Magnesium uptake characteristics in Arabidopsis revealed by 28 Mg tracer studies.

Main Conclusion: The Mg ²⁺ uptake system in Arabidopsis roots is Gd ³⁺ - and Fe ²⁺ -sensitive, and responds to a changing Mg ²⁺ concentration within 1 h with the participation of AtMRS2 transporters. Magnesium (Mg ²⁺ ) absorption and the mechanism regulating its activity have not been clarified yet. To address these issues, it is necessary to reveal the characteristics of Mg ²⁺ uptake in roots. Therefore, we first investigated the Mg ²⁺ uptake characteristics in roots of 1-week-old Arabidopsis plants using ²⁸ Mg. The Mg ²⁺ uptake system in roots was up-regulated within 1 h in response to the low Mg ²⁺ 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 Mg ²⁺ conditions. In addition, the Mg deficiency-induced Mg ²⁺ uptake system was shut-down within 5 min when Mg ²⁺ was resupplied to the environment. An inhibition study showed that the constitutive mechanism functioning in Mg ²⁺ uptake under Mg ²⁺ sufficient conditions was sensitive to a number of divalent and trivalent cations, particularly Gd ³⁺ and Fe ²⁺ , but not to K ⁺ .