Drought and salt stress tolerance of Arabidopsis (Arabidopsis thaliana) plants increased following treatment with the nonprotein amino acid beta-aminobutyric acid (BABA), known as an inducer of ...resistance against infection of plants by numerous pathogens. BABA-pretreated plants showed earlier and higher expression of the salicylic acid-dependent PR-1 and PR-5 and the abscisic acid (ABA)-dependent RAB-18 and RD-29A genes following salt and drought stress. However, non-expressor of pathogenesis-related genes 1 and constitutive expressor of pathogenesis-related genes 1 mutants as well as transgenic NahG plants, all affected in the salicylic acid signal transduction pathway, still showed increased salt and drought tolerance after BABA treatment. On the contrary, the ABA deficient 1 and ABA insensitive 4 mutants, both impaired in the ABA-signaling pathway, could not be protected by BABA application. Our data demonstrate that BABA-induced water stress tolerance is based on enhanced ABA accumulation resulting in accelerated stress gene expression and stomatal closure. Here, we show a possibility to increase plant tolerance for these abiotic stresses through effective priming of the preexisting defense pathways without resorting to genetic alterations.
Melatonin is an important secondary messenger in plant innate immunity against the bacterial pathogen Pseudomonas syringe pv. tomato (Pst) DC3000 in the salicylic acid (SA)- and nitric oxide ...(NO)-dependent pathway. However, the metabolic homeostasis in melatonin-mediated innate immunity is unknown. In this study, comparative metabolomic analysis found that the endogenous levels of both soluble sugars (fructose, glucose, melibose, sucrose, maltose, galatose, tagatofuranose and turanose) and glycerol were commonly increased after both melatonin treatment and Pst DC3000 infection in Arabidopsis. Further studies showed that exogenous pre-treatment with fructose, glucose, sucrose, or glycerol increased innate immunity against Pst DC3000 infection in wild type (Col-0) Arabidopsis plants, but largely alleviated their effects on the innate immunity in SA-deficient NahG plants and NO-deficient mutants. This indicated that SA and NO are also essential for sugars and glycerol-mediated disease resistance. Moreover, exogenous fructose, glucose, sucrose and glycerol pre-treatments remarkably increased endogenous NO level, but had no significant effect on the endogenous melatonin level. Taken together, this study highlights the involvement of sugars and glycerol in melatonin-mediated innate immunity against bacterial pathogen in SA and NO-dependent pathway in Arabidopsis.
The plant cell wall is a dynamic cellular compartment consisting of a complex matrix of components that can change dramatically in response to environmental stresses. During pathogen attack, for ...instance, a wide spectrum of proteins that participate in various sequential processes involved in plant defense is secreted into the cell wall. In this study, a mass spectrometry, data-independent acquisition approach known as LC/MS (E) was used to assess temporal changes in the cell wall proteome in response to different levels of an endogenous inducer of plant disease defense responses, salicylic acid (SA). LC/MS (E) was used as a label-free method that enabled simultaneous protein identification and absolute femtomole quantification of each protein secreted into the extracellular matrix. A total of 74 secreted proteins were identified, 63 of which showed increased specific secretion in response to SA. A majority of this induced secretion occurred within 2 h of treatment, indicating that many proteins are involved in the early stages of plant defenses. We also identified a number of apparently nonclassically secreted proteins, suggesting that, as in many nonplant systems, Golgi/ER-independent mechanisms exist for plant protein secretion. These results provide new insight into plant apoplastic defense mechanisms and demonstrate that LC/MS (E) is a powerful tool for obtaining both relative and absolute proteome-scale quantification that can be applied to complex, time- and dose-dependent experimental designs.
Salicylic acid (SA) is synthesised by plants in response to challenge by a diverse range of phytopathogens and is essential to the establishment of both local and systemic-acquired resistance (SAR). ...SA application induces accumulation of pathogenesis-related (PR) proteins. Mutations leading to either reduced SA production or impaired SA perception enhance susceptibility to avirulent and virulent pathogens. However, our knowledge of the primary signalling components activating SA biosynthesis and linking to PR proteins accumulation is rudimentary. We review progress towards characterising key players (NPR1, MPK4) and processes (methylation, amino acid conjugation,
S-nitrosylation) contributing to SA-signalling and perception pathways. Further, we examine emerging data on how pathogens have evolved strategies (e.g. ABA modulation and coronatine production) to suppress SA-mediated plant defence.
Crosstalk between hormones and secondary metabolites regulates the interactions between plants and stress. However, little is known about the effects of hormone crosstalk on the concentration of ...flavonoids in seeds. In this study, we identified abscisic acid (ABA) as a negative regulator of flavonoid accumulation in soybean seeds under drought‐stress conditions. Alterations in flavonoid accumulation at several intensities of water stress, followed by a recovery period, were measured during the soybean seed‐filling stage. Low soil moisture (SM 10%) significantly decreased the total flavonoid content in seeds. The decline in flavonoid content was proportional to the severity of drought stress and was dependent on the activities of phenylalanine ammonia‐lyase (PAL) and chalcone synthase (CHS), two key phenylpropanoid pathway enzymes. The expression of phenylalanine ammonia‐lyase 1 (GmPAL1), chalcone isomerase 1A (GmCHI1A), and chalcone synthase 8 (GmCHS8) was associated with phenolic and flavonoid accumulation in soybean seeds of plants subjected to drought stress. Interestingly, the expression levels of GmCHS8 were highly correlated with flavonoid levels under drought stress and water recovery conditions. Cinnamic acid, which is a biosynthesis precursor shared by both phenylpropanoid metabolism and salicylic acid (SA) biosynthesis, decreased under drought stress conditions. Notably, exogenous ABA suppressed the expression of GmPAL1, which encodes the first rate‐limiting enzyme in the phenylpropanoid biosynthesis pathway and affects downstream products such as SA and flavonoids. In conclusion, drought stress altered the phenylpropanoid‐derived compounds, at least with regard to flavonoid and SA accumulation in seeds, which was regulated by antagonistic interactions with ABA.
Hormones play an important role in plant disease resistance and defense. Transcriptome data of late blight-resistant potato genotype SD20 treated by ethylene (ET), jasmonate (JA), salicylic acid ...(SA), and
CN152 was analyzed to assess the role of the ET/JA/SA regulatory network in plant disease resistance and defense and predict key resistant genes. The results show that there was significant crossover of differentially expressed genes among all treatments, and common and specific plant disease interaction genes for the ET, JA, and SA treatments were differentially expressed in the CN152 treatment. The resistance and defense genes of the potato genotype SD20 could be induced to regulate metabolic and hormone signaling pathways by alternative splicing in all treatments. Further analysis found that JA and ET pathways can work together synergistically. JA/ET and SA pathways antagonize each other to initiate the expression of calmodulin-domain protein kinases and calmodulin/calmodulin-like and RPM1-interacting protein 4 genes, and they activate
mediated hypersensitive response and defense-related genes. Meanwhile, nine defense genes, including wound-responsive AP2-like factor, glutathione-s-transferase, serine/threonine-protein kinase BRI1, and Avr9/Cf-9 rapidly elicited protein genes, were obtained using weighted gene coexpression network analysis, which provided reliable targets for functional verification. This study provides a theoretical reference for the comprehensive application of plant hormones to improve resistance to potato late blight disease.
One of the most important phytohormones is salicylic acid (SA), which is essential for the regulation of plant growth, development, ripening, and defense responses. The role of SA in plant-pathogen ...interactions has attracted a lot of attention. Aside from defense responses, SA is also important in responding to abiotic stimuli. It has been proposed to have great potential for improving the stress resistance of major agricultural crops. On the other hand, SA utilization is dependent on the dosage of the applied SA, the technique of application, and the status of the plants (e.g., developmental stage and acclimation). Here, we reviewed the impact of SA on saline stress responses and the associated molecular pathways, as well as recent studies toward understanding the hubs and crosstalk between SA-induced tolerances to biotic and saline stress. We propose that elucidating the mechanism of the SA-specific response to various stresses, as well as SA-induced rhizosphere-specific microbiome modeling, may provide more insights and support in coping with plant saline stress.
The unfolded protein response (UPR) is an ancient signaling pathway designed to protect cells from the accumulation of unfolded and misfolded proteins in the endoplasmic reticulum (ER). Because ...misregulation of the UPR is potentially lethal, a stringent surveillance signaling system must be in place to modulate the UPR. The major signaling arms of the plant UPR have been discovered and rely on the transcriptional activity of the transcription factors bZIP60 and bZIP28 and on the kinase and ribonuclease activity of IRE1, which splices mRNA to activate bZIP60. Both bZIP28 and bZIP60 modulate UPR gene expression to overcome ER stress. In this study, we demonstrate at a genetic level that the transcriptional role of bZIP28 and bZIP60 in ER-stress responses is antagonized by nonexpressor of PR1 genes 1 (NPR1), a critical redox-regulated master regulator of salicylic acid (SA)-dependent responses to pathogens, independently of its role in SA defense. We also establish that the function of NPR1 in the UPR is concomitant with ER stress-induced reduction of the cytosol and translocation of NPR1 to the nucleus where it interacts with bZIP28 and bZIP60. Our results support a cellular role for NPR1 as well as a model for plant UPR regulation whereby SA-independent ER stress-induced redox activation of NPR1 suppresses the transcriptional role of bZIP28 and bZIP60 in the UPR.
It is well known that parasitic weeds such as Orobanche (broomrape) significantly decrease crop growth and yield. Although hormonal priming is a well-known inducer of plant resistance against ...broomrapes (Orobanche spp.), the metabolic events associated with such resistance are poorly understood. Therefore, the current work was undertaken to elucidate the role of SA in inducing tomato resistance against Orobanche, considering its impact on carbon and nitrogen metabolism of the host. Total carbon and nitrogen and levels of carbon (sugars, organic acids and fatty acids) and nitrogen (amino acids and polyamines)-containing metabolites as well as the activities of some key enzymes involved in their metabolic pathways were evaluated. Broomrape infection significantly disrupted C/N ratio in the host roots. On contrary, SA treatment markedly induced accumulation of sugars, organic acids, fatty acids, amino acids as well as polyamines in healthy plants. Under broomrape challenge, SA mitigated the infection-induced growth inhibition by improving the level of nitrogen-containing osmoprotectants (proline, arginine and some polyamines). However, a decrease was observed in some C and N assimilates which are well known to be potentially transferred to the parasite, such as sucrose, asparagine, alanine, serine and glutamate. Interestingly, SA treatment induced the catapolism of polyamines and fatty acids in the host root. Accordingly, our study suggests that SA-induced resistance against broomrape relies on the rational utilization of C and N assimilates in a manner that disturbs the sink strength of the parasite and/or activates the defense pool of the host.
Infographic diagram that summarizes the influence of SA-seed priming upon carbon and nitrogen metabolism in tomato plants under the challenge of Orobanche infection. Display omitted
•Orobanche infection caused a dramatic damage in tomato growth, one of the most economically important crops.•SA treatment improved C and N metabolites in host tissue but denied availability of the major metabolites to the parasite.•SA treatment improved osmoregulatory status of the host plant.•SA treatment improved fatty acids and organic acids in healthy and infected tomato.•SA treatment seems to regulate the redox status in host plants.
Signal transducer and activator of transcription 3 (Stat3) protein is a cytosolic transcription factor that is aberrantly activated in numerous human cancers. Inhibitors of activated Stat3–Stat3 ...protein complexes have been shown to hold therapeutic promise for the treatment of human cancers harboring activated Stat3. Herein, we report the design and synthesis of a focused library of salicylic acid containing Stat3 SH2 domain binders. The most potent inhibitor, 17o, effectively disrupted Stat3–phosphopeptide complexes (Ki=13μM), inhibited Stat3–Stat3 protein interactions (IC50=19μM) and silenced intracellular Stat3 phosphorylation and Stat3-target gene expression profiles. Inhibition of Stat3 function in both breast and multiple myeloma (MM) tumor cells correlated with induced cell death (EC50=10 and 16μM, respectively).
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