Table_5_Enhancement of Nicotiana tabacum Resistance Against Dehydration-Induced Leaf Senescence via Metabolite/Phytohormone-Gene Regulatory Networks Modulated by Melatonin.XLSX

Melatonin (MEL) is a pleiotropic agent with crucial functions reported in a variety of stress responses and developmental processes. Although MEL involvement in plant defense against natural leaf senescence has been widely reported, the precise regulatory mechanisms by which it delays stress-induced senescence remain unclear. In this study, we found that foliar spraying of melatonin markedly ameliorated dehydration-induced leaf senescence in Nicotiana tabacum, accompanied by attenuated oxidative damage, expression of senescence-related genes, and reduced endogenous ABA production. Metabolite profiling indicated that melatonin-treated plants accumulated higher concentrations of sugars, sugar alcohol, and organic acids, but fewer concentrations of amino acids in the leaves, than untreated plants after exposure to dehydration. Gene expression analysis revealed that the delayed senescence of stressed plants achieved by melatonin treatment might be partially ascribed to the upregulated expression of genes involved in ROS scavenging, chlorophyll biosynthesis, photosynthesis, and carbon/nitrogen balances, and downregulated expression of senescence-associated genes. Furthermore, hormone responses showed an extensively modulated expression, complemented by carotenoid biosynthesis regulation to achieve growth acceleration in melatonin-treated plants upon exposure to dehydration stress. These findings may provide more comprehensive insights into the role of melatonin in alleviating leaf senescence and enhancing dehydration resistance.

褪黑素（MEL）作为一种多效性活性物质，其在多种应激反应和发育过程中发挥着至关重要的作用。尽管褪黑素在植物抵御自然叶片衰老过程中的参与作用已被广泛报道，但其延迟由应激诱导的衰老的精确调控机制尚不明确。在本研究中，我们发现，通过叶片喷施褪黑素，可以有效改善烟草（Nicotiana tabacum）在脱水诱导的叶片衰老过程中的状况，伴随着氧化损伤的减轻、衰老相关基因的表达以及内源ABA产量的减少。代谢组学分析表明，与未处理植物相比，经褪黑素处理的植物在暴露于脱水后，叶片中糖、糖醇和有机酸的含量较高，而氨基酸的含量较低。基因表达分析揭示，通过褪黑素处理延迟应激植物衰老的可能部分归因于参与活性氧清除、叶绿素生物合成、光合作用以及碳/氮平衡相关基因的上调表达，以及衰老相关基因的下调表达。此外，激素反应的广泛调节表达，辅以类胡萝卜素生物合成的调控，使得褪黑素处理的植物在暴露于脱水应激后能够实现生长加速。这些发现可能为深入理解褪黑素在缓解叶片衰老和增强脱水抗性中的作用提供更为全面的见解。