Methyl Jasmonate Acts as a Crucial Player in Abiotic Stress Responses in Grape

Abstract

Abiotic stresses are the major factors limiting grape production in the world. They significantly impede grape growth and production. However, during the grape production stage, plant growth regulators play a crucial role in regulating grape developmental progress, especially methyl jasmonate (MeJA). The exogenous MeJA participates in different crop production, gene expression, signaling transduction, natural defense, stress resistance, hormone balance, osmotic regulation, cellular metabolic process, and thermostatic regulation. Grape crop resilience to different abiotic and biotic stresses was overall fascinated by exogenous applications of MeJA. Therefore, in this review, we focus on the MeJA hormone in abiotic stress relief and discovery, application, significance, occurrence, growth via development, stress responses, interaction, molecular modulation, and biological signaling in the grape. Exogenous MeJA in abiotic stress responses explained the physiological change and the signaling pathway has emerged as one of the key plant metabolic processes vs. photosynthetic productivity, playing a substantial role in gene expression, quality parameters, fruit attribution, protein differentiation, cellular programming, and reprogramming, and tolerance mechanism. MeJA hormone has been discovered after a broader study as abiotic stress-responsive methyl jasmonate/Jasmonic acid, which could be a pivotal target not only for grape production but also for other crops.

1. Introduction

Abiotic and biotic stresses have detrimental effects on growth and lead to a potential crop reduction in grapes (Vitis vinifera L.) [1]. They perturbed a wide series of host species, including grapes, horticultural crops, ornamental fruits, and agricultural sectors around the world [2]. There are essential challenges in biotic and abiotic stress control due to their complex life, growth phases, winery production, climate change, soil deprivation, insufficient water availability, heavy metals, and potential to reproduce biologically, making them incredibly challenging to manage during harsh environments [3,4,5]. These stresses commonly exhibit symptoms including defoliation, leaf yellowing, poor growth, significant economic loss, water deficit, dysfunction of cellular organelles, imbalance in mineral ions, reduced hormonal performance, disturbance in photosynthesis, stress protectors, reduced oxidative damage, osmoprotectants, senescence and even death of the grapes [6,7]. Study shows that biotic and abiotic stresses lead to a worldwide grape reduction in major vineyard production by 10–25%, which was predicted to elevate 15–40% for every degree of increase in worldwide temperature due to global warming [8].

Plant growth regulators (PGRs) are the most commonly employed techniques for preventing and controlling biotic and abiotic stresses in grape growth and development [9]. Nevertheless, PGR treatments substantially elevate production costs, and prolonged PGR application can rapidly promote the cultivation of plant tolerance [10]. Additionally, PGRs can perturbate the natural environment and predators of biotic and abiotic stresses. Therefore, cultivating high-quality, stress-resistant, moderate, and sensitive grape varieties will be essential as it provides the viticultural solutions to mitigate the threats and injuries caused by abiotic stress on horticultural plants [11]. Grape exhibits a rich ecological diversity and different biological mechanisms underlying hormones for mediating the potential feedback to enhance the resilience of plants against stresses [12,13]. The PGRs had been generally considered as the eco-friendly activators for grape developmental growth, photosynthesis, germination, metabolism, and yield cultivation [14]. These PGRs regulate plant developmental stages, molecular changes, growth promotion, adaptation to different environments, life activities, stress tolerance, disease resistance, and plant organs play an important role against environmental constraints [15,16]. The PGRs can mitigate biological regulation in grapes, which contains a diverse number of genes, proteins, transcription factors, secondary metabolism, molecular markers, plant-microbe interactions, activation of antioxidant enzymes, and stress responses [16,17]. Among these PGRs, methyl jasmonate (MeJA) is an influential class of polyhydroxylated steroidal floral hormone that is associated with grape development, cell homeostasis, photosynthetic, regulating photomorphogenesis, photoreceptors, chlorophyll fluorescence, accumulation of organic solutes, osmotic stress, hormonal pathways, cellular communication between environment and plant adaptation to stresses [18,19]. MeJA hormone belongs to the jasmonate family at the hormonal level Jasmonate (involving JA, MeJA, and alternative shapes of JA descendent) [20]. Biosynthesis and biological pathways of the PGRs have been extensively investigated in exemplary crops such as Arabidopsis thaliana, leading to an inclusive comprehension of MeJA regulation via its metabolic resistance to stresses [21,22]. To our knowledge, there is a gap in a comprehensive review of abiotic stresses in grape coping with MeJA. Therefore, this review describes the discovery, applications, importance, and occurrence of MeJA in grapes. In addition, its role in growth and development, its responses to abiotic stresses, the interaction between plants and MeJA, and molecular activities are elucidated, and in the end, MeJA’s signaling in grapes is also discussed.

2. Discovery of MeJA/JA

MeJA was isolated from the odorant of ‘Jasminium grandiflorum’ and ‘Rosmarinus officinalis’ flowers and leaves tissue to promote growth and development [23]. MeJA has been discovered as a stimulant for grape gene modulation and signaling transduction. MeJA was subsequently named ‘Jasmonic acid’. MeJA, the most active JA, was isolated through the culture extraction of a fungus, e.g., (Lasiodiplodia theobromae) [24]. The most significant findings were JA from different backgrounds and probably attained as a combination of the diastereomers 3(R),7(R)-(−)-MeJA/JA and 3(R),7(S)-(+)-epi-MeJA/JA because of quick isomerization of biosynthesized (+)-7-epi-JA throughout the extraction phenomenon via genetical background levels [25,26]. Trans-(3R,7R)-epimer to the cis-(3R,7S) epimer ratio was close to 9:1 at thermodynamic equilibrium (cis and trans illustrates the applicable configuration of the side chains concerning a cyclopentanone circle). Since the discovery of JA, a huge number of chemically diverse MeJA have been discovered throughout plant kingdom, which involves bryophytes, pteridophytes, gymnosperm, angiosperm, dioecious and monoecious plants, describing that MeJA was evolved during crop evolution, which includes four stereoisomers (Figure 1) and could be degraded by more stereoisomers that are linked with side chain trans-double bond. These isomers, including native and synthetic, provide response mechanisms to herbivorous attacks, predators, nematodes, arthropods, parasites, repellents, and volatile emissions in nature with active JA regulations [27]. Among all the MeJA investigated to date, Methyldolichosterone (MDS), Jasmonic acid (JA), Castasterone (CS), Dolichosterone (DS), 3-DehydroTE (3-DT), Teasterone (TE), 6-deoxocastasterone (6-deoxoCS), and typhasterol (2-deoxycastasterone) were familiarly present in different crop species throughout distinctive habitats [16,28,29].

3. Applications

The MeJA is a steroidal phytohormone, which is responsible for fruit ripening, biotic and abiotic tolerance, seed germination, defense response, growth and development, dormancy rate, and phenolic composition, etc. (Figure 2) [31,32,33,34]. MeJA has been linked to the regulation of grape berries and is thought to be the primary regulator of fruit ripening [35]. It carries a pivotal role in the stress responses of the grape. For instance, metabolic regulation, hormonal biosynthesis, alkaloid formulation, and fruit quality [36]. MeJA has shown a great influence on “table grape” grape maturation and berries standard via bioactive compounds, which depend upon accessible doses [37]. MeJA revealed its significance as an adaptable carrier, including biotic and abiotic stress responses; thus, it is an endogenous messenger at various levels of sustainable growth. MeJA enhanced the resistance of vinery grafting and cultivation management in response to abiotic stress with Cabernet Sauvignon cultivar [38]. MeJA was considered to be the most blessing hormone in grape plant growth, which improved physiological responses [39]. MeJA elevates an essential role in plant acclimation to the genomic levels association with abiotic via biotic stresses related genes, proteins (DNA, RNA, and mRNA), transcription factors, and enzymes with defense mechanisms [38]. Therefore, such applications might be eco-friendly, simpler, time-saving, and logical schemes for enhancing morphological, biochemical, anatomical, ecological, and genetic indicators for grape varieties, thereby elevating economic growth and wine quality.

4. Importance

The endogenous MeJA hormones are important for various molecular, physiological, and biological responses in plants. For instance, 1-Deoxy-D-xylulose-5-phosphate synthase (DXS), 3-hydroxy-3-methylglutaryl-coenzyme reductase (HMGCR), and Terpene synthases-14 (TPS14) regulated berry skin color in response to MeJA [40]. MeJA application improved the photochemical efficiency, chlorophyll fluorescence, lipid peroxidation, osmotic stress, thermoregulation, chemical changes, fresh weight, and number of nodes and shoots in Iranian grapes [41]. MeJA delays grape maturity and enhances the ratio of various aromas in the range of 3 to 6 μg/g of fruits [42]. It activated the biosynthetic pathway, molecular transformations, antioxidant responses, environmental modifications, and protein synthesis in grapes [42]. It provides a significant intracellular regulator mediating numerous developmental responses such as defense mechanisms, flavonoids, anthocyanin accumulation, and increased bioactive compounds in grapes [39]. It even helps in the maturation phase that determines the production of volatile organic compounds, cell periphery, soil organic matter, and vinery promotion [43].

5. Occurrence

Endogenous MeJA has been found in all kinds of tissues of the plant, involving different organs such as cells, shoots, stems, buds, flowers, branches, pollen, anthers, and ovaries [44]. It is universally present in all kinds of growing tissues of grapes, while higher concentrations have been found in seeds and fruits [34]. The level of MeJA in plant tissues ranges from 10 to 100 ng/g (FW⁻¹), even higher up to 3 µg/g (FW⁻¹) in other plant tissues [45]. The significantly up-regulated ratio of MeJA was found in plant tissue, including berries, juice vesicles, floral parts, seed coats, endocarp, and the tip of leaves [46]. In addition, lower amounts of MeJA and JA can be found in the parts of cell membranes and fruits [35].

6. MeJA in the Grape Growth and Development

MeJA plays different roles in the developmental progress of grapes under abiotic stress (Figure 3) [34,47]. For instance, photomorphogenesis, senescence, cell wall formation, regeneration, defense mechanisms, fruit growth, plastidial signaling pathway, regulatory network, and seed maturation [48]. Male fertility growth, increased metabolism, sex determination, and cell division [49]. Root growth, flower development, inflorescence, seed growth, shoot elongation, and abiotic stress tolerance [50]. It plays a diverse role in hypocotyl elongation, the ripening process, ethylene-related responses, signaling regulations, post-harvest disorders, and softening of fruits [51]. Furthermore, it maintained galactose metabolism, plant hormone signal transduction, chlorophyll metabolism, flavonoid biosynthesis, diterpenoid biosynthesis, and secondary metabolism [52]. In addition, it also maintained carotenoid biosynthesis, photosynthesis, cellular respiration, nitrogen (N) metabolism, carbon fixation in higher organisms, and terpene biosynthesis [53]. Moreover, ABC transporters, mitogen-activated protein kinases (MAPK-signaling), biosynthesis of unsaturated fatty acids, amino sugar, and natural defense mechanisms were generated for better cultivation and development of plants [54]. On the other hand, diverse tolerance responses were involved, including energy metabolism, environmental adaptation, signal transduction, cellular protein modification process, and response to external stresses [55]. Interestingly, fruit development [34] and disease resistance investigations were observed [56]. MeJA in ‘Cabernet Sauvignon’ leads to a better influence on stilbene production in grapes [57]. In grapes, reactive oxygen species (ROS) and trans-resveratrol were enhanced under MeJA [58].

The application of MeJA enhanced gene expression, photorespiration, and biosynthesis while decreasing chlorophyll pigmentation in grapes. For instance, ‘Thompson Seedless’ grape leaves were sprayed with 50 μM (MeJA) treatments, and results showed that VvmTERF genes played essential roles in mitochondrial transcription activities under hormonal and abiotic stresses [59]. The ‘Cabernet-Sauvignon’ grape was sprayed with 25 μM concentration of MeJA against Erysiphe necator, and it determined that hormonal treatments triggered an enhancement of phenylpropanoid biosynthesis by synergistically involving stilbene accumulation and phenylalanine ammonia-lyase (PAL) and steroid sulfatase (STS) genes [60]. The ‘Sultana’ (moderately salt-tolerant) and ‘Rishbaba’ (least salt-tolerant) were spared with (0, 50 and 100 µM) of MeJA under salt stress, foliar spray of MeJA at 50 and 100 µM positively reduced ion leakage and malondialdehyde, while increased photosynthetic pigments, soluble sugars, and flavonoid measurements were highly activated in ‘Sultana’ when compared with ‘Rishaba’ grape cultivars [61]. Under cold stress, the ‘Shuangyou’ grape was sprayed with 100 μM MeJA, and it determined that VaMYB44 gene intermediate stress responses involved with hormones and negatively regulated cold tolerance in Arabidopsis thaliana [62]. The ‘Crimson Seedless’ grape was sprayed with 5 mM MeJA under abiotic response and showed that signaling modulations were activated, such as metabolic process, oxidative stress, redox homeostasis, and defense mechanism [63]. Fruit clusters of the ‘Jingxiangyu’ were immersed in 10 mM MeJA solution 45 days before flowering, and determined that jasmonate-induced oxygenase (JOX), jasmonates (JAs), and downy mildew resistant 6 (DMR6) were involved in their corresponding hormones [64]. During two seasons, 2016–2017, two grape cultivars ‘Magenta’ and ‘Crimson’, were sprayed with 1, 5, and 10 mM MeJA in 2016 and 0.01, 0.1, and 1 mM MeJA in 2017, which delineated the berry ripening and decreased weight, volume and yield production. Total soluble solids, whole clusters, color quality, and relative agronomic traits were enhanced by MeJA [65]. Flame Seedless and Perlette grape cultivars were sprayed with MeJA (0, 3, and 6 mM) under NaCl (0, 25, 50, 75, and 100 mM), in which MeJA dose, especially (6 mM) elevated the contents of proline, chlorophyll, and photosynthesis, and decreased electrolyte leakage in grape [66]. Based on the above findings, we could explore the practical agricultural applications of MeJA in actual agricultural practices and food security. For instance, post-harvest crop techniques, crop rotation, greenhouse trials, invitro culture, integrated crop animal farming, intercropping, harvesting and post-harvest practices, plant diversity, digital farming, and work hygiene and sanitary facilities can be translated into different plants, such as mango, rapeseed, tomato, and rice under abiotic stresses [67,68,69].

7. Role of MeJA Against Different Stresses in Grape

The role of MeJA against different stresses in grapes is listed in (Figure 4), for instance, herbivorous, oomycetes, earthworms, nematodes, parasites, stress-resistant, climate precipitation, soil composition, living beings, and Botrytis cinerea [2,70]. Adaptation to vineyard growth, germplasm resources, stomatal density, and berry infection have clear genetic linkage with susceptibility to downy mildew [71]. Photosynthetic pigments found on berry surfaces are a possible selection for phytopathology [72] and showed a possible model with MeJA for grape improvement against abiotic stress (Figure 5) [73]. To address this, we conducted a comprehensive analysis in terms of a series of biotic and abiotic stress tolerance in grapes for better growth and cultivation. For instance, MeJA enhanced the stress tolerance of grape foliar cuttings against the pathogen Erysiphe necator in cv. Cabernet Sauvignon [38]. Under salinity stress, MeJA improved stress resistance and fruit quality and decreased sodium ions in grapes [74]. Under heavy metal toxicity, JA enhanced hormonal signals, tissue communication, survival rate, and environmental conditions by cell surface receptors in grapes [75,76]. Under boron stress, MeJA improved gene expression responses, antioxidant enzymes, phenolic compounds, and malondialdehyde in grapes [77]. Under water stress, MeJA enhanced physiological responses, stress tolerance, regulatory mechanism, signal transactivation, and cell division in the wine grape cultivar Corvina [78]. Such chemical compounds played a diverse role in grape growth by different stresses such as drought [79], waterlogging [80], and cold [81]. MeJA was involved in the synthesis of secondary compounds [33] and leaf pavement cell development in grapes [82]. MeJA has been involved in anatomical and biochemical responses by coordinating the different grape development via upgrading crop adaptation by cooperating with plant hormones [83]. MeJA signaling influences numerous developmental schemes containing morphological, physiological, and ecological responses in some tissues, including roots [84], and seeds [85]. Likewise, it promoted insensitive signaling events at the organ, tissue, and cellular level [86]. It increased transfer production, pollen movement, and cultivar tissue benefits [86].

8. Interaction Between Grape and MeJA Under Abiotic Stresses

Coordinated interaction between grape crops and MeJA signaling under abiotic stresses was largely dependent on species’ life cycles, environmental changes, and cellular structures [87]. During the grape crop life cycle, when it encounters different stresses such as phenanthrene, precipitation, climate change, herbicides, thermotolerance, and salinity, the crop species elevates ROS production. ROS disturbed the chemical damage at the growth cycle, cellular structures, organellar, and tissue levels of the grape [88]. The derivatives of JA and relative factors via MJ vs. di-dihydro were recognized to provoke a phenomenon known as (ISR-induced systematic resistance), which contributes to the production of a life cycle, developmental phases, cellular activities, stress modulation, and pathogenic relief. However, JA and their components were common waxes, lubricants, and oils that were incapable of mixing with hydrogen peroxide (H₂O₂), leading to cellular perturbation and signaling problems [45,89]. Application of MeJA to grapes may reduce the pomological manpower via upgrading the cellular growth of arid stem scratches to the fruits; simultaneously, it could enhance the standardization of machine-based table grapes at the time of stress tolerance [90]. Prolonged exposure to stressful circumstances may allow the grapes to be harvested, not including damage to the crop species connected on account of modern technique yield, thereupon eradicating the requirement of high-priced manual selection [90]. The procedure applying JA was designated for reducing tuber sprouting and enhancing their capacity for food processing and growth phases. When food is processed by heating or frying, the tubers’ sprouting and/or melanization should be regulated by exposing them to a sufficient quantity of JA. It was possible to overcome the color quality factor for the market acceptance rate of grapes by applying three MeJA and oligogalacturonides. Different responses in plants were regulated by several physiological and biochemical processes, and measuring the total anthocyanin content is all made possible by a procedure that allows for appropriate control over the fruit quality. Different inventors have developed several formulations that provide strategies for treating seeds, buds, and other cell constituents and new schemes for safeguarding plant life cycles in response to abiotic stresses [91]. These formulations have been used to treat seeds at different stresses. However, they also described that treating seeds with JA interactions or other jasmonate family members caused a plant growing from the treated seed to develop a resistance mechanism against one or more pests for better survival [92].

9. MeJA Regulation of Gene Expression with Transcription Factors and Disease Resistance in Grape Under Abiotic Stresses

MeJA controls different genes against biotic and abiotic stresses in the grape. For instance, the relative expression of VvMeJA1 regulated several plant growth regulators, molecular activities, and breeding approaches in grapes under abiotic stress [93]. Under drought stress, VvNAC17 modulated JA biosynthesis, abscisic acid regulation, increased stress-related genes, and drought tolerance [94]. Under copper stress, autophagy-related genes (VvARGs) regulated plant growth, seed abortion, and vinery relief, further see (

Table 1. Biotic and abiotic stress-related genes by MeJA in grape varieties.

Genes/MeJA	Gene Functions	Plant/Cultivar	Stress Levels	References
VvMJEA1	Involved in the homology modeling and demethylation reaction mechanisms	Vitis vinifera	Heat, cold, and UV-B	[102]
VaNAC17	Enhancement of abscisic acid and no apical meristem modulation.	Vitis amurensis	Drought	[89]
VvARGs	Autophagy-related genes (ARGs) were involved in embryonic development, protein degradation pathways, and seed abortion.	Vitis vinifera	Copper	[103]
VvCSDs	Sex determination system, protein initiation, regulation of cell death, and ROS scavenging systems	Vitis vinifera	Oxidative stress	[104]
VaCPK20	Involved in calcium-dependent protein kinase, increased the accumulation of proteins, crop resistant, and regulated hormone relief.	Vitis amurensis Rupr	Cold and drought	[95]
VaCPK21	Involved in calcium-dependent protein kinase, contribution of hormones to stress tolerance, and accumulation of compatible solutes	Vitis amurensis Rupr	Salt	[96]
VvT4SS	Involved in hormonal regulation, favoring hyphal growth, and virulence to the pathogens	Vitis vinifera	Pathogenic microorganism	[105]
VvRUN1 and VvREN1	Involved in the defense responses, fungal tolerance, disease management, and resistance to vinery disease	Crimson seedless	Powdery mildew	[106]

). The study reported that MeJA worked in grapes with several stresses, especially cold, drought, and salt tolerance [95,96]. The VvCDPK genes observation of the consisting 19 uniform events in wild-type grape V. pseudoreticulata coping with stresses and growth regulator applications discovered that a greater number of VpCPK genes acknowledged to the trial treatments, showing a significant concern of VpCPKs in the stimuli of the wild grape to the surrounding and growth regulator responses [97]. MeJA induced three ERF (ethylene response factor) members as VpERF1, VpERF2, and VpERF3 genes which are responsible for (PM)-resistance in Chinese grape pseudo-reticulata [98]. The use of TTG2-Like WRKY transcription factors (TFs) and genes has the potential to regulate cellular ions, gene movement, and structural variations in grapes under stressful environments [99]. MeJA-induced NAC TFs play a positive role in drought tolerance in grapes [89]. MeJA pathways could have an integral part in the grape’s recuperation from bois noir disease of grape [100]. The VvWRKY30 TFs mediated the regulation of polyphenols, N metabolism, and signal transduction in grapes under salt stress [101].

In a study, grape was endangered to blast from different environmental stress-related biological agents causing diseases, for instance, powdery mildew (PM) [107], downy mildew (DM) [108], and gray mold (GM) [109]. Among them, powdery mildew was a compatible challenge that grape crop production growers face worldwide due to PM disease harming the plant quality of grape yields seriously. However, PM mostly affects the leaves, shoots, and fruits of grapes, caused by a fungal pathogen, which belongs to the biotrophic pathogen [110]. Genes associated with PM resistance, such as VvMLO7/6 [111], and PM resistance loci, such as Ren6/7, have been found in wild grapes to control environmental stress [112]. The MeJA resistance effect on crop PM as the VvZFP11 was confirmed to enhance the resistance of grapes against PM, especially with SA and MeJA [113]. Two levels, including transcriptional and post-transcriptional mechanisms, enhanced genes related to the SA and MeJA signaling pathways in grapes. Therefore, this study offers a theoretical basis for studying the zinc finger protein resistance to PM disease management and the breeding of grapes resistant to different pesticides and hyperthermal stress.

Gene names, elucidation of a gene, name of plant variety, and their function based on MeJA in grapes were mentioned (

Table 2. Gene linkage with MeJA regulation in a grape plant.

Genes	Elucidation of Gene	Crop/Variety	Functions	References
VvGH3-7 and VvGH3-9	Gretchen Hagen3 (GH3) proteins synthetases	Vitis vinifera	Play positive role in Jasmonic acid-isoleucine formation	[124]
DHNs	The Dehydrins (DHNs) gene superfamily desiccation harm over environmental stress	Vitis vinifera	Involved in the resistance to numerous pathogens	[125]
VvPR1	Pathogenesis-related gene 1 is a marker gene	Vitis vinifera	Carries an essential role in hormonal protection mechanism	[126]
VvSTS	The stilbene synthase for pathway	Vitis vinifera	Probably enclosed in controlling cell-dropping.	[127]
VviGT	The gene encoding for glycosyltransferases	Gewürztraminer grapes	Synthesis of terpene and glycosidic linkage	[35]
VvChs1, VvChs2 and VvChs3	Play a significant role in transcription regulation	Cabernet Sauvignon	They are probably responsible for promoting coloration	[117]
UFGT	Genes encoding with the berry skin coloration	Shiraz grapes	Enhanced expression level of anthocyanin biosynthesis	[116]
UFGT	UDP glucose-flavonoid 3-o-glucosyl transferase (UFGT)	Colored grapes	Involved in increasing anthocyanin synthesis	[115]

) to regulate plant development. For instance, VvGH3-7 and VvGH3-9 proteins were involved in JA modulation, reproductive organs, and fruit ripening [114]. Pathogen-related PR proteins (CHIT4c and PIN), and relative expression of gene involvement with secondary metabolites pathogenesis-related protein-1 (PR1), phenylalanine ammonia-lyase (PAL), stilbene synthases (STS), chalcone synthase (CHS), and flavonoid-3-O-glucosyltransferase (UFGT) were found [115,116,117]. Pérez-Castro et al. [118] suggested that the VvBOR1 gene showed stunted growth of grape plants. Protein microarray technology was used in grape and visualized global omics delineating around 200 defense-related proteins, which were controlled by MeJA [44]. In which 125 were induced or enhanced and 75 were repressed in response to MeJA hormone. These proteins increased the berry quality, vinery products, storage process, quality parameters, and bioactive compounds in grapes [37]. However, MeJA maintained fruit ripening [34], increased quality [119] and wine production [120], and triggered the accumulation of berry colorations in grapes [121]. Secondary biological catalysts, including bioflavonoids, alkaloids, terpenoids, polyketides, sesquiterpenes, and anti-fungal factors, were activated [122,123].

10. MeJA Signaling Mechanisms

Abiotic stresses induced a small amount of MeJA by enhancing gene signal transduction to develop growth development. The transduction pathway has a critical role in adapting to environmental changes and cultivation of grapevine crops under salt stress [128]. Signaling transduction associations represent grape plant 2-oxoglutarate-dependent dioxygenase (2OGD) receptor kinases located on the cytosol perceive JA outside of the cellular parts, which regulates berry development, methylation, epimerization, hormone metabolism, and stress tolerance [64]. JA interacts with (VvDWF4) BR-associated receptors (Brassinosteroids), maintaining the influential regulators of the JA signaling cascade in grapes during the post-harvest stage [16]. Enhanced MeJA treatment results in superoxide radical (O₂⁻) and hydroxyl radical (·OH), which facilitates antioxidant enzymes, DAN amplification, protein interaction, amino acid composition, and hormone-responsive genes of plants under chilling injury [129,130]. Grape usually maintained the relative expression of a downstream gene through transcription factors under abiotic stresses. MeJA and epibrassinolide maintained the growth of grapes via gene differentiation, either repressing or inducing downstream genes while increasing lipid peroxidation and decreasing photosynthetic pigments under salinity stress [127]. MeJA has fascinated much scientific research investigation in the past few decades because of its dynamic roles in grape growth and crop production. Generally, the MeJA signaling molecules in grape crops are one of the well-studied biological pathways under abiotic or biotic stresses [131]. Different transcription factors, expressed genes, and stress-responsive pathways have been recognized in downstream MeJA signaling cascades. For instance, Mitochondrial transcription termination factor (VvmTERF), salt overly sensitive (VvSOS), MYB proto-oncogene (VhMYB15), and transcriptional modulation are considered to be essential factors in grapes under salt and drought stresses [132]. Signaling responses were linked with JA and salicylic acid (SA) pathways protecting root gall in response to soil microbes in the grape, thereby suppressing transcriptional activities and induction of exogenous hormones [133]. A basic helix loop helix (bHLH), (MAPK), vacuolar processing enzymes (VPEs), and Papain-like cysteine proteases (PLCPs) domains in grapes induce the relative expression of downstream proteins, genes, and improved root development, mineral ions, and soil microbial activity with MeJA and other signaling cascades under Plasmopara viticola or cold stress [134,135]. In addition, (Figure 6) delineates the signaling pathways via defensive genes underlying MeJA in grapes under abiotic stress tolerance. The generation of abiotic stress tolerance or susceptibility through the MeJA derivative holds versatile potential. Providing the ecological impacts caused by abiotic stress, the capability to elevate grape tolerance in response to MeJA contribution to minimize vinery production, improving berry quality, and advancing the efficacy of hormonal balance.

11. Conclusions and Future Perspectives

Abiotic stresses are major grape threats, hindering crop yield and economic loss. Generally, grapes have modulated various mechanisms in response to abiotic stresses, involving the mutual understanding of methyl jasmonate (MeJA). It manipulated biological regulations and improved crop production. It plays an important role in agricultural productivity, sustainable farming, expression of downstream transcription factors, and genetic variation in grapes against abiotic stresses. With the advancement of scientific research, different studies on MeJA have fascinated the consideration of vinery scientists due to their involvement in different cultivation and biochemical regulation in grapes. After well-known characterization with development and growth, they are now being recognized to perform essential roles in tolerance to the relief of abiotic stresses. MeJA modulated such valuable responses by regulating a wide range of signaling pathways, biochemical alterations, proteins, and relative expressed genes. In addition, future study needs to be delivered to deeply understand the participation of MeJA in grape maturation and mitigation in response to abiotic stresses.

Future studies in this direction may focus on determining and integrating abiotic and biotic tolerant agronomic traits into grape breeding strategies. Foliar spray with MeJA and subsequent techniques will offer a promising avenue for grape yield production with increased abiotic stress tolerance. Understanding the physiological and photomorphogenesis underlying stress responses, especially those related to photosynthesis, germination, chlorophyll pigments, translocation, membrane stability, and gene function, will be essential for such efforts. Further, exploring the dynamic roles of crop growth regulators, such as MeJA with grapes, in modulating abiotic stresses may provide insights into plant yield and growth performance with optimized stress resilience.

The outcome of this study will help researchers enhance sustainable agriculture with the application of exogenous phytohormones under environmental perturbation. The MeJA was critical in the published study for grape plant growth and their corresponding microbes under abiotic and biotic stresses; thereby, researchers and young scientists could pay more attention to conducting more scientific studies on MeJA-generating grapes under abiotic stress tolerance. We hope this review may not only provide a novel idea for MeJA to alleviate grape cultivars in response to abiotic stresses but also other agricultural sectors.