Table_2_Identification of ABA-Mediated Genetic and Metabolic Responses to Soil Flooding in Tomato (Solanum lycopersicum L. Mill).XLSX

Soil flooding is a compound abiotic stress that alters soil properties and limits atmospheric gas diffusion (O2 and CO2) to the roots. The involvement of abscisic acid (ABA) in the regulation of soil flooding-specific genetic and metabolic responses has been scarcely studied despite its key importance as regulator in other abiotic stress conditions. To attain this objective, wild type and ABA-deficient tomatoes were subjected to short-term (24 h) soil waterlogging. After this period, gas exchange parameters were reduced in the wild type but not in ABA-deficient plants that always had higher E and gs. Transcript and metabolite alterations were more intense in waterlogged tissues, with genotype-specific variations. Waterlogging reduced the ABA levels in the roots while inducing PYR/PYL/RCAR ABA receptors and ABA-dependent transcription factor transcripts, of which induction was less pronounced in the ABA-deficient genotype. Ethylene/O2-dependent genetic responses (ERFVIIs, plant anoxia survival responses, and genes involved in the N-degron pathway) were induced in hypoxic tissues independently of the genotype. Interestingly, genes encoding a nitrate reductase and a phytoglobin involved in NO biosynthesis and scavenging and ERFVII stability were induced in waterlogged tissues, but to a lower extent in ABA-deficient tomato. At the metabolic level, flooding-induced accumulation of Ala was enhanced in ABA-deficient lines following a differential accumulation of Glu and Asp in both hypoxic and aerated tissues, supporting their involvement as sources of oxalacetate to feed the tricarboxylic acid cycle in waterlogged tissues and constituting a potential advantage upon long periods of soil waterlogging. The promoter analysis of upregulated genes indicated that the production of oxalacetate from Asp via Asp oxidase, energy processes such as acetyl-CoA, ATP, and starch biosynthesis, and the lignification process were likely subjected to ABA regulation. Taken together, these data indicate that ABA depletion in waterlogged tissues acts as a positive signal, inducing several specific genetic and metabolic responses to soil flooding.

土壤淹水是一类复合非生物胁迫，可改变土壤理化性质并阻碍大气气体（氧气与二氧化碳）向根系的扩散。尽管脱落酸（abscisic acid, ABA）在其他非生物胁迫条件下作为关键调控因子发挥重要作用，但其参与调控土壤淹水特异性遗传与代谢响应的相关研究却较为匮乏。为达成这一研究目标，本研究将野生型与脱落酸缺陷型番茄暴露于短期（24小时）土壤渍水环境中。处理结束后，野生型植株的气体交换参数显著降低，而脱落酸缺陷型植株则无此变化，且始终维持更高的蒸腾速率（E）与气孔导度（gs）。转录本与代谢物的丰度变化在渍水组织中更为显著，且存在基因型特异性差异。土壤淹水处理降低了根系中的脱落酸水平，同时诱导了PYR/PYL/RCAR型脱落酸受体以及依赖脱落酸的转录因子的转录本表达，且该诱导效应在脱落酸缺陷型基因型中更为微弱。依赖乙烯/氧气的遗传响应（包括乙烯响应因子VIIs、植物缺氧存活相关基因以及参与N端规则途径的基因）在低氧组织中被诱导，且不受基因型影响。值得注意的是，编码参与一氧化氮（nitric oxide, NO）生物合成与清除以及乙烯响应因子VII稳定性调控的硝酸还原酶（nitrate reductase）与植物球蛋白（phytoglobin）的基因，在渍水组织中被诱导，但在脱落酸缺陷型番茄中的诱导程度更低。代谢层面，土壤淹水诱导的丙氨酸（Ala）积累在脱落酸缺陷型株系中进一步增强，且谷氨酸（Glu）与天冬氨酸（Asp）在低氧与通气组织中均呈现差异积累，这表明二者可作为草酰乙酸的来源，为渍水组织中的三羧酸循环（tricarboxylic acid cycle, TCA循环）供能，且在长期土壤淹水条件下可能成为潜在的适应优势。对上调基因的启动子分析表明，通过天冬氨酸氧化酶从天冬氨酸生成草酰乙酸的过程、乙酰辅酶A（acetyl-CoA）、三磷酸腺苷（adenosine triphosphate, ATP）与淀粉生物合成（starch biosynthesis）等能量代谢过程，以及木质化（lignification）过程，均可能受到脱落酸的调控。综上，本研究数据表明，渍水组织中脱落酸的耗竭作为一种正向信号，诱导了一系列针对土壤淹水的特异性遗传与代谢响应。