Daily profile of melatonin levels in Chenopodium rubrum L. depends on photoperiod
Summary
Melatonin is an animal hormone that regulates photoperiodic reactions in many vertebrates. Its level is usually higher at night, and the duration of elevated melatonin levels is proportional to the length of the night, thus giving information about day length. We have previously identified melatonin in the dicotyledonous plant Chenopodium rubrum. We compared melatonin daily profiles in C. rubrum shoots when given three different photoperiodic regimes with 8 h, 12 h, and 16 h of darkness. As in vertebrates, melatonin levels reached its maximum at night, but the duration of elevated melatonin content did not change with the photoperiod. The maximum melatonin content occurred at later times after lights off as night length increased, but always 6 h before lights on in all light/dark cycles. These results indicate differences in the regulation of melatonin levels between vertebrates and higher plants. We suggest that the timing of melatonin maximum relative to lights off may provide photoperiodic information for C. rubrum.
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Melatonin as plant growth regulator in sustainable agriculture
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Suggesting a prospect for melatonin-mediated orchid flowering under extreme conditions
2023, Scientia HorticulturaeAbiotic stress is a major constraint in the successful growth and development of ornamental plants under severe conditions. Since antiquity, melatonin homeostasis has been an effective contrivance in the strategies of abiotic stress tolerance in plants, although it is completely neglected in orchids, the champagne of flowers. Orchids with exceptionally long vegetative phase face a number of stresses and, therefore, stress alleviation has been a hot topic in orchid cultivation. The in-vitro flowering is a useful method for early identification of hybrids in crop improvement programs. We successfully achieved in-vitro leafless flowering in three Cymbidium orchids (C. sinense, C. goeringii and C. ensifolium), which are elite flowers in terms of versatile flower shapes, esthetic preference and price. Transcriptomic analysis was performed to compare the leafless flowers with leaves to identify genes related to tryptophan pathway and melatonin biosynthesis. More than 50 differentially expressed genes (DEGs) were identified in each species with contrasting expressions in the leafless flowers and leaves. The important melatonin pathway genes included serotonin N-acetyltransferase (SNAT), caffeic acid 3-O-methyltransferase (CAMT) and tryptophan decarboxylase (TDC). Moreover, clustering analysis pointed out the significant abiotic stress tolerance-related genes. This opening report, thus, provides a robust cradle to idealize the melatonin as an effective abiotic stress regulator to aid the long journey of vegetative growth and then flowering in precious orchids.
Interaction of melatonin on post-harvest physiology and quality of horticultural crops
2023, Scientia HorticulturaeMelatonin is a plant growth regulator and biostimulator that regulates plant growth and development, improves plant stress tolerance, and delays the aging process. As research has deepened, the role and application of melatonin in the preservation of fresh horticultural produce such as vegetables and fruits have also been reported in the literature. Recent research's shows that melatonin plays an important regulatory role in delaying post-harvest senescence and quality deterioration in horticultural crops. This article first briefly described the synthesis pathway of melatonin in plants, the levels of melatonin in some horticultural crops and its influencing factors, and focused on the effects of melatonin on post-harvest physiology (respiration, ethylene production, antioxidant enzyme) and the quality of melatonin in horticultural crops. (Color, biologically active substances, antioxidant activity) and finally analyze the problems and future research priorities of melatonin in post-harvest preservation of horticultural crops, providing a reference for melatonin research and application of in the future.
Melatonin alleviating drought stress in plants: A review
2023, South African Journal of BotanyWith recent global climate change, the consequences of common extreme meteorological events have attracted increasing attention worldwide. Drought is an extreme meteorological event whose duration, frequency, and spatial extent, among other abiotic stresses, exhibited an increasing trend and significantly affect agriculture production. Researchers are trying to enable different drought management strategies by developing transgenic methods and using exogenous organic and inorganic substances in agriculture. Melatonin, an indolamine molecule also present in plants, has proven its effectiveness against various abiotic stresses, including drought in several crops. The main purpose of this review is to describe the biological function of melatonin, including signaling pathways and mechanisms in plants under different stress conditions. The focus was the results suggesting the use of melatonin as a promising strategy to mitigate the negative effects of drought stress on plant biological and physiological functions. Moreover, the molecular and genetic mechanisms underlying the application of melatonin for different plant species and growth conditions are also included to provide insight into the biosynthesis and signaling pathways, functional characterization of genes, and gene expression regulation. Future perspectives are given to broaden the scope of studies on melatonin application optimization in order to understand the mechanisms involved and develop strategies to improve crop resilience to stress and the optimal dosage for agricultural settings.
Melatonin and tryptophan effects on tomato seed deterioration during long-term storage
2023, South African Journal of BotanySince the discovery of the melatonin, comprehensive research has been conducted to reveal the physiological role of melatonin and changes in melatonin contents in different plant species. Although variations in melatonin content of a plant within a day and roles of melatonin in tolerance to abiotic and biotic stressors were well-documented, there is not much information about fluctuations in seed melatonin and its pre-cursor-tryptophan contents and their potential effects on seed viability or ageing process. This study was conducted to unveil the changes in melatonin and tryptophan contents of tomato seeds stored for 28 months and to determine potential effects of pre-storage melatonin and tryptophan treatments on seed viability or ageing process. Tomato seeds were treated with melatonin and tryptophan (0 μM or 250 μM) for one day before storage and then stored at room temperature (25 °C) for up to 28 months. Effects of pre-storage melatonin and tryptophan treatments on seed quality and ageing were investigated through various tests and analyses. Seed melatonin contents changed significantly during the storage, reached the highest level at 12th and 24th months of storage, which corresponds to August 2018 and August 2019 while tryptophan levels exhibited an opposite trend during the months when melatonin peaked strongly. These results indicated that higher seed melatonin content in August is a strategy that tomato seeds have in order to ensure their life after leaving the mother plant and to establish their next generation. Pre-storage treatments reduced the ageing-induced damage significantly by lowering the seed MDA and H2O2 contents and improved germination performance especially at low temperature. Thus, melatonin and tryptophan treatments could be used as an effective tool to preserve seed viability, minimize storage losses and slow down the ageing process, which could have practical implications especially for long-term storage of seeds of endangered species or valuable breeding materials.
Synergistic effects of salicylic acid and light stress on bioactive metabolites in basil callus cultures
2021, Biocatalysis and Agricultural BiotechnologyCitation Excerpt :Plants have the capacity to interpret and process information to produce and evolve preferably from their biotic and abiotic environments. As an abiotic source, light plays a crucial role in a plant's growth and development by controlling indigenous metabolic processes and maintaining hormonal equilibrium (Wolf et al., 2001). SA, on the other hand, is known to control various biochemical and physiological activities, such as plant resistance, thermogenesis and biotic and abiotic stress response.
Thai basil is a well-known medicinal plant that is rich in bioactive antioxidant compounds having a variety of health benefits, including cancer, diabetes, and cardiovascular disease prevention. Plant cell and tissue culture technologies can be systematically developed as a valuable, low-cost biomass supply for the production of high-value phytochemicals. The aim of this study is to create an effective protocol for producing “Thai basil” leaf derived callus cultures with a high yield of biomass and antioxidants as an alternative to growing plants using salicylic acid and various light regimes as elicitors. Salicylic acid (SA) and light significantly affects many metabolic processes coupled with biosynthesis of secondary metabolites in plants. Callus was exploited with various SA concentrations under 3 different light regimes. Indeed, the results of our research disclose that continuous light with moderate SA concentration (10 μM) significantly increased total phenolic content (18.7 ± 1.13 mg/g DW), flavonoid content (7.2 ± 0.21 mg/g DW), eugenol (0.56 ± 0.015 mg/g DW), rosmarinic acid (54.35 ± 1.85 mg/g DW), chicoric acid (64.46 ± 6.71 mg/g DW) cyanidin (0.42 ± 0.021 mg/g DW) and peonidin (0.32 ± 0.002 mg/g DW) production followed by photoperiod and dark. SA treatment (25 μM) under photoperiod showed maximum biomass accumulation (FW: 226.6 ± 3.91 g/L and DW: 16.44 ± 0.59 g/L) and caffeic acid production (0.54 ± 0.025 mg/g DW). Moreover in vitro antioxidant potential (DPPH and ABTS) and cellular antioxidant capacity was found higher in continuous light treated callus along with 10 μM SA treatment. Callus extracts also showed biocompatibility with human erythrocytes that indicates their nontoxic nature and moderate potential against alpha-amylase inhibition which will help in regulating glucose level. Compared to commercial leaves, callus extracts showed higher production of chicoric acid and rosmarinic acid associated with higher antioxidant capacity. In addition, this biological system also has a large capacity for continuous biomass production, thus demonstrating its high potential for possible nutraceutical applications.