Chemical Interference of Pathogen-associated Molecular Pattern-triggered Immune Responses in Arabidopsis Reveals a Potential Role for Fatty-acid Synthase Type II Complex-derived Lipid Signals (original) (raw)
Related papers
Microbes and Infection, 2008
Lipopolysaccharides, the ubiquitous part of the outer membrane of Gram-negative bacteria, and their derivatives are recognised by plants to trigger or potentiate particular defence responses such as induction of genes encoding pathogenesis-related proteins. The molecular mechanisms of LPS perception that underpin these effects in plants are, however, unknown. Here, lipid A from Halomonas magadiensis, which is an antagonist of lipid A action in human cells, was used to investigate lipid A action in plants. Our findings offer an insight into the different structural requirements for direct induction and potentiation of plant defences by lipid A.
Molecular plant pathology, 2015
Natural and synthetic elicitors have significantly contributed to the study of plant immunity. Pathogen-derived proteins and carbohydrates, that bind to immune receptors allowed fine dissection of some defense pathways. Lipids of different nature that act as defense elicitors have also been studied, but their specific effects have been less characterized, and their receptors have not been identified. In animal cells, nanoliposomes of the synthetic cationic lipid 3-tetradecylamino-tert-butyl-N-tetradecylpropionamidine (diC14) activate the TLR4-dependent immune cascade. We here investigated if this lipid induces Arabidopsis defense responses. At the local level, diC14 activated early and late defense gene markers (FRK1, WRKY29, ICS1 and PR1) acting in a dose dependent manner. This lipid induced the salicylic acid (SA)-, but not jasmonic acid (JA)-, dependent pathway and protected plants against Pseudomonas syringae pv. tomato (Pst), but not Botrytis cinerea. diC14 was not toxic for pl...
Scientific Reports, 2016
Synthetic elicitors are drug-like compounds that are structurally distinct from natural defense elicitors. They can protect plants from diseases by activating host immune responses and can serve as tools for the dissection of the plant immune system as well as leads for the development of environmentally-safe pesticide alternatives. By high-throughput screening, we previously identified 114 synthetic elicitors that activate expression of the pathogen-responsive CaBP22 −333 ::GUS reporter gene in Arabidopsis thaliana (Arabidopsis), 33 of which are [(phenylimino)methyl]phenol (PMP) derivatives or PMP-related compounds. Here we report on the characterization of one of these compounds, 2,4-dichloro-6-{(E)-[(3-methoxyphenyl)imino]methyl}phenol (DPMP). DPMP strongly triggers disease resistance of Arabidopsis against bacterial and oomycete pathogens. By mRNA-seq analysis we found transcriptional profiles triggered by DPMP to resemble typical defense-related responses. Plant innate immunity is based on a complex set of integrated defense mechanisms protecting against microbial diseases 1-3. Plants can recognize microbe-associated molecular patterns (MAMPs), which are highly conserved molecular structures of microbes, via pattern recognition receptors (PRRs) on the surfaces of plant cells. These interactions activate pattern-triggered immunity (PTI) 4-11. To attenuate or block PTI, pathogens often secrete into plant cells effector molecules that enable them to use a given plant species as a host, resulting in compatible interactions, a condition also termed effector-triggered susceptibility (ETS). During this type of interaction plants can still exhibit a weakened immune response, called basal defense, which limits the spread of virulent pathogens, but is insufficient for preventing disease 11,12. As a countermeasure to ETS, plants often can recognize the presence or activity of effector proteins by highly specific plant resistance (R) proteins and induce effector-triggered immunity (ETI). This leads to incompatible interactions leaving the pathogen avirulent and the plant resistant 5,13. PTI, basal defense and ETI are controlled by a common set of defense signals including reactive oxygen intermediates (ROIs), Ca 2+ , salicylic acid (SA), ethylene (ET) and jasmonic acid (JA) 14. The massive release of ROIs at pathogen infection sites is one of the earliest observable features of a plant's defense program. Induced changes of ion fluxes typically precede this oxidative burst 15. The oxidative burst conditions a programmed form of localized cell death at infection sites, termed hypersensitive response (HR). HR can limit invasion of biotrophic pathogens, as these require host tissues to remain intact 16. These early responses are coordinated by various components of SA-dependent signaling mechanisms 14. In addition, crosstalk between the SA, JA and ET hormone pathways are important for the fine-tuning of plant defense responses 17 .
Activation of Defense Response Pathways by OGs and Flg22 Elicitors in Arabidopsis Seedlings
Molecular Plant, 2008
We carried out transcriptional profiling analysis in 10-d-old Arabidopsis thaliana seedlings treated with oligogalacturonides (OGs), oligosaccharides derived from the plant cell wall, or the bacterial flagellin peptide Flg22, general elicitors of the basal defense response in plants. Although detected by different receptors, both OGs and Flg22 trigger a fast and transient response that is both similar and comprehensive, and characterized by activation of early stages of multiple defense signaling pathways, particularly JA-associated processes. However, the response to Flg22 is stronger in both the number of genes differentially expressed and the amplitude of change. The magnitude of induction of individual genes is in both cases dose-dependent, but, even at very high concentrations, OGs do not induce a response that is as comprehensive as that seen with Flg22. While high doses of either microbe-associated molecular pattern (MAMP) elicit a late response that includes activation of senescence processes, SA-dependent secretory pathway genes and PR1 expression are substantially induced only by Flg22. These results suggest a lower threshold for activation of early responses than for sustained or SA-mediated late defenses. Expression patterns of amino-cyclopropane-carboxylate synthase genes also implicate ethylene biosynthesis in regulation of the late innate immune response.
Overexpression of a fatty acid amide hydrolase compromises innate immunity in Arabidopsis
Plant Journal, 2008
N-acylethanolamines are a group of lipid mediators that accumulate under a variety of neurological and pathological conditions in mammals. N-acylethanolamine signaling is terminated by the action of diverse hydrolases, among which fatty acid amide hydrolase (FAAH) has been well characterized. Here, we show that transgenic Arabidopsis lines overexpressing an AtFAAH are more susceptible to the bacterial pathogens Pseudomonas syringae pv. tomato and P. syringae pv. maculicola. AtFAAH overexpressors also were highly susceptible to non-host pathogens P. syringae pv. syringae and P. syringae pv. tabaci. AtFAAH overexpressors had lower amounts of jasmonic acid, abscisic acid and both free and conjugated salicylic acid (SA), compared with the wild-type. Gene expression studies revealed that transcripts of a number of plant defense genes, as well as genes involved in SA biosynthesis and signaling, were lower in AtFAAH overexpressors than wild-type plants. Our data suggest that FAAH overexpression alters phytohormone accumulation and signaling which in turn compromises innate immunity to bacterial pathogens.
The Plant Cell, 2012
Plant activators are compounds, such as analogs of the defense hormone salicylic acid (SA), that protect plants from pathogens by activating the plant immune system. Although some plant activators have been widely used in agriculture, the molecular mechanisms of immune induction are largely unknown. Using a newly established high-throughput screening procedure that screens for compounds that specifically potentiate pathogen-activated cell death in Arabidopsis thaliana cultured suspension cells, we identified five compounds that prime the immune response. These compounds enhanced disease resistance against pathogenic Pseudomonas bacteria in Arabidopsis plants. Pretreatments increased the accumulation of endogenous SA, but reduced its metabolite, SA-O-b-D-glucoside. Inducing compounds inhibited two SA glucosyltransferases (SAGTs) in vitro. Double knockout plants that lack both SAGTs consistently exhibited enhanced disease resistance. Our results demonstrate that manipulation of the active free SA pool via SA-inactivating enzymes can be a useful strategy for fortifying plant disease resistance and may identify useful crop protectants.
Chemical inducers of systemic immunity in plants
Journal of Experimental Botany, 2014
Systemic acquired resistance (SAR) is a highly desirable form of resistance that protects against a broad-spectrum of related or unrelated pathogens. SAR involves the generation of multiple signals at the site of primary infection, which arms distal portions against subsequent secondary infections. The last decade has witnessed considerable progress, and a number of chemical signals contributing to SAR have been isolated and characterized. The diverse chemical nature of these chemicals had led to the growing belief that SAR might involve interplay of multiple diverse and independent signals. However, recent results suggest that coordinated signalling from diverse signalling components facilitates SAR in plants. This review mainly discusses organized signalling by two such chemicals, glycerol-3-phoshphate and azelaic acid, and the role of basal salicylic acid levels in G3P-conferred SAR.
Fight Hard or Die Trying: Current Status of Lipid Signaling during Plant–Pathogen Interaction
Plants, 2021
Plant diseases pose a substantial threat to food availability, accessibility, and security as they account for economic losses of nearly $300 billion on a global scale. Although various strategies exist to reduce the impact of diseases, they can introduce harmful chemicals to the food chain and have an impact on the environment. Therefore, it is necessary to understand and exploit the plants’ immune systems to control the spread of pathogens and enable sustainable agriculture. Recently, growing pieces of evidence suggest a functional myriad of lipids to be involved in providing structural integrity, intracellular and extracellular signal transduction mediators to substantial cross-kingdom cell signaling at the host–pathogen interface. Furthermore, some pathogens recognize or exchange plant lipid-derived signals to identify an appropriate host or development, whereas others activate defense-related gene expression. Typically, the membrane serves as a reservoir of lipids. The set of l...