ascorbic-acid and jasmonic-acid

Vitamin C (ascorbate, AsA) is the most abundant water-soluble antioxidant in plants. Ascorbate provides the first line of defense against damaging reactive oxygen species (ROS), and helps protect plant cells from many factors that induce oxidative stress, including wounding, ozone, high salinity, and pathogen attack. Plant defenses against these stresses are also dependent upon jasmonates (JAs), a class of plant hormones that promote ROS accumulation. Here, we review evidence showing that wounding and JAs influence AsA accumulation in various plant species, and we report new data from Arabidopsis and tomato testing the influence of JAs on AsA levels in wounded and unwounded plants. In both species, certain mutations that impair JA metabolism and signaling influence foliar AsA levels, suggesting that endogenous JAs may regulate steady-state AsA. However, the impact of wounding on AsA accumulation was similar in JA mutants and wild type controls, indicating that this wound response does not require JAs. Our findings also indicate that the effects of wounding and JAs on AsA accumulation differ between species; these factors both enhanced AsA accumulation in Arabidopsis, but depressed AsA levels in tomato. These results underscore the importance of obtaining data from more than one model species, and demonstrate the complexity of AsA regulation.

Topics: Adaptation, Physiological; Antioxidants; Arabidopsis; Ascorbic Acid; Cyclopentanes; Ecosystem; Magnoliopsida; Oxidative Stress; Oxylipins; Plant Diseases; Reactive Oxygen Species; Solanum lycopersicum

Stomatal numbers are tightly controlled by environmental signals including light intensity and atmospheric CO(2) partial pressure. This requires control of epidermal cell development during the early phase of leaf growth and involves changes in both the density of cells on the leaf surface and the proportion of cells that adopt a stomatal fate. This paper reviews the current understanding of how stomata develop and describes recent advances that have given insights into the regulatory mechanisms involved using mutant Arabidopsis plants that implicates a role for long-chain fatty acids in cell-to-cell communication. Evidence is presented which indicates that long-distance signalling from mature to newly developing leaves forms part of the mechanism by which stomatal development responds to environmental cues. Analysis of mutant plants suggests that the plant hormones abscisic acid, ethylene and jasmonates are implicated in the long-distance signalling pathway and that the action may be mediated by reactive oxygen species.

Topics: Ascorbic Acid; Carbohydrate Metabolism; Carbon Dioxide; Cell Differentiation; Cell Division; Cyclopentanes; Ecosystem; Ethylenes; Mutation; Oxylipins; Plant Epidermis; Plant Growth Regulators; Plant Leaves; Reactive Oxygen Species; Signal Transduction

The cultivation of leafy vegetables on metal contaminated soil embodies a serious threat to yield and quality. In the present study, the potential role of exogenous jasmonic acid (JA; 0, 5, 10, and 20 µM) on mitigating chromium toxicity (Cr; 0, 150, and 300 µM) was investigated in choysum (Brassica parachinensis L.). With exposure to increasing Cr stress levels, a dose-dependent decline in growth, photosynthesis, and physio-biochemical attributes of choysum plants was observed. An increase in Cr levels also resulted in oxidative stress closely associated with higher lipoxygenase activity (LOX), hydrogen peroxide (H

Topics: Antioxidants; Ascorbic Acid; Brassica; Chromium; Cyclopentanes; Glutathione; Hydrogen Peroxide; Oxidation-Reduction; Oxidative Stress; Oxylipins; Photosynthesis; Plant Leaves; Soil Pollutants

Nitrogen (N), phosphorus (P), and potassium (K) are three essential macro-elements for plant growth and development. Used to improve yield in agricultural production, the excessive use of chemical fertilizers often leads to increased production costs and ecological environmental pollution. Vitamins C and E are antioxidants that play an important role in alleviating abiotic stress. However, there are few studies on alleviating oxidative stress caused by macro-element deficiency. Here, we used Arabidopsis vitamin E synthesis-deficient mutant

Topics: Antioxidants; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Chlorophyll; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Malondialdehyde; Oxidative Stress; Oxylipins; Plant Diseases; Plant Leaves; Reactive Oxygen Species; Seedlings; Seeds; Signal Transduction; Time Factors; Vitamin E

This study investigated the relationship between MEK1/2 and nitric oxide (NO) in jasmonic acid (JA)-regulated metabolism of ascorbate and glutathione in maize leaves. The results showed that JA increased the activities of APX, GR, MDHAR, DHAR, GalLDH, and γ-ECS; the contents of AsA and GSH; and the production of NO. Above increases except for γ-ECS activity and NO production were all suppressed by pre-treatments with MEK1/2 inhibitors PD98059 and U0126. Above increases were all suppressed by pre-treatments with nitric oxide synthase (NOS) inhibitor L-NAME and NO scavenger cPTIO. The results of western blot showed that JA enhanced the phosphorylation level of MEK1/2. Pre-treatments with L-NAME and cPTIO suppressed JA-induced phosphorylation level of MEK1/2. Our results suggested that JA-induced NO activated MEK1/2 by increasing the phosphorylation level, which, in turn, resulted in the upregulation of ascorbate and glutathione metabolism in maize leaves.

Topics: Ascorbic Acid; Benzoates; Butadienes; Cyclopentanes; Flavonoids; Glutathione; Imidazoles; Mitogen-Activated Protein Kinase Kinases; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitriles; Oxylipins; Phosphorylation; Plant Leaves; Zea mays

Environmental pollution by alkaline salts, such as Na

Topics: Ascorbic Acid; Carbonates; Cyclopentanes; Environmental Pollutants; Gene Expression Regulation, Plant; Glutathione; Lactoylglutathione Lyase; Oxidative Stress; Oxylipins; Photosynthesis; Plant Proteins; Seedlings; Thiolester Hydrolases; Up-Regulation; Zea mays

Plant tolerance to freezing temperatures is governed by endogenous constitutive components and environmental inducing factors. Nitric oxide (NO) is one of the endogenous components that participate in freezing tolerance regulation. A combined metabolomic and transcriptomic characterization of NO-deficient nia1,2noa1-2 mutant plants suggests that NO acts attenuating the production and accumulation of osmoprotective and regulatory metabolites, such as sugars and polyamines, stress-related hormones, such as ABA and jasmonates, and antioxidants, such as anthocyanins and flavonoids. Accordingly, NO-deficient plants are constitutively more freezing tolerant than wild type plants.

Topics: Abscisic Acid; Adaptation, Physiological; Anthocyanins; Antioxidants; Arabidopsis; Ascorbic Acid; Cyclopentanes; Freezing; Gene Expression Regulation, Plant; Glutathione; Glycolysis; Metabolome; Models, Biological; Mutation; Nitric Oxide; Osmosis; Oxylipins; Plant Growth Regulators; RNA, Messenger; Stress, Physiological; Transcriptome

Submergence induces hypoxia in plants; exposure to oxygen following submergence, termed reoxygenation, produces a burst of reactive oxygen species. The mechanisms of hypoxia sensing and signaling in plants have been well studied, but how plants respond to reoxygenation remains unclear. Here, we show that reoxygenation in Arabidopsis (

Topics: Adaptation, Physiological; Antioxidants; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Cyclopentanes; Gene Expression Regulation, Plant; Glutathione; Glutathione Synthase; Immersion; Mutation; Oxygen; Oxylipins; Plant Growth Regulators; Reverse Transcriptase Polymerase Chain Reaction; Transcriptional Activation; Water

To achieve host colonization, successful pathogens need to overcome plant basal defences. For this, (hemi)biotrophic pathogens secrete effectors that interfere with a range of physiological processes of the host plant. AvrLm4-7 is one of the cloned effectors from the hemibiotrophic fungus Leptosphaeria maculans 'brassicaceae' infecting mainly oilseed rape (Brassica napus). Although its mode of action is still unknown, AvrLm4-7 is strongly involved in L. maculans virulence. Here, we investigated the effect of AvrLm4-7 on plant defence responses in a susceptible cultivar of B. napus. Using two isogenic L. maculans isolates differing in the presence of a functional AvrLm4-7 allele [absence ('a4a7') and presence ('A4A7') of the allele], the plant hormone concentrations, defence-related gene transcription and reactive oxygen species (ROS) accumulation were analysed in infected B. napus cotyledons. Various components of the plant immune system were affected. Infection with the 'A4A7' isolate caused suppression of salicylic acid- and ethylene-dependent signalling, the pathways regulating an effective defence against L. maculans infection. Furthermore, ROS accumulation was decreased in cotyledons infected with the 'A4A7' isolate. Treatment with an antioxidant agent, ascorbic acid, increased the aggressiveness of the 'a4a7' L. maculans isolate, but not that of the 'A4A7' isolate. Together, our results suggest that the increased aggressiveness of the 'A4A7' L. maculans isolate could be caused by defects in ROS-dependent defence and/or linked to suppressed SA and ET signalling. This is the first study to provide insights into the manipulation of B. napus defence responses by an effector of L. maculans.

Topics: Abscisic Acid; Alleles; Antioxidants; Ascomycota; Ascorbic Acid; Brassica napus; Chromatography, Liquid; Cotyledon; Cyclopentanes; Ethylenes; Fungal Proteins; Host-Pathogen Interactions; Hydrogen Peroxide; Mass Spectrometry; Oxylipins; Plant Growth Regulators; Reverse Transcriptase Polymerase Chain Reaction; Salicylic Acid; Signal Transduction

In this paper, we investigated whether nitric oxide (NO) participated in the regulation of the ascorbate-glutathione (AsA-GSH) cycle by exogenous jasmonic acid (JA) in the leaves of wheat seedlings under drought stress. The findings of our study showed that drought stress significantly enhanced the AsA-GSH cycle by upregulating the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR). Drought stress also markedly increased electrolyte leakage (EL), malondialdehyde (MDA) content, NO content, and significantly reduced the ratios of reduced ascorbate/dehydroascorbic acid (AsA/DHA) and reduced glutathione/oxidized glutathione (GSH/GSSG) compared with control. Exogenous JA significantly increased the above indicators, compared with drought stress alone. All these effects of JA were inhibited by pretreatment with NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO). Meanwhile, exogenous JA markedly decreased MDA content and electrolyte leakage of wheat leaves under drought stress. Pretreatment with cPTIO reversed the above effects of exogenous JA. Our findings indicated that NO induced by exogenous JA upregulated the activity of the AsA-GSH cycle and had important role in drought tolerance.

Topics: Antioxidants; Ascorbic Acid; Cyclopentanes; Dehydration; Droughts; Glutathione; Lipid Peroxidation; Metabolic Networks and Pathways; Nitric Oxide; Oxidative Stress; Oxylipins; Plant Leaves; Reactive Oxygen Species; Seedlings; Signal Transduction; Triticum

Ascorbate and anthocyanins act as photoprotectants during exposure to high light (HL). They accumulate in Arabidopsis leaves in response to HL on a similar timescale, suggesting a potential relationship between them. Flavonoids and related metabolites were identified and profiled by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The ascorbate-deficient mutants vtc1, vtc2 and vtc3 accumulated less anthocyanin than wild-type (WT) during HL acclimation. In contrast, kaempferol glycoside accumulation was less affected by light and not decreased by ascorbate deficiency, while sinapoyl malate levels decreased during HL acclimation. Comparison of six Arabidopsis ecotypes showed a positive correlation between ascorbate and anthocyanin accumulation in HL. mRNA-Seq analysis showed that all flavonoid biosynthesis transcripts were increased by HL acclimation in WT. RT-PCR analysis showed that vtc1 and vtc2 were impaired in HL induction of transcripts of anthocyanin biosynthesis enzymes, and the transcription factors PAP1, GL3 and EGL3 that activate the pathway. Abscisic acid (ABA) and jasmonic acid (JA), hormones that could affect anthocyanin accumulation, were unaffected in vtc mutants. It is concluded that HL induction of anthocyanin synthesis involves a redox-sensitive process upstream of the known transcription factors. Because anthocyanins accumulate in preference to kaempferol glycosides and sinapoyl malate in HL, they might have specific properties that make them useful in HL acclimation.

Topics: Abscisic Acid; Acclimatization; Anthocyanins; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Cyclopentanes; Ecotype; Gene Expression Regulation, Plant; Glycosides; Kaempferols; Light; Malates; Mutation; Oxidation-Reduction; Oxidative Stress; Oxylipins; Pancreatitis-Associated Proteins; Phenylpropionates; Plant Growth Regulators; Plant Leaves; Time Factors; Transcription Factors

The cellular reduction-oxidation (redox) hub processes information from metabolism and the environment and so regulates plant growth and defense through integration with the hormone signaling network. One key pathway of redox control involves interactions with ABSCISIC ACID (ABA). Accumulating evidence suggests that the ABA-INSENSITIVE-4 (ABI4) transcription factor plays a key role in transmitting information concerning the abundance of ascorbate and hence the ability of cells to buffer oxidative challenges. ABI4 is required for the ascorbate-dependent control of growth, a process that involves enhancement of salicylic acid (SA) signaling and inhibition of jasmonic acid (JA) signaling pathways. Low redox buffering capacity reinforces SA- JA- interactions through the mediation of ABA and ABI4 to fine-tune plant growth and defense in relation to metabolic cues and environmental challenges. Moreover, ABI4-mediated pathways of sugar sensitivity are also responsive to the abundance of ascorbate, providing evidence of overlap between redox and sugar signaling pathways.

Topics: Abscisic Acid; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Carbohydrates; Cyclopentanes; Gene Expression Regulation, Plant; Genes, Plant; Oxidation-Reduction; Oxidative Stress; Oxylipins; Plant Growth Regulators; Salicylic Acid; Signal Transduction; Transcription Factors

This study investigated the role of the protein kinase MEK1/2 in the regulation of ascorbate and glutathione content by jasmonic acid in Agropyron cristatum leaves. The results showed that JA induced increases in the transcript levels and activities of APX, GR, MDHAR, DHAR, GalLDH and γ-ECS, the contents of AsA, GSH, total ascorbate and total glutathione, and the ratios of AsA/DHA and GSH/GSSG, and reduced the E(GSSG/2GSH). The increases, except for the transcript level and activity of γ-ECS and the reduction in E(GSSG/2GSH,) were all suppressed by pre-treatment with the MEK1/2 inhibitors PD98059 and U0126. The results of western blot analyses showed that JA induced increases in the phosphorylation level of MEK1/2. Our results suggest that JA could induce the activation of MEK1/2 by increasing the phosphorylation level, which, in turn, resulted in the up-regulation of ascorbate and glutathione content in A. cristatum leaves.

Topics: Agropyron; Ascorbic Acid; Base Sequence; Blotting, Western; Cyclopentanes; DNA Primers; Glutathione; MAP Kinase Kinase 1; Oxylipins; Plant Leaves; Reverse Transcriptase Polymerase Chain Reaction

Cellular redox homeostasis is a hub for signal integration. Interactions between redox metabolism and the ABSCISIC ACID-INSENSITIVE-4 (ABI4) transcription factor were characterized in the Arabidopsis thaliana vitamin c defective1 (vtc1) and vtc2 mutants, which are defective in ascorbic acid synthesis and show a slow growth phenotype together with enhanced abscisic acid (ABA) levels relative to the wild type (Columbia-0). The 75% decrease in the leaf ascorbate pool in the vtc2 mutants was not sufficient to adversely affect GA metabolism. The transcriptome signatures of the abi4, vtc1, and vtc2 mutants showed significant overlap, with a large number of transcription factors or signaling components similarly repressed or induced. Moreover, lincomycin-dependent changes in LIGHT HARVESTING CHLOROPHYLL A/B BINDING PROTEIN 1.1 expression were comparable in these mutants, suggesting overlapping participation in chloroplast to nucleus signaling. The slow growth phenotype of vtc2 was absent in the abi4 vtc2 double mutant, as was the sugar-insensitive phenotype of the abi4 mutant. Octadecanoid derivative-responsive AP2/ERF-domain transcription factor 47 (ORA47) and AP3 (an ABI5 binding factor) transcripts were enhanced in vtc2 but repressed in abi4 vtc2, suggesting that ABI4 and ascorbate modulate growth and defense gene expression through jasmonate signaling. We conclude that low ascorbate triggers ABA- and jasmonate-dependent signaling pathways that together regulate growth through ABI4. Moreover, cellular redox homeostasis exerts a strong influence on sugar-dependent growth regulation.

Topics: Abscisic Acid; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Cell Nucleus; Chloroplasts; Cyclopentanes; Gene Expression Regulation, Plant; Gibberellins; Glutathione; Homeostasis; Mutation; Oxidation-Reduction; Oxylipins; Plant Growth Regulators; Signal Transduction; Transcription Factors; Transcriptome

Glutathione is a major cellular thiol that is maintained in the reduced state by glutathione reductase (GR), which is encoded by two genes in Arabidopsis (Arabidopsis thaliana; GR1 and GR2). This study addressed the role of GR1 in hydrogen peroxide (H(2)O(2)) responses through a combined genetic, transcriptomic, and redox profiling approach. To identify the potential role of changes in glutathione status in H(2)O(2) signaling, gr1 mutants, which show a constitutive increase in oxidized glutathione (GSSG), were compared with a catalase-deficient background (cat2), in which GSSG accumulation is conditionally driven by H(2)O(2). Parallel transcriptomics analysis of gr1 and cat2 identified overlapping gene expression profiles that in both lines were dependent on growth daylength. Overlapping genes included phytohormone-associated genes, in particular implicating glutathione oxidation state in the regulation of jasmonic acid signaling. Direct analysis of H(2)O(2)-glutathione interactions in cat2 gr1 double mutants established that GR1-dependent glutathione status is required for multiple responses to increased H(2)O(2) availability, including limitation of lesion formation, accumulation of salicylic acid, induction of pathogenesis-related genes, and signaling through jasmonic acid pathways. Modulation of these responses in cat2 gr1 was linked to dramatic GSSG accumulation and modified expression of specific glutaredoxins and glutathione S-transferases, but there is little or no evidence of generalized oxidative stress or changes in thioredoxin-associated gene expression. We conclude that GR1 plays a crucial role in daylength-dependent redox signaling and that this function cannot be replaced by the second Arabidopsis GR gene or by thiol systems such as the thioredoxin system.

Topics: Antioxidants; Arabidopsis; Ascorbic Acid; Cyclopentanes; DNA, Bacterial; Gene Expression Profiling; Gene Expression Regulation, Plant; Glutathione; Glutathione Reductase; Hydrogen Peroxide; Intracellular Space; Mutagenesis, Insertional; Mutation; Oligonucleotide Array Sequence Analysis; Oxidative Stress; Oxylipins; Plant Leaves; RNA, Messenger; Salicylic Acid; Signal Transduction

Ascorbate and glutathione are major antioxidants and redox buffers in plant cells but also play key functions in growth, development, and stress responses. We have studied the regulation of ascorbate and homoglutathione biosynthesis in common bean (Phaseolus vulgaris) nodules under stress conditions and during aging. The expression of five genes of the major ascorbate biosynthetic pathway was analyzed in nodules, and evidence was found that L-galactono-1,4-lactone dehydrogenase, the last committed step of the pathway, is posttranscriptionally regulated. Also, in nodules under stress conditions, gamma-glutamylcysteine synthetase was translationally regulated, but homoglutathione synthetase (mRNA and activity) and homoglutathione (content and redox state) were not affected. Most interestingly, in nodules exposed to jasmonic acid, dehydroascorbate reductase activity was posttranslationally suppressed, ascorbate oxidase showed strong transcriptional up-regulation, and dehydroascorbate content increased moderately. These changes were not due to a direct effect of jasmonic acid on the enzyme activities but might be part of the signaling pathway in the response of nodules to stress. We determined ascorbate, homoglutathione, and ascorbate-glutathione pathway enzyme activities in two senescing stages of nodules undergoing oxidative stress. When all parameters were expressed on a nodule fresh weight basis, we found that in the first stage ascorbate decreased by 60% and homoglutathione and antioxidant activities remained fairly constant, whereas in the second stage ascorbate and homoglutathione, their redox states, and their associated enzyme activities significantly decreased. The coexistence in the same plants of nodules at different senescence stages, with different ascorbate concentrations and redox states, indicates that the life span of nodules is in part controlled by endogenous factors and points to ascorbate as one of the key players.

Topics: Adaptation, Physiological; Ascorbate Oxidase; Ascorbic Acid; Cyclopentanes; Gene Expression Regulation, Plant; Glutamate-Cysteine Ligase; Glutathione; Oxidation-Reduction; Oxidative Stress; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Oxylipins; Peptide Synthases; Phaseolus; Root Nodules, Plant

We have presented changes in the photosynthetic apparatus activity of Arabidopsis thaliana plants occurring within 15-144 h of 100 microM Cu or Cd action with regard to jasmonate (JA) as well as expression of the oxidative stress and non-enzymic defense mechanisms. The inhibitory effect of both heavy metals related to developing dissipative processes and lipid peroxide formation was expressed in dark-adapted state after the longest time as a decrease in potential quantum yield of PSII. In dark- and light-adapted state the heavy metals affected the enzymic phase of photosynthesis already from the 15th hour, which was related to the lipid peroxide formation. Photochemical quenching decrease was induced after 48th hour and did not show a close correlation with the JA pathway. Blockade of endogenously formed JA by propyl gallate decreased the effect of Cu and Cd on both the whole photosynthetic apparatus starting from the 48th hour and on the primary photochemistry of PSII after 144 h. In the case of Cu the effect was related to a lipid peroxidation decrease and to an increase in glutathione and phytochelatin (PC) levels, but in the case of Cd to lipid peroxidation, O.2- and especially to PCs increase. The obtained results indicated that JA after the longest time might enhance the sensitivity of A. thaliana to Cu and Cd stress. Asc enhanced toxic action of Cu and Cd after 15 h, but after a longer time it diminished the influence of Cd (but not Cu) on photosynthetic activity.

Topics: Antioxidants; Arabidopsis; Ascorbic Acid; Cadmium; Copper; Cyclopentanes; Glutathione; Lipid Peroxidation; Oxidative Stress; Oxylipins; Photosynthesis; Phytochelatins; Plant Growth Regulators; Plant Leaves; Time Factors

Rice microarray analysis showed that a number of stress-related genes are induced by external addition of L-ascorbic acid (AsA). The gene designated as AK073843 which is homologous to class capital SHA, Cyrillic chitinase was found to exhibit the highest induction among these genes. However, its crucial residues within the chitinase active site are substituted with other residues, suggesting that the protein has no chitinase activity. The recombinant protein which is encoded by the AK073843 gene produced in Escherichia coli has xylanase inhibitor activity, indicating that the gene encodes a novel rice XIP-type xylanase inhibitor protein (OsXIP). The expression of OsXIP was enhanced not only by exogenous AsA treatment but also by various stresses such as citrate and sodium chloride treatments, and wounding; however, it was not influenced by increasing endogenous AsA content. External AsA treatment caused a significant increase in electrolyte leakage from rice root. These results suggested that OsXIP was induced by stress which is caused by external AsA treatment. Rice XIP-family genes, OsXIP, riceXIP and RIXI, showed differential organ-specific expression. Also, these genes were differentially induced by stress and stress-related phytohormones. The transcripts of OsXIP and riceXIP were undetectable under normal conditions, and were drastically induced by wounding and methyl jasmonate (MeJA) treatment in the root. RIXI was constitutively expressed in the shoot but not induced by wounding and stress-related phytohormones. Thus, XIP-type xylanase inhibitors were suggested to be specialized in their function and involved in defense mechanisms in rice.

Topics: Acetates; Amino Acid Sequence; Ascorbic Acid; Blotting, Northern; Cyclopentanes; Gene Expression Regulation, Plant; Molecular Sequence Data; Oligonucleotide Array Sequence Analysis; Oryza; Oxylipins; Phylogeny; Plant Proteins; Salicylic Acid; Seedlings; Seeds; Sequence Alignment; Sequence Analysis, DNA; Xylosidases

Jasmonic acid (JA) and methyl jasmonate (MeJA), collectively termed jasmonates, are ubiquitous plant signalling compounds. Several types of stress conditions, such as wounding and pathogen infection, cause endogenous JA accumulation and the expression of jasmonate-responsive genes. Although jasmonates are important signalling components for the stress response in plants, the mechanism by which jasmonate signalling contributes to stress tolerance has not been clearly defined. A comprehensive analysis of jasmonate-regulated metabolic pathways in Arabidopsis was performed using cDNA macroarrays containing 13516 expressed sequence tags (ESTs) covering 8384 loci. The results showed that jasmonates activate the coordinated gene expression of factors involved in nine metabolic pathways belonging to two functionally related groups: (i) ascorbate and glutathione metabolic pathways, which are important in defence responses to oxidative stress, and (ii) biosynthesis of indole glucosinolate, which is a defence compound occurring in the Brassicaceae family. We confirmed that JA induces the accumulation of ascorbate, glutathione and cysteine and increases the activity of dehydroascorbate reductase, an enzyme in the ascorbate recycling pathway. These antioxidant metabolic pathways are known to be activated under oxidative stress conditions. Ozone (O3) exposure, a representative oxidative stress, is known to cause activation of antioxidant metabolism. We showed that O3 exposure caused the induction of several genes involved in antioxidant metabolism in the wild type. However, in jasmonate-deficient Arabidopsis 12-oxophytodienoate reductase 3 (opr3) mutants, the induction of antioxidant genes was abolished. Compared with the wild type, opr3 mutants were more sensitive to O3 exposure. These results suggest that the coordinated activation of the metabolic pathways mediated by jasmonates provides resistance to environmental stresses.

Topics: Acetates; Antioxidants; Arabidopsis; Ascorbic Acid; Cyclopentanes; DNA, Plant; Genes, Plant; Glucosinolates; Indoles; Models, Biological; Oligonucleotide Array Sequence Analysis; Oxidative Stress; Oxylipins; Ozone; Sulfur

Culture filtrate of Lasiodiplodia theobromae increased respiration rate, phenylalanine ammonia lyase activity, and levels of hydrogen peroxide, lipid peroxides and salicylic acid in B. nigra plants. Salicylic acid (SA) level increased for 1 hr of interaction and reduced later. Development of systemic acquired resistance (SAR) was found restricted in plants infected with L. theobromae due to deficiency of SA, which is a major signal for development of SAR. Exogenously supplied SA did develop resistance and plant death was delayed. It was hypothesized that deficiency of SA could be due to jasmonic acid produced by fungus that inhibits SA biosynthesis.

Topics: Ascomycota; Ascorbic Acid; Chromatography, High Pressure Liquid; Cyclopentanes; Hydrogen Peroxide; Immunity, Innate; Lipid Peroxides; Mustard Plant; Mycotoxins; Oxylipins; Reactive Oxygen Species; Salicylic Acid; Time Factors

Jasmonic acid (JA) has been shown to be a signaling compound which elicits the production of secondary metabolites including phytoalexins in plants. It has been shown that the phytoalexin production is elicited by exogenously applied JA in rice leaves. We now show that this phytoalexin production by exogenously applied JA is significantly counteracted by cytokinins, kinetin and zeatin. Kinetin and zeatin also inhibit the induction of naringenin-7-O-methyltransferase (a key enzyme in rice phytoalexin production) by JA. A natural free radical scavenger, ascorbic acid (AsA) shows both counteractive and enhancing effects on JA-inducible phytoalexin production, depending on its concentration. This effect of AsA suggests that active oxygen species (AOS) may play important roles in phytoalexin production by JA in rice leaves.

Topics: Adenine; Anti-Infective Agents; Ascorbic Acid; Cyclopentanes; Cytokinins; Enzyme Inhibitors; Free Radical Scavengers; Kinetin; Methyltransferases; Oryza; Oxylipins; Phytoalexins; Plant Extracts; Plant Growth Regulators; Plant Leaves; Sesquiterpenes; Terpenes; Zeatin