Exogenous Melatonin Confers Cadmium Tolerance by Counterbalancing the Hydrogen Peroxide Homeostasis in Wheat Seedlings

Abstract

Melatonin has emerged as a research highlight regarding its important role in regulating plant growth and the adaptation to the environmental stresses. In this study, we investigated how melatonin prevented the cadmium toxicity to wheat seedlings. The results demonstrated that cadmium induced the expression of melatonin biosynthesis-related genes and cause a significant increase of endogenous melatonin level. Melatonin treatment drastically alleviated the cadmium toxicity, resulting in increased plant height, biomass accumulation, and root growth. Cadmium and senescence treatment significantly increased the endogenous level of hydrogen peroxide, which was strictly counterbalanced by melatonin. Furthermore, melatonin treatment caused a significant increase of GSH (reduced glutathione) content and the GSH/GSSG (oxidized glutathione) ratio. The activities of two key antioxidant enzymes, ascorbate peroxidase (APX) and superoxide dismutase (SOD), but not catalase (CAT) and peroxidase (POD), were specifically improved by melatonin. Additionally, melatonin not only promoted the primary root growth, but also drastically enhanced the capacity of the seedling roots to degrade the exogenous hydrogen peroxide. These results suggested that melatonin played a key role in maintaining the hydrogen peroxide homeostasis, via regulation of the antioxidant systems. Conclusively, this study revealed a crucial protective role of melatonin in the regulation of cadmium resistance in wheat.

Exogenous melatonin alleviates cadmium uptake and toxicity in apple rootstocks

“…However, these beneficial effects were particularly strong in M. micromalus "qingzhoulinqin". Thus, exogenous melatonin alleviated the toxic effects of Cd in these plants, which aligns with previous reports , Ni et al 2018. Under Cd exposure conditions, more endogenous melatonin was found in the roots and leaves of M. baccata than in those of M. micromalus "qingzhoulinqin" (Figure 5).…”

“…Melatonin induces the antioxidant system to scavenge stress-induced ROS, prevent lipid peroxidation, and protect cells from oxidative damage (Romero et al 2014. In wheat, melatonin application mitigated Cd-induced ROS by upregulating SOD, POD, and APX (Ni et al 2018).…”

“…Melatonin is critical for Cd detoxification. Therefore, exogenous melatonin has been applied to Cd-stressed herbaceous plants such as tomato (Hasan et al 2015), rice (Byeon et al 2015), wheat (Ni et al 2018, Kaya et al 2019, and alfalfa (Gu et al 2017) in an attempt to enhance their Cd tolerance. To our knowledge, however, there are no studies on the efficacy of exogenous melatonin in enhancing Cd detoxification in woody fruit crops or the putative mechanisms involved.…”

Melatonin Positively Influences the Photosynthetic Machinery and Antioxidant System of Avena sativa during Salinity Stress

“…Similarly, melatonin increased the activity of antioxidant enzymes and promoted the accumulation of antioxidants in wheat seedlings subjected to cold stress [41]. Another recent report suggested that melatonin alleviated cadmium stress in wheat seedlings by increasing the activity of the key antioxidant enzymes APX, SOD, CAT, and POD (peroxidase) [42].…”

Sulfur-enriched leonardite and humic acid soil amendments enhance tolerance to drought and phosphorus deficiency stress in maize (Zea mays L.)

“…In the current experiment, total chlorophyll content was markedly reduced in the maize crop under water stress and P deficiency, but even more severe effect was observed when both stresses were combined. Previous research reports have shown that the stress-induced decline in chlorophyll content was primarily ascribed to considerable accumulation of H 2 O 2 in the plant leaves 85,86 . So, the decreased total chlorophyll content might be linked to considerable accumulation of H 2 O 2 in the maize plant leaves as observed under P deficiency and water stress.…”