United Graduate School of Agricultural Sciences, Iwate University, Morioka, Iwate, Japan.
Department of Plant Bio Sciences, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan.
Plant Commun. 2019 Nov 21;1(3):100009. doi: 10.1016/j.xplc.2019.100009. eCollection 2020 May 11.
Arsenic contamination is a major environmental issue, as it may lead to serious health hazard. The reduced trivalent form of inorganic arsenic, arsenite, is in general more toxic to plants compared with the fully oxidized pentavalent arsenate. The uptake of arsenite in plants has been shown to be mediated through a large subfamily of plant aquaglyceroporins, nodulin 26-like intrinsic proteins (NIPs). However, the efflux mechanisms, as well as the mechanism of arsenite-induced root growth inhibition, remain poorly understood. Using molecular physiology, synchrotron imaging, and root transport assay approaches, we show that the cellular transport of trivalent arsenicals in is strongly modulated by PIN FORMED 2 (PIN2) auxin efflux transporter. Root transport assay using radioactive arsenite, X-ray fluorescence imaging (XFI) coupled with X-ray absorption spectroscopy (XAS), and inductively coupled plasma mass spectrometry analysis revealed that plants accumulate higher concentrations of arsenite in roots compared with the wild-type. At the cellular level, arsenite specifically targets intracellular sorting of PIN2 and thereby alters the cellular auxin homeostasis. Consistently, loss of PIN2 function results in arsenite hypersensitivity in roots. XFI coupled with XAS further revealed that loss of PIN2 function results in specific accumulation of arsenical species, but not the other metals such as iron, zinc, or calcium in the root tip. Collectively, these results suggest that PIN2 likely functions as an arsenite efflux transporter for the distribution of arsenical species .
砷污染是一个主要的环境问题，因为它可能导致严重的健康危害。与完全氧化的五价砷酸盐相比，无机砷的还原三价形式亚砷酸盐对植物的毒性通常更大。已经表明，植物对亚砷酸盐的摄取是通过植物水通道蛋白的一个大亚家族，即类豆球蛋白 26 内在蛋白（NIPs）介导的。然而，外排机制以及亚砷酸盐诱导根生长抑制的机制仍知之甚少。使用分子生理学、同步辐射成像和根转运测定方法，我们表明，在 中，三价砷化物的细胞转运强烈受 PIN 形成 2（PIN2）生长素外排转运蛋白的调节。使用放射性亚砷酸盐的根转运测定、与 X 射线吸收光谱（XAS）结合的 X 射线荧光成像（XFI）以及电感耦合等离子体质谱分析表明，与野生型相比， 植物在根中积累了更高浓度的亚砷酸盐。在细胞水平上，亚砷酸盐专门针对 PIN2 的细胞内分拣，从而改变了细胞内生长素的动态平衡。一致地，PIN2 功能的丧失导致根中对亚砷酸盐的超敏反应。XFI 与 XAS 进一步表明，PIN2 功能的丧失导致砷化物物种的特异性积累，但不是其他金属，如铁、锌或钙在根尖的积累。总的来说，这些结果表明，PIN2 可能作为砷化物物种分布的亚砷酸盐外排转运蛋白发挥作用。
