Tan Xiao-Li, Zhao Ya-Ting, Shan Wei, Kuang Jian-Fei, Lu Wang-Jin, Su Xin-Guo, Tao Neng-Guo, Lakshmanan Prakash, Chen Jian-Ye
State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources/Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables/Engineering Research Center of Southern Horticultural Products Preservation, Ministry of Education, College of Horticulture, South China Agricultural University, Guangzhou 510642, China; Lingnan Guangdong Laboratory of Modern Agriculture, Guangzhou 510642, China; School of Chemical Engineering, Xiangtan University, Xiangtan 411105, China.
State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources/Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables/Engineering Research Center of Southern Horticultural Products Preservation, Ministry of Education, College of Horticulture, South China Agricultural University, Guangzhou 510642, China; Lingnan Guangdong Laboratory of Modern Agriculture, Guangzhou 510642, China.
Food Res Int. 2020 Dec;138(Pt B):109790. doi: 10.1016/j.foodres.2020.109790. Epub 2020 Oct 15.
Reactive oxygen species (ROS) trigger and accelerate leaf senescence. Melatonin, a low molecular compound with several biological functions in plants, is known to delay leaf senescence in different species, including Chinese flowering cabbage. However, the mechanism(s) underpinning melatonin-delayed leaf senescence remains unclear. Here, we found that melatonin lowered the expression of chlorophyll catabolic genes (BrPAO and BrSGR1) and senescence-associated genes (BrSAG12 and BrSEN4), decreased chlorophyll loss, minimized the alteration in Fv/Fm ratio and remarkably delayed senescence of Chinese flowering cabbage after harvest. Moreover, the over-accumulation of O, hydrogen peroxide (HO) and malondialdehyde contents and the expression of respiratory burst oxidase homologues (RBOH) genes (BrRbohB, BrRbohC, BrRbohD, BrRbohD2 and BrRbohE) were significantly inhibited by melatonin treatment. Melatonin-treated cabbages also showed higher O, OH and DPPH radical scavenging capacity and enhanced activities of peroxidase (POD), superoxide dismutase (SOD) and their gene expressions. Up-regulation of key components of ascorbate-glutathione (AsA-GSH) cycle, the metabolic pathway that detoxify HO, was also observed in melatonin-treated cabbages. These findings suggest that melatonin-delayed postharvest leaf senescence of postharvest Chinese flowering cabbage may be mediated, at least in part, by maintaining ROS homeostasis through restraining RBOHs-catalyzed ROS production and enhancing the activity of ROS-scavenging system including major antioxidant enzymes and AsA-GSH cycle.
活性氧（ROS）触发并加速叶片衰老。褪黑素是一种在植物中具有多种生物学功能的低分子化合物，已知它能延缓包括菜心在内的不同物种的叶片衰老。然而，褪黑素延缓叶片衰老的机制尚不清楚。在此，我们发现褪黑素降低了叶绿素分解代谢基因（BrPAO和BrSGR1）和衰老相关基因（BrSAG12和BrSEN4）的表达，减少了叶绿素损失，使Fv/Fm比值的变化最小化，并显著延缓了菜心采后的衰老。此外，褪黑素处理显著抑制了超氧阴离子（O）、过氧化氢（H₂O₂）和丙二醛含量的过度积累以及呼吸爆发氧化酶同源物（RBOH）基因（BrRbohB、BrRbohC、BrRbohD、BrRbohD2和BrRbohE）的表达。褪黑素处理的菜心还表现出更高的超氧阴离子、羟基自由基和二苯基苦味酰基自由基清除能力，以及过氧化物酶（POD）、超氧化物歧化酶（SOD）活性及其基因表达的增强。在褪黑素处理的菜心中还观察到抗坏血酸-谷胱甘肽（AsA-GSH）循环关键成分的上调，AsA-GSH循环是清除H₂O₂的代谢途径。这些发现表明，褪黑素延缓菜心采后叶片衰老可能至少部分是通过抑制RBOHs催化的ROS产生并增强包括主要抗氧化酶和AsA-GSH循环在内的ROS清除系统的活性来维持ROS稳态来介导的。
