μM Methyl Jasmonate Research Articles

Berry secondary metabolites and leaf physiological parameters are independently regulated by exogenous methyl jasmonate application in Sangiovese grapevines (Vitis vinifera L.)

The role of jasmonates as elicitor of secondary metabolites is well known, and many experiments have been conducted in grapevine to evaluate their effects on berry and wine quality. Even though most of these studies used foliar jasmonates applications, little investigations have been done to assess the effects on leaves which, in turn, may indirectly affect grape metabolism potentially involving a long distance signaling or crosstalk. In this experiment we jointly investigated the specific effect of jasmonates on grape berry secondary metabolites and leaf physiological parameters to better comprehend their elicitation mechanisms in grapevine. A 10 mM methyl jasmonate (MeJA) solution was applied during the lag-phase only on the leaves or only on the clusters and compared to an untreated control. The MeJA specifically affected leaf physiological parameters and berry metabolism in the treated area. When applied only on the leaves, gas exchange parameters and leaf efficiency were reduced, stimulating the senescence mechanisms, without affecting berry metabolism. On the contrary, MeJA applied on the clusters significantly delayed berry ripening, leading to hypothesize a re-route of the berry carbon resources through the biosynthesis of volatile organic compounds which were strongly increased, especially the monoterpenes in their glycosylated form.

Integrative effects of phytohormones in the phenolic acids production in Salvia verticillata L. under multi-walled carbon nanotubes and methyl jasmonate elicitation

Salvia verticillata L. is a well-known herb rich in rosmarinic acid (RA) and with therapeutic values. To better understand the possible roles of phytohormones in the production of phenolic acids in S. verticillata, in this work, we investigated some physiological and biochemical responses of the species to methyl jasmonate (MJ) and multi-walled carbon nanotubes (MWCNTs) as two effective elicitors. The leaves were sprayed with aqueous solutions containing 100 mg L−1 MWCNTs and 100 µM MJ and then harvested during interval times of exposure up to 96 h. The level of abscisic acid, as the first effective phytohormone, was altered in the leaves in response to MJ and MWCNTs elicitation (2.26- and 3.06-fold more than the control, respectively), followed by significant increases (P ˂ 0.05) detected in jasmonic acid and salicylic acid contents up to 8 h after exposure. Obtained data revealed that simultaneously with changes in phytohormone profiles, significant (P ˂ 0.05) rises were observed in the content of H2O2 (8.85- and 9.74-folds of control), and the amount of lipid peroxidation (10.18- and 17.01-folds of control) during the initial times after exposure to MJ and MWCNTs, respectively. Later, the content of phenolic acids increased in the elicited leaves due to changes in the transcription levels of key enzymes involved in their biosynthesis pathways, so 2.71- and 11.52-fold enhances observed in the RA content of the leaves after exposure to MJ and MWCNTs, respectively. It is reasonable to conclude that putative linkages between changes in some phytohormone pools lead to the accumulation of phenolic acids in the leaves of S. verticillata under elicitation. Overall, the current findings help us improve our understanding of the signal transduction pathways of the applied stimuli that led to enhanced secondary metabolite production in medicinal plants.

Methyl jasmonate improves resistance in scab-susceptible Red Delicious apple by altering ROS homeostasis and enhancing phenylpropanoid biosynthesis

Apple (Malus domestica) is an economically important rosaceous fruit crop grown at temperate climate zones. Nevertheless, its production is severely affected by scab disease caused by the ascomycetous fungus Venturia inaequalis (VI). Methyl jasmonate (MeJA) is a stress induced plant hormone, shown to induce resistance against wide range of pathogens. The current study investigated the role of MeJA in promoting scab tolerance in susceptible apple varieties through exogenous application of optimized (100 μM) MeJA concentration, followed by VI infection. According to our analysis, applying MeJA exogenously onto leaf surfaces resulted in increased membrane stability and decreased malondialdehyde levels in Red Delicious, suggesting that MeJA is capable of protecting tissues against oxidative damage through its role in restoring membrane stability. In addition, the changes in the levels of key antioxidative enzymes and reactive oxygen species (ROS) showed that exogenous MeJA maintains ROS homeostasis as well. Higher phenylalanine ammonia-lyase activity and increased accumulation of phenylpropanoids in MeJA-treated VI-infected plants indicated the MeJA reprogrammed phenylpropanoid biosynthesis pathway for scab tolerance. Our study of scab tolerance in apples induced by MeJA provides new insights into its physiological and biochemical mechanisms.

Exogenous methyl jasmonate regulates endogenous hormone synthesis of soilless cultivated Chinese chive to promote growth physiology and photosynthesis

Methyl jasmonate (MeJA) is involved in regulating various growth and development processes of plants, yet the underlying mechanisms remain unclear. Therefore, the objective of this study was to investigate the effects of exogenous MeJA on physiological growth, photosynthesis, and endogenous hormones in soilless cultivated Chinese chives. Four concentrations of MeJA (0, 300, 500, and 800 μM) were applied to the leaves of substrate-grown and hydroponics Chinese chives. The results showed that MeJA increased the leaf tissues water content and SPAD values of hydroponically Chinese chives, and 500 μM MeJA significantly enhanced the root activity and leaf carotenoids content of soilless cultivated Chinese chive, and promoted the activities of key enzymes of chlorophyll synthesis (ChlM and POR), thereby increasing chlorophyll a, chlorophyll b and total chlorophyll contents. Meanwhile, MeJA (500 μM) enhanced the activity of key enzymes in the Calvin cycle (Rubisco, FBA, FBPase, GAPDH, and TK), promoted CO2 fixation, improved photosynthetic carbon assimilation efficiency, and promoted Gs, Tr, and Pn, thereby enhancing photosynthesis. Moreover, MeJA (500 μM) significantly enhanced the instantaneous distribution (I-P) of the OJIP curve, enhanced the ability of the plastoquinone pool (PQ) to accept electrons, increased the quantum yield, promoted the apparent quantum flux per unit leaf area and energy flux ratio per unit PSII active reaction center, improved the electron transfer efficiency while reducing the heat dissipation energy flux per unit PSII active reaction center, and thus enhanced PSII activity. Additionally, exogenous MeJA (500 μM) promoted the accumulation of endogenous ZT, GA3, IAA, and ABA, but inhibited the upstream substrates for OPDA synthesis (MGDG and DGDG) in the JA synthesis pathway, and decreased the activities of JA synthases (LOX, AOC, and OPR), which in turn inhibited the synthesis of JA and MeJA. Changes in the relative content of MGDG/DGDG altered the membrane lipid composition of the photosynthetic membrane, which in turn altered the energy balance of the light reaction and improved the efficiency of electron transfer within the photosynthetic membrane, thereby enhancing the photosynthetic capacity. In conclusion, our study demonstrates that exogenous MeJA improves root activity and chlorophyll accumulation in soilless cultured Chinese chives, and adjusting the composition of photosynthetic membrane lipids by regulating the levels of endogenous hormones and JA-synthesizing substrates, promoting the efficiency of electron transfer, enhancing PSII activity, and promoting photosynthetic carbon fixation, thereby enhancing photosynthesis and promoting growth.

Metabolomics Reveals Rubiadin Accumulation and the Effects of Methyl Jasmonate Elicitation in Damnacanthus major Calli.

Callus suspension techniques have been considered attractive for improving bioactive metabolite productivity; methyl jasmonate (MeJA) is a widely used elicitor for stimulating synthetic pathways. In this study, a multivariate analysis-based metabolomics approach was employed to investigate the primary and specialized metabolites in the leaves, unelicited calli, and 100 or 200 μM MeJA elicited calli of Damnacanthus major. Rubiadin, a powerful anthraquinone with various therapeutic properties, was only identified in D. major calli, accumulating in a MeJA elicitation concentration-dependent manner. Callus cultures also contained high levels of amino acids, sugars, and phenolic compounds, indicating energy metabolism and metabolic adaptation responses for proliferation and stabilization. Regarding MeJA application, elicited calli contained higher amounts of quinic acid, kaempferol, and glucose with lower amounts of sucrose and raffinose than those in the unelicited control, which were closely related to protective mechanisms against MeJA. Moreover, excessive elicitation increased the asparagine, fructose, and raffinose levels and decreased the glucose and sucrose levels, which was ascribed to increased activation of the aminoacyl-tRNA biosynthesis pathway and wider utilization of glucose than of fructose after sucrose degradation. These results will be useful for optimizing plant cell culture techniques to achieve high production rates for valuable specialized metabolites.

Mechanism of exogenous methyl jasmonate in regulating the quality of fresh-cut Chinese water chestnuts.

Fresh-cut Chinese water chestnuts (CWCs) are susceptible to yellowing and browning during storage due to mechanical damage and the loss of protective outer skin, adversely affecting their marketability and shelf life. Methyl jasmonate (MeJA) is currently extensively used for food preservation, but it has not been used in Chinese water chestnuts. This study investigated the effect of MeJA treatment on the quality of fresh-cut CWCs. Fresh-cut CWCs immersed in 20 μM MeJA solution for 10min and stored at 10°C for 5d effectively delayed the yellowing process, reduced the respiration rate, and minimized the weight and soluble solids loss during storage. In addition, MeJA treatment induced the activities of superoxide dismutase (SOD) and catalase (CAT), which improved the antioxidant capacity of fresh-cut CWCs and inhibited the generation of reactive oxygen species (ROS). Meanwhile, MeJA treatment inhibited the activities of phenylalanine aminotransferase (PAL), polyphenol oxidase (PPO) and peroxidase (POD). The results of quantitative real-time PCR (qRT-PCR) showed that MeJA down-regulated the expression of CwCHS1, CwCHS2, CwCHS3 and CwCHI2 in freshly cut CWCs and inhibited the accumulation of flavonoids, thus delaying the surface discoloration of freshly cut CWCs.

Exploring novel insights: Methyl jasmonate treatment reveals novel lncRNA-mediated regulation of secondary metabolite biosynthesis pathways in Echinacea purpurea

RNA-seq analysis has revolutionized the discovery of long non-coding RNAs (lncRNAs) in medicinal plants like Echinacea purpurea (L.) Moench, commonly known as purple coneflower. These lncRNAs potentially play crucial roles in regulating the biosynthesis of bioactive secondary metabolites. Our study aimed to identify regulatory lncRNAs involved in these pathways by treating 40-day-old E. purpurea seedlings with 100 μM methyl jasmonate (MeJA). Subsequently, RNA-sequencing was performed, identifying 509 differentially expressed transcripts for co-expression network analysis. The correlation between differentially expressed lncRNAs and coding transcripts was calculated, constructing a gene network to identify hub lncRNAs and their associated genes. Gene ontology and KEGG enrichment analyses were conducted to gain insights into the functions of these hub differentially expressed lncRNAs (DElncRNAs). Results revealed that these hub DElncRNAs regulate key genes involved in various pathways. For instance, CSE and BEBT are associated with the conversion of caffeoylshikimate to caffeate and shikimate, respectively. Additionally, SAT and NEC3 contribute to alkaloid biosynthesis, while NES1 and CFAT are involved in the biosynthesis of aromatic compounds, phenylpropanoids, and terpenoids. HST and SILD are associated with lignin biosynthesis. Furthermore, these lncRNAs mediate the acyl group transfer on both shikimate and quinate in the phenylpropanoid and flavonoid biosynthesis pathways. In summary, our findings offer comprehensive insights into the transcriptomic and metabolomic changes induced by methyl jasmonate treatment. We provide novel insights into the regulatory mechanisms of secondary metabolite biosynthesis, specifically highlighting the role of lncRNAs in E. purpurea.

Methyl jasmonate suppressed the pericarp browning in postharvest longan fruit by modulating membrane lipid and energy metabolisms

Methyl jasmonate (MeJA) is an important bioactive metabolite in fruits and vegetables that regulates various physiological processes. The effects of MeJA on pericarp browning in longan fruit and its underlying mechanism were investigated. Results showed that treatment with 100 μM MeJA substantially suppressed the development of pericarp browning in harvested longan fruit. Compared to untreated fruit, MeJA-treated fruit exhibited reduced cell membrane permeability during storage. Meanwhile, MeJA-treated fruit displayed lower levels of phosphatidic acid and higher content of phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol, and phosphatidylethanolamine through suppressing the activities of key enzymes involved in membrane lipids metabolism, such as phospholipases, lipase and lipoxygenase. Furthermore, MeJA treatment enhances the energy status of the fruit, evidenced by elevated the levels of adenosine triphosphate and energy charge. This effect could be attributed to the enhanced activities of various energy metabolism enzymes. Overall, all results suggest that MeJA is a promising agent for inhibiting pericarp browning in longan fruit through modulation of membrane lipid and energy metabolisms.

Cell culture of Euphorbia fischeriana and enhancement of terpenoid accumulation through MeJA elicitation

Euphorbia fischeriana Steud is a perennial medicinal plant belonging to the Euphorbiaceae family, but its clinical application has been limited due to the scarcity of natural raw materials. Therefore, this study attempted to provide a new method for producing plant materials of E. fischeriana by cell culture. During cell culture, the effects of concentrations of plant growth regulators and sucrose were investigated to improve the culture efficiency. The results showed that the combination of 1.5 mg/L 6-benzylaminopurine and 0.2 mg/L naphthaleneacetic acid, together with a sucrose concentration of 20 g/L in the medium was appropriate for cell growth and terpenoid accumulation. Furthermore, this study applied an elicitation strategy with methyl jasmonate (MeJA) to enhance terpenoid production and investigated the involvement of signaling molecules, such as nitric oxide (NO) and hydrogen peroxide (H2O2). The results indicated that terpenoid accumulation depended on the concentration and treatment duration of MeJA. The maximum total terpenoid content was obtained when the cells were treated with 100 μM MeJA for 4 days. The levels of NO and H2O2 in the cells increased after MeJA treatment and peaked at 8 h and 18 h, respectively, suggesting the involvement of NO and H2O2 in MeJA-induced terpenoid synthesis. The findings of this study demonstrated the potential of cell culture as a method for obtaining plant materials of E. fischeriana.

Factors Affecting the Bioproduction of Resveratrol by Grapevine Cell Cultures under Elicitation.

Here we present a study of the characterization and optimization of the production of trans-Resveratrol (t-R) in grape (Vitis vinifera cv. Gamay) cell cultures elicited with methyl jasmonate (MeJA) and dimethyl-β-cyclodextrin (DIMEB). The aim of this study was to determine the influence of a number of factors of the grapevine cell culture on t-R production level in 250 mL shaken flasks that would enable the better control of this bioproduction system when it is upscaled to a 2 L stirred bioreactor. The factors included the optimal growth phase for elicitation, the concentration of elicitors and of biomass, the order of addition of elicitors, and the illumination regime and ageing of cells. We found out that the optimal biomass density for the production of t-R was 19% (w/v) with an optimal ratio of 0.5 g DIMEB/g biomass. The most productive concentrations of the elicitors tested were 50 mM DIMEB and 100 µM MeJA, reaching maximum values of 4.18 mg·mL-1 and 16.3 mg·g biomass-1 of t-R concentration and specific production, respectively. We found that the order of elicitor addition matters since, as compared with the simultaneous addition of both elicitors, the addition of MeJA 48 h before DIMEB results in ca. 40% less t-R production, whilst there is no significant difference when MeJA is added 48 h after DIMEB. Upon upscaling, the better conditions tested for t-R production were aeration at 1.7 vol/vol/min without agitation, 24 °C, and 30 g·L-1 sucrose, achieving production rates similar to those obtained in shaken flasks.

HS-SPME-GC-MS-based untargeted metabolomics reveals the enhancement of pungent flavor quality in soilless-cultivated Chinese chives by preharvest application of methyl jasmonate

To improve the pungent flavor quality of soilless cultivated Chinese chives (Allium tuberosum Rottler), the effect of foliar spraying with methyl jasmonate (MeJA) was studied. Electronic nose analysis showed that 500 μM MeJA significantly promoted the accumulation of aromatic compounds and organic sulfides in soilless-cultivated Chinese chives, as well as the content of pungent flavor metabolites, such as enzymatic pyruvic acid (24.9%–69.9%) and the garlic odor compounds alliin (22.1%–51.4%) and methionine (8.0%–62.7%). Using the HS-SPME-GC-MS technique, fifteen species of 186 volatile metabolites were detected in Chinese chive leaves treated with MeJA, and the sulfur compounds were dominating between them (49.6%–61.7%). Metabolomics and chemometrics analysis identified the volatile biomarkers of MeJA-treated substrate culture and hydroponic Chinese chives as dimethyl disulfide, dimethyl tetrasulfide, diallyl disulphide and allyl methyl sulfide, and methyl 2- propenyl disulfide, dimethyl tetrasulfide compound, respectively. Orthogonal partial least squares discriminant analysis indicated that MeJA treatment enhanced the pungency of Allium tuberosum mainly by increasing the accumulation of dimethyl sulfide and allyl sulfide compounds. Current study provides theoretical and technical basis for improving the pungent flavor quality of soilless-cultivated Chinese chives.

In vitro production of steroidal saponin, total phenols and antioxidant activity in callus suspension culture of Paris polyphylla Smith: an important Himalayan medicinal plant.

Paris polyphylla Smith (Melanthiaceae) family, which is native to the Himalayan region, has received a lot of attention recently due to its extensive history of usage in traditional medicine. The production of steroidal saponin from callus suspension cultures of P. polyphylla was observed in the current study. The current study attempted to develop a P. polyphylla plant callus suspension culture through optimization of cultivation technique for callus suspension, quantification of total phenolic components and estimation of the extract's antioxidant activity. A light-yellow callus was formed within six weeks of cultivating rhizomes on Murashige and Skoog (MS) media supplemented with Thidiazuron (TDZ). Furthermore, the effect of TDZ, Methyl Jasmonate (MeJA), and Yeast Extract (YE) on callus growth, steroidal saponin (dioscin and diosgenin), total phenolic content, total flavonoids, total tannin, and total antioxidant activity was also measured. The medium containing 0.5 μM TDZ depicted the maximum callus biomass (2.98 g fresh weight). Significantly high phenolic and tannin content was observed in the MS medium containing 50 μM MeJA, whereas, no significant increase was observed in total tannin production in any treatment. Three in vitro assays, DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2'-azino-bis (3-ethylbenzothiazoline- 6-sulfonic acid)) and FRAP (ferric ion reducing antioxidant potential) and FC (Folin-Ciocalteu), were used to assess antioxidant potential of callus. Maximum antioxidant analysis reported in 1.0 μM TDZ (6.89 mM AAE/100 g) containing medium followed by 50 μM MeJA (6.44 mM AAE/100g). The HPLC analysis showed a high presence of dioscin and diosgenin (5.43% and 21.09%, respectively) compared to the wild sample (2.56% and 15.05%, respectively). According to the results, callus produced on media supplemented with 50 μM MeJA have significant phenolic contents and elevated antioxidant activity; nevertheless, callus growth was greater in the presence of 0.5 μM TDZ. The findings of the current study have commercial implications since greater biomass production will result in active phytochemicals that the pharmaceutical and nutraceutical sectors are in need desperately.

Improvement of storage quality of ‘Hayward’ kiwifruit by MeJA combined with SA treatment through activation of phenylpropane metabolism

Kiwifruit are highly susceptible to pathogenic infestation, which can lead to spoilage during postharvest storage. Therefore, there is an urgent need to develop natural and efficient preservation methods. A compound preservative consisting of 10 μM MeJA (methyl jasmonate) and 1 mM SA (salicylic acid) was used to preserve kiwifruit during storage. Sensory, quality, and phenylpropane metabolism-related indicators were assessed at 20 °C during kiwifruit storage in groups treated with sterile water, MeJA, SA, or a combination of MeJA and SA. The results indicated that the hormone treatment groups exhibited varying degrees of efficacy in suppressing spoilage caused by pathogenic infestation. The combination treatment group demonstrated superior efficacy in comparison to the other treatment groups, as evidenced by its ability to suppress hardness reduction, delay decay rate, and disease index increase, retard soluble solids accumulation, activate enzymes PAL, C4H, and 4CL involved in phenylpropane metabolism and enhance total phenol content. The SA treatment group exhibited the second highest efficacy, whereas the MeJA treatment group demonstrated the lowest efficacy. The results showed that at the end of storage, the PAL activity and total phenolic content of kiwifruit in the combination treatment increased by 52.72%, 39.98%, 17.89%, and 98.19%, 22.47%, 14.93% compared to the control, MeJA and SA treatment alone, respectively. The findings of this study may serve as a theoretical foundation and technical guide for the utilization of MeJA in combination with SA during kiwifruit storage and preservation.

Effect of stress hormones on the metabolome of a suspension culture of the aromatic medicinal plant Cymbopogon schoenanthus subsp. proximus

The current study aimed to evaluate and compare the effect of different concentrations (0.0–200.0 µM) of jasmonic acid (JA), methyl jasmonate (MeJA), and salicylic acid (SA) on suspension culture mass production and untargeted metabolic profiling of the medicinal plant Cymbopogon schoenanthus subsp. proximus. The addition of 50 µM MeJA improved the fresh weight of embryogenic tissue significantly. MeJA and SA did not affect tissue dry weight, whereas JA significantly decreased it. Based on 1H and 1H–13C NMR data and NMR databases, 50 compounds were identified. The addition of stress hormones resulted in the biosynthesis of novel metabolites like theophylline and syringate that were absent in control samples. In addition, significant variations in the concentrations of numerous compounds, including sugars, amino acids, organic acids, phenols, and alkaloids, were observed. The upregulation of trigonelline concentration was observed upon the addition of a higher concentration of MeJA (200 µM), whereas all tested concentrations of SA resulted in its upregulation. Addition of JA and SA causes significant changes in aminoacyl-tRNA biosynthesis pathway and amino acid metabolism pathways, such as alanine-aspartate and glutamate metabolism and arginine and proline metabolism. MeJA had significant impacts on glycolysis and starch-glucose metabolism pathways in addition to amino acids metabolism pathways. The present findings were successful in demonstrating a correlation and distinction between the effects of JA, MeJA, and SA, on the metabolome of Cymbopogon schoenanthus, a valuable medicinal plant. The identified metabolites and their associated pathways would be valuable in future biotechnology applications of the genus Cymbopogon.

Multifunctionality of Jasmonic Acid Accumulation during Aphid Infestation in Altering the Plant Physiological Traits That Suppress the Plant Defenses in Wheat Cultivar XN979.

Crop plants have coevolved phytohormone-mediated defenses to combat and/or repel their colonizers. The present study determined the effects of jasmonic acid (JA) accumulation during aphid infestation on the preference and performance of Sitobion miscanthi Takahashi (Hemiptera: Aphididae), and its potential role in fine-tuning hormone-dependent responses in XN979 wheat cultivar seedlings was evaluated via the transcriptional profiles of marker genes related to JA- and salicylic acid (SA)-dependent responses. The preference experiment and the life table data reveal that direct foliage spraying of 2.5 mM methyl jasmonate (MeJA) exhibited weak negative or positive effects on the preferential selection and the population dynamics and oviposition parameters of S. miscanthi. The transcription level of phytohormone biosynthesis genes shows that foliage spraying of MeJA significantly upregulated the marker genes in the JA biosynthesis pathway while downregulating the SA pathway. In addition, either MeJA treatment or previous aphid infestation significantly induced upregulated transcription of the genes involved in the JA- and SA-dependent defense responses, and the transcription level of the tryptophan decarboxylase (TaTDC) gene, which facilitates the conversion of L-tryptophan to tryptamine, was rapidly upregulated after the treatments as well. The main products of tryptamine conversion could play a crucial role in suppressing SA-dependent defense responses. These results will provide more experimental evidence to enable understanding of the antagonistic interaction between hormone signaling processes in cereals under aphid infestation.

Biomass and volatile compounds of rose-scented geranium under various elicitors and cultivation systems

The current experiment was conducted to investigate the biomass and essential oil of rose-scented geranium when exposed to elicitors. The plants were grown either in a soil medium or a soilless cultivation system. Elicitors, namely methyl jasmonate (MeJA)(150 and 300 μM) and salicylic acid (SA)(0.75 and 1.5 mM), were used as foliar applications. The measurements included evaluating physiological and biochemical parameters, as well as essential oil content and concentration. Additionally, aromatic compounds of geranium were assessed using the headspace and GC/MS method. Photosynthetic capacity and biomass were significantly higher in soilless-grown plants compared to soil-grown plants, particularly in terms of chlorophyll content, stomatal conductance, and leaf area. The biomass produced in the soilless system was ten times greater than that in soil-grown plants. MeJA and SA enhanced growth parameters and essential oil production. The interaction between the cultivation system and elicitors had a significant impact on biochemical and physiological traits. Notably, the highest photosynthetic capacity, biomass, essential oil concentration, and yield were achieved in plants treated with 300 μM MeJA and 0.75 mM SA concentrations under soilless media. The main constituents of volatile components in soilless-grown plants were linalool, citronellal, citronellol, and citronellyl formate. On the other hand, geranial and geranyl propionate were the predominant compounds in plants grown in soil. The citronellol:geraniol ratio (C/G ratio) served as a qualitative indicator of essential oil compounds in rose-scented geranium. The highest value of this ratio and the greatest essential oil yield were obtained in soilless-grown plants treated with 300 μM MeJA.

Foliar application of methyl jasmonate affects impatiens walleriana growth and leaf physiology under drought stress

ABSTRACT In this study, the effects of foliar applied methyl jasmonate (MeJA) on drought-stressed Impatiens walleriana growth and leaf physiology parameters: stomatal conductance, chlorophyll, flavonoid, anthocyanin, and nitrogen balance index (NBI), were evaluated. These parameters could serve as indicators of drought tolerance of I. walleriana, a popular horticultural plant worldwide that is very sensitive to drought. The experiment included four treatments: control, drought-stressed plants sprayed with distilled water, drought-stressed plants sprayed with 5 µM MeJA, and drought-stressed plants sprayed with 50 µM MeJA. Foliar spraying with MeJA was performed twice: seven days before and on the day of drought induction. The stressed plant groups were non-irrigated to achieve soil water contents (SWC) of 15 and 5%, while control plants were well-watered throughout the experiment (35–37% SWC). The results of this study showed that drought significantly reduced I. walleriana fresh and dry shoot weight, as well as total leaf area, but did not impact on dry matter content. The foliar application of MeJA improved growth parameters of I. walleriana, depending on the elicitor concentration and drought intensity. Stomatal conductance was slightly reduced at 5% SWC, and foliar applied MeJA at both concentrations. The flavonoid index was slightly reduced at 15 and 5% SWC when 50 µM MeJA was foliar applied, while there were no observed changes in the anthocyanin index in any treatments. The foliar application of 50 µM MeJA increased the chlorophyll index and NBI of I. walleriana at 5% SWC, indicating a contribution of the elicitor to plant drought tolerance at the physiological level.

Methyl jasmonate (MeJA) enhances salt tolerance of okra (Abelmoschus esculentus L.) plants by regulating ABA signaling, osmotic adjustment substances, photosynthesis and ROS metabolism

Methyl jasmonate (MeJA), as a plant growth regulator, which is involves in many morphological and physiological processes, plays an important role in defense systems of plants under stress conditions. However, the roles of physiological and biochemical mechanisms of enhancing salt tolerance of okra plants based on application of MeJA is poorly understood. In this study, the application of the investigated 50 μM MeJA significantly improved salt tolerance of okra plants based on the germination rates and culture pot experiment under salt stress. Based on optimal concentration of MeJA inducing salt tolerance of okra plants, application of 5 mM diphenyleneiodonium (NADPH oxidase inhibitor, DPI) and 50 μM MeJA + 5 mM DPI, respectively, significantly increased salt tolerance of okra plants. Assays on the content of component matter indicated the significant increases of JA, ABA, proline, soluble protein, soluble sugar, photosynthetic pigment and relative water, glutathione (GSH) and ascorbic acid (AsA) content and the significant decreases of hydrogen peroxide (H2O2), superoxide radicals (O2−) and malondialdehyde (MDA) content and electrolyte leakage rates were observed in okra plants with 50 μM MeJA under salt stress. The activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and peroxidase (POD) related to ROS scavenging were also enhanced in okra plants by applied MeJA under salt stress. Furthermore, the marked decreases of H2O2, O2- and MDA content, and the significant increases of CAT, GR and APX activities and GSH and ASA content involved in ASA-GSH cycle were observed in MeJA-okra, DPI-okra and MeJA+DPI-okra plants under salt stress. H2O2 acted a toxic accumulation of ROS rather than as a second messenger for signal transduction in okra plants. These results demonstrate that exogenous MeJA increases the accumulation of JA, ABA and proline, which enhances salt tolerance of okra plants, by regulating osmotic balance and protecting membrane integrity and photosynthesis and activating ROS scavenging system. As a conclusion, treating okra plants with 50 μM MeJA could alleviate the harmful effects of abiotic stresses.

Concentration-dependent impacts of exogenous methyl jasmonate (MeJA) on chlorophyll degradation of apple fruit during ripening

Although jasmonates (JAs) have been proved to regulate degreening of apple fruit, the relevant molecular mechanisms have not yet been clarified. Previous reports revealed that the effects of JAs on degreening of harvested horticultural crops might be dependent on concentration applied. Whether a similar result can be obtained from apple fruit is still unclear. This research explored the impacts of different concentrations of methyl jasmonate (MeJA) treatment on chlorophyll (Chl) degradation of postharvest apple fruit. Apples (Malus × domestica Borkh.) of commercial maturity were treated with 10 or 1500 µM MeJA and then stored at 20 ± 0.5 °C. The results indicated that exogenous 10 µM MeJA delayed degreening and ripening of apple fruit, whereas 1500 µM MeJA treatment had the opposite effects. Treatment with 10 µM MeJA alleviated Chl-oxidation by reducing Chl-peroxidase (POX) activity and reactive oxygen species (ROS) levels in chloroplast of apple peel during ripening, whereas 1500 µM MeJA treatment had the opposite effects. Activities of Magnesium-dechelatase (MDcase) and pheophytinase (PPH) in apple peel were differentially suppressed by 10 µM MeJA treatment while promoted by 1500 µM MeJA treatment during ripening. Application of 10 µM MeJA delayed the peak of endogenous jasmonic acid (JA) content, reduced jasmonate resistant 1 (JAR1) content and allene oxide synthase (AOS) activity, and differentially down-regulated expression of MdNYC3, MdNYE1a, MdPPH1, MdPAO6, MdPAO8, MdRCCR2 and MdMYC2a in apple peel during ripening, whereas opposite results were obtained from the 1500 µM MeJA-treated apple fruit. At the late ripening stage, MdHCAR expression in apple peel was promoted by 10 µM MeJA treatment while reduced by 1500 µM MeJA treatment. Transcript levels of MdNYC1 and MdNOL2 were generally reduced by both treatments at the late ripening stage. Transient overexpression of MdMYC2a accelerated Chl degradation of apple peel by promoting PPH and MDcase activities and enhancing expression of the above Chl catabolic genes (CCGs), except MdHCAR whose expression was down-regulated by it during ripening. The AOS activity, JA and JAR1 contents in apple peel were increased after transient overexpression of MdMYC2a during ripening. These data indicated that the PAO pathway and Chl-oxidation were regulated by JA signal in apple peel during ripening, and exogenous MeJA regulated Chl degradation of apple fruit in a concentration-dependent manner.

Alterations in Physiological, Biochemical, and Molecular Responses of Impatiens walleriana to Drought by Methyl Jasmonate Foliar Application

Drought stress affects plant growth and development through several mechanisms, including the induction of oxidative stress. To cope with drought, plants have drought tolerance mechanisms at the physiological, biochemical, and molecular levels. In this study, the effects of foliar application of distilled water and methyl jasmonate (MeJA) (5 and 50 µM) on the physiological, biochemical, and molecular responses of Impatiens walleriana during two drought regimes (15 and 5% soil water content, SWC) were investigated. The results showed that plant response depended on the concentration of the elicitor and the stress intensity. The highest chlorophyll and carotenoid contents were observed at 5% SWC in plants pre-treated with 50 µM MeJA, while the MeJA did not have a significant effect on the chlorophyll a/b ratio in drought-stressed plants. Drought-induced formation of hydrogen peroxide and malondialdehyde in plants sprayed with distilled water was significantly reduced in plant leaves pretreated with MeJA. The lower total polyphenol content and antioxidant activity of secondary metabolites in MeJA-pretreated plants were observed. The foliar application of MeJA affected the proline content and antioxidant enzyme activities (superoxide dismutase, peroxidase, and catalase) in plants that suffered from drought. The expression of abscisic acid (ABA) metabolic genes (IwNCED4, IwAAO2, and IwABA8ox3) was the most affected in plants sprayed with 50 µM MeJA, while of the four analyzed aquaporin genes (IwPIP1;4, IwPIP2;2, IwPIP2;7, and IwTIP4;1), the expression of IwPIP1;4 and IwPIP2;7 was strongly induced in drought-stressed plants pre-treated with 50 µM MeJA. The study's findings demonstrated the significance of MeJA in regulating the gene expression of the ABA metabolic pathway and aquaporins, as well as the considerable alterations in oxidative stress responses of drought-stressed I. walleriana foliar sprayed with MeJA. The results improved our understanding of this horticulture plant's stress physiology and the field of plant hormones' interaction network in general.