Institute of Plant Science and Resources, Okayama University, Chuo, Kurashiki, Japan.
State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, China.
J Exp Bot. 2018 Apr 27;69(10):2743-2752. doi: 10.1093/jxb/ery107.
Reducing cadmium (Cd) accumulation in rice grain is an important issue for human health. The aim of this study was to manipulate both expression and tissue localization of OsHMA3, a tonoplast-localized Cd transporter, in the roots by expressing it under the control of the OsHMA2 promoter, which shows high expression in different organs including roots, nodes, and shoots. In two independent transgenic lines, the expression of OsHMA3 was significantly enhanced in all organs compared with non-transgenic rice. Furthermore, OsHMA3 protein was detected in the root pericycle cells and phloem region of both the diffuse vascular bundle and the enlarged vascular bundle of the nodes. At the vegetative stage, the Cd concentration in the shoots and xylem sap of the transgenic rice was significantly decreased, but that of the whole roots and root cell sap was increased. At the reproductive stage, the concentration of Cd, but not other essential metals, in the brown rice of transgenic lines was decreased to less than one-tenth that of the non-transgenic rice. These results indicate that expression of OsHMA3 under the control of the OsHMA2 promoter can effectively reduce Cd accumulation in rice grain through sequestering more Cd into the vacuoles of various tissues.
降低稻米中镉（Cd）的积累对人类健康至关重要。本研究旨在通过 OsHMA2 启动子控制 OsHMA3 的表达和组织定位来操纵其在根系中的表达，该启动子在包括根、节和茎在内的不同器官中均有高表达。在两个独立的转基因系中，与非转基因水稻相比，所有器官中 OsHMA3 的表达均显著增强。此外，在节点的弥散维管束和扩大维管束的根皮层细胞和韧皮部区域都检测到了 OsHMA3 蛋白。在营养生长阶段，转基因水稻地上部和木质部汁液中的 Cd 浓度显著降低，但整个根系和根细胞汁液中的 Cd 浓度增加。在生殖生长阶段，与非转基因水稻相比，转基因系糙米中的 Cd 浓度（而非其他必需金属）降低到十分之一以下。这些结果表明，通过将更多的 Cd 隔离到各种组织的液泡中，OsHMA3 在 OsHMA2 启动子的控制下的表达可以有效地降低稻米中 Cd 的积累。
