•CTS-g-SA coating had greater inhibition of CI than SA alone or plus chitosan.•CTS-g-SA coating increased the endogenous SA concentrations in fruit.•CTS-g-SA coating increased the antioxidant enzyme ...activities.
The effect of salicylic acid with and without chitosan, or a chitosan-g-salicylic acid complex, on chilling injury and post-harvest quality of cucumber stored at 2°C for 12days plus 2days at 20°C was investigated. The results showed the chitosan-g-salicylic acid coating inhibited chilling injury better than salicylic acid alone or with chitosan. Chitosan-g-salicylic acid also reduced weight loss and respiration rate, limited increases in malondialdehyde content and electrolyte leakage, and maintained higher total soluble solids, chlorophyll and ascorbic acid content. Furthermore, this coating increased the endogenous salicylic acid concentrations and antioxidant enzyme activities including superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase in cucumber during storage. Our study suggests that chitosan-g-salicylic acid alleviated chilling injury in cucumber through sustained-release of salicylic acid and the higher antioxidant enzymes concentrations.
This research was undertaken to assess the impact of 1mM salicylic acid (SA) and 0.5mM jasmonic acid (JA) on alleviation of oxidative, ionic and osmotic stresses of different levels of salinity (0, ...4, 7, 10 dS m−1 NaCl, respectively). Salinity increased the contents of glycine betaine, proline, soluble sugars, proteins and the activities of peroxidase, catalase, superoxide dismutase, ascorbate peroxidase, and the amount of malondialdehyde and sodium ion of soybean leaves, but decreased the leaf water content, membrane stability index, potassium and calcium ions, chlorophylls content, chlorophyll stability index, plant biomass and seed yield. Foliar spray of JA reduced Na+ entry to the cells, while enhancing the glycine betaine and soluble proteins content, antioxidant enzymes activity, membrane stability index and leaf water content. This treatment had no effect on potassium and the calcium ions content, chlorophyll contents, chlorophyll stability index, soluble sugars, plant biomass and seed yield. In contrast, SA enriched the leaf cells with potassium and calcium ions under different levels of salt stress and increased glycine betaine, soluble sugars, proteins, antioxidant enzymes, leaf water content, membrane stability index, chlorophyll content and chlorophyll stability index, but reduced proline content. These superiorities of SA treatment led to considerable improvement in plant biomass (10%) and seed yield (17%) of soybean.
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•Salt stress enhanced oxidative, osmotic and ionic stresses in soybean plants.•Chlorophyll content and plant performance reduced under salt stress.•Hormonal treatments mitigated oxidative, osmotic and ionic stresses.•JA did not improve general performance of soybean plants.•SA reduced salt stress injuries via enhancing antioxidant enzymes activities.
Tip growth is a common strategy for the rapid elongation of cells to forage the environment and/or to target to long-distance destinations. In the model tip growth system of Arabidopsis pollen tubes, ...several small-molecule hormones regulate their elongation, but how these rapidly diffusing molecules control extremely localized growth remains mysterious. Here we show that the interconvertible salicylic acid (SA) and methylated SA (MeSA), well characterized for their roles in plant defense, oppositely regulate Arabidopsis pollen tip growth with SA being inhibitory and MeSA stimulatory. The effect of SA and MeSA was independent of known NPR3/NPR4 SA receptor-mediated signaling pathways. SA inhibited clathrin-mediated endocytosis in pollen tubes associated with an increased accumulation of less stretchable demethylated pectin in the apical wall, whereas MeSA did the opposite. Furthermore, SA and MeSA alter the apical activation of ROP1 GTPase, a key regulator of tip growth in pollen tubes, in an opposite manner. Interestingly, both MeSA methylesterase and SA methyltransferase, which catalyze the interconversion between SA and MeSA, are localized at the apical region of pollen tubes, indicating of the tip-localized production of SA and MeSA and consistent with their effects on the apical cellular activities. These findings suggest that local generation of a highly diffusible signal can regulate polarized cell growth, providing a novel mechanism of cell polarity control apart from the one involving protein and mRNA polarization.
Salicylic acid (SA) and methylated SA (MeSA) inhibit and promote Arabidopsis pollen tube tip growth by regulating clathrin-mediated endocytosis. The enzymes interconverting them, MeSA methylesterase and SA methyltransferase, are localized to pollen tube tips. Thus, local synthesis of highly diffusible molecules such as SA and MeSA may provide a novel mechanism for the regulation of polar cell growth.
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•Arsenic (As) stress caused reduction in plant growth and physio-biochemical parameters in maize plants.•Externally supplied salicylic acid (SA) alleviated the As-induced oxidative ...stress.•SA supplementation improved endogenous NO that was effectively involved in promoting As stress tolerance in maize plants.•Application of cPTIO, a NO scavenger, decreased the levels of NO as well as hampered the antioxidant defence system.•NO is involved in As-induced enhanced As tolerance in maize plants.
The role of nitric oxide (NO) in salicylic acid (SA)-induced tolerance to arsenic (As) stress in maize plants is not reported in the literature. Before starting As stress (AsS) treatments, SA (0.5 mM) was sprayed to the foliage of maize plants. Thereafter, AsV (0.1 mM as sodium hydrogen arsenate heptahydrate) stress (AsS) was initiated and during the stress period, sodium nitroprusside (SNP 0.1 mM), a NO donor, was sprayed individually or in combination with SA. Furthermore, cPTIO (0.1 mM) was also applied as a NO scavenger during the stress period. Arsenic stress led to significant reductions in plant growth, photosynthesis, water relation parameters and endogenous NO content, but it increased hydrogen peroxide, malondialdehyde, electrolyte leakage, methylglyoxal, proline, the activities of major antioxidant enzymes, and leaf and root As content. The combined treatment of SA+SNP was more effective to reverse oxidative stress related parameters and reduce the As content in both leaves and roots, with a concomitant increase in antioxidant defense system, the ascorbate-glutathione (AsA-GSH) cycle-related enzymes, glyoxalase system enzymes, plant growth, and photosynthetic traits. The beneficial effects of SA were completely abolished with cPTIO supply by blocking the NO synthesis in AsS-maize plants, indicating that NO effectively participated in SA-improved tolerance to AsS in maize plants.
Salicylic acid (SA) is a signaling molecule utilized by plants in response to various stresses. Through conjugation with small organic molecules such as glucose, an inactive form of SA is generated ...which can be transported into and stored in plant vacuoles. In the model organism Arabidopsis thaliana, SA glucose conjugates are formed by two homologous enzymes (UGT74F1 and UGT74F2) that transfer glucose from UDP-glucose to SA. Despite being 77% identical and with conserved active site residues, these enzymes catalyze the formation of different products: UGT74F1 forms salicylic acid glucoside (SAG), while UGT74F2 forms primarily salicylic acid glucose ester (SGE). The position of the glucose on the aglycone determines how SA is stored, further metabolized, and contributes to a defense response. We determined the crystal structures of the UGT74F2 wild-type and T15S mutant enzymes, in different substrate/product complexes. On the basis of the crystal structures and the effect on enzyme activity of mutations in the SA binding site, we propose the catalytic mechanism of SGE and SAG formation and that SA binds to the active site in two conformations, with each enzyme selecting a certain binding mode of SA. Additionally, we show that two threonines are key determinants of product specificity.
Salicylic acid (SA) is an important phytohormone mediating both local and systemic defense responses in plants. Despite over half a century of research, how plants biosynthesize SA remains ...unresolved. In Arabidopsis, a major part of SA is derived from isochorismate, a key intermediate produced by the isochorismate synthase, which is reminiscent of SA biosynthesis in bacteria. Whereas bacteria employ an isochorismate pyruvate lyase (IPL) that catalyzes the turnover of isochorismate to pyruvate and SA, plants do not contain an IPL ortholog and generate SA from isochorismate through an unknown mechanism. Combining genetic and biochemical approaches, we delineated the SA biosynthetic pathway downstream of isochorismate in Arabidopsis. We found that PBS3, a GH3 acyl adenylase-family enzyme important for SA accumulation, catalyzes ATP- and Mg2+-dependent conjugation of L-glutamate primarily to the 8-carboxyl of isochorismate and yields the key SA biosynthetic intermediate, isochorismoyl-glutamate A. Moreover, we discovered that EPS1, a BAHD acyltransferase-family protein with a previously implicated role in SA accumulation upon pathogen attack, harbors a noncanonical active site and an unprecedented isochorismoyl-glutamate A pyruvoyl-glutamate lyase activity that produces SA from the isochorismoyl-glutamate A substrate. Together, PBS3 and EPS1 form a two-step metabolic pathway to produce SA from isochorismate in Arabidopsis, which is distinct from how SA is biosynthesized in bacteria. This study closes a major knowledge gap in plant SA metabolism and would help develop new strategies for engineering disease resistance in crop plants.
Combining genetic and biochemical approaches, we delineated the salicylic acid (SA) biosynthetic pathway downstream of isochorismate in Arabidopsis. Together, PBS3 (a GH3 acyl adenylase-family enzyme important for SA accumulation) and EPS1 (a BAHD acyltransferase-family protein with a previously implicated role in SA accumulation upon pathogen attack) form a two-step metabolic pathway to produce SA from isochorismate in Arabidopsis, which is distinct from how SA is biosynthesized in bacteria. This study closes a major knowledge gap in plant SA metabolism and should help to develop new strategies for engineering disease resistance in crop plants.
In plants, pathogen attack can induce an immune response known as systemic acquired resistance that protects against a broad spectrum of pathogens. In the search for safer agrochemicals, silica ...nanoparticles (SiO
NPs; food additive E551) have recently been proposed as a new tool. However, initial results are controversial, and the molecular mechanisms of SiO
NP-induced disease resistance are unknown. Here we show that SiO
NPs, as well as soluble Si(OH)
, can induce systemic acquired resistance in a dose-dependent manner, which involves the defence hormone salicylic acid. Nanoparticle uptake and action occurred exclusively through the stomata (leaf pores facilitating gas exchange) and involved extracellular adsorption in the air spaces in the spongy mesophyll of the leaf. In contrast to the treatment with SiO
NPs, the induction of systemic acquired resistance by Si(OH)
was problematic since high Si(OH)
concentrations caused stress. We conclude that SiO
NPs have the potential to serve as an inexpensive, highly efficient, safe and sustainable alternative for plant disease protection.
Plant benzoic acids (BAs) are building blocks or important structural elements for numerous primary and specialized metabolites, including plant hormones, cofactors, defense compounds, and ...attractants for pollinators and seed dispersers. Many natural products derived from plant BAs or containing benzoyl/benzyl moieties are also of medicinal or nutritional value to humans. Biosynthesis of BAs in plants is a network involving parallel and intersecting pathways spread across multiple subcellular compartments. In this review, a current overview on the metabolism of plant BAs is presented with a focus on the recent progress made on isolation and functional characterization of genes encoding biosynthetic enzymes and intracellular transporters. In addition, approaches for deciphering the complex interactions between pathways of the BAs network are discussed.
Plant benzoic acids are aromatic C6–C1 compounds that serve as precursors for a multitude of important products playing cardinal roles in plant fitness. This review highlights the recent progress made in elucidating the pathways comprising the plant benzoic acids biosynthetic network.
► Astaxanthin accumulation by H. pluvialis was induced effectively by SA. ► All eight carotenogenic genes were up-regulated by SA treatments. ► Carotenogenic genes exhibited different mRNA expression ...profiles when exposed to SA. ► Surface of alga cells changed drastically along with astaxanthin accumulation.
The green alga Haematococcus pluvialis can produce large amounts of pink carotenoid astaxanthin which is a high value ketocarotenoid. In our study, transcriptional expression patterns of eight carotenoid genes in H. pluvialis in response to SA were measured using qRT-PCR. Results indicated that both 25 and 50mg/L salicylic acid (SA) could increase astaxanthin productivity and enhance transcriptional expression of eight carotenoid genes in H. pluvialis. But these genes exhibited different expression profiles. Moreover, SA25 (25mg/L SA) induction had a greater effect on the transcriptional expression of ipi-1, psy, pds, crtR-B and lyc (more than 6-fold up-regulation) than on ipi-2, bkt and crtO, but SA50 (50mg/L SA) treatment had a greater impact on the transcriptional expression of ipi-1, ipi-2, pds, crtR-B and lyc than on psy, bkt and crtO. Furthermore, astaxanthin biosynthesis under SA was up-regulated mainly by ipi-1, ipi-2, psy, crtR-B, bkt and crtO at transcriptional level, lyc at post-transcriptional level and pds at both levels. Summarily, these results suggest that SA constitute molecular signals in the network of astaxanthin biosynthesis. Induction of astaxanthin accumulation by SA without any other stimuli presents an attractive application potential in astaxanthin production with H. pluvialis.
Pathogenic viruses are a constant threat to all organisms, including plants. However, in plants, a small group of cells (stem cells) protect themselves from viral invasion. Recently, Incarbone et al. ...uncovered a novel salicylic acid (SA) and RNAi mechanism of stem cell resistance, broadening our understanding of RNAi-mediated antiviral plant immunity.
Pathogenic viruses are a constant threat to all organisms, including plants. However, in plants, a small group of cells (stem cells) protect themselves from viral invasion. Recently, Incarbone et al. uncovered a novel salicylic acid (SA) and RNAi mechanism of stem cell resistance, broadening our understanding of RNAi-mediated antiviral plant immunity.
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