The protective role of melatonin under heavy metal-induced stress in Melissa Officinalis L.

Abstract

Heavy metals, due to their inability to degrade, pose a serious environmental and nutritional problem. The accumulation of essential and non-essential heavy metals in living organisms reduces normal growth and development, resulting in acute poisoning, disease and even death of organisms. Melatonin is a very important multifunctional molecule in protecting plants from oxidative stress due to its ability to directly neutralize reactive oxygen species (ROS). Also, melatonin has a chelating property, which may contribute in reducing metal-induced toxicity. In this paper, the protective role of melatonin in counteracting metal-induced free radical generation was highlighted. Using the HPLC-FLD technique melatonin was identified and quantified in the roots and leaves of lemon balm (Melissa officinalis L.), grown under photoperiod conditions. Furthermore, the response of plants pre-treated with exogenous 0.1 mM melatonin to the increased zinc (Zn) and cadmium (Cd) concentrations was observed, with changes in mineral (Ca, Mg), physiological and antioxidant status of the plant during heavy metals stress. The obtained melatonin concentrations were the highest published for dry plants so far. Elevated Cd and Zn levels in soil caused alternation in biochemical and physiological parameters of lemon balm leaves and roots. However, melatonin pre-treatment increased plant tolerance to heavy metals stress. Increased Cd 3 and Zn uptake and their translocation into the leaves were also improved, indicating the possible use of melatonin in phytoremediation.

Melatonin Confers NaCl Tolerance in Withania coagulans L. by Maintaining Na+/K+ Homeostasis, Strengthening the Antioxidant Defense System and Modulating Withanolides Synthesis-Related Genes

“…It has been shown that the external treatment of ML increases the level of internal ML by enhancing the level of enzymatic and non-enzymatic antioxidants through stimulating the expression of their biosynthesizing genes, diminishes the level of free radicals and ROS, and maintains redox homeostasis under stressful conditions [ 40 ]. Similar results of the induction effects of ML on enhancing the activity of antioxidant enzymes and reducing the endogenous level of ROS under salinity [ 39 ], cold [ 41 ], and heavy metal [ 12 ] stresses have already been documented, which confirms the role of ML in enhancing the plant’s antioxidant defense system. Therefore, these results prove that external application of ML can enhance the antioxidant defense system in NaCl-stressed Paneer-booti plants, which may play a significant function in improving plant tolerance by reducing ROS levels and protecting membrane lipids.…”

“…In addition to the role of ML as an antioxidant, it has been shown that ML has the ability to regulate the expression of genes involved in important plant metabolisms [ 8 , 11 ]. The beneficial effects of ML on the tolerance of plants under drought [ 7 ], heavy metal [ 12 ], cold [ 13 ], and salt [ 9 ] stress have been reported, which indicates the role of ML in inducing the plant’s defense mechanism under stressful conditions.…”

Proline-mediated regulation on jasmonate signals repressed anthocyanin accumulation through the MYB-bHLH-WDR complex in rice under chromium exposure

“…Also, exogenous amino acids (e.g., Pro, gamma-aminobutyric acid, and glutamate) can minimize heavy metal toxicity in rice, tomato, and brinjal ( Jiang et al, 2020 ; Suhel et al, 2022 ; Zhang et al, 2022 ) by mediating the transcription factors and the antioxidant systems. Additionally, exogenous plant hormones (e.g., JA, auxin, kinetin, and melatonin) can regulate metal uptake, photosynthetic pigments, and antioxidant systems to enhance stress resistance ( López et al, 2007 ; Wang et al, 2015 ; Dai et al, 2020 ; Hodžić et al, 2021 ). In this study, we displayed the effects of exogenous Pro on ATH accumulation through regulating Jasmonate signals and MYB-bHLH-WDR complex and protecting rice plants from Cr(VI) stress.…”

Melatonin-mediated development and abiotic stress tolerance in plants

“…Several studies have proposed that, under various abiotic stresses, the melatonin-mediated ascorbate–glutathione (AsA–GSH) cycle serves a crucial role in scavenging reactive oxygen species in cells ( Xie et al., 2022 ; Zhang et al., 2022 ). Specifically, melatonin enhances the AsA/DHA and GSH/GSSG ratios and antioxidant capacity by stimulating the AsA–GSH cycle, thereby improving the scavenging capacity of ­O 2 · − and ­H 2 O 2 , reducing oxidative stress and providing an approach to reduce organic residues through plant detoxification mechanisms ( Dong et al., 2018 ; Hodžić et al., 2021 ; Yan et al., 2022 ). In addition, melatonin could make a direct connection with various oxidizing agents, particularly with hydroxyl radicals, to reduce the damage to cell structures (one molecule of melatonin neutralizes a maximum of 10 molecules of ROS/RNS) ( Simlat et al., 2018 ; Kyoungwhan, 2021 ).…”