Delay of Postharvest Browning in Litchi Fruit by Melatonin via the Enhancing of Antioxidative Processes and Oxidation Repair

Abstract

Melatonin acts as a crucial signaling and antioxidant molecule with multiple physiological functions in organisms. To explore effects of exogenous melatonin on postharvest browning and its possible mechanisms in litchi fruit, 'Ziniangxi' litchi fruits were treated with an aqueous solution of melatonin at 0.4 mM and then stored at 25 °C for 8 days. The results revealed that melatonin strongly suppressed pericarp browning and delayed discoloration during storage. Melatonin treatment reduced relative membrane-leakage rate and inhibited the generation of superoxide radicals (O), hydrogen peroxide (HO), and malondialdehyde (MDA). Melatonin treatment markedly promoted the accumulation of endogenous melatonin; delayed loss of total phenolics, flavonoids, and anthocyanins; and enhanced the activities of antioxidant enzymes, including superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), and glutathione reductase (GR, EC 1.6.4.2). By contrast, the activities of browning-related enzymes including polyphenoloxidase (PPO, EC 1.10.3.1) and peroxidase (POD, EC 1.11.1.7) were reduced. In addition, melatonin treatment up-regulated the expression of four genes encoding enzymes for repair of oxidized proteins, including LcMsrA1, LcMsrA2, LcMsrB1, and LcMsB2. These findings indicate that the delay of pericarp browning and senescence by melatonin in harvested litchi fruit could be attributed to the maintenance of redox homeostasis by the improvement of the antioxidant capacity and modulation of the repair of oxidatively damaged proteins.

Melatonin delays leaf senescence of Chinese flowering cabbage by suppressing ABFs‐mediated abscisic acid biosynthesis and chlorophyll degradation

“…Melatonin retards leaf senescence in several plants including barley and detached apple leaves . In addition, melatonin is effective in maintaining the quality of postharvest fruits such as peach, banana, and litchi . For harvested green leafy vegetables such as Chinese flowering cabbage, leaf senescence is the most important factors affecting its shelf‐life and nutritional value during the postharvest storage and distribution.…”

“…15,16 In addition, melatonin is effective in maintaining the quality of postharvest fruits such as peach, banana, and litchi. [41][42][43] For harvested green leafy vegetables such as Chinese flowering cabbage, leaf senescence is the most important factors affecting its shelflife and nutritional value during the postharvest storage and distribution. In this work, we found that exogenous application of melatonin-alleviated senescence changes in Chinese flowering cabbage, with melatonin treatment maintaining a higher value of Fv/Fm and total chlorophyll content, while inhibiting the expression of chlorophyll catabolic and senescence marker genes.…”

Effect of glycine betaine on chilling injury in relation to energy metabolism in papaya fruit during cold storage

“…It is known that low temperature stress initiates membrane lipid phase transition from liquid crystalline to gelatin state as indicated by increased membrane permeability, which results in loss of membrane structure and function accompanying with CI development of fruit (Zhang et al., ). Process of membrane damage is generally involved in lipid peroxidation resulting from attack of overproduced reactive oxygen species (ROS), including ˙, H 2 O 2 , •OH, and 1 O 2 (Zhang et al., ). MDA is one of the low molecular weight end‐products of lipid peroxidation, and its level directly reflects the degree of oxidative damage to membrane (Dhindsa, Plumb‐Dhindsa, & Thorpe, ).…”

Melatonin Enhances Cold Tolerance by Regulating Energy and Proline Metabolism in Litchi Fruit

“…Fruit with a uniform size and free of visual blemishes were chosen and then disinfected with 0.5% NaClO for 30 s. After washing with deionized (di) H 2 O and drying, the fruit were divided into two groups with 540 fruit per group. One group was subdivided into nine equal batches, and then each batch of fruit (60) was dipped in 400 µM MLT (Solarbio Science and Technology Co. Ltd., Beijing, China) solution prepared with 10 L of diH 2 O at 25 • C for 20 min; this treatment process was operated under low-light conditions to avoid the decomposition of MLT [25]. Another group was dipped in diH 2 O using the same procedure, Foods 2020, 9,454 3 of 13 which served as a control.…”

“…MLT-conferred protection against chilling stress in these crops involves the inhibition of membrane lipid peroxidation, the reinforcement of cell wall structure, activated phenol metabolism, and promotion of the biosynthesis of osmotic-adjusting compounds. In a previous study, we noticed that exogenous treatment with MLT at 400 µM effectively delayed the evolution of pericarp browning in 'Ziniangxi' litchi fruit during natural senescence at ambient temperature (25 • C), which was attributed to suppressed phenolic oxidation, enhanced enzymatic and nonenzymatic antioxidant activities, and the improved repair capability of oxidative-damaged proteins via the up-regulation of the expression of the genes encoding methionine sulfoxide reductases [25]. However, to our knowledge, there is no information regarding the impact of MLT on CI in litchi fruit under chilling stress and the underlying regulatory mechanisms.Increased amounts of evidence have indicated that the maintenance of cellular energy status and the accumulation of osmolyte proline can account for the increased cold tolerance in a variety of harvested crop species [26,27].…”