Melatonin mediates the regulation of ABA metabolism, free-radical scavenging, and stomatal behaviour in two Malus species under drought stress

Abstract

Melatonin pre-treatment significantly increases the tolerance of both drought-tolerant Malus prunifolia and drought-sensitive M. hupehensis plants. Its beneficial effects include better water conservation in leaves, less electrolyte leakage, steady chlorophyll contents, and greater photosynthetic performance under stress conditions. Melatonin selectively down-regulates MdNCED3, an abscisic acid (ABA) synthesis gene, and up-regulates its catabolic genes, MdCYP707A1 and MdCYP707A2, thereby reducing ABA contents in drought-stressed plants. Melatonin also directly scavenges H2O2 and enhances the activities of antioxidant enzymes to detoxify H2O2 indirectly. These two mechanisms work synergistically to improve the functions of stomata, i.e. causing them to re-open. Plants can effectively regulate their water balance under drought conditions by up-regulating the expression of melatonin synthesis genes MdTDC1, MdAANAT2, MdT5H4, and MdASMT1. Therefore, inducing melatonin production is an important mechanism by which plants can counteract the influence of this abiotic stressor.

Melatonin Application to Pisum sativum L. Seeds Positively Influences the Function of the Photosynthetic Apparatus in Growing Seedlings during Paraquat-Induced Oxidative Stress

“…This finding verifies that melatonin enrichment of seeds significantly inhibited oxidative damage to membrane under PQ-generated stress. A similar effect was observed under drought stress in Malus species pre-treated with melatonin (Li et al, 2015). According to these authors, water status can be improved by dual protective mechanisms (reduced contents of both ABA and H 2 O 2 ) working synergistically to improve stomata functioning.…”

Melatonin treatment of pre-veraison grape berries modifies phenolic components and antioxidant activity of grapes and wine

“…A recent study from Li et al (2015) showed that melatonin treatment significantly up-regulated abscisic acid (ABA) catabolism genes and down-regulated ABA biosynthesis genes in cucumber and apple, respectively, resulting in a rapid decrease of ABA content. As is known to us, lower abscisic acid (ABA) content can result in delaying the ripening process of grapes and thus prevent the normal accumulation of anthocyanin content.…”

Melatonin: A Mitochondrial Targeting Molecule Involving Mitochondrial Protection and Dynamics

“…This results in decreased apoptosis, improved metabolic status, and an elevated survival rate of cultured cells, unicellular organisms, animals, and plants, which suffer with oxidative stress [37,38,39,40,41,42,43,44,45]. The mechanisms of melatonin as a mitochondrial protector not only relate to its excellent free radical scavenging capacity but also to its function as a signaling molecule to upregulate gene expression of antioxidant enzymes [46,47,48] and a spectrum of stress responsive genes [49,50,51,52,53,54,55,56]. In addition, melatonin acts on the mitochondrial specific proteins such as uncoupling proteins (UCPs) to dissipate the proton gradient across the inner membrane of the mitochondria to moderately reduce the inner membrane potential [57,58,59,60].…”