Melatonin maintained higher contents of unsaturated fatty acid and cell membrane structure integrity in banana peel and alleviated postharvest chilling injury

Effect of oat β-glucan on the freezing resistance of yeast and the underlying mechanism

The objective of this study was to investigate the protective effects of oat β-glucan (OβG) on yeast subjected to freeze-thaw cycle-induced stress. A range of analytical techniques were employed to identify the underlying molecular mechanisms, including flow cytometry, gas chromatography-mass spectrometry, and quantitative real-time PCR. Following three freeze-thaw cycles, the survival rate of yeast that had been supplemented with 0.5 % OβG was found to be significantly higher than that of the control sample, increasing from 36.21 % to 56.81 %. The addition of 0.5 % OβG resulted in a remarkable reduction in apoptosis, an improvement in cell membrane integrity, and an increase in superoxide dismutase, catalase activity and glutathione content compared to the control group. Furthermore, a noticeable increment in the intracellular trehalose content was observed, from 4.10 mg/g to 7.48 mg/g. OβG modulated the expression of trehalose metabolism-related genes (ATH1, NTH1, NTH2) throughout the freeze-thaw cycle. Therefore, it could be concluded that OβG protected yeast cells against excessive reactive oxygen species and minimised oxidative damage to cellular membranes by upregulating antioxidant enzyme activity and total antioxidant capacity. Moreover, the supplementation of OβG was also found to be effective in increasing intracellular trehalose levels, thereby enhancing the freezing resistance of yeast cells.

Comparative transcriptomic analysis reveals the reactive oxygen species metabolism involving in melatonin-alleviated chilling injury in postharvest banana fruit

Banana fruit is susceptible to chilling injury (CI) during cold storage, which causes quality deterioration and commodity value decline. Here, the effects of melatonin on CI alleviation and reactive oxygen species (ROS) metabolism in postharvest banana were studied. The results displayed that 500 μmol L-1 melatonin treatment effectively inhibited CI development in cold-stored banana during the 96 h of storage. Additionally, lower O2.- productive rate and H2O2 content, but higher contents of ascorbic acid (AsA) and glutathione (GSH) were found in melatonin-treated banana, compared with control fruits. Also, melatonin inhibited the declined activities of antioxidant enzymes. Moreover, a total of 1858 and 330 differentially expressed genes (DEGs) were identified between the comparison of CK48h (control bananas at 48 h) and MT48h (melatonin-treated bananas at 48 h), and CK96h (control bananas at 96 h) and MT96h (melatonin-treated bananas at 96 h) through comparative transcriptome analysis of banana fruit, respectively. Further KEGG displayed that DEGs were enriched in secondary metabolites biosynthesis, MAPK signaling pathway-plant and plant hormone signal transduction. The transcriptome expression profiling and RT-qPCR exhibited melatonin treatment improved the expressions of antioxidant enzyme genes (MaSOD, MaCAT, MaAPX and MaGR) but inhibited the expression of ROS production gene (MaRBOH). Collectively, these findings provide a comprehensive view of ROS metabolism associated with the melatonin-alleviated CI in cold-stored banana fruit.

Deciphering the Effect of Postharvest 1-MCP Treatment Coupled with Low-Temperature Storage on the Physiological Activities and Edible Quality of Melon

Fruits are an important source of a healthy diet due to their essential nutrients for daily intake. Melon is known as a significant fruit crop of the Cucurbitaceae family based on its various dietary benefits, but its shelf life needs to be maintained for long-term usage. 1-Methylcyclopropene (1-MCP) is a cyclopropene-derived synthetic plant growth regulator (PGR) that is used for significantly delaying the ripening process and maintaining the shelf life of climacteric fruits during storage. In this study, freshly harvested melon fruits were fumigated with various concentrations (1.0 µL·L-1, 2.0 µL·L-1, and 3.0 µL·L-1) of 1-MCP treatment for 12 h (h) and stored at low temperature (8 ± 1 °C) for 30 days (d). The obtained results showed that 1-MCP fumigation coupled with low-temperature treatment maintains the postharvest shelf life of melon fruit. It was noticed that the increase in color hue (a* (red/green), b* (blue/yellow), L* (lightness)) was slowed down and the external fresh color was effectively maintained. At the same time, the firmness, soluble solids, titratable acids (TAs), and vitamin C (VC) content seemed to be maintained at a high level; weight loss and cell permeability were reduced; respiratory intensity and ethylene emission were inhibited; and the accumulation of superoxide anions and malondialdehyde (MDA) was also reduced. In addition, an upsurge in the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) was noticed in melon fruits under the combined treatment of 1-MCP and low-temperature storage as compared with the control group (CK, without treatment), indicating that 1-MCP treatment can effectively enhance the antioxidant metabolism of melon fruits during storage. Overall, we can recommend that the 3.0 µL·L-1 concentration of 1-MCP had the best effect on maintaining the internal and external quality of sweet melon fruit during storage.

Hydrogen sulfide attenuates chilling injury in loquat fruit by alleviating oxidative stress and maintaining cell membrane integrity

The effects of hydrogen sulfide (H2S) on chilling injury (CI), reactive oxygen species (ROS) metabolism, sugar metabolism, pentose phosphate pathway (PPP), and membrane lipid metabolism in loquat fruit throughout the refrigerated period were investigated in this study. The findings indicated that H2S application restrained the increase in internal browning (IB), malondialdehyde (MDA) content, and electrolyte leakage, while sustaining higher total phenolic and total flavonoid levels, and lower soluble quinone content in loquat fruit. Besides, H2S promoted antioxidant accumulation and increased antioxidant enzyme activities by the regulation of ROS metabolism, along with increasing fructose and glucose levels and reducing power by activating sugar metabolism and PPP. Furthermore, H2S treatment retarded the degradation of phospholipids and fatty acids in loquat fruit by modulating membrane lipid metabolism relevant enzyme activities. These findings indicated that H2S application mitigated CI in loquat fruit by alleviating oxidative stress and maintaining cell membrane structural integrity.

Melatonin alleviated chilling injury of cold-stored passion fruit by modulating cell membrane structure via acting on antioxidant ability and membrane lipid metabolism

Fresh passion fruit is sensitive to chilling injury (CI) during storage at improper low temperature of 5 °C, which lowers the fruit quality and limits its shelf life. The present study aimed to determine the impacts of melatonin on CI development of passion fruit in relation to antioxidant ability and membrane lipid metabolism during refrigeration. In present study, passion fruit was treated with 0.50 mmol L-1 melatonin and distilled water (control) for 20 min, hereafter stockpiled at 5 °C. The results indicated that, in storage, melatonin-treated passion fruit showed the lower CI index and cell membrane permeability, lower superoxide anion production rate and malondialdehyde level, greater activities of catalase, superoxide dismutase and ascorbate peroxidase, higher levels of ascorbic acid and glutathione, and higher 1, 1-diphenyl-2-picrylhydrazyl radical scavenging capacity than control passion fruit. Besides, lower membrane lipid-degrading enzyme activities, lower contents of phosphatidic acid and saturated fatty acids (SFAs), higher levels of phosphatidylcholine, phosphatidylinositol and unsaturated fatty acids (USFAs), and greater ratio of USFAs to SFAs and index of USFAs were revealed in melatonin-treated passions than control passions. Thus, these results indicated that melatonin retained cell membrane structure via boosting antioxidant capacity and restricting membrane lipid degradation, accordingly increased the chilling resistance and delayed the CI development in fresh passion fruit.

Exogenous dopamine ameliorates chilling injury of banana fruits during cold storage

This study investigated postharvest dopamine treatment efficiency in ameliorating chilling injury of banana fruits during storage at 7 ºC for 21 days. Our results showed that dopamine treatment at 150 µM promoted phenols and flavonoids biosynthesis acquired by higher phenylalanine ammonia-lyase (PAL) expression and activity concurrent with lower polyphenol oxidase (PPO) expression and activity leading to higher DPPH, FRAP, and ABTS radicals scavenging activity. In addition, dopamine treatment at 150 µM promoted endogenous proline biosynthesis by activating pyrroline-5-carboxylate synthetase (P5CS) and ornithine δ-aminotransferase (OAT) expression and activity concurrent with suppressing proline dehydrogenase (ProDH) expression and activity. Furthermore, higher endogenous γ-aminobutyric acid (GABA) biosynthesis in banana fruits by 150 µM dopamine treatment was accompanied by higher glutamate decarboxylase (GAD) and GABA transaminase (GABA-T) expression and activity. Therefore, our results suggest that dopamine treatment at 150 µM might be employed for banana fruits chilling injury amelioration by enhancing phenylpropanoid pathway activity and boosting endogenous proline and GABA biosynthesis.

Melatonin Treatment Alleviates Chilling Injury of Loquat Fruit via Modulating ROS Metabolism

Cold storage is one of the most effective methods to maintain postharvest fruit quality. However, loquat fruits are prone to chilling injury (CI) during cold storage, appearing as symptoms such as browning and pitting, which leads to quality deterioration and economic losses. In this study, the effects of melatonin on CI alleviation and the potential role of reactive oxygen species (ROS) metabolism in loquat fruit were investigated. The results showed that 50 μM melatonin was the optimal concentration to inhibit the increase in CI index and cell membrane permeability. Moreover, compared to control fruits, 50 μM melatonin inhibited the malonaldehyde (MDA) content, O2-. production rate and H2O2 content (ROS accumulation) by 17.8%, 7.2% and 11.8%, respectively, during cold storage. Compared to non-treated loquats, 50 μM melatonin maintained higher levels of 1-diphenyl-2-picrylhydrazyl radical-scavenging ability and reducing power, as well as the contents of ascorbic acid (AsA) and glutathione (GSH). Additionally, 50 μM melatonin enhanced the activities of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) by increasing relevant gene expressions. The activities of SOD, CAT and APX were increased by up to 1.1-, 1.1- and 1.1-times (16 d) by melatonin, as compared with the control fruits. These findings indicate that melatonin mitigation of CI is involved in maintaining cellular redox apphomeostasis in loquat fruit during cold storage.

Banana Peel Extracts Enhance Climbing Ability and Extend Lifespan in Drosophila melanogaster

Banana peels, often discarded as waste, represent one of the most abundant food by-products, highlighting the need for effective waste management and resource recycling strategies. Due to their rich nutritional content, banana peels have been investigated for various health benefits, including anti-obesity effects. In this study, we examined the potential anti-aging properties of banana peel extracts (BPEs) in Drosophila melanogaster. Our findings demonstrated that flies fed with BPEs exhibited an extended lifespan and a significant improvement in age-related decline in climbing ability. Additionally, Dilp2 mRNA expression level is markedly decreased in aged flies fed with BPEs. These results suggest that BPEs may serve as a potential anti-aging agent by enhancing locomotor function and extending lifespan, potentially through the modulation of insulin signaling in D. melanogaster.

Phytomelatonin: From Intracellular Signaling to Global Horticulture Market

Melatonin (N-acetyl-5-methoxytryptamine), a well-known mammalian hormone, has been having a great relevance in the Plant World in recent years. Many of its physiological actions in plants are leading to possible features of agronomic interest, especially those related to improvements in tolerance to stressors and in the postharvest life of fruits and vegetables. Thus, through the exogenous application of melatonin or by modifying the endogenous biosynthesis of phytomelatonin, some change can be made in the functional levels of melatonin in tissues and their responses. Also, acting in the respective phytomelatonin biosynthesis enzymes, regulating the expression of tryptophan decarboxylase (TDC), tryptamine 5-hydroxylase (T5H), serotonin N-acetyltransferase (SNAT), N-acetylserotonin O-methyltransferase (ASMT), and caffeic acid O-methyltransferase (COMT), and recently the possible action of deacetylases on some intermediates offers promising opportunities for improving fruits and vegetables in postharvest and its marketability. Other regulators/effectors such as different transcription factors, protein kinases, phosphatases, miRNAs, protein-protein interactions, and some gasotransmitters such as nitric oxide or hydrogen sulfide were also considered in an exhaustive vision. Other interesting aspects such as the role of phytomelatonin in autophagic responses, the posttranslational reprogramming by protein-phosphorylation, ubiquitylation, SUMOylation, PARylation, persulfidation, and nitrosylation described in the phytomelatonin-mediated responses were also discussed, including the relationship of phytomelatonin and several plant hormones, for chilling injury and fungal decay alleviating. The current data about the phytomelatonin receptor in plants (CAND2/PMTR1), the effect of UV-B light and cold storage on the postharvest damage are presented and discussed. All this on the focus of a possible new action in the preservation of the quality of fruits and vegetables.

Exogenous melatonin activates the antioxidant system and maintains postharvest organoleptic quality in Hami melon (Cucumis. melo var. inodorus Jacq.)

Hami melon is prone to postharvest perishing. Melatonin is a signaling molecule involved in a variety of physiological processes in fruit, and it improves fruit quality. We hypothesized that melatonin treatment would improve the storage quality of Hami melon by altering its respiration and reactive oxygen species (Graphical abstract). Our results indicated that optimal melatonin treatment (0.5 mmol L-1) effectively slowed the softening, weight loss, and respiratory rate of the Hami melon fruit. Furthermore, melatonin markedly improved the antioxidant capacity of the fruit and protected it from oxidative damage by decreasing its contents of superoxide anions, hydrogen peroxide, and malondialdehyde. Melatonin significantly enhanced the activities of superoxide dismutase, catalase, ascorbate peroxidase, and peroxidase. The total phenol, total flavonoids, and ascorbic acid contents were maintained by melatonin treatment. This treatment also repressed the activities of lipase, lipoxygenase, and phospholipase D, which are related to lipid metabolism. Thus, exogenous melatonin can maintain postharvest organoleptic quality of Hami melon fruit by increasing its antioxidant activity and inhibiting reactive oxygen species production.

Exogenous Melatonin Enhances the Low Phosphorus Tolerance of Barley Roots of Different Genotypes

Melatonin (N-acetyl-5-methoxytryptamine) plays an important role in plant growth and development, and in the response to various abiotic stresses. However, its role in the responses of barley to low phosphorus (LP) stress remains largely unknown. In the present study, we investigated the root phenotypes and metabolic patterns of LP-tolerant (GN121) and LP-sensitive (GN42) barley genotypes under normal P, LP, and LP with exogenous melatonin (30 μM) conditions. We found that melatonin improved barley tolerance to LP mainly by increasing root length. Untargeted metabolomic analysis showed that metabolites such as carboxylic acids and derivatives, fatty acyls, organooxygen compounds, benzene and substituted derivatives were involved in the LP stress response of barley roots, while melatonin mainly regulated indoles and derivatives, organooxygen compounds, and glycerophospholipids to alleviate LP stress. Interestingly, exogenous melatonin showed different metabolic patterns in different genotypes of barley in response to LP stress. In GN42, exogenous melatonin mainly promotes hormone-mediated root growth and increases antioxidant capacity to cope with LP damage, while in GN121, it mainly promotes the P remobilization to supplement phosphate in roots. Our study revealed the protective mechanisms of exogenous MT in alleviating LP stress of different genotypes of barley, which can be used in the production of phosphorus-deficient crops.

Melatonin ameliorates acute lung injury caused by paraquat poisoning by promoting PINK1 and BNIP3 expression

Paraquat (PQ) poisoning can result in multiple organ dysfunction syndrome, mainly manifesting as acute lung injury and acute respiratory distress syndrome. No specific cure exists for PQ poisoning. However, by scavenging mitochondrial DNA (mtDNA), the damage-associated molecular pattern during PQ poisoning, mitophagy can ameliorate the downstream inflammatory pathways activated by mtDNA. Melatonin (MEL), however, can promote the expression of PINK1 and BNIP3, which are key proteins involved in mitophagy. In this study, we first explored whether MT could reduce PQ-induced acute lung injury by affecting mitophagy in animal models, and then, we studied the specific mechanism associated with this process through in vitro experiments. We also evaluated MEL intervention in the PQ group, while inhibiting the expression of PINK1 and BNIP3, to further determine whether the protective effects of MEL are associated with its effect on mitophagy. We found that when the expression of PINK1 and BNIP3 was inhibited, MEL intervention could not reduce mtDNA leakage and the release of inflammatory factors caused by PQ exposure, suggesting that the protective effect of MEL was blocked. These results suggest that by promoting the expression of PINK1 and BNIP3 and activating mitophagy, MEL can reduce mtDNA/TLR9-mediated acute lung injury during PQ poisoning. The results of this study could provide guidance for the clinical treatment of PQ poisoning to reduce associated mortality.

Melatonin Treatments Reduce Chilling Injury and Delay Ripening, Leading to Maintenance of Quality in Cherimoya Fruit

Spain is the world's leading producer of cherimoya, a climacteric fruit highly appreciated by consumers. However, this fruit species is very sensitive to chilling injury (CI), which limits its storage. In the present experiments, the effects of melatonin applied as dipping treatment on cherimoya fruit CI, postharvest ripening and quality properties were evaluated during storage at 7 °C + 2 days at 20 °C. The results showed that melatonin treatments (0.01, 0.05, 0.1 mM) delayed CI, ion leakage, chlorophyll losses and the increases in total phenolic content and hydrophilic and lipophilic antioxidant activities in cherimoya peel for 2 weeks with respect to controls. In addition, the increases in total soluble solids and titratable acidity in flesh tissue were also delayed in melatonin-treated fruit, and there was also reduced firmness loss compared with the control, the highest effects being found for the 0.05 mM dose. This treatment led to maintenance of fruit quality traits and to increases in the storage time up to 21 days, 14 days more than the control fruit. Thus, melatonin treatment, especially at 0.05 mM concentration, could be a useful tool to decrease CI damage in cherimoya fruit, with additional effects on retarding postharvest ripening and senescence processes and on maintaining quality parameters. These effects were attributed to a delay in the climacteric ethylene production, which was delayed for 1, 2 and 3 weeks for 0.01, 0.1 and 0.05 mM doses, respectively. However, the effects of melatonin on gene expression and the activity of the enzymes involved in ethylene production deserves further research.

Crosstalk between melatonin and reactive oxygen species in fruits and vegetables post-harvest preservation: An update

Fruits and vegetables contain numerous nutrients, such as vitamins, minerals, phenolic compounds, and dietary fibers. They reduce the incidence of cardiovascular diseases and the risk of certain chronic diseases, and improve the antioxidant and anti-inflammatory capacity. Moreover, melatonin was found in various fruits and vegetables species. Melatonin acts as a multifunctional compound to participate in various physiological processes. In recent years, many advances have been found that melatonin is also appraised as a key modulator on the fruits and vegetables post-harvest preservation. Fruits and vegetables post-harvest usually elicit reactive oxygen species (ROS) generation and accumulation. Excess ROS stimulate cell damage, protein structure destruction, and tissue aging, and thereby reducing their quality. Numerous studies find that exogenous application of melatonin modulates ROS homeostasis by regulating the antioxidant enzymes and non-enzymatic antioxidants systems. Further evidences reveal that melatonin often interacts with hormones and other signaling molecules, such as ROS, nitric oxide (NO), hydrogen sulfide (H₂S), and etc. Among these 'new' molecules, crosstalks of melatonin and ROS, especially the H₂O₂ produced by RBOHs, are provided in fruits and vegetables post-harvest preservation in this review. It will provide reference for complicated integration of both melatonin and ROS as signal molecules in future study.

Silencing of Sly-miR171d increased the expression of GRAS24 and enhanced postharvest chilling tolerance of tomato fruit

The role of Sly-miR171d on tomato fruit chilling injury (CI) was investigated. The results showed that silencing the endogenous Sly-miR171d effectively delayed the increase of CI and electrolyte leakage (EL) in tomato fruit, and maintained fruit firmness and quality. After low temperature storage, the expression of target gene GRAS24 increased in STTM-miR171d tomato fruit, the level of GA₃ anabolism and the expression of CBF1, an important regulator of cold resistance, both increased in STTM-miR171d tomato fruit, indicated that silencing the Sly-miR171d can improve the resistance ability of postharvest tomato fruit to chilling tolerance.