Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Natsushimacho, Yokosuka, Kanagawa 237-0068, Japan.
Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan.
Metallomics. 2021 Apr 14;13(4). doi: 10.1093/mtomcs/mfab009.
We performed micro-X-ray fluorescence imaging of frozen-hydrated sections of a root of Pteris vittata for the first time, to the best of our knowledge, to reveal the mechanism of arsenic (As) uptake. The As distribution was successfully visualized in cross sections of different parts of the root, which showed that (i) the major pathway of As uptake changes from symplastic to apoplastic transport in the direction of root growth, and (ii) As and K have different mobilities around the stele before xylem loading, despite their similar distributions outside the stele in the cross sections. These data can reasonably explain As reduction, axially observed around the root tip in the direction of root growth and radially observed in the endodermis in the cross sections, as a consequence of the incorporation of As into the cells or symplast of the root. In addition, previous observations of As species in the midrib can be reconciled by ascribing a reduction capacity to the root cells, which implies that As reduction mechanisms at the cellular level may be an important control on the peculiar root-to-shoot transport of As in P. vittata.
我们首次对凤尾蕨根的冰冻水合切片进行了微 X 射线荧光成像，据我们所知，这是为了揭示砷（As）吸收的机制。As 的分布在根不同部位的横切面上成功地可视化了，这表明：（i）As 吸收的主要途径在根生长的方向上从共质体向质外体运输发生变化；（ii）尽管 As 和 K 在茎外的横切面上分布相似，但在木质部装载之前，它们在中柱周围的移动性不同。这些数据可以合理地解释轴向在根尖周围观察到的、沿根生长方向观察到的 As 还原，以及在横切面上观察到的内皮层中的径向 As 还原，这是由于 As 被整合到根的细胞或共质体中。此外，以前在中脉观察到的 As 物种可以通过将还原能力归因于根细胞来协调，这意味着细胞水平的 As 还原机制可能是控制凤尾蕨中 As 特殊的根到茎运输的一个重要因素。
