Takaaki Ogura1, Natsuko I Kobayashi1, Hisashi Suzuki2, Ren Iwata3, Tomoko M Nakanishi1, Keitaro Tanoi4,5. 1. Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan. 2. National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba, Chiba, 263-8555, Japan. 3. Cyclotron and Radioisotope Center, Tohoku University, 6-3, Aoba, Aramaki, Aoba-ku, Sendai, Miyagi, 980-8578, Japan. 4. Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan. uktanoi@g.ecc.u-tokyo.ac.jp. 5. PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan. uktanoi@g.ecc.u-tokyo.ac.jp.
Abstract
MAIN CONCLUSION: The Mg2+ uptake system in Arabidopsis roots is Gd3+- and Fe2+-sensitive, and responds to a changing Mg2+ concentration within 1 h with the participation of AtMRS2 transporters. Magnesium (Mg2+) absorption and the mechanism regulating its activity have not been clarified yet. To address these issues, it is necessary to reveal the characteristics of Mg2+ uptake in roots. Therefore, we first investigated the Mg2+ uptake characteristics in roots of 1-week-old Arabidopsis plants using 28Mg. The Mg2+ uptake system in roots was up-regulated within 1 h in response to the low Mg2+ condition. This induction was inhibited in Arabidopsis "mitochondrial RNA splicing 2/magnesium transport" mutants atmrs2-4/atmgt6 and atmrs2-7/atmgt7, while the expression of AtMRS2-4/AtMGT6 and AtMRS2-7/AtMGT7 genes in the Arabidopsis wild-type was not responsive to Mg2+ conditions. In addition, the Mg deficiency-induced Mg2+ uptake system was shut-down within 5 min when Mg2+ was resupplied to the environment. An inhibition study showed that the constitutive mechanism functioning in Mg2+ uptake under Mg2+ sufficient conditions was sensitive to a number of divalent and trivalent cations, particularly Gd3+ and Fe2+, but not to K+.
MAIN CONCLUSION: The Mg2+ uptake system in Arabidopsis roots is Gd3+- and Fe2+-sensitive, and responds to a changing Mg2+ concentration within 1 h with the participation of AtMRS2 transporters. Magnesium (Mg2+) absorption and the mechanism regulating its activity have not been clarified yet. To address these issues, it is necessary to reveal the characteristics of Mg2+ uptake in roots. Therefore, we first investigated the Mg2+ uptake characteristics in roots of 1-week-old Arabidopsis plants using 28Mg. The Mg2+ uptake system in roots was up-regulated within 1 h in response to the low Mg2+ condition. This induction was inhibited in Arabidopsis "mitochondrial RNA splicing 2/magnesium transport" mutants atmrs2-4/atmgt6 and atmrs2-7/atmgt7, while the expression of AtMRS2-4/AtMGT6 and AtMRS2-7/AtMGT7 genes in the Arabidopsis wild-type was not responsive to Mg2+ conditions. In addition, the Mg deficiency-induced Mg2+ uptake system was shut-down within 5 min when Mg2+ was resupplied to the environment. An inhibition study showed that the constitutive mechanism functioning in Mg2+ uptake under Mg2+ sufficient conditions was sensitive to a number of divalent and trivalent cations, particularly Gd3+ and Fe2+, but not to K+.
Authors: Simon J Conn; Vanessa Conn; Stephen D Tyerman; Brent N Kaiser; Roger A Leigh; Matthew Gilliham Journal: New Phytol Date: 2011-01-24 Impact factor: 10.151