Route and Regulation of Zinc, Cadmium, and Iron Transport in Rice Plants (Oryza sativa L.) during Vegetative Growth and Grain Filling: Metal Transporters, Metal Speciation, Grain Cd Reduction and Zn and Fe Biofortification

International Journal of Molecular Sciences

Tadakatsu Yoneyama²  Satoru Ishikawa³  Shu Fujimaki¹ 

[1] Quantum, Beam Science Center, Japan Atomic Energy Agency, Takasaki, Gunma 370-1292, Japan; E-Mail:;Department of Applied Biological Chemistry, The University of Tokyo, Tokyo 113-8657, Japan;Soil Environment Division, National Institute for Agro-Environmental Sciences, Tsukuba, Ibaraki 305-8604, Japan; E-Mail:

关键词: cadmium;    iron;    metals in grains;    metal speciation;    metal transporter;    rice (Oryza sativa L.);    xylem-to-phloem transport;    zinc;   

DOI  :  10.3390/ijms160819111

来源: mdpi

【 摘 要 】

Zinc (Zn) and iron (Fe) are essential but are sometimes deficient in humans, while cadmium (Cd) is toxic if it accumulates in the liver and kidneys at high levels. All three are contained in the grains of rice, a staple cereal. Zn and Fe concentrations in rice grains harvested under different levels of soil/hydroponic metals are known to change only within a small range, while Cd concentrations show greater changes. To clarify the mechanisms underlying such different metal contents, we synthesized information on the routes of metal transport and accumulation in rice plants by examining metal speciation, metal transporters, and the xylem-to-phloem transport system. At grain-filling, Zn and Cd ascending in xylem sap are transferred to the phloem by the xylem-to-phloem transport system operating at stem nodes. Grain Fe is largely derived from the leaves by remobilization. Zn and Fe concentrations in phloem-sap and grains are regulated within a small range, while Cd concentrations vary depending on xylem supply. Transgenic techniques to increase concentrations of the metal chelators (nicotianamine, 2′-deoxymugineic acid) are useful in increasing grain Zn and Fe concentrations. The elimination of OsNRAMP5 Cd-uptake transporter and the enhancement of root cell vacuolar Cd sequestration reduce uptake and root-to-shoot transport, respectively, resulting in a reduction of grain Cd accumulation.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.