Abstract
As a ubiquitous molecule, melatonin plays a crucial role in tolerance to multiple stresses in plants. In the present work, we report the role of exogenous melatonin in relieving oxidative stress induced by methyl viologen (MV) in poplar (Populus alba × Populus glandulosa) leaf. Leaf discs pretreated with melatonin exhibited increased tolerance to MV-mediated oxidative stress. It was observed that melatonin pretreatment effectively reduced membrane damage and lipid oxidation as demonstrated by decreased relative electrolyte leakage and malonaldehyde content in poplar leaf discs. Exogenous melatonin also stimulated activities of antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX), and enhanced accumulation of non-enzymatic antioxidants of AsA and GSH in leaf discs exposed to MV. In addition, pretreatment of melatonin prompted expression of genes for those antioxidant enzymes. Notably, exogenous melatonin increased expression of P5CS, a key gene for proline biosynthesis, under MV treatment. It was further observed that pretreatment with melatonin boosted activity of P5CS as well as accumulation of proline in leaf discs under MV-mediated oxidative stress. Collectively, this work provides evidence for the ameliorative effect of melatonin on MV-induced oxidative stress in poplar leaf.
Highlights
Being sessile, plants are constantly challenged by a variety of environmental factors, such as drought, extreme temperatures, salinity, nutrient deficiency, and excessive toxic metals
To investigate the effect of melatonin on methyl viologen (MV)-mediated oxidative stress in poplar leaves, we first examined how melatonin pretreatment affected poplar leaf discs incubated in MV solution
After 24 h exposure to MV, leaf discs without melatonin pretreatment exhibited severe oxidative damage and evident chlorophyll loss, in contrast, leaf discs pretreated with melatonin were much less injured by MV (Figure 1), indicating the role of melatonin in the alleviation of MV-mediated oxidative stress
Summary
Plants are constantly challenged by a variety of environmental factors, such as drought, extreme temperatures, salinity, nutrient deficiency, and excessive toxic metals. These unfavorable factors hamper plant growth and development, causing a huge loss in crop production [1]. Major sites of ROS production are chloroplasts and mitochondria where the electron transport chain is impaired due to environmental stress to plants [4,5]. The oxidation of macromolecules results in the breakdown of normal cellular activities and leads to retarded growth, reduced fertility and hastened senescence in plants [3,6]
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