Exogenous Application Of Methyl Jasmonate Research Articles

Induction of Jasmonic Acid-Associated Defenses by Thrips Alters Host Suitability for Conspecifics and Correlates with Increased Trichome Densities in Tomato.

Plant defenses inducible by herbivorous arthropods can determine performance of subsequent feeding herbivores. We investigated how infestation of tomato (Solanum lycopersicum) plants with the Western flower thrips (Frankliniella occidentalis) alters host plant suitability and foraging decisions of their conspecifics. We explored the role of delayed-induced jasmonic acid (JA)-mediated plant defense responses in thrips preference by using the tomato mutant def-1, impaired in JA biosynthesis. In particular, we investigated the effect of thrips infestation on trichome-associated tomato defenses. The results showed that when offered a choice, thrips preferred non-infested plants over infested wild-type plants, while no differences were observed in def-1. Exogenous application of methyl jasmonate restored the repellency effect in def-1. Gene expression analysis showed induction of the JA defense signaling pathway in wild-type plants, while activating the ethylene signaling pathway in both genotypes. Activation of JA defenses led to increases in type-VI leaf glandular trichome densities in the wild type, augmenting the production of trichome-associated volatiles, i.e. terpenes. Our study revealed that plant-mediated intraspecific interactions between thrips are determined by JA-mediated defenses in tomato. We report that insects can alter not only trichome densities but also the allelochemicals produced therein, and that this response might depend on the magnitude and/or type of the induction.

Effects of jasmonic acid signalling on the wheat microbiome differ between body sites

Jasmonic acid (JA) signalling helps plants to defend themselves against necrotrophic pathogens and herbivorous insects and has been shown to influence the root microbiome of Arabidopsis thaliana. In this study, we determined whether JA signalling influences the diversity and functioning of the wheat (Triticum aestivum) microbiome and whether these effects are specific to particular parts of the plant. Activation of the JA pathway was achieved via exogenous application of methyl jasmonate and was confirmed by significant increases in the abundance of 10 JA-signalling-related gene transcripts. Phylogenetic marker gene sequencing revealed that JA signalling reduced the diversity and changed the composition of root endophytic but not shoot endophytic or rhizosphere bacterial communities. The total enzymatic activity and substrate utilisation profiles of rhizosphere bacterial communities were not affected by JA signalling. Our findings indicate that the effects of JA signalling on the wheat microbiome are specific to individual plant compartments.

Jasmonate Regulates Plant Responses to Postsubmergence Reoxygenation through Transcriptional Activation of Antioxidant Synthesis.

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 (Arabidopsis thaliana) involves rapid accumulation of jasmonates (JAs) and increased transcript levels of JA biosynthesis genes. Application of exogenous methyl jasmonate improved tolerance to reoxygenation in wild-type Arabidopsis; also, mutants deficient in JA biosynthesis and signaling were very sensitive to reoxygenation. Moreover, overexpression of the transcription factor gene MYC2 enhanced tolerance to posthypoxic stress, and myc2 knockout mutants showed increased sensitivity to reoxygenation, indicating that MYC2 functions as a key regulator in the JA-mediated reoxygenation response. MYC2 transcriptionally activates members of the VITAMIN C DEFECTIVE (VTC) and GLUTATHIONE SYNTHETASE (GSH) gene families, which encode rate-limiting enzymes in the ascorbate and glutathione synthesis pathways. Overexpression of VTC1 and GSH1 in the myc2-2 mutant suppressed the posthypoxic hypersensitive phenotype. The JA-inducible accumulation of antioxidants may alleviate oxidative damage caused by reoxygenation, improving plant survival after submergence. Taken together, our findings demonstrate that JA signaling interacts with the antioxidant pathway to regulate reoxygenation responses in Arabidopsis.

An incoherent feed-forward loop mediates robustness and tunability in a plant immune network.

Immune signaling networks must be tunable to alleviate fitness costs associated with immunity and, at the same time, robust against pathogen interferences. How these properties mechanistically emerge in plant immune signaling networks is poorly understood. Here, we discovered a molecular mechanism by which the model plant species Arabidopsis thaliana achieves robust and tunable immunity triggered by the microbe-associated molecular pattern, flg22. Salicylic acid (SA) is a major plant immune signal molecule. Another signal molecule jasmonate (JA) induced expression of a gene essential for SA accumulation, EDS5 Paradoxically, JA inhibited expression of PAD4, a positive regulator of EDS5 expression. This incoherent type-4 feed-forward loop (I4-FFL) enabled JA to mitigate SA accumulation in the intact network but to support it under perturbation of PAD4, thereby minimizing the negative impact of SA on fitness as well as conferring robust SA-mediated immunity. We also present evidence for evolutionary conservation of these gene regulations in the family Brassicaceae Our results highlight an I4-FFL that simultaneously provides the immune network with robustness and tunability in A.thaliana and possibly in its relatives.

Exogenous application of methyl jasmonate induces defence against Meloidogyne hapla in soybean

Phytohormones play important roles in plant defence against plant-parasitic nematodes, although the role of jasmonate (JA) in defence against root-knot nematodes (RKN, Meloidogyne spp.) in soybean (Glycine max) was unknown. In this study, two commercial soybean cultivars, cvs DongSheng1 (DS1) and SuiNong14 (SN14), were identified as susceptible and resistant, respectively, to M. hapla. Quantitative reverse transcription (qRT)-PCR analysis showed that the expression of genes involved in JA synthesis or signalling was significantly induced in both susceptible and resistant roots at 24 and 48 h after inoculation. Exogenous application of methyl jasmonate induced defence against RKN in susceptible cv. DS1, which might be involved in altered activities of defence-related enzymes (chitinase and β-1,3 glucanase) and pathogenesis-related gene PR5 expression. The results indicate that exogenous application of JA might be an alternative strategy to induce soybean resistance against RKN.

Role of hydrogen sulfide in the methyl jasmonate response to cadmium stress in foxtail millet.

Methyl jasmonate (MeJA), a vital cellular regulator, mediates diverse developmental processes and defense responses against environmental stresse. Recently, a novel gasotransmitter, hydrogen sulfide (H2S), was found to have similar functions, but the interactions between H2S and MeJA in the acquisition of cadmium (Cd) tolerance have not been reported. Treating foxtail millet with 1 microM MeJA not only enhanced Cd tolerance and alleviated growth inhibitions but also decreased the contents of hydrogen peroxide, malondialdehyde and Cd in seedlings under 200 microM of Cd stress. Exogenous application of MeJA inhibited the transcript levels of the Natural Resistance-Associated Macrophage Protein (NRAMP1 and NRAMP6) and intensified Cd-induced expression of the homeostasis-related genes (MTP1, MTP12, CAX2 and ZIP4, besides HMA3). In addition, treatment with MeJA induced the production of endogenous H2S. Fumigation with sodium hydrosulfide (H2S donor) significantly enhanced MeJA-induced Cd tolerance, but this ability was weakened when H2S biosynthesis was inhibited with hydroxylamine. These results suggest that pretreatment with MeJA alleviated Cd stress and that this improvement was mediated by H2S in foxtail millet.

An (E,E)-α-farnesene synthase gene of soybean has a role in defence against nematodes and is involved in synthesizing insect-induced volatiles.

SummaryPlant terpene synthase genes (TPSs) have roles in diverse biological processes. Here, we report the functional characterization of one member of the soybean TPS gene family, which was designated GmAFS. Recombinant GmAFS produced in Escherichia coli catalysed the formation of a sesquiterpene (E,E)‐α‐farnesene. GmAFS is closely related to (E,E)‐α‐farnesene synthase gene from apple, both phylogenetically and structurally. GmAFS was further investigated for its biological role in defence against nematodes and insects. Soybean cyst nematode (SCN) is the most important pathogen of soybean. The expression of GmAFS in a SCN‐resistant soybean was significantly induced by SCN infection compared with the control, whereas its expression in a SCN‐susceptible soybean was not changed by SCN infection. Transgenic hairy roots overexpressing GmAFS under the control of the CaMV 35S promoter were generated in an SCN‐susceptible soybean line. The transgenic lines showed significantly higher resistance to SCN, which indicates that GmAFS contributes to the resistance of soybean to SCN. In soybean leaves, the expression of GmAFS was found to be induced by Tetranychus urticae (two‐spotted spider mites). Exogenous application of methyl jasmonate to soybean plants also induced the expression of GmAFS in leaves. Using headspace collection combined with gas chromatography–mass spectrometry analysis, soybean plants that were infested with T. urticae were shown to emit a mixture of volatiles with (E,E)‐α‐farnesene as one of the most abundant constituents. In summary, this study showed that GmAFS has defence roles in both below‐ground and above‐ground organs of soybean against nematodes and insects, respectively.

Higher Activities of Defense-Associated Enzymes may Contribute to Greater Resistance of Manchurian Ash to Emerald Ash Borer Than A closely Related and Susceptible Congener.

Emerald ash borer (EAB) is an invasive beetle native to Asia that infests and kills ash (Fraxinus spp.) in North America. Previous experiments indicated that larvae feeding on co-evolved, resistant Manchurian ash (F. mandshurica) have increased antioxidant and quinone-protective enzyme activities compared to larvae feeding on susceptible North American species. Here, we examined mechanisms of host-generated oxidative and quinone-based stress and other putative defenses in Manchurian ash and the closely related and chemically similar, but susceptible, black ash (F. nigra), with and without exogenous application of methyl jasmonate (MeJA) to induce resistance mechanisms. Peroxidase activities were 4.6-13.3 times higher in Manchurian than black ash, although both species appeared to express the same three peroxidase isozymes. Additionally, peroxidase-mediated protein cross-linking activity was stronger in Manchurian ash. Polyphenol oxidase, β-glucosidase, chitinase, and lipoxygenase activities also were greater in Manchurian ash, but only lipoxygenase activity increased with MeJA application. Phloem H2O2 levels were similar and were increased by MeJA application in both species. Lastly, trypsin inhibitor activity was detected in methanol and water extracts that were not allowed to oxidize, indicating the presence of phenolic-based trypsin inhibitors. However, no proteinaceous trypsin inhibitor activity was detected in either species. In response to MeJA application, Manchurian ash had higher trypsin inhibitor activity than black ash using the unoxidized water extracts, but no treatment effects were detected using methanol extracts. Based on these results we hypothesize that peroxidases, lignin polymerization, and quinone generation contribute to the greater resistance to EAB displayed by Manchurian ash.

Arabidopsis JINGUBANG Is a Negative Regulator of Pollen Germination That Prevents Pollination in Moist Environments

The molecular mechanism of pollen germination and pollen tube growth has been revealed in detail during the last decade, while the mechanism that suspends pollen grains in a dormant state is largely unclear. Here, we identified the JINGUBANG (JGB) gene by screening pollen-specific genes for those that are unnecessary for pollen germination. We showed that the pollen of the jgb loss-of-function mutant exhibited hyperactive germination in sucrose-only medium and inside the anther, while this phenotype was rescued by the transgenic expression of JGB in jgb plants. JGB contains seven WD40 repeats and is highly conserved in flowering plants. Overexpression of JGB inhibits pollen germination. These results indicate that JGB is a novel negative regulator of pollen germination. In addition, we found that jasmonic acid (JA) abundance was significantly elevated in jgb pollen, while exogenous application of methyl jasmonate rescued the inhibition of pollen germination in plants overexpressing JGB Based on the molecular features of JGB and on the finding that it interacts with a known JA biosynthesis-related transcription factor, TCP4, we propose that JGB, together with TCP4, forms a regulatory complex that controls pollen JA synthesis, ensuring pollination in moist environments.

Methyl jasmonate-induced accumulation of metabolites and transcriptional responses involved in triterpene biosynthesis in Siraitia grosvenorii fruit at different growing stages

The cucurbitane-type triterpenoid glycosides, mogrosides, are the main active components of <em>Siraitia grosvenorii</em> fruit. Squalene and cucurbitadienol are among the intermediates of the biosynthetic pathway for the formation of cucurbitane-type triterpenoid backbones of mogrosides. It is recognized that the exogenous application of methyl jasmonate (MeJA) increases the accumulation of secondary metabolites in various plant species. Here, the effect of MeJA (50, 200, and 500 μM) on the accumulation of squalene and cucurbitadienol in the fruits of <em>S. grosvenorii</em> at 10, 20, and 30 days after flowering (DAF) was tested for the first time. Since mogroside II E is the main cucurbitane-type triterpenoid present at this time, its concentration was also determined. The results show that MeJA can indeed promote squalene and cucurbitadienol accumulation, the application of 500 μM MeJA at 30 DAF being optimal. The concentration of squalene and cucurbitadienol increased up to 0.43 and 4.71 μg/g dry weight (DW), respectively, both of which were 1.2-fold greater than that of the control. The content of mogroside II E increased by 15% over the untreated group. We subsequently analyzed the expression of key genes involved in the mogroside biosynthetic pathway, including the 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene (<em>SgHMGR</em>), squalene synthetase gene (<em>SgSQS</em>), cucurbitadienol synthase gene (<em>SgCS</em>), and cytochrome P450 (<em>SgCYP450</em>) with quantitative real-time PCR. The results showed that transcriptional levels of these genes were upregulated following the treatment described above. Additionally, their responses in the presence of MeJA was related to the concentration and timing of MeJA treatment.

Intraspecific variation in defense against a generalist lepidopteran herbivore in populations of Eruca sativa (Mill.)

Populations of Eruca sativa (Brassicaceae) from desert and Mediterranean (Med) habitats in Israel differ in their defense against larvae of the generalist Spodoptera littoralis but not the specialist Pieris brassicae. Larvae of the generalist insect feeding on plants of the Med population gained significantly less weight than those feeding on the desert plants, and exogenous application of methyl jasmonate (MJ) on leaves of the Med plants significantly reduced the level of damage created by the generalist larvae. However, MJ treatment significantly induced resistance in plants of the desert population, whereas the generalist larvae caused similar damage to MJ-induced and noninduced plants. Analyses of glucosinolates and expression of genes in their synthesis pathway indicated that defense in plants of the Med population against the generalist insect is governed by the accumulation of glucosinolates. In plants of the desert population, trypsin proteinase inhibitor activity was highly induced in response to herbivory by S. littoralis. Analysis of genes in the defense-regulating signaling pathways suggested that in response to herbivory, differences between populations in the induced levels of jasmonic acid, ethylene, and salicylic acid mediate the differential defenses against the insect. In addition, expression analysis of myrosinase-associated protein NSP2 suggested that in plants of the desert population, glucosinolates breakdown products were primarily directed to nitrile production. We suggest that proteinase inhibitors provide an effective defense in the desert plants, in which glucosinolate production is directed to the less toxic nitriles. The ecological role of nitrile production in preventing infestation by specialists is discussed.

Exogenously applied methyl jasmonate improves the drought tolerance in wheat imposed at early and late developmental stages

Drought stress is one of the most detrimental abiotic stresses limiting wheat productivity worldwide. Methyl Jasmonate (MeJA), a stress signaling compound, may be effective in alleviating drought-induced adversities in wheat. Current study examined the role of exogenously applied MeJA in improving drought tolerance in five different wheat cultivars (Yu-Mai-1, Lu-Nong-116, Huai-Mai-19, Yan-Nong-19, Bai-Maizi). Drought stress (35 % field capacity) was imposed either at jointing (DS1), heading (DS2) or grain filling (DS3) stage. A control was maintained at field capacity of 90 % for comparison. The MeJA was applied at 0.5 mM after 1 week after imposition of drought. Data regarding different growth and yield attributes was recorded. Results depicted that drought stress at any growth stage substantially reduced the growth and yield of all wheat cultivars. More severe reductions in plant height, peduncle length, dry biomass (leaves, culm, root), and in yield components were observed in DS1 compared with DS2 or DS3. Exogenous application of MeJA effectively assuaged the damaging effects of drought. Beneficial effects of MeJA on dry biomass, number of grains per spike, and grain weight led to higher grain and biological yield in MeJA–treated plants under drought as well as control conditions. Variations were also apparent among cultivars regarding their response to drought stress. The cultivar Yu-Mai-1 remained superior to rest of cultivars in terms of wheat yield. In summary, our results suggested the involvement of MeJA in improving the drought tolerance of wheat by maintaining growth and yield performance of plants.

Exogenous methyl jasmonate regulates cytokinin content by modulating cytokinin oxidase activity in wheat seedlings under salinity

The treatment of 4-days-old wheat seedlings with methyl jasmonate (MeJA) in concentration optimal for their growth (0.1μM) resulted in a rapid transient almost two-fold increase in the level of cytokinins (CKs). MeJA-induced accumulation of CKs was due to inhibition of both cytokinin oxidase (CKX) (cytokinin oxidase/dehydrogenase, EC 1.5.99.12) gene expression and activity of this enzyme. Pretreatment of wheat seedlings with MeJA decreased the growth-retarding effect of sodium chloride salinity and accelerated growth recovery after withdrawal of NaCl from the incubation medium. We speculate that this protective effect of the hormone might be due to MeJA's ability to prevent the salinity-induced decline in CK concentration that was caused by inhibition of gene expression and activity of CKX in wheat seedlings. The data might indicate an important role for endogenous cytokinins in the implementation of growth-promoting and protective effects of exogenous MeJA application on wheat plants.

Spatial modulation and abiotic elicitors responses of the biosynthesis related genes of mono/triterpenes in black cumin (Nigella sativa)

Black cumin (Nigella sativa) is a medicinal herb belongs to the Ranunculacea which raised attention due to its pharmaceutical properties. Medical significance of N. sativa mainly attributed to its oxygenated monoterpenes and triterpene saponins which are biosynthesized via the methyl erythritol phosphate (MEP) and MVA (mevalonic acid) pathways, respectively. In order to improve our understanding of monoterpene and triterpene metabolism the partial sequence of a hypothetical monoterpene synthase (MTS) was isolated from N. sativa for the first time and subsequently the relative gene expression of two genes of monoterpene metabolism including geranyl diphosphate synthase (GDS), the isolated monoterpene synthase (MTS) and two genes of triterpene saponins biosynthesis including squalene epoxidase (SQE) and β- amyrin synthase (βAS) were monitored in response to two universal abiotic elicitors including methyl jasmonate (MJ) and salicylic acid (SA), also in different tissues of N. sativa including leaves, stems, roots, capsules and immature seeds. Results of semi quantitative reverse transcription PCR revealed differential regulation of these genes in N. sativa tissues and also in response to abiotic elicitors. Each gene followed a different expression profile and expression level in target tissues. The expression of all studied genes were up-regulated by exogenous application of MJ and SA on N. sativa leaves (at 24h after treatments), except of GDS which its transcript was not induced by SA. The higher expression of these genes in response to abiotic elicitors might reflect an elevation in the corresponding metabolites; hence elicitation is an applicable tool for enhancement of pharmaceutically active mono/triterpenes in N. sativa.

Transcriptional responses and flavor volatiles biosynthesis in methyl jasmonate-treated tea leaves.

BackgroundTea (Camellia sinensis) has long been consumed worldwide for its amazing flavor and aroma. Methyl jasmonate (MeJA), which acts as an effective elicitor among the plant kingdom, could mostly improve the quality of tea aroma by promoting flavor volatiles in tea leaves. Although a variety of volatile secondary metabolites that contribute to aroma quality have been identified, our understanding of the biosynthetic pathways of these compounds has remained largely incomplete. Therefore, information aboaut the transcriptome of tea leaves and, specifically, details of any changes in gene expression in response to MeJA, is required for a better understanding of the biological mechanisms of MeJA-mediated volatiles biosynthesis. Moreover, MeJA treatment could exaggerate the responses of secondary metabolites and some gene expression which offer a better chance to figure out the mechanism.ResultsThe results of two-dimensional gas-chromatograph mass-spectrometry showed that the terpenoids content in MeJA-treated tea leaves increased, especially linalool, geraniol, and phenylethyl alcohol. More importantly, we carried out RNA-seq to identify the differentially expressed genes (DEGs) related to volatiles biosynthesis pathways induced by MeJA treatment (0 h, 12 h, 24 h and 48 h) in tea leaves. We identified 19245, 18614, 11890 DEGs respectively in the MeJA_12h, MeJA_24 h and MeJA_48 h samples. The α-Lenolenic acid degradation pathway was firstly responded resulting in activating the JA-pathway inner tea leaves, and the MEP/DOXP pathway significantly exaggerated. Notably, the expression level of jasmonate O-methyltransferase, which is associated with the central JA biosynthesis pathway, was increased by 7.52-fold in MeJA_24 h tea leaves. Moreover, the genes related to the terpenoid backbone biosynthesis pathway showed different expression patterns compared with the untreated leaves. The expression levels of 1-deoxy-D-xylulose-phosphate synthase (DXS), all-trans-nonaprenyl-diphosphate synthase, geranylgeranyl reductase, geranylgeranyl diphosphate synthase (type II), hydroxymethylglutaryl-CoA reductase and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase increased by approximately 2–4-fold.ConclusionsThe results of two-dimension gas-chromatography mass-spectrometry analysis suggested that exogenous application of MeJA could induce the levels of volatile components in tea leaves, especially the geraniol, linalool and its oxides. Moreover, the transcriptome analysis showed increased expression of genes in α-Lenolenic acid degradation pathway which produced massive jasmonic acid and quickly activated holistic JA-pathway inner tea leaves, also the terpenoid backbones biosynthesis pathway was significantly affected after MeJA treatment. In general, MeJA could greatly activate secondary metabolism pathways, especially volatiles. The results will deeply increase our understanding of the volatile metabolites biosynthesis pathways of tea leaves in response to MeJA.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0609-z) contains supplementary material, which is available to authorized users.

Progress and gaps in understanding mechanisms of ash tree resistance to emerald ash borer, a model for wood-boring insects that kill angiosperms.

We review the literature on host resistance of ash to emerald ash borer (EAB, Agrilus planipennis), an invasive species that causes widespread mortality of ash. Manchurian ash (Fraxinus mandshurica), which coevolved with EAB, is more resistant than evolutionarily naïve North American and European congeners. Manchurian ash was less preferred for adult feeding and oviposition than susceptible hosts, more resistant to larval feeding, had higher constitutive concentrations of bark lignans, coumarins, proline, tyramine and defensive proteins, and was characterized by faster oxidation of phenolics. Consistent with EAB being a secondary colonizer of coevolved hosts, drought stress decreased the resistance of Manchurian ash, but had no effect on constitutive bark phenolics, suggesting that they do not contribute to increased susceptibility in response to drought stress. The induced resistance of North American species to EAB in response to the exogenous application of methyl jasmonate was associated with increased bark concentrations of verbascoside, lignin and/or trypsin inhibitors, which decreased larval survival and/or growth in bioassays. This finding suggests that these inherently susceptible species possess latent defenses that are not induced naturally by larval colonization, perhaps because they fail to recognize larval cues or respond quickly enough. Finally, we propose future research directions that would address some critical knowledge gaps.

Parthenolide accumulation and expression of genes related to parthenolide biosynthesis affected by exogenous application of methyl jasmonate and salicylic acid in Tanacetum parthenium.

Up-regulation of germacrene A synthase and down-regulation of parthenolide hydroxylase genes play key role in parthenolide accumulation of feverfew plants treated with methyl jasmonate and salicylic acid. Parthenolide is an important sesquiterpene lactone due to its anti-migraine and anti-cancer properties. Parthenolide amount was quantified by high-performance liquid chromatography after foliar application of methyl jasmonate (100µM) or salicylic acid (1.0mM) on feverfew leaves in time course experiment (3-96h). Results indicate that exogenous application of methyl jasmonate or salicylic acid activated parthenolide biosynthesis. Parthenolide content reached its highest amount at 24h after methyl jasmonate or salicylic acid treatments, which were 3.1- and 1.96-fold higher than control plants, respectively. Parthenolide transiently increased due to methyl jasmonate or salicylic acid treatments until 24h, but did not show significant difference compared with control plants at 48 and 96h time points in both treatments. Also, the transcript levels of early pathway (upstream) genes of terpene biosynthesis including 3-hydroxy-3-methylglutaryl-coenzyme A reductase, 1-deoxy-D-xylulose-5-phosphate reductoisomerase and hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate reductase and the biosynthetic genes of parthenolide including germacrene A synthase, germacrene A oxidase, costunolide synthase and parthenolide synthase were increased by methyl jasmonate and salicylic acid treatments, but with different intensity. The transcriptional levels of these genes were higher in methyl jasmonate-treated plants than salicylic acid-treated plants. Parthenolide content measurements along with expression pattern analysis of the aforementioned genes and parthenolide hydroxylase as side branch gene of parthenolide suggest that the expression patterns of early pathway genes were not directly consistent with parthenolide accumulation pattern; hence, parthenolide accumulation is probably further modulated by the expression of its biosynthetic genes, especially germacrene A synthase and also its side branch gene, parthenolide hydroxylase.

Exogenous application of methyl jasmonate induces a defense response and resistance against Sclerotinia sclerotiorum in dry bean plants

Sclerotinia sclerotiorum (Lib.) de Bary is a necrotrophic fungal pathogen that causes a disease known as white mold, which is a major problem for dry bean (Phaseolus vulgaris L.) and other crops in many growing areas in Brazil. To investigate the role of methyl jasmonate (MeJA) in defending dry bean plants against S. sclerotiorum, we used suppression subtractive hybridization (SSH) of cDNA and identified genes that are differentially expressed during plant–pathogen interactions after treatment. Exogenous MeJA application enhanced resistance to the pathogen, and SSH analyses led to the identification of 94 unigenes, presumably involved in a variety of functions, which were classified into several functional categories, including metabolism, signal transduction, protein biogenesis and degradation, and cell defense and rescue. Using RT–qPCR, some unigenes were found to be differentially expressed in a time-dependent manner in dry bean plants during the interaction with S. sclerotiorum after MeJA treatment, including the pathogenesis-related protein PR3 (chitinase), PvCallose (callose synthase), PvNBS-LRR (NBS-LRR resistance-like protein), PvF-box (F-box family protein-like), and a polygalacturonase inhibitor protein (PGIP). Based on these expression data, the putative roles of differentially expressed genes were discussed in relation to the disease and MeJA resistance induction. Changes in the activity of the pathogenesis-related proteins β-1,3-glucanase, chitinase, phenylalanine ammonia-lyase, and peroxidase in plants after MeJA treatment and following inoculation of the pathogen were also investigated as molecular markers of induced resistance. Foliar application of MeJA induced partial resistance against S. sclerotiorum in plants as well as a consistent increase in pathogenesis-related protein activities. Our findings provide new insights into the physiological and molecular mechanisms of resistance induced by MeJA in the P. vulgaris–S. sclerotiorum pathosystem.

Methyl Jasmonate Strengthens Wheat Plants Against Root and Crown Rot Pathogen Fusarium culmorum Infection

Root and crown rot of wheat, caused by Fusarium culmorum (Fc), is a serious disease worldwide, particularly in Iran. Currently, the mechanisms underlying resistance to Fusarium-caused diseases are still unknown. Methyl jasmonate (MeJA) has been identified as a vital cellular regulator, and the effect of exogenous MeJA application during wheat-Fc interaction has not been studied previously at the molecular level. This study, using real-time quantitative PCR, was carried out to determine the expression of seven host defense-associated genes consisting of PR3, PR4, PR5, TaPERO, LOX, PAL and cytochrome P450 gene (CYP709C1) at 48, 72 and 96 h after Fc-inoculation (hai) and to investigate the relationship between the induced resistance by MeJA application and the gene expression patterns. The results showed that several genes were induced earlier (48 hai) and to higher levels in the resistant cv. Sumai3 than in susceptible cv. Falat. Many Fc-induced genes were also activated and induced by MeJA particularly during the later stages of infection; however, in contrast to defense-gene induction by the pathogen, there was not a general trend of higher induction in Sumai3 compared to Falat following this chemical treatment. The chemically induced protection significantly reduced the development of necrotic symptoms in both cultivars over a 3-week period after inoculation; however, this reduction was greater in Falat than in Sumai3 relative to the controls. Surprisingly, the expression of these genes was also expressed in crown tissue that had not yet been in contact with the fungus, signifying that a form of systemic response was taking place in this interaction. This is the first work reporting the effect of timing application of MeJA during Fc infection and comparing the defense-related gene expression between root and crown tissues of wheat genotypes. Moreover, soil-drench application of MeJA resulted in strong induction, verifying the success of this application method in systemically activating JA signaling for the first time. These results provided important intimations for designing strategies to curtail diseases caused by Fusarium.

Priming of seeds with methyl jasmonate induced resistance to hemi-biotroph Fusarium oxysporum f.sp. lycopersici in tomato via 12-oxo-phytodienoic acid, salicylic acid, and flavonol accumulation

Methyl jasmonate (MeJA) was tested by seed treatment for its ability to protect tomato seedlings against fusarium wilt caused by the soil-borne fungal pathogen Fusarium oxysporum f.sp. lycopersici. Isolated from Solanum lycopersicon L. seeds, cv. Beta fungus was identified as F. oxysporum f.sp. lycopersici Race 3 fungus by using phytopathological and molecular methods. MeJA applied at 0.01, 0.1 and 1mM reduced spore germination and mycelial growth in vitro. Soaking of tomato seeds in MeJA solution at 0.1mM for 1h significantly enhanced the resistance level against the tested fungus in tomato seedlings 4 weeks after inoculation. The extracts from leaves of 15-day-old seedlings obtained from previously MeJA soaked seeds had the ability to inhibit in vitro spore germination of tested fungus. In these seedlings a significant increase in the levels phenolic compounds such as salicylic acid (SA), kaempferol and quercetin was observed. Up-regulation of phenylalanine ammonia-lyase (PAL5) and benzoic acid/salicylic acid carboxyl methyltransferase (BSMT) genes and down-regulation of the isochorysmate synthase (ICS) gene in response to exogenous MeJA application indicate that the phenylalanine ammonia-lyase (PAL), not the isochorismate (IC) pathway, is the primary route for SA production in tomato. Moreover, the increased accumulation of the flavonols quercetin and kaempferol appears closely related to the increase of PAL5, chalcone synthase (CHS) and flavonol synthase/flavanone 3-hydroxylase-like (FLS) genes. Elevated levels of salicylic acid in seedlings raised from MeJA-soaked seeds were simultaneously accompanied by a decrease of jasmonic acid, the precursor of MeJA, and an increase of 12-oxo-phytodienoic acid (OPDA), the precursor of jasmonic acid. The present results indicate that the priming of tomato seeds with 0.1mM MeJA before sowing enables the seedlings grown from these seeds to reduce the attack of the soil-borne fungal pathogen F. oxysporum f.sp. lycopersici, so it can be applied in practice.