Melatonin-mediated endogenous nitric oxide coordinately boosts stability through proline and nitrogen metabolism, antioxidant capacity, and Na+/K+ transporters in tomato under NaCl stress

Hydrogen sulfide mechanism of action in plants; from interaction with regulatory molecules to persulfidation of proteins

Hydrogen sulfide (H2S), previously known as a toxic gas, is currently considered one of the most important gaseous transmitters in plants. This novel signaling molecule has been determined to play notable roles in plant growth, development, and maturation. In addition, pharmacological and genetic evidence indicated that this regulatory molecule effectively ameliorates various plant stress conditions. H2S is involved in these processes by changing gene expression, enzyme activities, and metabolite concentrations. During its regulatory function, H2S interacts with other signaling pathways such as hydrogen peroxide (H2O2), nitric oxide (NO), Ca2+, carbon monoxide (CO), phosphatidic acid (PA), phytohormones, etc. The H2S mechanism of action may depend on the persulfidation post-translational modification (PTM), which attacks the cysteine (Cys) residues on the target proteins and changes their structure and activities. This review summarized H2S biosynthesis pathways, its role in sulfide state, and its donors in plant biology. We also discuss recent progress in the research on the interactions of H2S with other signaling molecules, as well as the role of persulfidation in modulating various plant reactions.

Rhizobial, passenger nodule endophytes and phyllosphere bacteria in combination with acyl homoserine lactones enhances the growth and yield of groundnut

Quorum sensing (QS) mechanisms play an essential role in mediating several signals and plant-bacteria interactions, promoting plant growth. This study demonstrated production of multiple Homoserine lactone (HSL) molecules like C6 HSL, C7 HSL, C8 HSL, 3-Hydroxy-C8-HSL and 3-oxo-C14 HSL in rhizobial and passenger endophytes and phyllospheric bacteria which regulated production of plant growth promoting traits viz., indole acetic acid and exo-polysaccharide production, biofilm formation, and motility. Quorum quenching (QQ) molecules like salicylic acid, gallic acid, and disalicylic acid impaired these traits, but exogenous addition of QS molecules (C7HSL and 3-oxo-C14 HSL) restored these inhibitory effects of QQ compounds. The pot culture experiment revealed that the treatment involving Methylobacterium populi TMV7-4 or Enterobacter cloacae S23 with salicylic acid, C7HSL and 3-oxo-C14 HSL significantly enhanced plant growth including root length, nodulation, pod formation, soil available nutrients and plant nutrients uptake. In future field validation is required for the use of QS molecules in improving groundnut production.

Nitric Oxide and Melatonin Cross Talk on Photosynthetic Machinery

Nitric oxide (NO) and melatonin (MT) significantly influence photosynthetic processes by modulating redox homeostasis, chlorophyll content, stomatal conductance, and gene expression, particularly under abiotic stress conditions. This review summarizes the intricate crosstalk between NO and melatonin, focusing on their coordinated roles in regulating photosynthetic efficiency. Evidence from various plant species indicates that the application of exogenous NO and melatonin enhances chlorophyll content, photosystem efficiency (particularly PSII), and photosynthetic performance, mitigating stress-induced damage. Molecular analysis demonstrates that both molecules influence key photosynthetic gene modulating photosystems I and II, and Calvin cycle activities. Moreover, NO and melatonin collaboratively regulate stomatal movements through ABA, Ca2⁺, and H2O2 signaling pathways, involving genes such as PMRT1, CIPKs, and OST1. Experimental data from diverse plant species under stress conditions, including drought, salinity, heavy metals, and flooding, highlight their synergistic protective effects. Exploring these mechanisms further may enable practical agricultural strategies involving combined NO and melatonin treatments to improve crop resilience and productivity under increasingly challenging environmental conditions. Future research directions should emphasize unraveling detailed molecular interactions, enabling targeted biotechnological applications in crop improvement programs for enhanced global food security.

Unraveling the Intricacies of Powdery Mildew: Insights into Colonization, Plant Defense Mechanisms, and Future Strategies

Powdery mildew, a debilitating phytopathogen caused by biotrophic fungi within the order Erysiphales, endangers crop yields and global food security. Although traditional approaches have largely emphasized resistant cultivar development and chemical control, novel strategies are necessary to counter the advent of challenges, such as pathogen adaptation and climate change. This review fully discusses three principal areas of pathogen effector functions, e.g., the reactive oxygen species (ROS)-suppressive activity of CSEP087, and host susceptibility factors, like vesicle trafficking regulated by Mildew Locus O (MLO). It also briefly mentions the transcriptional regulation of resistance genes mediated by factors, like WRKY75 and NAC transcription factors, and post-transcriptional regulation via alternative splicing (As). In addition, this discussion discusses the intricate interactions among powdery mildew, host plants, and symbiotic microbiomes thereof, highlighting the mechanism through which powdery mildew infections disrupt the foliar microbiota balance. Lastly, we present a new biocontrol approach that entails synergistic microbial consortia, such as combinations of Bacillus and Trichoderma, to induce plant immunity while minimizing fungicide dependency. Through the study of combining knowledge of molecular pathogenesis with ecological resilience, this research offers useful insights towards climate-smart crop development and sustainable disease-management strategies in the context of microbiome engineering.

Nitric oxide in plants: an insight on redox activity and responses toward abiotic stress signaling

Plants, as sessile organisms, are subjected to diverse abiotic stresses, including salinity, desiccation, metal toxicity, thermal fluctuations, and hypoxia at different phases of plant growth. Plants can activate messenger molecules to initiate a signaling cascade of response toward environmental stresses that results in either cell death or plant acclimation. Nitric oxide (NO) is a small gaseous redox-active molecule that exhibits a plethora of physiological functions in growth, development, flowering, senescence, stomata closure and responses to environmental stresses. It can also facilitate alteration in protein function and reprogram the gene profiling by direct or indirect interaction with different target molecules. The bioactivity of NO can be manifested through different redox-based protein modifications including S-nitrosylation, protein nitration, and metal nitrosylation in plants. Although there has been considerable progress in the role of NO in regulating stress signaling, still the physiological mechanisms regarding the abiotic stress tolerance in plants remain unclear. This review summarizes recent advances in understanding the emerging knowledge regarding NO function in plant tolerance against abiotic stresses. The manuscript also highlighted the importance of NO as an abiotic stress modulator and developed a rational design for crop cultivation under a stress environment.

Effects of foliar spraying with melatonin and chitosan Nano-encapsulated melatonin on tomato (Lycopersicon esculentum L. cv. Falcato) plants under salinity stress

Melatonin has been found to be crucial in the growth and development of plants under stress conditions. In this study, the effects of melatonin and nano melatonin regarding the growth and development of tomato plants, along with their photosynthetic pigment, phenol, and antioxidant activity, were investigated under saline conditions. The study was conducted using a completely randomized design with three replications, and the applied treatments were salt stress and foliar spraying of melatonin at a concentration of 0 (control), melatonin (Mel), and nano capsule-melatonin (Nano-Mel) at 500 µM. Salinity treatments included application of sodium chloride with two concentration of 0 mM NaCl (S1) and 50 mM NaCl (S2). Under saline conditions, Mel and Nano-Mel increased both shoot and root fresh and dry weights, improved relative water content (RWC), and enhanced antioxidant activity and phenolic content. Salinity elevated leaf ABA content, unaffected by Mel or Nano-Mel. Chlorophyll fluorescence and SPAD values demonstrated resilience to salinity with Mel and Nano-Mel applications. Nano-Mel notably mitigated Na + accumulation in leaves under salinity, helping maintain K + homeostasis. Proline levels rise due to salinity but decreased with Mel and Nano-Mel treatments. Electrolyte leakage (EL) increased under salinity but is significantly reduced by Mel, indicating enhanced membrane stability. The findings reveal that salinity stress significantly reduced plasma membrane intrinsic protein (PIP) expression in roots and leaves, whereas Mel and Nano-Mel treatments enhance PIP expression, particularly in roots. The study concludes that Mel and Nano-Mel effectively alleviate salinity-induced stress, promoting growth and maintaining physiological homeostasis in tomato plants.

Relative effects of melatonin and hydrogen sulfide treatments in mitigating salt damage in wheat

Soil salinity poses a significant threat to agricultural productivity, impacting the growth and yield of wheat (Triticum aestivum L.) plants. This study investigates the potential of melatonin (MT; 100 µM) and hydrogen sulfide (H2S; 200 µM sodium hydrosulfide, NaHS) to confer the tolerance of wheat plants to 100 mM NaCl. Salinity stress induced the outburst of reactive oxygen species (ROS) resulting in damage to the chloroplast structure, growth, photosynthesis, and yield. Application of either MT or NaHS augmented the activity of antioxidant enzymes, superoxide dismutase, ascorbate peroxidase, glutathione reductase, and reduced glutathione (GSH) levels, upregulated the expression of Na+ transport genes (SOS1, SOS2, SOS3, NHX1), resulting in mitigation of salinity stress. Thus, improved stomatal behavior, gas-exchange parameters, and maintenance of chloroplast structure resulted in enhanced activity of the Calvin cycle enzymes and overall enhancement of growth, photosynthetic, and yield performance of plants under salinity stress. The use of DL-propargylglycine (PAG, an inhibitor of hydrogen sulfide biosynthesis) and p-chlorophenyl alanine (p-CPA, an inhibitor of melatonin biosynthesis) to plants under salt stress showed the comparative necessity of MT and H2S in mitigation of salinity stress. In the presence of PAG, more pronounced detrimental effects were observed than in the presence of p-CPA, emphasizing that MT was involved in mitigating salinity through various potential pathways, one of which was through H2S.

The ameliorating effects of cinnamic acid-based nanocomposite against salt stress in peppermint

Nanoparticles (NPs) are important in regulating plant tolerance to salt stress. Peppermint is one of the most widely used aromatic plants, with a high sensitivity to salt stress. The present study investigated physiological and biochemical factors to understand better the behavior of cinnamic acid (CA) and cinnamic acid nanocomposite in salinity control in peppermint plants. The first factor was salt stress with different salt concentrations, including 0, 50, 100, and 150 mg/L, the second factor was 50 μM CA, and the third factor was 50 μM CA nanocomposite based on carboxymethyl cellulose (CMC-CA NC). Results showed that stress markers increased with increasing salinity levels. On the contrary, plants treated with salinity showed a decrease in physiological and photosynthetic parameters, while the application of CA and CMC CA NC increased these critical parameters. Under salinity, compared to the control, malondialdehyde and hydrogen peroxide contents decreased by 11.3% and 70.4%, respectively. Furthermore, CA and CMC-CA NC enhanced peppermint tolerance to salinity by increasing compatible solute content such as proline, free amino acids, protein content, and soluble carbohydrates, increasing antioxidant enzymes, and decreasing stress markers in plant tissues. Compared to the control, chlorophyll fluorescence and proline content increased by 1.1% and 172.1%, respectively. Salinity stress negatively affected all physiological and biochemical parameters, but CA and CMC-CA NC treatments improved them. We concluded that the nanocomposite, a biostimulant, significantly enhances mint tolerance under salinity conditions.

Foliar applied potassium nanoparticles (K-NPs) and potassium sulfate on growth, physiological, and phytochemical parameters in Melissa officinalis L. under salt stress

Salinity stress significantly constrains agricultural productivity and vegetation decline worldwide, particularly in Iran. Potassium, the second most prevalent nutrient in plants, is well known to be essential for cell metabolism. Here, the effects of potassium fertilizer in two biogenic nanoparticles (K-NPs) and conventional (potassium sulfate) forms (0.1 mg/ml) on Melissa officinalis L. under salinity (0, 50, 100, and 150 mM) were investigated. The results demonstrated that stress markers (electrolyte leakage, malondialdehyde, and hydrogen peroxide) increased as salinity levels increased. Plant growth parameters (shoot and root length, fresh and dry weight of shoot and root) and physiological and photosynthetic parameters (stomatal conductance, relative water content, chlorophyll fluorescence, and photosynthetic pigments) were reduced in salinized plants. The highest reduction in fresh weight root, dry weight root, fresh weight shoot, dry weight shoot, root length, and shoot length was recorded under 150 mM NaCl by 30.2%, 51.6%, 30.5%, 24.7%, 26.4%, and 21%, respectively. In contrast, bulk potassium sulfate and K-NPs increased these parameters. Furthermore, K-NPs improved M. officinalis tolerance to NaCl toxicity by enhancing the content of osmolytes such as proline, soluble sugars, and antioxidant enzymes, improving antioxidant contents such as phenols, tannins, anthocyanins, and flavonoids; increasing total protein; and lowering stress markers in plant tissues. Given the results of the physiological, biochemical, and phytochemical parameters obtained from this study, it can be stated that K-NPs, in comparison to the conventional form of potassium fertilizer, exhibit a greater potential to mitigate damages caused by salinity stress in M. officinalis plants.

Effect of naringenin based nanocomposites and pure naringenin on cumin (Cuminum cyminum L.) under drought stress

Key message

Naringenin based nanocomposite alleviate the harmful effects of drought stress in Cuminum cyminum and enhance carefully the plant tolerance against drought condition with different mechanisms.

Abstract

In the recent years, drought stress is considered as one of the most important stressful conditions for agricultural plants. Reducing the effects of drought on plants is a crucial need nowadays, which calls for innovative methods. Naringenin is one of the most known plant flavonoids with antioxidant properties. In the present work, a naringenin based nanocomposite containing carboxymethylcellulose (CMC) as carrier (CMC-Nar) with an average size of 65 nm were synthesized by coacervation method. In order to investigate the effect of CMC nanocomposites containing naringenin (CMC-Nar) and pure naringenin in modulating the effects of drought stress, cultivation of Cuminum cyminum (varieties: Isfahan and Kashan) was carried out in greenhouse conditions. Drought stress was imposed as 30% of the field capacity. Various physiological, biochemical, and phytochemical assays were performed after treating the plants in drought conditions (30%). The results indicated that treatment of nanocomposites (CMC-Nar) and pure naringenin at drought conditions increased growth and photosynthetic parameters such as germination, shoot and root fresh weight, shoot dry weight, and chlorophyll content of the Cumin. Stress markers such as malondialdehyde, H2O2, and electrolyte leakage decreased under the treatment of narinjenin and especially nanocomposites (CMC-Nar) under drought conditions. Moreover, under same condition and treatments, some biochemical parameters including soluble sugar and total protein increased but the activity of antioxidant enzymes and the level of free amino acids has gone down. Compatible Solutes (Proline and glycine betaine) also increased. There was an increase in phytochemical parameters such as total phenols, flavonoids, anthocyanin, and tannins under naringenin and nanocomposites (CMC-Nar) treatment in drought conditions. In general, nanocomposites and pure naringenin reduced the harmful effects of drought stress, and the ameliorating impacts of nanocomposites (CMC-Nar) are more than pure naringenin. According to the results: In most cases, the impact of drought stress was modulated to a greater extent by (CMC-Nar) nanocomposites in the Isfahan variety compared to the Kashan variety. This research tries to propose a new method to reduce the effects of drought stress on Cuminum cyminum.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01460-7.

Nano-enabled agrochemicals: mitigating heavy metal toxicity and enhancing crop adaptability for sustainable crop production

The primary factors that restrict agricultural productivity and jeopardize human and food safety are heavy metals (HMs), including arsenic, cadmium, lead, and aluminum, which adversely impact crop yields and quality. Plants, in their adaptability, proactively engage in a multitude of intricate processes to counteract the impacts of HM toxicity. These processes orchestrate profound transformations at biomolecular levels, showing the plant's ability to adapt and thrive in adversity. In the past few decades, HM stress tolerance in crops has been successfully addressed through a combination of traditional breeding techniques, cutting-edge genetic engineering methods, and the strategic implementation of marker-dependent breeding approaches. Given the remarkable progress achieved in this domain, it has become imperative to adopt integrated methods that mitigate potential risks and impacts arising from environmental contamination on yields, which is crucial as we endeavor to forge ahead with the establishment of enduring agricultural systems. In this manner, nanotechnology has emerged as a viable field in agricultural sciences. The potential applications are extensive, encompassing the regulation of environmental stressors like toxic metals, improving the efficiency of nutrient consumption and alleviating climate change effects. Integrating nanotechnology and nanomaterials in agrochemicals has successfully mitigated the drawbacks associated with traditional agrochemicals, including challenges like organic solvent pollution, susceptibility to photolysis, and restricted bioavailability. Numerous studies clearly show the immense potential of nanomaterials and nanofertilizers in tackling the acute crisis of HM toxicity in crop production. This review seeks to delve into using NPs as agrochemicals to effectively mitigate HM toxicity and enhance crop resilience, thereby fostering an environmentally friendly and economically viable approach toward sustainable agricultural advancement in the foreseeable future.

Exploring the power of nitric oxide and nanotechnology for prolonging postharvest shelf-life and enhancing fruit quality

Nitric oxide (NO) is a versatile signaling molecule that plays a crucial role in regulating postharvest fruit quality. The utilization of NO donors to elevate endogenous NO levels and induce NO-mediated responses represents a promising strategy for extending fruit shelf-life after harvest. However, the effectiveness of NO treatment is influenced by various factors, including formulation and application methods. In this review, we investigate the impact of NO supply on different fruits, aiming to prolong postharvest shelf-life and enhance fruit quality. Furthermore, we delve into the underlying mechanisms of NO action, particularly its interactions with ethylene and reactive oxygen species (ROS). Excitingly, we also highlight the emerging field of nanotechnology in postharvest applications, discussing the use of nanoparticles as a novel approach for achieving sustained release of NO and enhancing its effects. By harnessing the potential of nanotechnology, our review is a starting point to help identify gaps and future directions in this important, emerging field.

The variations in gene expression of GAPDH in Ocimum basilicum cultivars under drought-induced stress conditions

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) holds a pivotal role within the glycolytic pathway of higher plants. It has garnered attention as a significant target protein in instances of oxidative stress, where it can engage in thiolation reactions within its active site. Numerous genes encoding cytosolic iterations of GAPDH have been identified and analyzed in specific plant species. This investigation was conducted to gain insights into GAPDH's function amidst drought-induced stress. Within this framework, the basil plant (Ocimum basilicum) was chosen for focused exploration, encompassing the cloning of the comprehensive cDNA of basil GAPDH (ObGAPDH) and scrutinizing its patterns of expression. The complete sequence of Ob-GAPDH spanned 1315 base pairs. The resultant protein derived from this sequence comprised 399 amino acids, projecting a molecular weight of approximately 42.54 kDa and an isoelectric point (pI) of 6.01. An examination of the evolutionary connections among various GAPDH proteins unveiled ObGAPDH's shared lineage with GAPDH proteins sourced from other plants, such as Salvia splendens and Sesamum indicum. Furthermore, computational methodologies were harnessed to predict the potential oxidative role of ObGAPDH in response to external signals. Molecular docking simulations illuminated the interaction between ObGAPDH and hydrogen peroxide (H2O2) as a ligand. Scrutinizing the expression patterns of the ObGAPDH gene under conditions of water scarcity stress brought to light diverse levels of transcriptional activity. Collectively, these findings underscore the notion that the regulation of ObGAPDH expression is contingent upon both the specific plant cultivar and the presence of stress stemming from drought conditions.

Unravelling the molecular and biochemical responses in cotton plants to biochar and biofertilizer amendments for Pb toxicity mitigation

Over the past few years, there has been a rising interest in employing biochar (BC) and biofertilizers (BF) as a means of restoring soils that have been polluted by heavy metals. The primary objective of this study was to examine how the application of BC and BF affects the ability of cotton plants to withstand Pb toxicity at varying concentrations (0, 500, and 1000 mg/kg soil). The findings revealed that exposure to Pb stress, particularly at the 1000 mg/kg level, led to a decline in the growth and biomass of cotton plants. Pb toxicity triggered oxidative damage, impaired the photosynthetic apparatus, and diminished the levels of photosynthetic pigments. By increasing the expression of Rubisco-S, Rubisco-L, P5CR, and PRP5 genes and regulating proline metabolism, BC and BF increased the levels of proline and photosynthetic pigments and protected the photosynthetic apparatus. The application of BC and BF resulted in an upregulation of genes such as CuZnSOD, FeSOD, and APX1, as well as an increase in the activity of the glyoxalase system and antioxidant enzymes. These changes enhanced the antioxidant capacity of the plants and provided protection to membrane lipids from oxidative stress caused by Pb. The inclusion of BC and BF offered protection to photosynthesis and other essential intracellular processes in leaves by minimizing the transfer of Pb to leaves and promoting the accumulation of thiol compounds. This protective effect helped mitigate the negative impact of the toxic metal Pb on leaf function. By improving plant tolerance, reducing metal transfer, strengthening the antioxidant defense system, and enhancing the level of protective substances, these amendments show promise as valuable tools in tackling heavy metal pollution.

Genetic basis of genome size variation of wheat

Research on various species has revealed a connection between genome size variation and the physiological and ecological characteristics of the species, suggesting that it could be a crucial factor influencing a species' adaptability to different environments. Wheat, being one of the world's three primary grains, holds significance in this regard. Investigating the genome size of wheat and analyzing the genetic factors contributing to its variation could offer valuable insights for enhancing wheat agronomic traits. This project has developed a conservative site ratio calculation approach to determine the size of the wheat genome. Additionally, it employs flow cytometry and k-mer distribution analysis to validate this method. Furthermore, the researchers use re-sequencing data to investigate the impact of environmental selection pressure and transposon dynamics on the variation in the size of the wheat genome. The findings from this study demonstrate a strong relationship between the size of the wheat genome and several environmental factors. These results serve as a valuable reference for understanding the development of variation in the size of the hetero-hexaploid wheat genome. Moreover, they contribute to advancing fundamental research on the genetic mechanisms underlying wheat characteristics. Additionally, the study paves the way for exploring new research directions in wheat breeding, which holds promise for future advancements in this field.

A comprehensive model for predicting the development of defense system of Capparis spinosa L.: a novel approach to assess the physiological indices

Capparis spinosa L. (caper) is a halophytic plant that grows in semi-arid or arid environments. The current study used an integrated experimental and computational approach to investigate the network of inter-correlated effective variables on the activity of antioxidant enzymes, proline, and photosynthetic pigments in stressed caper. To investigate the possible relationships among intercorrelated variables and understand the possible mechanisms, predictive regression modelling, principal component analysis (PCA), Pearson's correlation, and path analysis were implemented. PCA successfully discerned different salt ratio- and drought-specific effects in data in the current study, and treatments with higher growth indices are easily recognizable. Different salt ratios did not have a significant effect on the activity of four antioxidant enzymes, proline and photosynthesis pigments content of caper. While at the mean level, the activity of four antioxidant enzymes of SOD, POD, CAT, and APX significantly increased under drought stress by 54.0%, 71.2%, 79.4%, and 117.6%, respectively, compared to 100% FC. The drought stress also significantly increased the content of carotemoid (29.3%) and proline (by 117.7%). Predictive equation models with highly significant R² were developed for the estimation of antioxidant enzyme activity and proline content (> 0.94) as well as pigments (> 0.58) were developed. Path analysis studies revealed that proline is the most important regressor in four antioxidant enzyme activities, while leaf tissue density was the most effective variable in the case of chlorophylls. Furthermore, the network of intercorrelated variables demonstrated a close relationship between caper's antioxidant defence system, pigments, and morphological parameters under stress conditions. The findings of this study will be a useful guide to caper producers as well as plant ecophysiological researchers.

Melatonin Confers NaCl Tolerance in Withaniacoagulans L. by Maintaining Na+/K+ Homeostasis, Strengthening the Antioxidant Defense System and Modulating Withanolides Synthesis-Related Genes

As a multifunctional signaling molecule, melatonin (ML) is widely considered to induce the defense mechanism and increase the accumulation of secondary metabolites under abiotic stresses. Here, the effects of different concentrations of ML (100 and 200 µM) on the biochemical and molecular responses of Withania coagulans L. in hydroponic conditions under 200 mM NaCl treatment were evaluated. The results showed that NaCl treatment impaired photosynthetic function and reduced plant growth by decreasing photosynthetic pigments and gas exchange parameters. NaCl stress also induced oxidative stress and membrane lipid damage, disrupting Na+/K+ homeostasis and increasing hydrogen peroxide levels. NaCl toxicity decreased nitrogen (N) assimilation activity in leaves by reducing the activity of enzymes associated with N metabolism. However, adding ML to NaCl-stressed plants improved gas exchange parameters and increased photosynthesis efficiency, resulting in improved plant growth. By enhancing the activity of antioxidant enzymes and reducing hydrogen peroxide levels, ML ameliorated NaCl-induced oxidative stress. By improving N metabolism and restoring Na+/K+ homeostasis in NaCl-stressed plants, ML improved N uptake and plant adaptation to salinity. ML increased the expression of genes responsible for the biosynthesis of withanolides (FPPS, SQS, HMGR, DXS, DXR, and CYP51G1) and, as a result, increased the accumulation of withanolides A and withaferin A in leaves under NaCl stress. Overall, our results indicate the potential of ML to improve plant adaptation under NaCl stress through fundamental changes in plant metabolism.

Supplementary Information

The online version contains supplementary material available at 10.1134/S1021443723600125.

The Effect of Glycine Betaine on Nitrogen and Polyamine Metabolisms, Expression of Glycoside-Related Biosynthetic Enzymes, and K/Na Balance of Stevia under Salt Stress

The beneficial role of glycine betaine (GB) in the adaptation of plants to abiotic stresses is well known; therefore, the study of physiological and molecular responses induced by exogenous GB under NaCl stress can provide a suitable reference for the application of this compound to enhance the adaptation of plants to salinity. The present study was conducted under in vitro conditions to evaluate the effect of GB (25 and 50 mM) on the growth, physiological, and molecular traits of Stevia rebaudiana during NaCl toxicity (50 mM). The results showed that applying NaCl treatment increased Na accumulation, induced oxidative stress, and disrupted N metabolism and K/Na homeostasis, which, as a result, decreased the stevia plant's growth and biomass. However, application of GB improved the adaptation of NaCl-stressed plants by improving N metabolism and modulating the metabolism of polyamines. By increasing the activity of antioxidant enzymes, GB diminished oxidative stress, protected the plasma membrane, and restored photosynthetic pigments under NaCl toxicity. By reducing Na accumulation and increasing K accumulation, GB maintained the K/Na balance and reduced the effects of toxicity caused by the high Na concentration in stevia leaves. GB increased the leaf accumulation of rebaudioside A in NaCl-stressed plants by modulating the expression of genes (KAH, UGT74G1, UGT76G1, and UGT85C2) involved in the sugar compounds of the stevia plants. Our results provide a broad understanding of GB-induced responses in NaCl-stressed plants, which can help increase our knowledge of the role of GB in the defense mechanisms of plants under abiotic stresses.