Comparative physiological and proteomic analyses reveal the actions of melatonin in the reduction of oxidative stress in Bermuda grass (Cynodon dactylon (L). Pers.)

The fact of melatonin as an important antioxidant in animals led plant researchers to speculate that melatonin also acts in the similar manner in plants. Although melatonin has significant effects on alleviating stress-triggered reactive oxygen species (ROS), the involvement of melatonin in direct oxidative stress and the underlying physiological and molecular mechanisms remain unclear in plants. In this study, we found that exogenous melatonin significantly alleviated hydrogen peroxide (H₂O₂)-modulated plant growth, cell damage, and ROS accumulation in Bermuda grass. Additionally, 76 proteins significantly influenced by melatonin during mock or H₂O₂ treatment were identified by gel-free proteomics using iTRAQ (isobaric tags for relative and absolute quantitation). Metabolic pathway analysis showed that several pathways were markedly enhanced by melatonin and H₂O₂ treatments, including polyamine metabolism, ribosome pathway, major carbohydrate metabolism, photosynthesis, redox, and amino acid metabolism. Taken together, this study provides more comprehensive insights into the physiological and molecular mechanisms of melatonin in Bermuda grass responses to direct oxidative stress. This may relate to the activation of antioxidants, modulation of metabolic pathways, and extensive proteome reprograming.