Research Institute for Bioresources, Okayama University, Kurashiki, Japan.
Plant Cell. 2009 Sep;21(9):2878-83. doi: 10.1105/tpc.109.069831. Epub 2009 Sep 4.
The concentration of essential mineral nutrients in the edible portion of plants such as grains may affect the nutritional value of these foods, while concentrations of toxic minerals in the plant are matter of food safety. Minerals taken up by the roots from soils are normally redirected at plant nodes before they are finally transported into developing seeds. However, the molecular mechanisms involved in this process have not been identified so far. Herein, we report on a transporter (Lsi6) responsible for the redirection of a plant nutrient at the node. Lsi6 is a silicon transporter in rice (Oryza sativa), and its expression in node I below the panicles is greatly enhanced when the panicle is completely emerged. Lsi6 is mainly localized at the xylem transfer cells located at the outer boundary region of the enlarged large vascular bundles in node I. Knockout of Lsi6 decreased Si accumulation in the panicles but increased Si accumulation in the flag leaf. These results suggest that Lsi6 is a transporter involved in intervascular transfer (i.e., transfer of silicon from the large vascular bundles coming from the roots to the diffuse vascular bundles connected to the panicles). These findings will be useful for selectively enhancing the accumulation of essential nutrients and reducing toxic minerals in the edible portion of cereals.
植物可食用部分的必需矿物质营养浓度可能会影响这些食物的营养价值，而植物中有毒矿物质的浓度则是食品安全的问题。根部从土壤中吸收的矿物质通常会在最终运输到发育中的种子之前，在植物节点处重新定向。然而，到目前为止，还没有确定参与这个过程的分子机制。在这里，我们报告了一个负责在节点处重新定向植物养分的转运蛋白（Lsi6）。Lsi6 是水稻（Oryza sativa）中的一种硅转运蛋白，当穗完全伸出时，其在穗下第一节点的表达大大增强。Lsi6 主要定位于节点 I 中扩大的大维管束外边界区域的木质部转移细胞。Lsi6 的敲除减少了穗中的硅积累，但增加了旗叶中的硅积累。这些结果表明，Lsi6 是一种参与血管间转移的转运蛋白（即，将来自根部的大维管束中的硅转移到与穗相连的弥散维管束中）。这些发现将有助于选择性地增强谷物可食用部分中必需营养物质的积累和减少有毒矿物质的含量。
