The water-intensive cultivation of rice in flooded conditions poses a great challenge to global water resources, particularly in the face of climate change. Wheat requires significantly less water than rice with fairly high yields. A main research question is whether there are any drought adaptive mechanisms in rice similar to those existing in wheat. We report a study, where precise moisture stress was imposed at the vegetative stage using a high-throughput drought simulator phenomics facility. Variability in stress response was captured through untargeted metabolome analysis. In the first experiment, using two rice cultivars with contrasting drought responses (IR64 and Apo) and a wheat cultivar, Weebill, we found distinct variations in regulation of metabolite levels under well-watered or water-limited conditions, both between and within species. Several biosynthetic pathways, including those of polyamines, flavonoids, flavones, and specific metabolites like sphinganine-1-phosphate and anthranilate were enhanced under water-limited conditions. These metabolites were more abundant in wheat than in rice. Among the rice cultivars, Apo had higher abundance of metabolites than IR64. Regulatory patterns governing these metabolic pathways provided basis for stress responses of the tolerant rice cultivar and wheat. A second experiment was conducted to screen rice germplasm lines for acquired tolerance traits contrasting for drought responsiveness. Eight genotypes (four sensitive and four tolerant ones) were selected to validate the candidate metabolites from the first experiment. In the third experiment, an RT-PCR analysis of the key regulatory genes governing the metabolic pathways was conducted, using plant materials from both experiments. The results of this third experiment provided a strong validation for the relevance of these metabolic pathways under stress in rice. We identified promising rice genotypes that exhibited fold change levels of stress resistance metabolites comparable to those of the wheat cultivar Weebill. This study helped identify key candidate metabolites that can be either developed as markers or as elicitors, and genotypes that can be used as trait donor lines for rice improvement.

中文翻译：

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水稻和小麦基因型对干旱不同反应的分子基础

在洪水条件下进行的高耗水水稻种植对全球水资源构成了巨大挑战，特别是在气候变化的情况下。小麦所需的水量比水稻少得多，但产量相当高。一个主要的研究问题是水稻是否存在与小麦相似的干旱适应机制。我们报告了一项研究，其中使用高通量干旱模拟器表型组学设施在营养阶段施加精确的水分胁迫。通过非靶向代谢组分析捕获应激反应的变异性。在第一个实验中，我们使用两个具有对比干旱反应的水稻品种（IR64 和 Apo）和一个小麦品种 Weebill，发现在水分充足或限水条件下，物种间和物种内的代谢水平调节存在明显差异。几种生物合成途径，包括多胺、类黄酮、黄酮和特定代谢物（如 1-磷酸二氢鞘氨醇和邻氨基苯甲酸）的生物合成途径在限水条件下得到增强。这些代谢物在小麦中比在水稻中更丰富。在水稻品种中，Apo 的代谢产物丰度高于 IR64。控制这些代谢途径的调节模式为耐受水稻品种和小麦的胁迫反应提供了基础。进行第二个实验，筛选水稻种质系的后天耐受性状，与干旱反应性对比。选择八种基因型（四种敏感基因型和四种耐受基因型）来验证第一个实验的候选代谢物。在第三个实验中，使用两个实验中的植物材料对控制代谢途径的关键调控基因进行了 RT-PCR 分析。第三个实验的结果为水稻胁迫下这些代谢途径的相关性提供了强有力的验证。我们发现了有前途的水稻基因型，其抗逆代谢物的倍数变化水平与小麦品种 Weebill 相当。这项研究帮助确定了可作为标记或诱导子开发的关键候选代谢物，以及可用作水稻改良性状供体系的基因型。