Deoxymugineic acid increases Zn translocation in Zn-deficient rice plants

Suzuki, Motofumi*; Tsukamoto, Takashi*; Inoue, Haruhiko*; Watanabe, Satoshi; Matsuhashi, Shimpei; Takahashi, Michiko*; Nakanishi, Hiromi*; Mori, Satoshi*; Nishizawa, Naoko*

Rice secretes Deoxymugineic acid (DMA) in response to Fe deficiency to take up Fe in the form of Fe(III)-DMS complex. In contrast with barley, the roots of which secrete DMS in response to Zn deficiency, the amount of DMA secreted by rice roots was slightly decreased under conditions of low Zn supply. There was a concomitant increase in endogenous DMA in rice shoots, suggesting that DMA plays a role in the translocation of Zn within Zn-deficient rice plants. The expression of and was not increased in Zn-deficient roots but that of was increased in Zn-deficient roots and shoots. The expression of was also increased in Zn-deficient roots and dramatically increased in shoots; correspondingly, HPLC analysis was unable to detect nicotianamine in Zn-deficient shoots. The expression of was increased in Zn-deficient shoots. Analyses using the positron-emitting tracer imaging system (PETIS) showed that Zn-deficient rice roots absorbed less Zn-DMA than Zn. Importantly, supply of Zn-DMA rather than Zn increased the translocation of Zn into the leaves of Zn-deficient plants. This was especially evident in the discrimination center (DC). These results suggest that DMA in Zn-deficient rice plants has an important role in the distribution of Zn within the plant rather than in the absorption of Zn from the soil.