Foliar spraying of melatonin confers cadmium tolerance in Nicotiana tabacum L

Numan

et al. 2020

Plants

156

Melatonin is a multifunctional signaling molecule that is ubiquitously distributed in different parts of a plant and responsible for stimulating several physio-chemical responses to adverse environmental conditions. In this review, we show that, although plants are able to biosynthesize melatonin, the exogenous application of melatonin to various crops can improve plant growth and development in response to various abiotic and biotic stresses (e.g., drought, unfavorable temperatures, high salinity, heavy metal contamination, acid rain, and combined stresses) by regulating antioxidant machinery of plants. Current knowledge suggests that exogenously applied melatonin can enhance the stress tolerance of plants by regulating both the enzymatic and non-enzymatic antioxidant defense systems. Enzymic antioxidants upregulated by exogenous melatonin include superoxide dismutase, catalase, glutathione peroxidase, and enzymes involved in the ascorbate–glutathione cycle (ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, and glutathione reductase), whereas levels of non-enzymatic antioxidants such as ascorbate, reduced glutathione, carotenoids, tocopherols, and phenolics are also higher under stress conditions. The enhanced antioxidant system consequently exhibits lower lipid peroxidation and greater plasma membrane integrity when under stress. However, these responses vary greatly from crop to crop and depend on the intensity and type of stress, and most studies to date have been conducted under controlled conditions. This means that a wider range of crop field trials and detailed transcriptomic analysis are required to reveal the gene regulatory networks involved in the between melatonin, antioxidants, and abiotic stress.

Section: Superoxide Dismutase (Sod)mentioning

confidence: 97%

Section: Crop Plantmentioning

confidence: 99%

Melatonin: Awakening the Defense Mechanisms during Plant Oxidative Stress

Numan

et al. 2020

Plants

156

“…Melatonin is useful for protecting plants from heavy metal stress. For example, treating seeds with melatonin prior to sowing protected red cabbage (Brassica oleracea rubrum) seedlings against toxic copper ion concentrations (Posmyk et al, 2008), and foliar spraying of melatonin conferred cadmium tolerance in tobacco (Nicotiana tabacum; Wang et al, 2019). The enhanced plant performance following pharmacological melatonin treatment, together with the increased expression of melatonin biosynthetic genes in plants, suggests that manipulating melatonin activity in plants could lead to the development of more robust crops with increased tolerance to heavy metal stress.…”

Section: Melatonin Levels and Biosynthesis In Plants Under Stress Conmentioning

confidence: 99%

Melatonin: A master regulator of plant development and stress responses

Sun

Liu

Wang

et al. 2020

JIPB

297

203

Melatonin is a pleiotropic molecule with multiple functions in plants. Since the discovery of melatonin in plants, numerous studies have provided insight into the biosynthesis, catabolism, and physiological and biochemical functions of this important molecule. Here, we describe the biosynthesis of melatonin from tryptophan, as well as its various degradation pathways in plants. The identification of a putative melatonin receptor in plants has led to the hypothesis that melatonin is a hormone involved in regulating plant growth, aerial organ development, root morphology, and the floral transition. The universal antioxidant activity of melatonin and its role in preserving chlorophyll might explain its anti‐senescence capacity in aging leaves. An impressive amount of research has focused on the role of melatonin in modulating postharvest fruit ripening by regulating the expression of ethylene‐related genes. Recent evidence also indicated that melatonin functions in the plant's response to biotic stress, cooperating with other phytohormones and well‐known molecules such as reactive oxygen species and nitric oxide. Finally, great progress has been made towards understanding how melatonin alleviates the effects of various abiotic stresses, including salt, drought, extreme temperature, and heavy metal stress. Given its diverse roles, we propose that melatonin is a master regulator in plants.

“…Melatonin (N-acetyl-5-methoxytryptamine) is a pleiotropic molecule ubiquitously distributed in diverse kingdoms, covering bacteria, insects, animals, and plants [16]. Melatonin in plants has been reported to play important roles in regulating multiple cellular and physiological activities, including improvement of seed vigor and germination [17], alleviation of leaf senescence [18], acceleration of growth, flowering and development [19], and resistance to stress conditions such as heavy metal, drought, chilling, and salinity [20][21][22][23]. As an endogenous scavenger and antioxidant, melatonin can directly remove excess ROS based on its extremely strong scavenging capacity [24].…”

Section: Introductionmentioning

confidence: 99%

Melatonin Priming Alleviates Aging-Induced Germination Inhibition by Regulating β-oxidation, Protein Translation, and Antioxidant Metabolism in Oat (Avena sativa L.) Seeds

Yan

Jia

Mao

2020

IJMS

Although melatonin has been reported to play an important role in regulating metabolic events under adverse stresses, its underlying mechanisms on germination in aged seeds remain unclear. This study was conducted to investigate the effect of melatonin priming (MP) on embryos of aged oat seeds in relation to germination, ultrastructural changes, antioxidant responses, and protein profiles. Proteomic analysis revealed, in total, 402 differentially expressed proteins (DEPs) in normal, aged, and aged + MP embryos. The downregulated DEPs in aged embryos were enriched in sucrose metabolism, glycolysis, β-oxidation of lipid, and protein synthesis. MP (200 μM) turned four downregulated DEPs into upregulated DEPs, among which, especially 3-ketoacyl-CoA thiolase-like protein (KATLP) involved in the β-oxidation pathway played a key role in maintaining TCA cycle stability and providing more energy for protein translation. Furthermore, it was found that MP enhanced antioxidant capacity in the ascorbate-glutathione (AsA-GSH) system, declined reactive oxygen species (ROS), and improved cell ultrastructure. These results indicated that the impaired germination and seedling growth of aged seeds could be rescued to a certain level by melatonin, predominantly depending on β-oxidation, protein translation, and antioxidant protection of AsA-GSH. This work reveals new insights into melatonin-mediated mechanisms from protein profiles that occur in embryos of oat seeds processed by both aging and priming.