Department of Materials, University of Oxford, Oxford OX1 3PH, United Kingdom.
Plant Physiol. 2011 Jun;156(2):913-24. doi: 10.1104/pp.111.173088. Epub 2011 Apr 13.
Rice (Oryza sativa) takes up arsenite mainly through the silicic acid transport pathway. Understanding the uptake and sequestration of arsenic (As) into the rice plant is important for developing strategies to reduce As concentration in rice grain. In this study, the cellular and subcellular distributions of As and silicon (Si) in rice roots were investigated using high-pressure freezing, high-resolution secondary ion mass spectrometry, and transmission electron microscopy. Rice plants, both the lsi2 mutant lacking the Si/arsenite efflux transporter Lsi2 and its wild-type cultivar, with or without an iron plaque, were treated with arsenate or arsenite. The formation of iron plaque on the root surface resulted in strong accumulation of As and phosphorous on the epidermis. The lsi2 mutant showed stronger As accumulation in the endodermal vacuoles, where the Lsi2 transporter is located in the plasma membranes, than the wild-type line. As also accumulated in the vacuoles of some xylem parenchyma cells and in some pericycle cells, particularly in the wild-type mature root zone. Vacuolar accumulation of As is associated with sulfur, suggesting that As may be stored as arsenite-phytochelatin complexes. Si was localized in the cell walls of the endodermal cells with little apparent effect of the Lsi2 mutation on its distribution. This study reveals the vacuolar sequestration of As in rice roots and contrasting patterns of As and Si subcellular localization, despite both being transported across the plasma membranes by the same transporters.
水稻（Oryza sativa）主要通过硅酸运输途径摄取亚砷酸盐。了解砷（As）进入水稻植株的吸收和固定对于开发降低水稻籽粒中 As 浓度的策略非常重要。在这项研究中，使用高压冷冻、高分辨率二次离子质谱和透射电子显微镜研究了水稻根中的 As 和硅（Si）的细胞和亚细胞分布。用砷酸盐或亚砷酸盐处理有或没有铁斑的 lsi2 突变体（缺乏 Si/砷外排转运蛋白 Lsi2）及其野生型培养物的水稻植物。在根表面形成铁斑会导致表皮上强烈积累 As 和磷。与野生型系相比，lsi2 突变体在内皮层液泡中积累了更强的 As，Lsi2 转运蛋白位于质膜中。As 还积累在一些木质部薄壁细胞和一些皮层细胞的液泡中，特别是在野生型成熟根区。液泡中 As 的积累与硫有关，表明 As 可能作为亚砷酸盐-植物螯合肽复合物储存。Si 定位于内皮层细胞的细胞壁中，Lsi2 突变对其分布几乎没有明显影响。本研究揭示了水稻根中 As 的液泡隔离以及 As 和 Si 亚细胞定位的对比模式，尽管两者都通过相同的转运蛋白穿过质膜运输。
