Table_6_Integrated Analysis of the Transcriptome and Metabolome Revealed the Molecular Mechanisms Underlying the Enhanced Salt Tolerance of Rice Due to the Application of Exogenous Melatonin.XLSX

High salinity is one of the major abiotic stresses limiting rice production. Melatonin has been implicated in the salt tolerance of rice. However, the molecular basis of melatonin-mediated salt tolerance in rice remains unclear. In the present study, we performed an integrated transcriptome and metabolome profiling of rice seedlings treated with salt, melatonin, or salt + melatonin. The application of exogenous melatonin increased the salt tolerance of rice plants by decreasing the sodium content to maintain Na+/K+ homeostasis, alleviating membrane lipid oxidation, and enhancing chlorophyll contention. A comparative transcriptome analysis revealed that complex molecular pathways contribute to melatonin-mediated salt tolerance. More specifically, the AP2/EREBP–HB–WRKY transcriptional cascade and phytohormone (e.g., auxin and abscisic acid) signaling pathways were activated by an exogenous melatonin treatment. On the basis of metabolome profiles, 64 metabolites, such as amino acids, organic acids, nucleotides, and secondary metabolites, were identified with increased abundances only in plants treated with salt + melatonin. Several of these metabolites including endogenous melatonin and its intermediates (5-hydroxy-L-tryptophan, N1-acetyl-N2-formyl-5-methoxykynuramine), gallic acid, diosmetin, and cyanidin 3-O-galactoside had antioxidant functions, suggesting melatonin activates multiple antioxidant pathways to alleviate the detrimental effects of salt stress. Combined transcriptome and metabolome analyses revealed a few gene–metabolite networks related to various pathways, including linoleic acid metabolism and amino acid metabolism that are important for melatonin-mediated salt tolerance. The data presented herein may be useful for further elucidating the multiple regulatory roles of melatonin in plant responses to abiotic stresses.

高盐胁迫是限制水稻生产的主要非生物胁迫之一。褪黑素（Melatonin）已被证实参与水稻的耐盐调控，但其介导水稻耐盐性的分子机制仍未明确。本研究对分别经盐胁迫、褪黑素处理以及盐胁迫+褪黑素复合处理的水稻幼苗开展了整合转录组与代谢组分析。结果表明，外源褪黑素的施用可通过降低植株钠含量以维持Na+/K+稳态、缓解膜脂过氧化以及提升叶绿素含量，增强水稻的耐盐性。比较转录组分析显示，复杂的分子通路参与了褪黑素介导的耐盐调控；具体而言，外源褪黑素处理激活了AP2/EREBP–HB–WRKY转录级联通路以及植物激素（如生长素、脱落酸）信号通路。基于代谢组分析，本研究鉴定得到仅在盐胁迫+褪黑素复合处理植株中丰度显著上调的64种代谢物，包括氨基酸、有机酸、核苷酸及次生代谢物。其中多种代谢物具有抗氧化功能，包括内源褪黑素及其中间体（5-羟基-L-色氨酸、N1-乙酰基-N2-甲酰基-5-甲氧基犬尿胺）、没食子酸、香叶木素以及矢车菊素3-O-半乳糖苷，这提示褪黑素可激活多条抗氧化通路以减轻盐胁迫带来的毒害作用。整合转录组与代谢组分析还揭示了多条与不同通路相关的基因-代谢物调控网络，其中亚油酸代谢与氨基酸代谢对于褪黑素介导的水稻耐盐性具有重要作用。本研究提供的数据可为进一步解析褪黑素在植物应对非生物胁迫过程中的多重调控功能提供参考依据。