Magnesium deficiency-induced magnesium uptake revealed by radiotracer studies
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba-city, Chiba 263-8555, Japan.
- Cyclotron and Radioisotope Center, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
- PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
It has been hypothesized that plants regulate the membrane transport of Mg2+ to maintain the optimum concentration in cells for growth. However, some studies suggest that gene expression of Mg2+ transporters does not increase in response to low Mg2+condition. To investigate the mechanism of Mg2+ transport, we tried to elucidate whether and how Mg2+ uptake responds to environmental changes. To investigate Mg2+ uptake rate in root, we prepared 1-week-old Arabidopsis plants and performed Mg2+uptake experiments using agarose plates with 28Mg as a radiotracer. The Mg2+ uptake rate in root increased in response to low Mg2+ condition for 24 h, however, this increase was not observed in the Mg2+ transporter mutants atmrs2-4 and atmrs2-7. In addition, AtMRS2-4 and AtMRS2-7 gene expression in wild-type Arabidopsis did not increase in low Mg2+ condition. In wild-type Arabidopsis, Mg2+ uptake rate increased within 30 minutes at earliest. The low-Mg2+-induced increase was repressed within 5 minutes when Mg2+ was resupplied. An additional experiment to investigate Mg2+ uptake inhibition with other cations under Mg2+sufficient condition showed that the Mg2+ uptake system was sensitive to a number of divalent and trivalent cations, but not to K+.