Table_6_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）是一种具有多效性作用的物质，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作用已被广泛报道，但其通过何种精确的调节机制延缓由应激引起的衰老尚不明确。在本研究中，我们发现，对烟草（Nicotiana tabacum）叶片进行褪黑素喷施显著改善了脱水引起的叶片衰老，伴随着氧化损伤的减轻、衰老相关基因的表达以及内源性ABA（脱落酸）产量的减少。代谢组学分析表明，与未处理植株相比，褪黑素处理后的植株在脱水处理后叶片中积累的糖、糖醇和有机酸浓度更高，而氨基酸浓度则更低。基因表达分析揭示，通过褪黑素处理实现的应激植物延迟衰老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/氮平衡的基因的上调表达，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株在暴露于脱水应激时能够实现生长加速。这些发现可能为深入了解褪黑素在缓解叶片衰老和增强脱水耐受性中的作用提供更为全面的认识。