anderson ◽  
Karen A. Cherkis ◽  
Terry F. Law ◽  
Qingli L. Liu ◽  
...  

Detection of pathogens by plants is mediated by intracellular nucleotide-binding site leucine-rich repeat (NLR) receptor proteins. NLR proteins are defined by their stereotypical multidomain structure: an N-terminal Toll–interleukin receptor (TIR) or coiled-coil (CC) domain, a central nucleotide-binding (NB) domain, and a C-terminal leucine-rich repeat (LRR). The plant innate immune system contains a limited NLR repertoire that functions to recognize all potential pathogens. We isolated Response to the bacterial type III effector protein HopBA1 (RBA1), a gene that encodes a TIR-only protein lacking all other canonical NLR domains. RBA1 is sufficient to trigger cell death in response to HopBA1. We generated a crystal structure for HopBA1 and found that it has similarity to a class of proteins that includes esterases, the heme-binding protein ChaN, and an uncharacterized domain ofPasteurella multocidatoxin. Self-association, coimmunoprecipitation with HopBA1, and function of RBA1 require two previously identified TIR–TIR dimerization interfaces. Although previously described as distinct in other TIR proteins, in RBA1 neither of these interfaces is sufficient when the other is disrupted. These data suggest that oligomerization of RBA1 is required for function. Our identification of RBA1 demonstrates that “truncated” NLRs can function as pathogen sensors, expanding our understanding of both receptor architecture and the mechanism of activation in the plant immune system.


2010 ◽  
Vol 107 (5) ◽  
pp. 2349-2354 ◽  
Author(s):  
Mike Wilton ◽  
Rajagopal Subramaniam ◽  
James Elmore ◽  
Corinna Felsensteiner ◽  
Gitta Coaker ◽  
...  

Plant immunity can be induced by two major classes of pathogen-associated molecules. Pathogen- or microbe-associated molecular patterns (PAMPs or MAMPs) are conserved molecular components of microbes that serve as “non-self” features to induce PAMP-triggered immunity (PTI). Pathogen effector proteins used to promote virulence can also be recognized as “non-self” features or induce a “modified-self” state that can induce effector-triggered immunity (ETI). The Arabidopsis protein RIN4 plays an important role in both branches of plant immunity. Three unrelated type III secretion effector (TTSE) proteins from the phytopathogen Pseudomonas syringae, AvrRpm1, AvrRpt2, and AvrB, target RIN4, resulting in ETI that effectively restricts pathogen growth. However, no pathogenic advantage has been demonstrated for RIN4 manipulation by these TTSEs. Here, we show that the TTSE HopF2Pto also targets Arabidopsis RIN4. Transgenic plants conditionally expressing HopF2Pto were compromised for AvrRpt2-induced RIN4 modification and associated ETI. HopF2Pto interfered with AvrRpt2-induced RIN4 modification in vitro but not with AvrRpt2 activation, suggestive of RIN4 targeting by HopF2Pto. In support of this hypothesis, HopF2Pto interacted with RIN4 in vitro and in vivo. Unlike AvrRpm1, AvrRpt2, and AvrB, HopF2Pto did not induce ETI and instead promoted P. syringae growth in Arabidopsis. This virulence activity was not observed in plants genetically lacking RIN4. These data provide evidence that RIN4 is a major virulence target of HopF2Pto and that a pathogenic advantage can be conveyed by TTSEs that target RIN4.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hernan G. Rosli ◽  
Emilia Sirvent ◽  
Florencia N. Bekier ◽  
Romina N. Ramos ◽  
Marina A. Pombo

AbstractPlants rely on (in)direct detection of bacterial pathogens through plasma membrane-localized and intracellular receptor proteins. Surface pattern-recognition receptors (PRRs) participate in the detection of microbe-associated molecular patterns (MAMPs) and are required for the activation of pattern-triggered immunity (PTI). Pathogenic bacteria, such as Pseudomonas syringae pv. tomato (Pst) deploys ~ 30 effector proteins into the plant cell that contribute to pathogenicity. Resistant plants are capable of detecting the presence or activity of effectors and mount another response termed effector-triggered immunity (ETI). In order to investigate the involvement of tomato’s long non-coding RNAs (lncRNAs) in the immune response against Pst, we used RNA-seq data to predict and characterize those that are transcriptionally active in leaves challenged with a large set of treatments. Our prediction strategy was validated by sequence comparison with tomato lncRNAs described in previous works and by an alternative approach (RT-qPCR). Early PTI (30 min), late PTI (6 h) and ETI (6 h) differentially expressed (DE) lncRNAs were identified and used to perform a co-expression analysis including neighboring (± 100 kb) DE protein-coding genes. Some of the described networks could represent key regulatory mechanisms of photosynthesis, PRR abundance at the cell surface and mitigation of oxidative stress, associated to tomato-Pst pathosystem.


Science ◽  
2020 ◽  
Vol 367 (6479) ◽  
pp. 763-768 ◽  
Author(s):  
Bradley Laflamme ◽  
Marcus M. Dillon ◽  
Alexandre Martel ◽  
Renan N. D. Almeida ◽  
Darrell Desveaux ◽  
...  

Effector-triggered immunity (ETI), induced by host immune receptors in response to microbial effectors, protects plants against virulent pathogens. However, a systematic study of ETI prevalence against species-wide pathogen diversity is lacking. We constructed the Pseudomonas syringae Type III Effector Compendium (PsyTEC) to reduce the pan-genome complexity of 5127 unique effector proteins, distributed among 70 families from 494 strains, to 529 representative alleles. We screened PsyTEC on the model plant Arabidopsis thaliana and identified 59 ETI-eliciting alleles (11.2%) from 19 families (27.1%), with orthologs distributed among 96.8% of P. syringae strains. We also identified two previously undescribed host immune receptors, including CAR1, which recognizes the conserved effectors AvrE and HopAA1, and found that 94.7% of strains harbor alleles predicted to be recognized by either CAR1 or ZAR1.


2019 ◽  
Vol 32 (1) ◽  
pp. 5-5
Author(s):  
John M. McDowell

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


2021 ◽  
Vol 8 (4) ◽  
Author(s):  
Gagan Kumar Panigrahi ◽  
Annapurna Sahoo ◽  
Kunja Bihari Satapathy

The plant immune system is equipped with several defensive layers to evade pathogen attack. One of the primary defense includes plasma membrane-localized receptors explicitly detect conserved pathogen-associated molecular patterns. Transcriptional reprogramming of resistant genes confers PAMP-triggered immunity. Consequently basal immunity is triggered which is primarily mediated by several intracellular nucleotide-binding leucine rich repeat receptors. Subsequently, nucleotide-binding leucine rich repeat receptors sense pathogens and activate another defense response known as effector triggered immunity. Both the PTI and ETI are mediated by resistant genes. Interestingly, the detailed molecular function of resistant genes is not yet fully revealed. Resistant genes are also well involved in non pathophysiological conditions such as during cold stress, heat stress, duration of exposure of light and drought stress. Here, we have reported that the Arabidopsis resistant genes AT1G17600, AT4G14368, AT4G16860, AT5G40910 and AT5G45050 are temperature regulated. We found that the transcript levels of AT1G58400, AT2G14080, AT2G17055, AT3G51560, AT4G16950, AT5G40910 and AT5G45050 were significantly raised for the plant samples grown under short-day conditions. The transcript levels of AT1G17600, AT1G27180, AT1G33560, AT2G14080, AT3G51560, AT4G16860 and AT4G16950 were upregulated for plants grown under drought stress conditions. In Arabidopsis, the transcriptional reprogramming is modulated by decapping protein factors. There was no significant change in the protein level of DCPs. Our results suggest that under abiotic stress conditions, the resistant genes differentially express independent of the decapping event.


2019 ◽  
Author(s):  
Chih-Hang Wu ◽  
Sophien Kamoun

AbstractBacterial speck, caused by the pathogen Pseudomonas syringae pv. tomato, is one of the most common diseases in tomato production. Together with Pto kinase, the NLR (nucleotide-binding domain leucine-rich repeat containing) protein Prf confers resistance against the bacterial speck pathogen by recognizing AvrPto and AvrPtoB, two Type III effector proteins secreted by P. syringae pv. tomato. This Prf/Pto pathway is part of a complex NLR network in solanaceous plants that mediates resistance to diverse pathogens through the helper NLR proteins NRCs (NLR required for cell death). We previously showed that, in Nicotiana benthamiana, the hypersensitive cell death elicited by expression of AvrPto and Pto, which activate immunity through the endogenous Prf ortholog NbPrf, requires functionally redundant NRC2 and NRC3. However, whether tomato (Solanum lycopersicum) Prf (SlPrf) confers resistance to the bacterial speck pathogen through NRC2 and NRC3 has not been determined. In this study, we show that SlPrf requires NRC2 and NRC3 to trigger hypersensitive cell death and disease resistance in both N. benthamiana and tomato. We found that the hypersensitive cell death induced by AvrPtoB/Pto/SlPrf in N. benthamiana is compromised when NRC2 and NRC3 are silenced, indicating that SlPrf is an NRC2/3-dependent NLR. We validated this finding by showing that silencing NRC2 and NRC3 in the bacterial speck resistant tomato ‘Rio Grande 76R’ compromised Prf-mediated resistance. These results indicate that the NRC network extends beyond N. benthamiana to solanaceous crops.


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