OsHAC1;1 and OsHAC1;2 Function as Arsenate Reductases and Regulate Arsenic Accumulation
OsHAC1;1 and OsHAC1;2 Function as Arsenate Reductases and Regulate Arsenic Accumulation
复制标题
OsHAC1;1 和 OsHAC1;2 作为砷酸还原酶发挥作用并调节砷积累
DOI：
10.1104/pp.16.01332
复制
发表时间：
2016-11-01
期刊：
影响因子：
7.4
通讯作者：
Zhao, Fang-Jie
中科院分区：
文献类型：
--
作者：
Shi, Shulin;Wang, Tao;Zhao, Fang-Jie
大米是有毒的类金属砷（As）的主要膳食来源。减少其在水稻籽粒中的积累对食品安全至关重要。水稻根系吸收砷酸盐和亚砷酸盐取决于当时的土壤条件。砷酸盐解毒的第一步是将其还原为亚砷酸盐，但水稻中催化这一反应的酶仍不清楚。在这里，我们确定OsHAC 1; 1和OsHAC 1; 2为水稻中的砷酸还原酶。OsHAC1; 1和OsHAC 1; 2能够补充缺乏内源性砷酸盐还原酶的大肠杆菌突变体，并将砷酸盐还原为亚砷酸盐。OsHAC1：1和OsHAC 1; OsHAC 1; 2主要在根中表达，其中OsHAC 1; 1在表皮、根毛和周皮细胞中丰富，而OsHAC 1; 2在表皮、皮层外层和内皮层细胞中丰富。砷暴露诱导这两个基因的表达。敲除OsHAC 1; 1或OsHAC 1; 2降低了根中砷酸盐向亚砷酸盐的还原，减少了亚砷酸盐向外部介质的流出。亚砷酸盐流出的损失也与增加作为在地上部的积累。在两个基因的双突变体中观察到更大的影响。相反，OsHAC 1; 1或OsHAC 1; 2的过表达增加了砷的流出，减少了As的积累，并增强了砷酸盐耐受性。当生长在有氧土壤条件下，OsHAC 1; 1或OsHAC 1; 2的过表达也降低了As在水稻籽粒中的积累，而在敲除突变体中籽粒As增加。OsHAC 1; 1和OsHAC 1; 2是限制水稻地上部和籽粒中砷积累的重要砷还原酶。
Rice is a major dietary source of the toxic metalloid arsenic (As). Reducing its accumulation in rice (Oryza sativa) grain is of critical importance to food safety. Rice roots take up arsenate and arsenite depending on the prevailing soil conditions. The first step of arsenate detoxification is its reduction to arsenite, but the enzyme(s) catalyzing this reaction in rice remains unknown. Here, we identify OsHAC1; 1 and OsHAC1; 2 as arsenate reductases in rice. OsHAC1; 1 and OsHAC1; 2 are able to complement an Escherichia coli mutant lacking the endogenous arsenate reductase and to reduce arsenate to arsenite. OsHAC1: 1 and OsHAC1; 2 are predominantly expressed in roots, with OsHAC1; 1 being abundant in the epidermis, root hairs, and pericycle cells while OsHAC1; 2 is abundant in the epidermis, outer layers of cortex, and endodermis cells. Expression of the two genes was induced by arsenate exposure. Knocking out OsHAC1; 1 or OsHAC1; 2 decreased the reduction of arsenate to arsenite in roots, reducing arsenite efflux to the external medium. Loss of arsenite efflux was also associated with increased As accumulation in shoots. Greater effects were observed in a double mutant of the two genes. In contrast, overexpression of either OsHAC1; 1 or OsHAC1; 2 increased arsenite efflux, reduced As accumulation, and enhanced arsenate tolerance. When grown under aerobic soil conditions, overexpression of either OsHAC1; 1 or OsHAC1; 2 also decreased As accumulation in rice grain, whereas grain As increased in the knockout mutants. We conclude that OsHAC1; 1 and OsHAC1; 2 are arsenate reductases that play an important role in restricting As accumulation in rice shoots and grain.