• Iron (Fe) is a major micronutrient and is required for plant growth and development. Nongrass species have evolved a reduction‐based strategy to solubilize and take up Fe. The secretion of Fe‐mobilizing coumarins (e.g. fraxetin, esculetin and sideretin) by plant roots plays an important role in this process. Although the biochemical mechanisms leading to their biosynthesis have been well described, very little is known about their cellular and subcellular localization or their mobility within plant tissues.
• Spectral imaging was used to monitor, in Arabidopsis thaliana, the in planta localization of Fe‐mobilizing coumarins and scopolin. Molecular, genetic and biochemical approaches were also used to investigate the dynamics of coumarin accumulation in roots.
• These approaches showed that root hairs play a major role in scopoletin secretion, whereas fraxetin and esculetin secretion occurs through all epidermis cells. The findings of this study also showed that the transport of coumarins from the cortex to the rhizosphere relies on the PDR9 transporter under Fe‐deficient conditions. Additional experiments support the idea that coumarins move throughout the plant body via the xylem sap and that several plant species can take up coumarins present in the surrounding media.
• Altogether, the data presented here demonstrate that coumarin storage and accumulation in roots is a highly complex and dynamic process.

中文翻译：

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拟南芥中香豆素的积累和贩运：一个复杂而动态的过程

• 铁（Fe）是一种主要的微量营养素，是植物生长发育所需的。非草类物种已发展出一种基于还原的策略来溶解和吸收铁。植物根系分泌铁动员的香豆素（例如弗拉西汀，七叶皂苷和sideretin）在该过程中起重要作用。尽管已经很好地描述了导致其生物合成的生化机制，但对其细胞和亚细胞的定位或它们在植物组织中的移动性知之甚少。
• 光谱成像是用来监测，在拟南芥中，在植物中的Fe-动员香豆素和scopolin的定位。分子，遗传和生化方法也用于研究香豆素在根中积累的动力学。
• 这些方法表明，根毛在碱的分泌中起主要作用，而法拉汀和七叶皂甙的分泌则通过所有表皮细胞发生。这项研究的结果还表明，在缺乏铁的条件下，香豆素从皮质向根际的转运依赖于PDR9转运蛋白。额外的实验支持了香豆素通过木质部汁液在整个植物体内移动的想法，并且几种植物可以吸收周围培养基中存在的香豆素。
• 总之，这里提供的数据表明香豆素在根中的存储和积累是一个高度复杂和动态的过程。