Application Of Methyl Jasmonate Research Articles

Exogenous Application of Methyl Jasmonate Enhanced the Cold Tolerance of Jasminum sambac through Changes in Metabolites and Antioxidants

Jasminum sambac is an excellent ornamental species that is renowned worldwide for its pure white flowers and strong fragrance. However, its intolerance to low temperatures limits its cultivation range. Methyl jasmonate (MeJA), an essential plant growth regulator, plays a significant role in assisting plants to resist various stresses. Hence, this study was carried out to decipher the capabilities of diverse concentrations of MeJA in helping J. sambac to resist cold stress by measuring different physiological indexes. A normal temperature (15 °C/10 °C) and low temperature (7 °C/2 °C) were applied to J. sambac seedlings, and a one-way analysis of variance followed by a Duncan’s multiple range test was adopted to compare the differences between the indicators under 5 μmol·L−1, 10 μmol·L−1 and 20 μmol·L−1 of MeJA treatments. The results showed that cold stress significantly decreased the contents of soluble sugar and soluble protein, while the application of MeJA at 10 μmol·L−1 and 20 μmol·L−1 resulted in a partial recovery. In addition, cold stress dramatically hindered the accumulation of total chlorophyll in leaves. Exogenous MeJA elevated the total chlorophyll content during the whole sampling period. The hydrogen peroxide and malondialdehyde levels generally increased in response to low temperatures, and they caused adverse effects on J. sambac, whereas this was effectively alleviated through the application of MeJA. MeJA was also able to improve the resistance of J. sambac by boosting the activity of antioxidant enzymes to remove the excess of reactive oxygen species. In conclusion, we highlighted that exogenous MeJA could attenuate the negative consequences of cold stress for J. sambac, and 10 μmol·L−1 of MeJA treatment could be a feasible strategy for enhancing the resistance of J. sambac to low temperatures and promoting its growth.

The Arabidopsis ARID-HMG DNA-BINDING PROTEIN 15 modulates JA signaling by regulating MYC2 during pollen development.

The intricate process of male gametophyte development in flowering plants is regulated by jasmonic acid (JA) signaling. JA signaling initiates with the activation of the basic-helix-loop-helix (bHLH) transcription factor (TF), MYC2, leading to the expression of numerous JA-responsive genes during stamen development and pollen maturation. However, the regulation of JA signaling during different stages of male gametophyte development remains less understood. This study focuses on the characterization of the plant ARID-HMG DNA-BINDING PROTEIN 15 (AtHMGB15), and its role in pollen development in Arabidopsis (Arabidopsis thaliana). Phenotypic characterization of a T-DNA insertion line (athmgb15-4) revealed delayed bolting, shorter siliques, and reduced seed set in mutant plants compared to the wildtype. Additionally, AtHMGB15 deletion resulted in defective pollen morphology, delayed pollen germination, aberrant pollen tube growth, and a higher percentage of non-viable pollen grains. Molecular analysis indicated the down-regulation of JA biosynthesis and signaling genes in the athmgb15-4 mutant. Quantitative analysis demonstrated that jasmonic acid and its derivatives were approximately tenfold lower in athmgb15-4 flowers. Exogenous application of methyl jasmonate could restore pollen morphology and germination, suggesting that the low JA content in athmgb15-4 impaired JA signaling during pollen development. Furthermore, our study revealed that AtHMGB15 physically interacts with MYC2 to form a transcription activation complex. This complex promotes the transcription of key JA signaling genes, the R2R3-MYB TFs MYB21 and MYB24, during stamen and pollen development. Collectively, our findings highlight the role of AtHMGB15 as a positive regulator of the JA pathway, controlling the spatiotemporal expression of key regulators involved in Arabidopsis stamen and pollen development.

Effects of Exogenous Application of Methyl Jasmonate and Salicylic Acid on the Physiological and Molecular Response of 'Dusa' Avocado to Rosellinia necatrix.

Methyl jasmonate (MeJA) and salicylic acid (SA) are important in mediating plant responses to abiotic and biotic stresses. MeJA and SA can act as elicitors by triggering plant defense responses similar to those induced by pathogens and may even provide long-term protection against them. Thus, exogenous application of MeJA and SA could protect susceptible avocado plants against white root rot (WRR) disease caused by the necrotrophic fungus Rosellinia necatrix, one of the main diseases affecting avocado orchards. This work evaluates the effects of MeJA or SA on the physiological and molecular response of susceptible 'Dusa' avocado rootstock and their ability to provide some protection against WRR. The application of MeJA and SA in avocado increased photoprotective mechanisms (nonphotochemical chlorophyll fluorescence quenching) and upregulated the glutathione S-transferase, suggesting the triggering of mechanisms closely related to oxidative stress relief and reactive oxygen species scavenging. In contrast to SA, MeJA's effects were more pronounced at the morphoanatomical level, including functional traits such as high leaf mass area, high stomatal density, and high root/shoot ratio, closely related to strategies to cope with water scarcity and WRR disease. Moreover, MeJA upregulated a greater number of defense-related genes than SA, including a glu protease inhibitor, a key gene in avocado defense against R. necatrix. The overall effects of MeJA increased 'Dusa' avocado tolerance to R. necatrix by inducing a primed state that delayed WRR disease symptoms. These findings point toward the use of MeJA application as an environmentally friendly strategy to mitigate the impact of this disease on susceptible avocado orchards.

Effects of foliar application of methyl jasmonate and/or urea, conventional or via nanoparticles, on grape volatile composition.

Viticulture has adapted foliar applications of biostimulants as a tool to improve crop quality. Recently, nanotechnology has been incorporated as a strategy to reduce the loss of biostimulants and treat nutrient deficiencies. Therefore, the present study aimed to investigate the effect of foliar applications of amorphous calcium phosphate nanoparticles (ACP) doped with methyl jasmonate (ACP-MeJA) and urea (ACP-Ur), individually or together (ACP-MeJA+Ur), on the content of volatile compounds in 'Tempranillo' grapes, compared to the conventional application of MeJA and Ur, individually or in combination (MeJA+Ur). The results showed that nanoparticle treatments reduced the total C6 compounds and some carbonyl compounds in the grape musts. This is of novel interest because their presence at high levels is undesirable to quality. In addition, some aroma-positive compounds such as nerol, neral, geranyl acetone, β-cyclocitral, β-ionone, 2-phenylethanal and 2-phenylethanol increased, despite applying MeJA and Ur at a lower dose. Consequently, although few differences in grape volatile composition were detected, nanotechnology could be an option for improving the aromatic quality of grapes, at the same time as reducing the required doses of biostimulants and generating more sustainable agricultural practices. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Training System and Methyl Jasmonate Application: A Tool to Improve Major Polyphenol Consumed by the Brazilian Population in Grape Juice

Training System and Methyl Jasmonate Application: A Tool to Improve Major Polyphenol Consumed by the Brazilian Population in Grape Juice

The ameliorative effects of exogenous methyl jasmonate on grapevines under drought stress: Reactive oxygen species, carbon and nitrogen metabolism

Drought stress is recognized as one of the foremost abiotic stresses for worldwide agriculture. Methyl jasmonate (MeJA) is a vital phytohormone that is involved in plant growth, development, and stress adaptation. This study aimed to investigate the influence of exogenous MeJA on carbon and nitrogen metabolism in grapevine leaves under drought stress. Two-year-old grape cuttings (Vitis vinifera L.) were foliar sprayed with either 100 μM MeJA solution or distilled water and then exposed to drought stress. The results showed that exogenous MeJA increased the activities of superoxide dismutase (21 %) and catalase (16 %), resulting in decreased accumulation of reactive oxygen species. Drought stress critically disturbed the processes of photosynthesis, sucrose and starch metabolism, nitrogen assimilation, and amino acid metabolism. MeJA pretreatment improved the photosynthetic capacity and decreased the activities of sucrose synthase (31 %), acid invertase (15 %), and neutral invertase (27 %), thereby improving the accumulation of starch (10 %) and sucrose (90 %). In addition, MeJA pretreatment promoted nitrogen assimilation under drought stress. An increase in activities of nitrate reductase (60 %) and glutamine synthetase (13 %), and a decrease in NH4+ content was observed. Meanwhile, the MeJA application promoted the accumulation of proline and γ-aminobutyric acid, which contributed to the osmotic adjustment and ROS scavenging. In conclusion, exogenous MeJA could promote drought tolerance of grapevines by alleviating oxidative damage and regulating carbon and nitrogen metabolism.

Comparative effects of two elicitors on the essential oil biosynthesis of simulated hail-damaged rose geranium (Pelargonium graveolens L’Hér. cv. ‘BOURBON’)

Extreme abiotic stress factors such as hail, defoliation, salinity, and moisture stress can affect the biosynthesis of essential oils. To mitigate this, most commercial farmers globally use agricultural crop insurance; however, this is not the case for most smallholder and emerging farmers in southern Africa, as agricultural insurance tends to be expensive when included in the production system. Therefore, this study aimed to investigate the comparative effects between two elicitors: abscisic acid (ABA) and methyl jasmonate (MeJA) on essential oil biosynthesis of simulated hail-damaged rose geranium (Pelargonium graveolens L’Hér.) as an alternative strategy to improve the essential oil biosynthesis following severe hail damage of rose geranium. The study was conducted in a 72 m2 temperature-controlled greenhouse, using a 4 x 2 factorial treatment design arranged in a randomized complete block design. Treatments comprised four levels of two elicitors at 75 µM (ABA), 150 μM (ABA), 10 mM (MeJA), and 20 mM (MeJA), applied in two different application periods (daily application for either 7 or 14 days). The simulation of hail damage was through 100% defoliation, with decapitation of the terminal buds. A significant interaction was observed between the elicitor treatment, and length of the period of application on essential oil yield (mass), where the highest yield was observed when MeJA (10 mM) was applied for seven consecutive days compared to the 14-day treatment. Geraniol esters were partially improved by the application of MeJA at 10 mM. Application of the two elicitors improved citronellol, geraniol, and linalool, regardless of the length of the period of application. The citronellol to geraniol ratio, a determining factor of essential oil quality, was 2.7:1 when MeJA was applied at 10 mM, significantly better than any application level of ABA. Therefore, it could be concluded that the application of MeJA at 10 mM may improve the essential oil biosynthesis of hail-damaged rose geranium plants compared to ABA at any level, and this may be adopted as a possible mitigating strategy by the emerging farmers and growers in southern Africa for improving the biosynthesis of rose geranium post hail damage. On the other hand, where growers are interested in higher contents of linalool and citronellol, ABA may be used at any level. Key words: Defoliation, essential oil, yield, phytohormone, citronellol, geraniol, linalool

Magnaporthe oryzae infection triggers rice resistance to brown planthopper through the influence of jasmonic acid on the flavonoid biosynthesis pathway.

In agroecosystems, plants are constantly exposed to attack from diverse herbivorous insects and microbes, and infestation with one species may change the plant defense response to other species. In our investigation of the relationships among rice plants, the brown planthopper Nilaparvata lugens (Stål) and the rice blast fungus Magnaporthe oryzae, we observed a significant increase in the resistance of rice treated with rice blast to N.lugens, as evidenced by improved plant survival rates in a small population resistance study. Subsequent transcriptome data analysis revealed that the rice blast fungus can induce the expression of genes in the jasmonic acid (JA) and flavonoid pathways. Similar to the flavonoid pathway, the JA pathway also contains 2 types of genes that exhibit similar and opposite trends in response to N.lugens and rice blast. Among these genes, the osjaz1 mutant and the osmyc2 mutant were phenotypically confirmed to positively and negatively regulate rice resistance to N.lugens and rice blast, respectively. Subsequent mass spectrometry and quantification experiments showed that the exogenous application of methyl jasmonate (MeJA) can induce the accumulation of eriodictyol, naringenin and quercetin, as well as the expression of OsF3H, Os4CL5 and OsCHI in the flavonoid pathway. This suggests a close connection between the JA pathway and the flavonoid pathway. However, OsF3'H, which negatively regulates rice resistance to N.lugens and rice blast, did not show increased expression. Phenotypic and molecular experiments confirmed that OsMYC2 can bind to and inhibit the expression of OsF3'H, thus revealing the mechanism of rice resistance to N.lugens after treatment with rice blast. These findings will deepen our understanding of the interactions among rice, N.lugens and rice blast.

Effect of methyl jasmonate and GA3 on canola (Brassica napus L.) growth, antioxidants activity, and nutrient concentration cultivated in salt-affected soils

Salinity stress is a significant challenge in agricultural production. When soil contains high salts, it can adversely affect plant growth and productivity due to the high concentration of soluble salts in the soil water. To overcome this issue, foliar applications of methyl jasmonate (MJ) and gibberellic acid (GA3) can be productive amendments. Both can potentially improve the plant’s growth attributes and flowering, which are imperative in improving growth and yield. However, limited literature is available on their combined use in canola to mitigate salinity stress. That’s why the current study investigates the impact of different levels of MJ (at concentrations of 0.8, 1.6, and 3.2 mM MJ) and GA3 (0GA3 and 5 mg/L GA3) on canola cultivated in salt-affected soils. Applying all the treatments in four replicates. Results indicate that the application of 0.8 mM MJ with 5 mg/L GA3 significantly enhances shoot length (23.29%), shoot dry weight (24.77%), number of leaves per plant (24.93%), number of flowering branches (26.11%), chlorophyll a (31.44%), chlorophyll b (20.28%) and total chlorophyll (27.66%) and shoot total soluble carbohydrates (22.53%) over control. Treatment with 0.8 mM MJ and 5 mg/L GA3 resulted in a decrease in shoot proline (48.17%), MDA (81.41%), SOD (50.59%), POD (14.81%) while increase in N (10.38%), P (15.22%), and K (8.05%) compared to control in canola under salinity stress. In conclusion, 0.8 mM MJ + 5 mg/L GA3 can improve canola growth under salinity stress. More investigations are recommended at the field level to declare 0.8 mM MJ + 5 mg/L GA3 as the best amendment for alleviating salinity stress in different crops.

Elicitation of salicylic acid and methyl jasmonate provides molecular and physiological evidence for potato susceptibility to infection by Erwinia carotovora subsp. carotovora

Among the range of severe plant diseases, bacterial soft rot caused by Erwinia carotovora is a significant threat to crops. This study aimed to examine the varying response patterns of distinct potato cultivars to the influence of E. carotovora. Furthermore, it seeks to highlight the potential role of salicylic acid (SA) and methyl jasmonate (MeJA) in stimulating the antioxidant defence system. We collected eight bacterial isolates from diseased and rotted tubers which were morphologically and physiologically identified as E. carotovora subsp. carotovora. We conducted a greenhouse experiment to analyse the antioxidant responses of three different potato cultivars (Diamont, Kara, and Karros) at various time intervals (2, 4, 6, 8, 12, and 24 h) after bacterial infection (hpi). We assessed the extent of disease damage by applying a foliar spray of 0.9 mM salicylic acid (SA) and 70 μM methyl jasmonate (MeJA). Inoculating with Ecc led to an increase in total phenolic levels, as well as the activities and gene expression of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POX) as time progressed. Additionally, the application of SA and MeJA resulted in a further increase relative to the diseased treatments. The Karros cultivar, unlike the Diamont and Kara cultivars, demonstrated the highest expression levels of PAL, PPO and POX through inoculation, reflecting its higher levels of activity and resistance. Furthermore, the genetic response of potato cultivars to infection at 0 hpi varied depending on their susceptibility. The examination of the rate of PAL activity upregulation following SA or MeJA stimulation clarifies the cultivars' susceptibility over time. In conclusion, the study identified E. carotovora subsp. carotovora as the most virulent isolate causing soft rot disease in potato tubers. It further revealed that the Karros cultivar displayed superior resistance with high activities and gene expression of PAL, PPO and POX, while the cv. Diamont exhibited sensitivity. Additionally, foliar exposure to SA and MeJA induced antioxidant responses, enhancing the potato plants' resistance against Ecc pathogenesis and overall plant defence.

Transcriptomic data reveals the dynamics of terpenoids biosynthetic pathway of fenugreek

Medicinal plants are rich sources for treating various diseases due their bioactive secondary metabolites. Fenugreek (Trigonella foenum-graecum) is one of the medicinal plants traditionally used in human nutrition and medicine which contains an active substance, called diosgenin, with anticancer properties. Biosynthesis of this important anticancer compound in fenugreek can be enhanced using eliciting agents which involves in manipulation of metabolite and biochemical pathways stimulating defense responses. Methyl jasmonate elicitor was used to increase diosgenin biosynthesis in fenugreek plants. However, the molecular mechanism and gene expression profiles underlying diosgening accumulation remain unexplored. In the current study we performed an extensive analysis of publicly available RNA-sequencing datasets to elucidate the biosynthesis and expression profile of fenugreek plants treated with methyl jasmonate. For this purpose, seven read datasets of methyl jasmonate treated plants were obtained that were covering several post-treatment time points (6–120 h). Transcriptomics analysis revealed upregulation of several key genes involved in diosgenein biosynthetic pathway including Squalene synthase (SQS) as the first committed step in diosgenin biosynthesis as well as Squalene Epoxidase (SEP) and Cycloartenol Synthase (CAS) upon methyl jasmonate application. Bioinformatics analysis, including gene ontology enrichment and pathway analysis, further supported the involvement of these genes in diosgenin biosynthesis. The bioinformatics analysis led to a comprehensive validation, with expression profiling across three different fenugreek populations treated with the same methyl jasmonate application. Initially, key genes like SQS, SEP, and CAS showed upregulation, followed by later upregulation of Δ24, suggesting dynamic pathway regulation. Real-time PCR confirmed consistent upregulation of SQS and SEP, peaking at 72 h. Additionally, candidate genes Δ24 and SMT1 highlighted roles in directing metabolic flux towards diosgenin biosynthesis. This integrated approach validates the bioinformatics findings and elucidates fenugreek’s molecular response to methyl jasmonate elicitation, offering insights for enhancing diosgenin yield. The assembled transcripts and gene expression profiles are deposited in the Zenodo open repository at https://doi.org/10.5281/zenodo.8155183.

Influence of Elicitors on Growth and Yield of Black Cumin (Nigella sativa L.) Varieties

Black cumin is a miracle herb, an emerging seed spice and a medicinal plant of great demand. Black cumin has been used since thousands of years as a spice and food preservative as well as a protective and curative remedy for several disorders. A field experiment was conducted at the Department of Plantation, Spices, Medicinal and Aromatic Crops, College of Horticulture, UHS Campus, GKVK, Bengaluru, from November 2018 to March 2019. The experiment followed a randomized complete block design (RCBD) with three replications and included two factors: varieties and elicitors. Among the various treatment combinations, foliar application of methyl jasmonate at 100 ppm resulted in the highest recorded values for plant height (46.7 cm), primary branches (5.43), stem diameter (4.62 mm), dry weight of plants (8.42 g), and plant spread (397 cm2) when applied with nitric oxide (Sodium Nitroprusside (SNP)) at 2 mM on Pant Krishna variety. Conversely, the significantly highest chlorophyll content in leaves was observed in the Azad Kalonji variety sprayed with salicylic acid at 100 ppm. Furthermore, the significantly highest numbers of capsules (22.60), seeds per capsule (84.28), and seed yield per hectare (12.40 q) were recorded in Pant Krishna sprayed with methyl jasmonate at 100 ppm. The present study concludes that all varieties, including Azad Kalonji, AN-20, and Pant Krishna, performed equally well regarding growth and yield attributes in this location. Among the elicitors tested, methyl jasmonate and salicylic acid at 100 ppm show promise for commercial cultivation of black cumin.

Exogenous methyl jasmonate enhanced kenaf (Hibiscus cannabinus) tolerance against lead(Pb) toxicity by improving antioxidant capacity and osmoregulators.

In this study, the effects of exogenous methyl jasmonate (MeJA) on metal uptake and its ability to attenuate metal toxicity in kenaf plants under Pb stress were investigated. The experiment was conducted with five different MeJA concentrations (0, 40, 80, 160, and 320 μM) as a foilar application to kenaf plants exposed to 200 μM Pb stress. The results revealed that pretreatmen of MeJA significantly increased plant dry weight, plant height, and root architecture at all concentrations tested, with the most significant increase at 320 μM. Foliar application of MeJA at 160 μM and 320 μM increased the Pb concentrations in leaves and stems as well as the translocation factor (TF) from root to leaf. However, the bioaccumulation factor in the shoot initially decreased and then increased with increasing MeJA concentration. By increasing enzymatic (SOD, POD, and CAT) and non-enzymatic (AsA and non-protein thiols) antioxidants, MeJA pretreatment decreased lipid peroxidation, O2- and H2O2 accumulation and recovered photosynthetic pigment content under Pb stress. Increased osmolytes (proline, sugar, and starch) and protein content after MeJA pretreatment under Pb stress restore cellular homeostasis and improved kenaf tolerance. Our results suggest that MeJA pretreatment modifies the antioxidant machinery of kenaf and inhibits stress-related processes that cause lipid peroxidation, hence enhancing plant tolerance to Pb stress.

Influence of methyl jasmonate and methyl jasmonate plus urea foliar applications on amino acids composition throughout ‘Tempranillo’ grape ripening over two seasons

This work studies the impact of foliar application of methyl jasmonate (MeJA) and methyl jasmonate plus urea (MeJA + Ur) on the evolution of amino acid content in ‘Tempranillo’ grapes during ripening, across two vintages. To achieve this goal, sample grapes were harvested at five different timing. Fol1: 1 day before first foliar application; Fol2: 1 day before second foliar application; Preharvest: 15 days after second foliar application; Harvest: the day of harvest; and Postharvest: 15 days after harvest. The effect of foliar treatments was season dependent, being effective to improve the amino acids content of grapes only in the first vintage. Among the treatments studied, foliar application of MeJA-Ur showed better results. The evolution of amino acids during ripening also was different among seasons. Overall, in the 2019, amino acids reached their highest content at Preharvest or Harvest samples, whereas in the 2020 season, these highest concentrations were reached at Postharvest. Asparagine might serve as a suitable amino acid for controlling grape ripening, as its content decreased from Fol1 to Postharvest in the two vintages. Moreover, differences on the total amino acids content at Harvest date between vintages were observed, probably due to different climatological conditions. Therefore, this study pioneers the examination of the impact of foliar applications of MeJA and MeJA + Ur on the amino acids evolution in ‘Tempranillo’ grapes during ripening. The need for further research is clear to comprehend the complex interaction between foliar treatments and grape amino acids dynamics for optimizing nitrogen quality of grapes.

A Phytophthora infestans RXLR effector PiAVR3b suppresses plant immunity by perturbing jasmonic acid biosynthesis

P. infestans, the causative agent of the most destructive potato disease, significantly diminishes crop yields. The pathogen's RXLR effector, PiAVR3b, dampens pattern-triggered immunity (PTI) and mitigates cell necrosis caused by other effectors, thus playing a pivotal role in P. infestans infection. The mechanism by which PiAVR3b undermines plant defenses, however, has remained obscure. Our research establishes that PiAVR3b's transient expression promotes P. infestans colonization in Nicotiana benthamiana and that PiAVR3b-transgenic potato lines show reduced PTI to flg22 and heightened susceptibility to P. infestans. Transcriptomic analysis indicate that PiAVR3b expression downregulates genes associated with phenylpropanoid, monoterpenoid biosynthesis, and phenylalanine, alpha-linolenic acid metabolism, leading to a substantial reduction in jasmonic acid (JA) synthesis. Moreover, application of methyl jasmonate (MeJA) on both wild-type and transgenic lines bolsters resistance to P. infestans and activates JA signaling pathways. Our findings reveal that PiAVR3b is a virulence factor that compromises JA-mediated defense, thus facilitating P. infestans invasion.

Methyl Jasmonate Improves Antioxidants, Protecting Photosynthetic Apparatus in Blueberry Plants under Water Deficit

The plant water status is crucial for growth and production, but the current climate change scenario makes it challenging to match the water plant demand. Blueberries are an economically important crop and play an acknowledged role in human health due to their antioxidant compounds. This research aimed to determine whether the exogenous application of methyl jasmonate (MeJA) improves the antioxidant defense mechanisms for protecting the photosynthetic performance in the blueberry plant cultivar ‘Brigitta’ under the stress condition of a water deficit (WD). A greenhouse experiment was carried out under a 16-h light period, at 20 °C, and 60–80% relative humidity for two weeks before the application of MeJA to the blueberry plants (Vaccinium corymbosum, cultivar ‘Brigitta’). The following treatments were maintained for 7-days: (i) 80% field capacity (NoWD), (ii) 80% field capacity plus MeJA application (NoWD + MeJA), (iii) 20% field capacity (WD), and (iv) 20% field capacity plus MeJA application (WD + MeJA). The MeJA was sprayed as an aqueous solution of 10 µM MeJA over the plant’s foliar system. At the end of the assay, the blueberry leaves were analyzed for their relative water content, specific leaf area, lipid peroxidation, total antioxidant activity, total phenols, total anthocyanins, anthocyanidin compounds, and photosynthetic performance. The ‘Brigitta’ cultivar showed a significant decrease in the oxidative stress at leaf levels, with an increase in antioxidant activity, phenolic compounds, total anthocyanins, delphinidin, petunidin, antheraxanthin, zeaxanthin, and an improvement in photosynthetic performance parameters. The ‘Brigitta’ blueberry cultivar was shown to be susceptible to WD, which mainly decreased photosynthesis. However, the application of MeJA to the leaves induced metabolic changes through an increase of the antioxidant strategy within the plant to counteract the negative effects of WD and protect the photosynthetic apparatus, which allowed the ‘Brigitta’ cultivar to withstand the period of a WD.

Jasmonates Improve Drought Tolerance of Hordeum vulgare L. After Biochar Treatment

To investigate how and in what amounts biochar and methyl jasmonate can improve drought tolerance of barley. A two-year experimental study was conducted in a factorial randomized complete block design (n = 5) in the research greenhouse of Zanjan University, Iran, to investigate the possible effects of biochar and methyl jasmonate on some traits of winter barley under drought conditions. Two irrigation regimes, D0 (full irrigation in soil field capacity as control) and D1 (withholding irrigation immediately after flowering stage), three methyl jasmonate spray densities [0 (M0), 50 (M50), and 100 (M100) μM] and four levels of biochar in soil [0% (B0), 0.25% (B0.25), 0.5% (B0.5), 1% (B1) per soil weight] were used in this experiment. In this study, drought reduced two-year average leaf area (LA) by 96%, stomatal conductance (gs) by 84%, and photosynthetic water use efficiency (PWUE) by 64%. In addition, drought reduced chlorophyll-b by 1.5% and 81% and transpiration rate (Tr) by 2.5% and 78% in the first and second years, respectively. However, the application of biochar and methyl jasmonate improved all the traits studied in both D0 and D1 drought-treated plants. For most of the parameters studied, the optimal combination of biochar and methyl jasmonate that optimized water use efficiency and alleviated drought was 0.25% and 50 μM, respectively. The synergistic action of biochar and jasmonates improved the tolerance of barley to water stress.

Preharvest Methyl Jasmonate Treatment Affects the Mineral Profile, Metabolites, and Antioxidant Capacity of Radish Microgreens Produced without Substrate.

This study investigated the impact of Methyl Jasmonate (MeJA) application on the nutritional content and yield of five different colored radish microgreens. Microgreens were produced without substrate and subjected to 0.5 mM and 1.0 mM MeJA treatments on the 7th day, three days before harvest. The parameters measured included yield, dry matter, minerals, amino acids, secondary metabolites such as chlorophylls (Chls), anthocyanins, flavonoids, phenolics, glucosinolates (GSLs), vitamin C, and antioxidant capacity. MeJA at 1.0 mM generally improved yield and dry weight across cultivars, and all microgreens exhibited rich mineral and amino acid composition, with the influence of cultivar being more significant than MeJA treatment. However, MeJA enhanced all cultivars' anthocyanins, GSLs, phenolics, flavonoids, and antioxidant activities. Generally, as the antioxidant capacity is the primary factor influencing the nutritional quality of microgreens, MeJA-treated microgreens, especially with selected superior cultivars such as 'Asia purple' and 'Koregon red', could offer a potential for cultivation of value-added, eco-friendly microgreens with substrate-free cultivation.

Physiological and Transcriptomic Analyses Reveal the Mechanisms Underlying Methyl Jasmonate-Induced Mannitol Stress Resistance in Banana.

Exogenous methyl jasmonate (MeJA) application has shown promising effects on plant defense under diverse abiotic stresses. However, the mechanisms underlying MeJA-induced stress resistance in bananas are unclear. Therefore, in this study, we treated banana plants with 100 μM MeJA before inducing osmotic stress using mannitol. Plant phenotype and antioxidant enzyme activity results demonstrated that MeJA improved osmotic stress resistance in banana plants. Thereafter, to explore the molecular mechanisms underlying MeJA-induced osmotic stress resistance in banana seedlings, we conducted high-throughput RNA sequencing (RNA-seq) using leaf and root samples of "Brazilian" banana seedlings treated with MeJA for 0 h and 8 h. RNA-seq analysis showed that MeJA treatment upregulated 1506 (leaf) and 3341 (root) genes and downregulated 1768 (leaf) and 4625 (root) genes. Then, we performed gene ontology and Kyoto Encyclopedia of Genes and Genomes analyses on the differentially expressed genes. We noted that linoleic acid metabolism was enriched in both root and leaf samples, and the genes of this pathway exhibited different expression patterns; 9S-LOX genes were highly induced by MeJA in the leaves, whereas 13S-LOX genes were highly induced in the roots. We also identified the promoters of these genes, as the differences in response elements may contribute to tissue-specific gene expression in response to MeJA application in banana seedlings. Overall, the findings of this study provide insights into the mechanisms underlying abiotic stress resistance in banana that may aid in the improvement of banana varieties relying on molecular breeding.

Exposure to Light of the Abaxial versus Adaxial Side of Detached Kalanchoë blossfeldiana Leaves Affects Anthocyanin Content and Composition Differently.

The accumulation and composition of anthocyanins in leaves of Kalanchoë blossfeldiana, detached and kept for five days under natural light conditions, were investigated. The presence of fifteen derivatives of cyanidin, petunidin, and delphinidin was found. Changes in the content of each anthocyanin in the leaves before and after exposure to light on the abaxial (naturally upper) and adaxial (naturally lower) sides of the leaves were compared. When the adaxial side was exposed to light, the anthocyanin contents of the leaves did not change. In contrast, when the abaxial side of detached leaves was exposed to light, there was enhanced accumulation of delphinidin-rhamnoside-glucoside, cyanidin-rhamnoside-glucoside, cyanidin-glucoside-glucoside, and two unknown derivatives of petunidin and delphinidin. Application of methyl jasmonate (JA-Me) on the abaxial side exposed to light inhibited the accumulation of these anthocyanins. This effect could probably be due to the presence of these anthocyanins in the epidermal cells of K. blossfeldiana leaves and was visible in the microscopic view of its cross-section. These anthocyanins were directly exposed to JA-Me, leading to inhibition of their formation and/or accumulation. The lack of significant effects of JA-Me on anthocyanin mono- and tri-glycosides may indicate that they are mainly present in the mesophyll tissue of the leaf.