Table_4_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）作为一种多效性生物调节剂，其在多种应激反应和发育过程中发挥的关键作用已得到广泛报道。尽管褪黑素在植物抵御自然叶片衰老过程中的作用已有大量研究，但其延缓由应激诱导的衰老的精确调控机制仍不明确。在本研究中，我们发现，通过叶面喷施褪黑素显著改善了烟草（Nicotiana tabacum）的脱水诱导叶片衰老，伴随减轻的氧化损伤、衰老相关基因的表达以及内源ABA产量的降低。代谢组学分析表明，与未经处理的植物相比，褪黑素处理的植物在脱水暴露后叶片中积累了更高的糖、糖醇和有机酸浓度，但氨基酸浓度较低。基因表达分析揭示了通过褪黑素处理实现的应激植物延缓衰老可能部分归因于参与活性氧清除、叶绿素生物合成、光合作用和碳/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，激素反应显示出广泛的调节表达，并由类胡萝卜素生物合成的调节共同作用，以实现褪黑素处理植物在脱水胁迫下的生长加速。这些发现可能为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认识。