Antagonistic Effect Of Salicylic Acid Research Articles

The antagonistic relationships between salicylic acid and simvastatin on phyto-biochemical components in Hymenocrater longiflorus Benth. under in vitro conditions

Hymenocrater longiflorus Benth. (Sura-halala) is a pharmaceutical plant with anti-inflammatory, anti-allergic, and sedative impacts on human. Accordingly, the phyto-biochemical responses of Sura-halala to salicylic acid (SA) and simvastatin (SV) under in vitro conditions were investigated, to clarify the cross-relationship and the interaction effects of SA and SV. Four levels of SA (0, 0.5, 1, and 2 mM) and of SV (0, 5, 10, and 20 μM) were assessed during the experiments. The results demonstrated that in vitro production of H. longiflorus is not only achievable, but also commercially applicable. The findings verified the significant impacts of SA and SV on Surahalala growth as well as phyto-biochemical contents. SV was found capable of increasing the contents of most essential oils such as α-pinene and n-decane. Furthermore, multivariate statistical methods, i.e., biplot, heatmap, and canonical correlation, pointed out antagonistic effects of SA and SV on biochemical and phytochemical contents of Sura-halala. Additionally, the analytical methods were able to differentiate the two groups of features: one involving shoot fresh weight and the biochemical parameters and the other one involving the essential oils. SA was more closely related to the former group, and SV was mainly associated with the latter one. In addition, the overall results revealed that the, based on our results, appropriate levels of both SA and SV, i.e., 1 mM SA and 10 mM SV, could obtain higher growth coupled with higher content of suitable phyto-biochemical compounds in Sura-halala under in vitro propagation.

Revealing Shared and Distinct Genes Responding to JA and SA Signaling in Arabidopsis by Meta-Analysis.

Plant resistance against biotrophic and necrotrophic pathogens is mediated by mutually synergistic and antagonistic effects of salicylic acid (SA) and jasmonic acid (JA) signals. However, the unique and shared genes responding to the defense mediated by JA/SA signals were largely unclear. To reveal discrete, synergistic and antagonistic JA/SA responsive genes in Arabidopsis thaliana, Meta-Analysis was employed with 257 publicly available Arabidopsis thaliana RNA-Seq gene expression profiles following treatment of mock, JA or SA analogs. JA/SA signalings were found to co-induce broad-spectrum disease-response genes, co-repress the genes related to photosynthesis, auxin, and gibberellin, and reallocate resources of growth toward defense. JA might attenuate SA induced immune response by inhibiting the expression of resistance genes and receptor-like proteins/kinases. Strikingly, co-expression network analysis revealed that JA/SA uniquely regulated genes showing highly coordinated co-expression only in their respective treatment. Using principal component analysis, and hierarchical cluster analysis, JA/SA analogs were segregated into separate entities based on the global differential expression matrix rather than the expression matrix. To accurately classify JA/SA analogs with as few genes as possible, 87 genes, including the SA receptor NPR4, and JA biosynthesis gene AOC1 and JA response biomarkers VSP1/2, were identified by three feature selection algorithms as JA/SA markers. The results were confirmed by independent datasets and provided valuable resources for further functional analyses in JA- or SA- mediated plant defense. These methods would provide cues to build a promising approach for probing the mode of action of potential elicitors.

Differential proteomics: Effect of growth regulators on salt stress responses in safflower seedlings

Productivity of safflower (Carthamus tinctorius L.) is markedly reduced by salt stress. This study is based on analysis of proteins profile of safflower plants treated with 200 mM NaCl, with exogenously applied salicylic acid (SA) and penconazole (PEN), as growth regulators. Plants were investigated through a gel-based proteomic approach, which resulted in the identification of 17 salt-responsive proteins related to different metabolic modifications. Of these, seven different proteins were up or down regulated by both SA and PEN, suggesting the synergistic and antagonistic effects of SA and PEN. The classification of differentially expressed proteins showed that salt-responsive proteins were mainly involved in photosynthesis, ion homeostasis, and oxidative stress response, as well as nitrogen, protein, and carbohydrate metabolism. The identified stress-responsive proteins in this study could pave the way to develop salt tolerance in safflower, thus sustaining its productivity under salinity. In addition, SA and PEN may be considered as a foliar application to ameliorate salinity effects, due to their low price and availability.

Tomato yellow leaf curl virus differentially influences plant defence responses to a vector and a non-vector herbivore.

Plants frequently engage in simultaneous interactions with diverse classes of biotic antagonists. Differential induction of plant defence pathways by these antagonists, and interactions between pathways, can have important ecological implications; however, these effects are currently not well understood. We explored how Tomato yellow leaf curl virus (TYLCV) influenced the performance of its vector (Bemisia tabaci) and a non-vector herbivore (Tetranychus urticae) occurring separately or together on tomato plants (Solanum lycopersicum). TYLCV enhanced the performance of B. tabaci, although this effect was statistically significant only in the absence of T. urticae, which adversely affected B. tabaci performance regardless of infection status. In contrast, the performance of T. urticae was enhanced (only) by the combined presence of TYLCV and B. tabaci. Analyses of phytohormone levels and defence gene expression in wild-type tomatoes and various plant-defence mutants indicate that the enhancement of herbivore performance (for each species) entails the disruption of downstream defences in the jasmonic acid (JA) pathway. For T. urticae, this disruption appears to involve antagonistic effects of salicylic acid (SA), which is cumulatively induced to high levels by B. tabaci and TYLCV. In contrast, TYLCV was found to suppress JA-mediated responses to B. tabaci via mechanisms independent of SA.

Different shades of JAZ during plant growth and defense.

Ever since their discovery as key regulators of the jasmonate (JA) signaling pathway, repressor proteins of the JASMONATE ZIM-domain (JAZ) family are rising stars in research on hormonal regulation of plant growth and defense. In plant cells, JAZ repressor proteins interact with an E3 ubiquitin ligase complex (SCFCOI1) that together functions as a JA receptor. In uninduced cells, JAZs block the activity of transcriptional regulators of JA responses by physically binding to them. Upon perception of bioactive JAs, JAZ proteins are rapidly degraded via the ubiquitin/26S proteasome-dependent proteolytic pathway. This releases the JAZ-bound transcription factors, resulting in the activation of downstream JA responses. JAs play a dominant role in regulating defense responses against herbivorous insects and necrotrophic pathogens, and in adaptive responses to beneficial soil-borne microbes. In addition, JAs have a signal function in a myriad of other processes, including abiotic stress reactions and plant growth responses to environmental cues. The JA pathway functions in the context of a complex network of hormone-regulated signaling pathways that, depending on the environmental or developmental condition, can act antagonistically or synergistically on each other to finely balance resource allocation between growth and defense and minimize fitness tradeoffs. In the process of balancing plant growth and defense, gibberellins (GAs) emerged as dominant antagonists of the JA signaling output. GAs regulate different aspects of plant growth via DELLA repressor proteins that block the activity of transcriptional regulators of GA responses by physically binding to them. Analogous to the role of JAZs in the JA pathway, DELLAs are degraded upon perception of GAs, resulting in the activation of downstream growth responses. Interestingly, DELLAs also interact with JAZs, thereby mutually limiting the cellular binding capacity to their cognate transcription factors. Consequently, GA-mediated degradation of DELLAs enhances the cellular binding capacity of JAZs to their cognate transcription factors, thus reducing the potential JA signaling output. This GA-mediated antagonistic effect on the JA pathway becomes apparent during the shade-avoidance response of plants that grow in dense vegetation stands. Shade-intolerant plant species respond to competition for light by increasing apical dominance and accelerating stem and petiole elongation. These growth and developmental responses occur in response to a drop in the red:far-red (R:FR) light ratio that is sensed by the phytochrome photoreceptors, predominantly phyB, and are GA-dependent through GA-mediated degradation of DELLA proteins. This allows them to outgrow neighboring plants, but at the cost of a reduced defensive capacity against necrotrophic pathogens and insect herbivores. In this issue of New Phytologist, Leone and co-workers zoomed in on the specific role of the Arabidopsis thaliana (Arabidopsis) JAZ10 protein in this process and shed light on the involvement of DELLAs in GA-JA crosstalk during the shade avoidance response. Besides growth-related hormones, also effector proteins of pathogens and plant growth-promoting mycorrhizal fungi have recently been shown to target JAZ repressor proteins, thereby changing the defense-related signaling circuitry for their own benefit. Hence, JAZ repressor proteins are emerging as central targets in the rewiring of the hormone-regulated signaling circuitry that regulates growth and defense.

Comparative Proteomic Analysis of the Effects of Salicylic Acid and Abscisic Acid on Maize (Zea mays L.) Leaves

The phytohormones salicylic acid (SA) and abscisic acid (ABA) play essential roles in regulating plant growth, development, and stress responses. Using a proteomics-based approach, we compared the roles of SA and ABA in the modulation of the proteome of maize leaves. Fifty-six protein spots that showed significant expression changes on 2-DE were identified by MALDI-TOF-MS/MS. Of these, three different proteins were regulated by both SA and ABA, with consistent or inconsistent expression patterns, suggesting the synergistic and antagonistic effects of SA and ABA. The classification of differentially expressed proteins showed that both SA and ABA responsive proteins were mainly involved in photosynthesis, stress and defense response, energy and metabolism, and protein turnover. Quantitative real-time PCR analysis for selected SA and ABA responsive proteins showed that individual protein change was not predictable based on transcriptome level. This study represents the first attempt at global proteome profiling in response to SA and ABA, and it provides a better understanding of the molecular mechanisms regulated by SA and ABA.

Low Red/Far-Red Ratios Reduce Arabidopsis Resistance toBotrytis cinereaand Jasmonate Responses via a COI1-JAZ10-Dependent, Salicylic Acid-Independent Mechanism

Light is an important modulator of plant immune responses. Here, we show that inactivation of the photoreceptor phytochrome B (phyB) by a low red/far-red ratio (R:FR), which is a signal of competition in plant canopies, down-regulates the expression of defense markers induced by the necrotrophic fungus Botrytis cinerea, including the genes that encode the transcription factor ETHYLENE RESPONSE FACTOR1 (ERF1) and the plant defensin PLANT DEFENSIN1.2 (PDF1.2). This effect of low R:FR correlated with a reduced sensitivity to jasmonate (JA), thus resembling the antagonistic effects of salicylic acid (SA) on JA responses. Low R:FR failed to depress PDF1.2 mRNA levels in a transgenic line in which PDF1.2 transcription was up-regulated by constitutive expression of ERF1 in a coronatine insensitive1 (coi1) mutant background (35S::ERF1/coi1). These results suggest that the low R:FR effect, in contrast to the SA effect, requires a functional SCFCOI1-JASMONATE ZIM-DOMAIN (JAZ) JA receptor module. Furthermore, the effect of low R:FR depressing the JA response was conserved in mutants impaired in SA signaling (sid2-1 and npr1-1). Plant exposure to low R:FR ratios and the phyB mutation markedly increased plant susceptibility to B. cinerea; the effect of low R:FR was (1) independent of the activation of the shade-avoidance syndrome, (2) conserved in the sid2-1 and npr1-1 mutants, and (3) absent in two RNA interference lines disrupted for the expression of the JAZ10 gene. Collectively, our results suggest that low R:FR ratios depress Arabidopsis (Arabidopsis thaliana) immune responses against necrotrophic microorganisms via a SA-independent mechanism that requires the JAZ10 transcriptional repressor and that this effect may increase plant susceptibility to fungal infection in dense canopies.

SA-ABA antagonism in defense responses

Until recently, phytohormones were mostly studied separately. However, recent studies have suggested that the signaling pathways involved are highly interconnected. We recently reported the antagonistic effects of salicylic acid (SA) and abscisic acid (ABA) in the lesion mimic mutants, cpr22 and ssi4. After shifting these mutants from high humidity, where the lesion mimic phenotype is suppressed to permissive low humidity condition, both SA and ABA pathways were up-regulated. However, the increased levels of SA were able to block downstream ABA responses even though ABA signaling genes and endogenous ABA were elevated. Furthermore, these lesion mimic mutants displayed a partial ABA insensitivity with respect to germination, guard cell opening, and water loss. This increased water loss in detached mutant plants could also be mimicked by treating wild type plants with SA. An active SA analog, 5-chloro-salicylic acid also induced enhanced water loss, while an inactive analog, 4-hydroxy-benzoic acid, did not. Here, we report that the biological analogs of SA, the systemic acquired resistance (SAR) activators, BTH (benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester) and BIT (1,2-benzisothiazol-3(2H)-one1,1-dioxide), did not have the same effect as SA, suggesting that SA may have additional roles to defense, and that SAR activators may not mimic all SA effects.

Kinetics of Salicylate-Mediated Suppression of Jasmonate Signaling Reveal a Role for Redox Modulation

Cross talk between salicylic acid (SA) and jasmonic acid (JA) signaling pathways plays an important role in the regulation and fine tuning of induced defenses that are activated upon pathogen or insect attack. Pharmacological experiments revealed that transcription of JA-responsive marker genes, such as PDF1.2 and VSP2, is highly sensitive to suppression by SA. This antagonistic effect of SA on JA signaling was also observed when the JA pathway was biologically activated by necrotrophic pathogens or insect herbivores, and when the SA pathway was triggered by a biotrophic pathogen. Furthermore, all 18 Arabidopsis (Arabidopsis thaliana) accessions tested displayed SA-mediated suppression of JA-responsive gene expression, highlighting the potential significance of this phenomenon in induced plant defenses in nature. During plant-attacker interactions, the kinetics of SA and JA signaling are highly dynamic. Mimicking this dynamic response by applying SA and methyl jasmonate (MeJA) at different concentrations and time intervals revealed that PDF1.2 transcription is readily suppressed when the SA response was activated at or after the onset of the JA response, and that this SA-JA antagonism is long lasting. However, when SA was applied more than 30 h prior to the onset of the JA response, the suppressive effect of SA was completely absent. The window of opportunity of SA to suppress MeJA-induced PDF1.2 transcription coincided with a transient increase in glutathione levels. The glutathione biosynthesis inhibitor l-buthionine-sulfoximine strongly reduced PDF1.2 suppression by SA, suggesting that SA-mediated redox modulation plays an important role in the SA-mediated attenuation of the JA signaling pathway.

Characterization of NtChitIV, a class IV chitinase induced by β-1,3-, 1,6-glucan elicitor from Alternaria alternata 102: Antagonistic effect of salicylic acid and methyl jasmonate on the induction of NtChitIV

Tobacco BY-2 class IV chitinases (TBC-1, TBC-3) were rapidly and transiently induced by the β-1,3-, 1,6-glucan elicitor from Alternaria alternata 102 (AaGlucan). The full-length cDNA and 5′-flanking region of a gene encoding class IV chitinases were isolated on the basis of the amino acid sequence of TBC-1. Sequence analysis indicated that NtChitIV encoded TBC-1, TBC-3, or both. Since purified TBC-1 and TBC-3 from BY-2 cells lack a chitin binding domain in the N-terminal region, these enzymes suggested to be derived from NtChitIV by post-translational proteolytic processing. The transcripts of NtChitIV accumulated rapidly within 1 h after treatment with AaGlucan. Accumulation was maximal 3 h after treatment. Reporter gene assays were used to analyze the promoter regions involved in the transcriptional control of NtChitIV, and these assays revealed that the 1.89-kb NtChitIV promoter was activated by AaGlucan but not by salicylic acid (SA) or methyl jasmonate (MeJA). The AaGlucan-induced transcriptional activation via 1.89-kb NtChitIV promoter was attenuated by pretreatment with SA or MeJA. These results suggest that NtChitIV expression is particularly induced by AaGlucan and that the AaGlucan-dependent signaling pathway is different from the SA- and MeJA-dependent signaling pathways.

Antagonistic Effect of Salicylic Acid and Jasmonic Acid on the Expression of Pathogenesis-Related (PR) Protein Genes in Wounded Mature Tobacco Leaves

Salicylic acid (SA) and jasmonic acid (JA) are essential compounds in the pathogen- and wound-signaling path­ ways accompanying induced expression of acidic and basic pathogenesis-related (PR) protein genes, respectively. How­ ever, on the effect of exogenously supplied SA and JA in in­ duction of PR gene expression, conflicting results have been obtained using various plant materials at different de­ velopmental stages. There is no clear evidence on these effects in the presence of both signals at the same time. We analyzed the effect of SA on wound- and JA-induced basic PR gene expression and that of JA on SA-induced acidic PR gene expression in mature tobacco leaves. Wound-in­ duced accumulation of transcripts for all 4 basic PR genes tested was enhanced in the presence of MeJA, and in­ hibited in the presence of SA. On the other hand, expres­ sion of all 3 acidic PR genes tested was induced by SA and was inhibited by MeJA. Using antibodies raised against acidic PR-l and PR-2 proteins, these effects were confirm­ ed at the protein level. These results indicated that JA works as an inducer of basic PR genes, and also as an inhib­ itor for acidic PR genes, while SA does the opposite.

Salicylamide reverses the aspirin-antagonistic effect of salicylic acid on rat platelet cyclooxygenase

The antagonistic effect of salicylic acid (SA), the major metabolite of aspirin, on aspirin (ASA)-induced inhibition of cyclooxygenase has been recognized in vivo and in vitro. Salicylamide is available with aspirin in some analgesic preparations. Salicylamide shares important characteristics with salicylic acid including the lack of effect on cyclooxygenase and platelet aggregation as well as a close structural resemblance. This prompted us to study the interaction of salicylamide with aspirin and/or SA on rat platelet and cyclooxygenase. Our results showed that salicylamide has, unlike SA, no blocking effect on the anti-cyclooxygenase effect of aspirin in vitro. Moreover, salicylamide could dose-dependently prevent the aspirin-blocking effect of SA on platelet cyclooxygenase. These results suggest that salicylamide and SA compete for a receptor on cyclooxygenase different to that of aspirin. A functional model of cyclooxygenase enzyme is proposed.