Content uploaded by Dr Sadaf Jan
Author content
All content in this area was uploaded by Dr Sadaf Jan on Nov 13, 2021
Content may be subject to copyright.
A preview of the PDF is not available
Salicylic acid and ROS crosstalk in plants for pathogen resistance
Figures
Figures - uploaded by Dr Sadaf Jan
Author content
All figure content in this area was uploaded by Dr Sadaf Jan
Content may be subject to copyright.
ResearchGate has not been able to resolve any citations for this publication.
Growth, nutritional status of the trees, colouration %, yield as well as physical and chemical characters of Anna apple fruits in response to foliar application of salicylic acid (SA) once, twice, thrice or four times at 50, 100, 200 or 400 ppm were examined during 2009 and 2010 seasons. Results showed that varying concentrations (50 to 400 ppm) and frequencies (1, 2, 3 or 4 times) of SA had a substantial effect on all the investigated parameters comparing with non-application. There was a gradual promotion on the leaf area, nutrients (N, P, K and Mg), colouration % as well as yield and all quality parameters with increasing concentrations (from 50 to 400 ppm) and frequencies (from once to four times) of SA. Meaningless promotion on these measurements was noticed among the higher two concentrations (200 and 400 ppm) and frequencies (three or four times) of SA. In sandy saline soil, supplying Anna apple trees via foliage with salicylic acid three times (at growth start, just after fruit setting and at 14 days later) with salicylic acid at 200 ppm gave an economical yield, hastened colouration and improved fruit quality. Such promising treatment gave a net profit of 7000 and 7800 Egyptian pounds per feddan over the check treatment in both seasons, respectively.
Section
Key Message
Using disease bioassays and transcriptomic analysis we show that intact SA-signalling is required for potato defences against the necrotrophic fungal pathogen Alternaria solani.
AbstractSection
Abstract
Early blight, caused by the necrotrophic fungus Alternaria solani, is an increasing problem in potato cultivation. Studies of the molecular components defining defence responses to A. solani in potato are limited. Here, we investigate plant defence signalling with a focus on salicylic acid (SA) and jasmonic acid (JA) pathways in response to A. solani. Our bioassays revealed that SA is necessary to restrict pathogen growth and early blight symptom development in both potato foliage and tubers. This result is in contrast to the documented minimal role of SA in resistance of Arabidopsis thaliana against necrotrophic pathogens. We also present transcriptomic analysis with 36 arrays of A. solani inoculated SA-deficient, JA-insensitive, and wild type plant lines. A greater number of genes are differentially expressed in the SA-deficient mutant plant line compared to the wild type and JA- insensitive line. In wild type plants, genes encoding metal ion transporters, such as copper, iron and zinc transporters were upregulated and transferase-encoding genes, for example UDP-glucoronosyltransferase and Serine-glyoxylate transferase, were downregulated. The SA-deficient plants show upregulation of genes enriched in GO terms related to oxidoreductase activity, respiratory chain and other mitochondrial-related processes. Pathogenesis-related genes, such as genes encoding chitinases and PR1, are upregulated in both the SA-deficient and wild type plants, but not in the JA-insensitive mutants. The combination of our bioassays and the transcriptomic analysis indicate that intact SA signalling, and not JA signalling, is required for potato defences against the necrotrophic pathogen A. solani.
Plant-parasitic nematodes secrete a series of effectors to promote parasitism by modulating host immunity, but the detailed molecular mechanism is ambiguous. Animal parasites secrete macrophage migration inhibitory factor (MIF)-like proteins for evasion of host immune systems, in which their biochemical activities play essential roles. Previous research demonstrated that MiMIF-2 effector was secreted by Meloidogyne incognita and modulated host immunity by interacting with annexins. In this study, we show that MiMIF-2 had tautomerase activity and protected nematodes against H2O2 damage. MiMIF-2 expression not only decreased the amount of H2O2 generation during nematode infection in Arabidopsis, but also suppressed Bax-induced cell death by inhibiting reactive oxygen species burst in Nicotiana benthamiana. Further, RNA-seq transcriptome analysis and RT-qPCR showed that the expression of some heat-shock proteins was down regulated in MiMIF-2 transgenic Arabidopsis. After treatment with flg22, RNA-seq transcriptome analysis indicated that the differentially expressed genes in MiMIF-2 expressing Arabidopsis were pointed to plant hormone signal transduction, compound metabolism and plant defense. RT-qPCR and metabolomic results confirmed that salicylic acid (SA) related marker genes and SA content were significantly decreased. Our results provide a comprehensive understanding of how MiMIF-2 modulates plant immunity and broaden knowledge of the intricate relationship between M. incognita and host plants.
Different abiotic and biotic stresses lead to the production and accumulation of reactive oxygen species (ROS) in various cell organelles such as in mitochondria, resulting in oxidative stress, inducing defense responses or programmed cell death (PCD) in plants. In response to oxidative stress, cells activate various cytoprotective responses, enhancing the antioxidant system, increasing the activity of alternative oxidase and degrading the oxidized proteins. Oxidative stress responses are orchestrated by several phytohormones such as salicylic acid (SA). The biomolecule SA is a key regulator in mitochondria-mediated defense signaling and PCD, but the mode of its action is not known in full detail. In this review, the current knowledge on the multifaceted role of SA in mitochondrial ROS metabolism is summarized to gain a better understanding of SA-regulated processes at the subcellular level in plant defense responses.
Mutualisms may be “key innovations” that spur lineage diversification by augmenting niche breadth, geographic range, or population size, thereby increasing speciation rates or decreasing extinction rates. Whether mutualism accelerates diversification in both interacting lineages is an open question. Research suggests that plants that attract ant mutualists have higher diversification rates than non-ant associated lineages. We ask whether the reciprocal is true: does the interaction between ants and plants also accelerate diversification in ants, i.e. do ants and plants cooperate-and-radiate? We used a novel text-mining approach to determine which ant species associate with plants in defensive or seed dispersal mutualisms. We investigated patterns of lineage diversification across a recent ant phylogeny using BiSSE, BAMM, and HiSSE models. Ants that associate mutualistically with plants had elevated diversification rates compared to non-mutualistic ants in the BiSSE model, with a similar trend in BAMM, suggesting ants and plants cooperate-and-radiate. However, the best-fitting model was a HiSSE model with a hidden state, meaning that diversification models that do not account for unmeasured traits are inappropriate to assess the relationship between mutualism and ant diversification. Against a backdrop of diversification rate heterogeneity, the best-fitting HiSSE model found that mutualism actually decreases diversification: mutualism evolved much more frequently in rapidly diversifying ant lineages, but then subsequently slowed diversification. Thus, it appears that ant lineages first radiated, then cooperated with plants.
Evolutionary theory suggests that the conditions required for the establishment of mutualistic symbioses through mutualism alone are highly restrictive, often requiring the evolution of complex stabilising mechanisms. Exploitation, whereby initially the host benefits at the expense of its symbiotic partner and mutual benefits evolve subsequently through trade-offs, offers an arguably simpler route to the establishment of mutualistic symbiosis. In this review, we discuss the theoretical and experimental evidence supporting a role for host exploitation in the establishment and evolution of mutualistic microbial symbioses, including data from both extant and experimentally evolved symbioses. We conclude that exploitation rather than mutualism may often explain the origin of mutualistic microbial symbioses.
Introduction
Grapevine protection is an important issue in viticulture. To reduce pesticide use, sustainable disease control strategies are proposed, including a promising alternative method based on the elicitor-triggered stimulation of the grapevine natural defense responses. However, detailed investigations are necessary to characterize the impact of such defense induction on the primary metabolism.
Objectives
Our aim was to use a metabolomics approach to assess the impact on grapevine of different elicitors dependent on the salicylic acid (SA) and/or jasmonic acid (JA) pathway. For this purpose, leaves of grapevine foliar cuttings were treated with methyl jasmonate, acibenzolar-S-methyl or phosphonates.
Methods
According to the elicitor, common and discriminating metabolites were elucidated using ¹H NMR measurements and principal component analysis.
Results
A wide range of compounds including carbohydrates, amino acids, organic acids, phenolics and amines were identified. The score plots obtained by combining PC1 versus PC2 and PC1 versus PC3 allowed a clear separation of samples, so metabolite fingerprinting showed an extensive reprogramming of primary metabolic pathways after elicitation.
Conclusion
The methods applied were found to be accurate for the rapid determination and differential characterization of plant samples based on their metabolic composition. These investigations can be very useful because the application of plant defense stimulators is gaining greater importance as an alternative strategy to pesticides in the vineyard.
The majority of genes encoding gibberellin (GA) biosynthesis and deactivation enzymes have been identified to date. Recent studies have highlighted the occurrence of previously unrecognized deactivation mechanisms, including epoxidation and methylation. GA concentrations in plant tissues are carefully optimized by a number of internal and external signals. Studies have recently shown that, in many cases, bioactive GA levels are modulated through coordinated regulation of GA biosynthesis and deactivation. In addition, the identification of transcription factors that directly regulate GA biosynthesis and deactivation genes has started to uncover the molecular mechanisms for fine-tuning the hormone levels. In this article, I summarize our current understanding of the GA biosynthesis and deactivation pathways in plants, and discuss how the concentration of bioactive GAs is regulated in several selected systems.
Phytohormones salicylic acid and strigolactones play critical roles in mediating plant responses to environmental stress including drought stress. This study investigated whether foliar application of salicylic acid and strigolactones in the form of GR24 will improve the drought tolerance of winter wheat (Triticum aestivum L.) plants. Exogenous application of strigolactone and salicylic acid increased proline and soluble sugar content as well as stomatal conductance, photosynthesis and transpiration rate of wheat plants. Higher amounts of all above mentioned characteristics are indicative of the higher drought tolerance of hormone-treated plants. In this experiment, application of hormones decreased the drought-induced rise in the content of H2O2 a factor known to lead to membrane lipid peroxidation, toxicity, and cell death. Hormones external application dampened leaf water potential that contributes to plant-level physiological drought tolerance. Drought tolerance features magnified when we used both hormones together. Our finding suggests that hormonal application can improve osmotic adjustment and decrease adverse effects of drought stress on wheat plants
Spontaneous degradation in hormone synthesis
The phytohormone salicylic acid (SA) helps plants respond to biological and physical stresses. Rekhter et al. identified the biosynthetic pathway that produces SA in response to pathogens. A precursor, isochorismic acid, is formed in the chloroplast and then exported to the cytosol. There, enzymatically produced isochorismate-9-glutamate spontaneously decomposes to release SA plus a by-product. The results clarify key steps in the mechanisms involved in synthesizing this important regulator of plant immunity.
Science , this issue p. 498