Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
J Exp Bot. 2011 Oct;62(14):4843-50. doi: 10.1093/jxb/err136. Epub 2011 Jun 22.
Cadmium (Cd) is a heavy metal toxic to humans and the accumulation of Cd in the rice grain is a major agricultural problem, particularly in Asia. The role of the iron transporter OsNRAMP1 in Cd uptake and transport in rice was investigated here. An OsNRAMP1:GFP fusion protein was localized to the plasma membrane in onion epidermal cells. The growth of yeast expressing OsNRAMP1 was impaired in the presence of Cd compared with yeast transformed with an empty vector. Moreover, the Cd content of OsNRAMP1-expressing yeast exceeded that of the vector control. The expression of OsNRAMP1 in the roots was higher in a high Cd-accumulating cultivar (Habataki) than a low Cd-accumulating cultivar (Sasanishiki) regardless of the presence of Cd, and the amino acid sequence of OsNRAMP1 showed 100% identity between Sasanishiki and Habataki. Over-expression of OsNRAMP1 in rice increased Cd accumulation in the leaves. These results suggest that OsNRAMP1 participates in cellular Cd uptake and Cd transport within plants, and the higher expression of OsNRAMP1 in the roots could lead to an increase in Cd accumulation in the shoots. Our results indicated that OsNRAMP1 is an important protein in high-level Cd accumulation in rice.
镉（Cd）是一种对人类有毒的重金属，其在稻米中的积累是一个主要的农业问题，尤其是在亚洲。本研究调查了水稻中铁转运蛋白 OsNRAMP1 在镉吸收和转运中的作用。OsNRAMP1:GFP 融合蛋白在洋葱表皮细胞中定位于质膜。与转化空载体的酵母相比，表达 OsNRAMP1 的酵母在存在镉的情况下生长受到抑制。此外，表达 OsNRAMP1 的酵母中的镉含量超过了载体对照。在存在或不存在镉的情况下，高镉积累品种（Habataki）的根系中 OsNRAMP1 的表达高于低镉积累品种（Sasanishiki），并且 Sasanishiki 和 Habataki 之间的 OsNRAMP1 氨基酸序列完全相同。在水稻中过表达 OsNRAMP1 会增加叶片中的镉积累。这些结果表明，OsNRAMP1 参与了细胞内镉的吸收和植物内镉的转运，而根系中 OsNRAMP1 的高表达可能导致地上部镉的积累增加。我们的结果表明，OsNRAMP1 是水稻中高水平镉积累的重要蛋白。
