Abstract：
The stress-protective effect of melatonin (N-acetyl-5-methoxytryptamine) on plant cells is mediated by key signaling mediators, in particular calcium ions and reactive oxygen species (ROS). However, the links between changes in calcium and redox homeostasis and the formation of adaptive responses of cultivated cereals (including wheat) to the action of high temperatures have not yet been studied. In the present study, we investigated the possible involvement of ROS and calcium ions as signaling mediators in developing heat resistance in wheat (Triticum aestivum L.) seedlings and activating their antioxidant system. Treatment of 3-day-old etiolated seedlings with melatonin solutions at concentrations 0.01-10 µM increased their survival after exposure to 45 °C for 10 min. The most significant stress-protective effect was exerted by melatonin treatment at 1 µM concentration. Under the influence of melatonin, a transient enhancement of superoxide anion radical (O2•-) generation and an increase in hydrogen peroxide content were observed in roots, with a maximum at 1 h. Four hours after treatment with melatonin, the activity of catalase and guaiacol peroxidase increased in roots, while the activity of superoxide dismutase did not change significantly. After exposure to 45 °C, the activity of catalase and guaiacol peroxidase was higher in the roots of melatonin-treated wheat seedlings, and the indices of ROS generation, content of the lipid peroxidation product malonic dialdehyde, and cell membrane damage were lower than in control seedlings. Melatonin-induced changes in root ROS generation and antioxidant enzyme activities were eliminated by pretreatment with the hydrogen peroxide scavenger dimethylthiourea (DMTU), NADPH oxidase inhibitor imidazole, and calcium antagonists (the extracellular calcium chelator EGTA and phospholipase C inhibitor neomycin). Treatment with DMTU, imidazole, EGTA, and neomycin also abolished the melatonin-induced increase in survival of wheat seedlings after heat stress. The role of calcium ions and ROS, generated with the participation of NADPH oxidase, as signaling mediators in the melatonin-induced antioxidant system and heat stress resistance of wheat seedlings have been demonstrated.
摘要：
褪黑激素（N-乙酰-5-甲氧基色胺）对植物细胞的应激保护作用是由关键信号介导的，特别是钙离子和活性氧(ROS)。然而,钙和氧化还原稳态的变化与栽培谷物（包括小麦）对高温作用的适应性反应形成之间的联系尚未研究。在本研究中,我们研究了ROS和钙离子作为信号介质在小麦（TriticumaestivumL.）幼苗发展耐热性和激活其抗氧化系统中的可能参与。用浓度为0.01-10µM的褪黑激素溶液处理3天大的黄化幼苗，在暴露于45°C10分钟后增加了它们的存活率。通过在1µM浓度下的褪黑激素处理发挥了最显著的应激保护作用。在褪黑激素的影响下，在根部观察到超氧阴离子自由基（O2•-）生成的瞬时增强和过氧化氢含量的增加，用褪黑激素治疗后4小时，根系过氧化氢酶和愈创木酚过氧化物酶的活性增加，而超氧化物歧化酶的活性没有明显变化。暴露于45°C后，褪黑素处理的小麦幼苗根中过氧化氢酶和愈创木酚过氧化物酶的活性较高，以及ROS生成指数，脂质过氧化产物丙二醛的含量，细胞膜损伤低于对照幼苗。通过用过氧化氢清除剂二甲基硫脲（DMTU）预处理，消除了褪黑素诱导的根ROS产生和抗氧化酶活性的变化，NADPH氧化酶抑制剂咪唑，和钙拮抗剂（细胞外钙螯合剂EGTA和磷脂酶C抑制剂新霉素）。用DMTU治疗，咪唑,EGTA,新霉素也消除了褪黑激素诱导的热胁迫后小麦幼苗存活率的增加。钙离子和ROS的作用，在NADPH氧化酶的参与下产生，作为褪黑素诱导的抗氧化系统中的信号介质和小麦幼苗的热胁迫抗性已被证明。
