Melatonin Solution Research Articles

Melatonin-Mediated Modulation of Grapevine Resistance Physiology, Endogenous Hormonal Dynamics, and Fruit Quality Under Varying Irrigation Amounts.

Grapevine, as a globally significant economic fruit tree, is highly sensitive to water stress, which not only damages its growth but also affects the formation of fruit quality. Melatonin (MT), acting as a signaling molecule, plays a crucial role in plant stress responses. However, the regulatory mechanisms of MT on grape leaf physiological characteristics and fruit quality under different irrigation amounts have not been fully elucidated. In this experiment, grape leaves were treated with a 150 μmol·L-1 MT solution at 0, 30, 60, and 90 days after flowering under different irrigation amounts (360, 300, 240, and 180 mm). It was found that MT significantly increased the contents of osmotic adjustment substances in leaves, reduced the level of reactive oxygen species, enhanced the activity of antioxidant enzymes, and promoted the metabolism of the ascorbic acid-glutathione cycle, thereby improving the antioxidant capacity of grapes and effectively alleviating the damage caused by a water deficit. At the same time, MT also maintains the dynamic balance of endogenous hormones by upregulating and downregulating the expression levels of related genes, thereby improving fruit quality. In summary, this study reveals the potential application value of MT in enhancing the drought resistance and fruit quality of grapes.

Lipopeptides from Bacillus atrophaeus MCM61 and melatonin suppress gray mold-induced oxidative stress in cut roses (Rosa hybrida L.) and improve vase life.

Application of melatonin and lipopeptides (LPs) derived from Bacillus strains is considered an efficient strategy to control plant diseases atboth pre and postharvest stages. However, the combined application of melatonin and LPs has not been studied yet. Therefore, the present study presents the synergistic effect of melatonin and LPs produced by Bacillus atrophaeus strain MCM61 against gray mold disease and its impact on quality parameters and vase life of cut roses. The stems of cut roses alongwith flowers were dipped in the melatonin solution at concentration (0, 0.2, 0.4, 0.6, and 0.8mM) and the results indicated thatthe vase life of flowers treated with the melatonin was enhanced compared to control. Melatonin at 0.6mM concentration showed the highest vase life of cut roses at day 8. Synergistic treatment with melatonin and LPs of B. atrophaeus MCM61 revealed that MDA and H2O2 content showed the highest decrease in cut roses. Similarly, relative water content, total phenol content, GSH content, and defense enzymes i.e., APX, SOD, PPO, POD, and CAT activities were increased in cut roses treated with co-application of B. atrophaeus MCM61 LPsand melatonin compared to single treatments and control treatment. Furthermore, the longevity of cut roses was also improved in flowers treated with a combined application of MCM61 and melatonin compared to other treatments.

Estimation of the adaptogenic potential of melatonin on salinity resistance of spring wheat seeds and sprouts

The current paper is devoted to the study of melatonin as an adaptogen capable of increasing wheat tolerance to stress caused by excess levels of easily soluble salts in the environment. The purpose of the study was to evaluate, within the framework of a laboratory model experiment, the ability of melatonin to increase seed germination and stimulate growth processes in wheat sprouts against the background of salinity. The study was conduc ted at the FSBI All-Russian Scientific Research Institute of Agrochemistry named after D.N. Pryanishnikov in 2024. The study objects were seeds of the spring wheat variety ‘Darya’. Before the experiment, the seeds were treated with aqueous solutions of melatonin in concentrations of 0; 0.01; 0.1; 1 and 10 mg/l using the priming method. Distilled water and a 150 mM sodium chloride solution were used as background solutions for germination. As a result, there has been shown that within the framework of the experiment, there is an increase in seed germination against the background of treatment with melatonin solutions in concentrations from 0.1 to 10 mg/l against a saline background. Seed treatment with melatonin has demonstrated a pronounced growth-stimulating effect on wheat sprouts, especially in relation to the root system. However, the strength of this effect was somewhat reduced on a saline background compared to control conditions. There was a maximum growth-stimulating effect of melatonin on both backgrounds when using a solution with a concentration of 1 mg/l. There was also established that priming seeds with melatonin promoted water retention in seedling root cells, which may be one of the mechanisms for increasing plant resistance to salinity.

Salt stress in melon (Cucumis melo L.) is alleviated by seed treatment with melatonin, modifying physiological and biochemical parameters

Melatonin (N-acetyl-5-methoxytryptamine) is a molecule with a reported importance in increasing tolerance to several types of stress. The present study investigates the effect of melon (Cucumis melo L.) seed treatment with melatonin solutions (0, 10, 50 and 100 μM) at two durations (6 and 12 h) on germination and initial growth of melon plants in salt stress. Germination under salt stress (14 dS m-1 EC) suffered a decrease, which is reversed after seed treatment with melatonin and followed to 80% with 10 and 50 μM solutions. Then, considering plant growing in salt stress (8 dS m-1 EC), the best growth and physiological and biochemical responses (xylem water potential, leaf relative water content, total chlorophyll, root viability, proline, malondialdehyde content, peroxidase and catalase activity) were measured in plants derived from 50 μM seed treatment. No changes were observed at the anatomical level. Results suggest that melatonin can alleviate the effect of salt stress during seed germination and early plant growth. There is a dose-dependent response.

The Physiological Mechanism of Exogenous Melatonin on Improving Seed Germination and the Seedling Growth of Red Clover (Trifolium pretense L.) under Salt Stress.

Salt stress can affect various physiological processes in plants, ultimately hindering their growth and development. Melatonin (MT) can effectively resist multiple abiotic stresses, improving plant stress resistance. To analyze the mechanism of exogenous MT to enhance salt tolerance in red clover, we conducted a comprehensive study to examine the influence of exogenous MT on various parameters, including seed germination indices, seedling morphological traits, and physiological and photosynthetic indicators, using four distinct red clover varieties (H1, H2, H3, and H4). This investigation was performed under various salt stress conditions with differing pH values, specifically utilizing NaCl, Na2SO4, NaHCO3, and Na2CO3 as the salt stressors. The results showed that MT solution immersion significantly improved the germination indicators of red clover seeds under salt stress. The foliar spraying of 50 μM and 25 μM MT solution significantly increased SOD activity (21-127%), POD activity, soluble sugar content, proline content (22-117%), chlorophyll content (2-66%), and the net photosynthetic rate. It reduced the MDA content (14-55%) and intercellular CO2 concentration of red clover seedlings under salt stress. Gray correlation analysis and the Mantel test further verified that MT is a key factor in enhancing seed germination and seedling growth of red clover under salt stress; the most significant improvement was observed for NaHCO3 stress. MT is demonstrated to improve the salt tolerance of red clover through a variety of mechanisms, including an increase in antioxidant enzyme activity, osmoregulation ability, and cell membrane stability. Additionally, it improves photosynthetic efficiency and plant architecture, promoting energy production, growth, and optimal resource allocation. These mechanisms function synergistically, enabling red clover to sustain normal growth and development under salt stress.

Anti-browning action of melatonin is dependent on the type of tissue in minimally processed sweet potatoes

This study explored the impact of exogenous melatonin on oxidative damage, protective mechanisms against oxidation, and reactions leading to browning, as well as the accumulation of antioxidants in minimally processed white-fleshed and orange sweet potato roots. Sweet potato roots with white and orange pulp were subjected to minimal processing and immersion in melatonin solutions at concentrations of 0, 10, 100, and 1000 µmol L−1. Following packaging, these were stored at 5 ± 2 °C for 20 days. Results indicate that increasing melatonin concentrations significantly reduced browning symptoms in both white and orange sweet potato slices. This reduction was associated with decreased levels of hydrogen peroxide (H2O2), thiobarbituric acid-reactive substances (TBARs), and electrolyte leakage, indicating reduced cell membrane damage. Enhanced protection was observed through increased activity of antioxidant enzymes superoxide dismutase, catalase, and ascorbate peroxidase and higher levels of antioxidant metabolites, including vitamin C and phenolic compounds, as confirmed by in vitro assays for antioxidant capacity (FRAP and DPPH), however, the levels of total carotenoids, anthocyanins, and yellow flavonoids did not show a significant difference between the melatonin treatments. Notably, sweet potato slices treated with higher melatonin doses of 100 and 1000 µmol L−1 exhibited reduced phenylalanine ammonia-lyase activity and phenolic compound accumulation. This effect, coupled with lower polyphenol oxidase (PPO) and peroxidase (POD) activities, likely contributed to prolonged preservation quality by maintaining cellular redox homeostasis.

Impact of Local Melatonin Application on Expression Level of Osteogenic Marker (Runx2) and Post-orthodontic Relapse in Ovine Model: A Split Mouth Study

Background: Retaining teeth in their proper alignment after orthodontic treatment can be highly challenging. This study aimed to estimate the effectiveness of locally injected melatonin in improving bone remodelling and reducing post-orthodontic relapse. Methods: The third incisors on the right and left quadrants of six sheep were removed and the second and fourth incisors were brought close together by using a sectional orthodontic appliance. Melatonin solution was injected near and parallel to the mesial surface of the second incisor and the distal surface of the fourth incisor on one quadrant while the other quadrant received 1% dimethyl sulphoxide as a control. Four weeks later, the orthodontic appliance was debonded and the teeth were allowed to move back. By utilizing digital analysis, the relapse distance of the approximated incisors was measured at 21 and 42 days respectively after appliance removal. Histological and mRNA expression analysis of osteogenic marker (Runx2) were conducted to evaluate the periodontal space width and the surrounding alveolar bone of the melatonin-treated and control side incisors. Result: clinical and histological measurements showed that the approximated incisors in the melatonin-treated quadrant had a significantly shorter relapse distance (p≤0.05), significantly smaller periodontal ligament width (p≤0.05) and significantly larger new bone area formation (p≤0.05) than in the control quadrant. The mRNA expression level of the osteogenic marker (Runx2) was significantly larger (p≤0.05) in the melatonin-treated quadrant than in the control quadrant. The outcomes of this research suggest that melatonin can enhance bone remodelling and reduce post-orthodontic relapse in sheep.

Involvement of ROS and calcium ions in developing heat resistance and inducing antioxidant system of wheat seedlings under melatonin's effects.

The stress-protective effect of melatonin (N-acetyl-5-methoxytryptamine) on plant cells is mediated by key signaling mediators, in particular calcium ions and reactive oxygen species (ROS). However, the links between changes in calcium and redox homeostasis and the formation of adaptive responses of cultivated cereals (including wheat) to the action of high temperatures have not yet been studied. In the present study, we investigated the possible involvement of ROS and calcium ions as signaling mediators in developing heat resistance in wheat (Triticum aestivum L.) seedlings and activating their antioxidant system. Treatment of 3-day-old etiolated seedlings with melatonin solutions at concentrations 0.01-10µM increased their survival after exposure to 45°C for 10min. The most significant stress-protective effect was exerted by melatonin treatment at 1µM concentration. Under the influence of melatonin, a transient enhancement of superoxide anion radical (O2•-) generation and an increase in hydrogen peroxide content were observed in roots, with a maximum at 1h. Four hours after treatment with melatonin, the activity of catalase and guaiacol peroxidase increased in roots, while the activity of superoxide dismutase did not change significantly. After exposure to 45°C, the activity of catalase and guaiacol peroxidase was higher in the roots of melatonin-treated wheat seedlings, and the indices of ROS generation, content of the lipid peroxidation product malonic dialdehyde, and cell membrane damage were lower than in control seedlings. Melatonin-induced changes in root ROS generation and antioxidant enzyme activities were eliminated by pretreatment with the hydrogen peroxide scavenger dimethylthiourea (DMTU), NADPH oxidase inhibitor imidazole, and calcium antagonists (the extracellular calcium chelator EGTA and phospholipase C inhibitor neomycin). Treatment with DMTU, imidazole, EGTA, and neomycin also abolished the melatonin-induced increase in survival of wheat seedlings after heat stress. The role of calcium ions and ROS, generated with the participation of NADPH oxidase, as signaling mediators in the melatonin-induced antioxidant system and heat stress resistance of wheat seedlings have been demonstrated.

Effects of exogenous melatonin on the osmotic regulation and antioxidant capacity of Ginkgo biloba seedlings under salt stress.

We investigated the effects of exogenous melatonin on the osmotic regulation and antioxidant capacity of 4-year-old Ginkgo biloba seedlings under salt stress. There were three treatments, with low (50 mmol·L-1), medium (100 mmol·L-1), and high (200 mmol·L-1) NaCl stress. Leaves were sprayed and the soil was watered with melatonin solution (0, 0.02, 0.1, 0.5 mmol·L-1). The results showed that saline stress significantly inhibited the osmoregulation and antioxidant capacities of G. biloba seedlings. Application of exogenous melatonin at appropriate concentrations (0.02, 0.1 mmol·L-1) under salt stress could promote plant growth, reduce the rate of electrolyte leakage, decrease the content of flavonoids and malonic dialdehyde, and enhance peroxidase and superoxide dismutase activities in leaves. High concentration (0.5 mmol·L-1) of exogenous melatonin would aggravate the oxidative and osmotic stresses. The 0.02 and 0.1 mmol·L-1 exogenous melatonin alleviated osmotic stress and oxidative stress in G. biloba seedlings under salt stress, while the 0.02 mmol·L-1 exogenous melatonin treatment had the best effect on NaCl stress alleviation. Ground diameter, branch width, branch length, electrolyte leakage rate, superoxide dismutase activity, and flavonoids content could be used as the key indices for rapid identification of the degree of salt stress in G. biloba seedlings.

The Effect of Subcutaneously Administered Crystal's Oily Solution on Estrus and Conception Rates in Ewes

The study aims to evaluate the effects of subcutaneously (SC) injected oily solution of melatonin crystal at different doses in 2-3 years, healthy, multiparous sheep during the anoestrus period on serum melatonin and prolactin levels, estrus occurrence, mating, conception, and pregnancy rates. The study group consists of 350 ewes. The ewes were divided into 5 groups: MEL10 (n=70, 10mg melatonin), MEL20 (n=70, 20mg melatonin), MEL40 (n=70, 40mg melatonin), placebo (n=70), and control (n=70) groups. The melatonin groups received SC injections of the oily melatonin solution 11 days before ram introduction. The placebo group received only the oily solution. The control group did not receive any treatment. Blood samples were collected from all groups before the melatonin injection and on the 11th day after the injection. The data showed that the melatonin level in the blood samples collected before and after the injection increased in the MEL10 (P:0.045) and MEL20 (P:0.0359) groups. Additionally, the prolactin level decreased in the second blood sample collected from all groups (P>0.05). Regarding reproductive parameters, the estrus rate in the MEL10, MEL20, MEL40, placebo, and control groups was 75.71%, 58.57%, 54.28%, 51.42%, and 52.85%, respectively. The mating rate was 61.42%, 57.14%, 52.85%, 48.57%, and 50% in the same groups, and the pregnancy rate was 60%, 52.85%, 42.85%, 41.42%, and 38.57%, respectively. The conception rate was determined as 97%, 92%, 81%, 85%, and 77% in the MEL10, MEL20, MEL40, placebo, and control groups, respectively. In conclusion, subcutaneous injection of melatonin at appropriate doses to sheep can indirectly simulate the breeding season, and stimulate heat. Additionally, it can increase pregnancy and conception rates. This method can considered a potential alternative to melatonin implants or different synchronization methods in the future.

Melatonin alleviates pyroptosis by regulating the SIRT3/FOXO3α/ROS axis and interacting with apoptosis in Atherosclerosis progression

BackgroundAtherosclerosis (AS), a significant contributor to cardiovascular disease (CVD), is steadily rising with the aging of the global population. Pyroptosis and apoptosis, both caspase-mediated cell death mechanisms, play an essential role in the occurrence and progression of AS. The human pineal gland primarily produces melatonin (MT), an indoleamine hormone with powerful anti-oxidative, anti-pyroptotic, and anti-apoptotic properties. This study examined MT’s anti-oxidative stress and anti-pyroptotic effects on human THP-1 macrophages treated with nicotine.MethodsIn vitro, THP-1 macrophages were induced by 1 µM nicotine to form a pyroptosis model and performed 30 mM MT for treatment. In vivo, ApoE-/- mice were administered 0.1 mg/mL nicotine solution as drinking water, and 1 mg/mL MT solution was intragastric administrated at 10 mg/kg/day. The changes in pyroptosis, apoptosis, and oxidative stress were detected.ResultsMT downregulated pyroptosis, whose changes were paralleled by a reduction in reactive oxygen species (ROS) production, reversal of sirtuin3 (SIRT3), and Forkhead box O3 (FOXO3α) upregulation. MT also inhibited apoptosis, mainly caused by the interaction of caspase-1 and caspase-3 proteins. Vivo studies confirmed that nicotine could accelerate plaque formation. Moreover, mice treated with MT showed a reduction in AS lesion area.ConclusionsMT alleviates pyroptosis by regulating the SIRT3/FOXO3α/ROS axis and interacting with apoptosis. Importantly, our understanding of the inhibitory pathways for macrophage pyroptosis will allow us to identify other novel therapeutic targets that will help treat, prevent, and reduce AS-associated mortality.

Metabolic Profiling and Molecular Mechanisms Underlying Melatonin-Induced Secondary Metabolism of Postharvest Goji Berry (Lycium barbarum L.).

Postharvest decay of goji berries, mainly caused by Alternaria alternata, results in significant economic losses. To investigate the effects of melatonin (MLT) on resistance to Alternaria rot in goji berries, the fruits were immersed in the MLT solutions with varying concentrations (0, 25, 50, and 75 μmol L-1) and then inoculated with A. alternata. The results showed that the fruits treated with 50 μmol L-1 MLT exhibited the lowest disease incidence and least lesion diameter. Meanwhile, endogenous MLT in the fruits treated with 50 μmol L-1 MLT showed higher levels than in the control fruits during storage at 4 ± 0.5 °C. Further, the enzymatic activities and expressions of genes encoding peroxidase, phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, 4-coumarate-CoA ligase, chalcone synthase, chalcone isomerase, and cinnamyl alcohol dehydrogenase were induced in the treated fruit during storage. UPLC-ESI-MS/MS revealed that secondary metabolites in the fruits on day 0, in order of highest to lowest levels, were rutin, p-coumaric acid, chlorogenic acid, ferulic acid, caffeic acid, naringenin, quercetin, kaempferol, and protocatechuic acid. MLT-treated fruits exhibited higher levels of secondary metabolites than the control. In conclusion, MLT treatment contributed to controlling the postharvest decay of goji fruit during storage by boosting endogenous MLT levels, thus activating the antioxidant system and secondary metabolism.

Prolong the postharvest shelf life of spinach through the antioxidative ability of melatonin.

Spinach is also known as Persian cuisine, it is rich in nutrients such as protein, vitamin C and minerals, and has high nutritional value. In this study, Spinach was treated with melatonin in order to prolong its shelf life. Melatonin has strong antioxidant effects as an endogenous free radical scavenger. The spinach was sprayed with 0.10, 0.20 and 0.30mg/mL melatonin solution after harvesting, and distilled water was used as control for low temperature storage at 4°C. The results showed that melatonin spraying Spinach delayed the degradation of chlorophyll, especially the treatment of 0.20mg/mL melatonin was the most effective. The content of soluble sugar and soluble protein in spinach tissue was kept high, the accumulation of malondialdehyde (MDA) was reduced, and the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were increased. These findings suggested that melatonin treatment may be a useful technique to prolong the postharvest life of spinach and improve its quality.

Melatonin induces resistance against Penicillium expansum in apple fruit through enhancing phenylpropanoid metabolism

Apple fruit is delicious fruit with great economic value. However, harvested apples are susceptible to the infection of Penicillium expansum, which results in quality degradation. ‘Golden Delicious’ apples were dipped with melatonin solution to investigate its influence on blue mold and the dynamic changes of the major metabolites contents and enzymes activities in phenylpropanoid metabolism. Melatonin markedly suppressed lesion development of P. expansum-inoculated apple fruit. Melatonin dipping also distinctly improved 4-coumarate coenzyme A ligase, cinnamic acid 4-hydroxylase, phenylalanine ammonia lyase, polyphenol oxidase, laccase, glucose-6-phosphate dehydrogenase, and glucose phosphate isomerase activities. Moreover, p-coumaric acid, total phenolic compounds, ferulic acid, flavonoids, erucic acid, caffeic acid, lignin, phenylalanine, tyrosine, and tryptophan contents were also enhanced by melatonin. All these findings indicate that melatonin treatment activates the key enzyme activity in phenylpropanoid metabolism to accelerate metabolites accumulation in apples, therefore inducing resistance to blue mold.

Effect of Acute Melatonin Injection on Metabolomic and Testicular Artery Hemodynamic Changes and Circulating Hormones in Shiba Goats under Sub-Tropical Environmental Conditions.

The beneficial effects of melatonin were investigated to mitigate various detrimental effects and toxicity on reproductive performance. The present study aimed, for the first time, to explore the effect of intravenous melatonin injection on testicular artery hemodynamics (TH) and metabolomic changes, reproductive hormones in heat-stressed bucks. Ten bucks were randomly split into two groups (five each): (1) the melatonin group, treated with a single intravenous dose of melatonin solution containing 10 mg melatonin each, and (2) the control group, which was treated with 10 mL of the vehicle without melatonin. Changes in the TH at the level of the supra testicular artery (STA) were assessed by triplex ultrasonography just before (0 h) and at 0.5, 2, 7, 24, and 168 h after melatonin or vehicle administration. Doppler velocity parameters of peak systolic velocity (PSV; cm/s), end-diastolic velocity (EDV; cm/s), and time average maximum velocity (TAMAX; cm/s) were measured. Doppler indices (resistive index; RI and pulsatility index; PI), systole/diastole (S/D) ratio and total arterial blood flow volume (TABFV; ml/minute) were measured. Peripheral concentrations of FSH, LH, inhibin, melatonin, testosterone (T), estradiol (E2), and cortisol were measured just before injection (0 h) and at 0.5, 2, 7, and 24 h and daily up to day 7 post administration in both groups. Results revealed reductions in the RI values and increases in the TABFV in the melatonin group compared to the control one, especially 2 h after administration. Significant increases in concentrations of FSH, T, E2, and melatonin and decreases in cortisol and inhibin in the melatonin group compared to the control one. Plasma metabolomic analysis at 2 h indicated the up-regulation of L-glutamine, L-arginine, sorbitol, D-glucose, ascorbic acid, and ornithine and the down-regulation of D-xylose, D-arabitol, ribitol, and oleic acid in the melatonin versus the control group. In conclusion, acute administration of melatonin (10 mg IV) enhanced testicular artery blood flow and plasma reproductive hormones in the Shiba goat under heat-stress circumstances.

Comparative Effect of Melatonin and 1-Methylcyclopropene Postharvest Applications for Extending ‘Hayward’ Kiwifruit Storage Life

Kiwifruit, like many other fruits, is susceptible to dehydration, leading to texture changes and a loss of flavour during storage. Exposing kiwifruit to suboptimal temperatures can control these changes but can cause internal browning. Postharvest treatments with substances such as 1-methylcyclopropene (1-MCP) are some of the most successful commercial technologies in the conservation of fruits and vegetables. In recent years, there has been a growing interest among researchers in alternative technologies based in postharvest treatments with plant growth regulators. In this sense, melatonin (MT) has been shown to improve fruit quality, extending shelf life. The aim of this study was to compare these two different technologies applied at postharvest to evaluate the impact on kiwifruit quality. Optimal 1-MCP fumigations and MT solutions were assayed on ‘Hayward’ kiwifruit under similar conditions. Quality parameters were evaluated at 14-day intervals during 84 days of cold storage plus 5 days at 20 °C. The results showed that both treatments were similarly effective in maintaining quality parameters such as weight loss, respiration, firmness, and acidity. Although 1-MCP treatments delayed the evolution of kiwifruit colour and chlorophyll degradation as compared to MT, MT treatments controlled chilling injury better than 1-MCP. This effect was not related to a greater cell membrane integrity since fruit batches treated with 1-MCP were the ones that showed the lowest electrolyte leakage level. In conclusion, both treatments maintained fruit quality and delayed ripening in a similar way. In this sense, the results suggest that MT immersion treatments could act as efficient delaying senescence as fumigations with 1-MCP maintaining kiwifruit quality during refrigerated storage.

Melatonin treatment alleviates chilling injury in mango fruit ‘Keitt’ by modulating proline metabolism under chilling stress

Mangoes often suffer from low temperature-induced chilling injury (CI) during postharvest cold storage. Therefore, advanced techniques are crucial and in high demand to solve the chilling stress of mango fruit for a higher value. This study addresses chilling stress modulation by investigating the effects of melatonin treatment on CI, proline metabolism, and related gene expressions of ‘Keitt’ mango during cold storage after dipped in 0 (control), 0.1 (MT1), and 0.2 mmol L-1 (MT2) melatonin solution for 30 min. The results revealed that melatonin treatment in MT1 significantly reduced CI development and increased proline content in mango fruit during cold storage compared to the control. These changes were along with increases in the activity of critical enzymes as well as the expression of encoding genes involved in proline biosynthesis, such as pyrroline-5-carboxylate synthetase (P5CS), pyrroline-5-carboxylate reductase (P5CR), ornithine D-aminotransferase (OAT), P5CS2, P5CR2, and OAT3. Additionally, proline dehydrogenase (PDH) activity and the expression of the PDH3 gene associated with proline dehydrogenation were lower in MT1-treated mangoes than the controlled group. Thus, melatonin treatment has regulated proline metabolism resulting in the accumulation of proline, subsequently contributing to enhancing the chilling tolerance of ‘Keitt’ mango fruit.

Melatonin reduces pink rib discoloration in wounded lettuce midribs

Pink rib discoloration is a physiological disorder resulting in loss of quality and marketability of minimally processed and whole head lettuce (Lactuca sativa L.). Although the biochemistry of pink rib is complex and a comprehensive understanding is lacking, multiple research efforts have focused on inhibiting or reducing pink rib through exogenous application of small molecules such as L-cysteine. In this study, the effects of naturally occurring phytochemicals [serotonin (0.5 or 1 g L−1), naringenin (0.5 g L−1), L-cysteine (0.5 g L−1), and melatonin (1 g L−1)] on pink rib expression were examined in iceberg and Romaine lettuce. The exogenous application of these natural compounds was investigated for reduced pink rib discoloration in lettuce during simulated commercial storage and examined for metabolite and enzymatic activity changes. Immersing wounded midribs for 30 s in serotonin, naringenin, or L-cysteine solutions had no or only a slight inhibitory effect to inhibit pink rib discoloration while those immersed in a melatonin solution had reduced development of pink rib in both iceberg and Romaine lettuces after 5 d at 5 °C. Phenylalanine ammonia lyase (PAL) activity and chlorogenic acid concentration increased upon pink rib discoloration, consistent with previous reports. However, melatonin-treated samples did not result in reduced PAL activity, chlorogenic acid content, or polyphenol oxidase (PPO) activity. Untargeted metabolite analysis showed that melatonin treatment resulted in a global effect on metabolite changes in the wounded lettuce midrib tissue. To compare the severity of pink rib among treatments, pink rib was quantified throughout storage visually and by converting digital images of the lettuce midribs to the L*a*b* color space. The a* component of L*a*b* represents redness versus greenness, thus its values were used to objectively measure pink rib severity. Melatonin was shown to be a promising compound to minimize development of pink rib discoloration at cut surfaces of iceberg and Romaine lettuce during commercial handling and storage.

Melatonin supplementation promotes muscle fiber hypertrophy and regulates lipid metabolism of skeletal muscle in weaned piglets.

Melatonin has been reported to play crucial roles in regulating meat quality, improving reproductive properties, and maintaining intestinal health in animal production, but whether it regulates skeletal muscle development in weaned piglet is rarely studied. This study was conducted to investigate the effects of melatonin on growth performance, skeletal muscle development, and lipid metabolism in animals by intragastric administration of melatonin solution. Twelve 28-d-old DLY (Duroc × Landrace × Yorkshire) weaned piglets with similar body weight were randomly divided into two groups: control group and melatonin group. The results showed that melatonin supplementation for 23 d had no effect on growth performance, but significantly reduced serum glucose content (P < 0.05). Remarkably, melatonin increased longissimus dorsi muscle (LDM) weight, eye muscle area and decreased the liver weight in weaned piglets (P < 0.05). In addition, the cross-sectional area of muscle fibers was increased (P < 0.05), while triglyceride levels were decreased in LDM and psoas major muscle by melatonin treatment (P < 0.05). Transcriptome sequencing showed melatonin induced the expression of genes related to skeletal muscle hypertrophy and fatty acid oxidation. Enrichment analysis indicated that melatonin regulated cholesterol metabolism, protein digestion and absorption, and mitophagy signaling pathways in muscle. Gene set enrichment analysis also confirmed the effects of melatonin on skeletal muscle development and mitochondrial structure and function. Moreover, quantitative real-time polymerase chain reaction analysis revealed that melatonin supplementation elevated the gene expression of cell differentiation and muscle fiber development, including paired box 7 (PAX7), myogenin (MYOG), myosin heavy chain (MYHC) IIA and MYHC IIB (P < 0.05), which was accompanied by increased insulin-like growth factor 1 (IGF-1) and insulin-like growth factor binding protein 5 (IGFBP5) expression in LDM (P < 0.05). Additionally, melatonin regulated lipid metabolism and activated mitochondrial function in muscle by increasing the mRNA abundance of cytochrome c oxidase subunit 6A (COX6A), COX5B, and carnitine palmitoyltransferase 2 (CPT2) and decreasing the mRNA expression of peroxisome proliferator-activated receptor gamma (PPARG), acetyl-CoA carboxylase (ACC) and fatty acid-binding protein 4 (FABP4) (P < 0.05). Together, our results suggest that melatonin could promote skeletal muscle growth and muscle fiber hypertrophy, improve mitochondrial function and decrease fat deposition in muscle.

Biochemical Mechanism of Fresh-Cut Lotus (Nelumbo nucifera Gaertn.) Root with Exogenous Melatonin Treatment by Multiomics Analysis

Browning limits the commercial value of fresh-cut lotus root slices. Melatonin has been reported to play crucial plant roles in growth and development. However, the mechanisms in repressing the browning of fresh-cut lotuses are still unclear. In this study, fresh-cut lotus root slices were treated with melatonin, the physical signs of browning were tested, and then the selected samples (0 d, 6 d, 12 d) were used in multiomics analysis. Fresh-cut lotus root slices with a thickness of 4 mm were soaked in a 40 mmol/L melatonin solution for 10 min; then, the slices were packed in pallets and packages and stored at 10 ± 1 °C. The results show that the 40 mmol/L melatonin selected for repressing the browning of lotus roots significantly delayed the decrease in water, total soluble solid content, and Vitamin C, decreased the growth of microorganisms, enhanced total phenolic content, improved total antioxidant capacity, and decreased ·OH, H2O2, and O2-· contents. Moreover, this treatment enhanced phenylalanine ammonialyase, polyphenol oxidase, superoxide dismutase, and catalase activities and reduced peroxidase activities and soluble quinones. NnSOD (104590242), NnCAT (104609297), and some NnPOD genes showed a similar transcript accumulation pattern with enzyme activity. It can be seen from these results that exogenous melatonin accelerated an enhancement in the antioxidant system and AsA-GSH cycle system by regulating ROS-metabolism-related genes, thereby improving the capacity to withstand browning and the quality of lotus root slices. The microbiome also showed that melatonin suppressed the fertility of spoilage organisms, such as Pseudomonas, Tolumonas, Acinetobacter, Stenotrophomonas, and Proteobacteria. Metabonomics data uncovered that the metabolites of flavonoid biosynthesis, phenylpropanoid biosynthesis, tyrosine metabolism, and phenylalanine metabolism were involved in the process.