Magnesium Transporter MGT6 Plays an Essential Role in Maintaining Magnesium Homeostasis and Regulating High Magnesium Tolerance in Arabidopsis.

Yu-Wei Yan,Sheng Luan,Lei Yang,Qing-Lin Tang,Xin-Xin Zhang,Jin-Liang Qi,Dan-Dan Mao,Yang-Ping Li,Ren-Jie Tang

doi:10.3389/fpls.2018.00274

Abstract

Magnesium (Mg) is one of the essential nutrients for all living organisms. Plants acquire Mg from the environment and distribute within their bodies in the ionic form via Mg2+-permeable transporters. In Arabidopsis, the plasma membrane-localized magnesium transporter MGT6 mediates Mg2+ uptake under Mg-limited conditions, and therefore is important for the plant adaptation to low-Mg environment. In this study, we further assessed the physiological function of MGT6 using a knockout T-DNA insertional mutant allele. We found that MGT6 was required for normal plant growth during various developmental stages when the environmental Mg2+ was low. Interestingly, in addition to the hypersensitivity to Mg2+ limitation, mgt6 mutants displayed dramatic growth defects when external Mg2+ was in excess. Compared with wild-type plants, mgt6 mutants generally contained less Mg2+ under both low and high external Mg2+ conditions. Reciprocal grafting experiments further underpinned a role of MGT6 in a shoot-based mechanism for detoxifying excessive Mg2+ in the environment. Moreover, we found that mgt6 mgt7 double mutant showed more severe phenotypes compared with single mutants under both low- and high-Mg2+ stress conditions, suggesting that these two MGT-type transporters play an additive role in controlling plant Mg2+ homeostasis under a wide range of external Mg2+ concentrations.

Highlights

Magnesium (Mg) is an essential macronutrient for plants
We have shown that knock-down of MGT6 in transgenic plants by RNA interference resulted in growth retardation under low-Mg conditions (Mao et al, 2014)
RT-PCR analyses showed that full-length MGT6 transcript was not detectable in the mgt6 mutant, while MGT4 gene located in the same chromosome is normally expressed (Figure 1B)

Summary

Introduction

Magnesium (Mg) is an essential macronutrient for plants. Being the most abundant free divalent cation in living cells, Mg2+ serves as a counter ion for nucleotides and a central metal for chlorophylls, and acts as a cofactor for many enzymes in catalytic processes. When the medium Mg2+ levels reached a moderate range (0.75, 1.25, and 3 mM), the growth of mgt6 mutants appeared comparable to that of wild-type (Figure 2A), primary root length or seedling fresh weight was slightly affected (Figures 2B,C).

Results

Conclusion