Arabidopsis Transporter MGT6 Mediates Magnesium Uptake and Is Required for Growth under Magnesium Limitation.

Although magnesium (Mg(2+)) is the most abundant divalent cation in plant cells, little is known about the mechanism of Mg(2+) uptake by plant roots. Here, we report a key function of Magnesium Transport6 (MGT6)/Mitochondrial RNA Splicing2-4 in Mg(2+) uptake and low-Mg(2+) tolerance in Arabidopsis thaliana. MGT6 is expressed mainly in plant aerial tissues when Mg(2+) levels are high in the soil or growth medium. Its expression is highly induced in the roots during Mg(2+) deficiency, suggesting a role for MGT6 in response to the low-Mg(2+) status in roots. Silencing of MGT6 in transgenic plants by RNA interference (RNAi) resulted in growth retardation under the low-Mg(2+) condition, and the phenotype was restored to normal growth after RNAi plants were transferred to Mg(2+)-sufficient medium. RNAi plants contained lower levels of Mg(2+) compared with wild-type plants under low Mg(2+) but not under Mg(2+)-sufficient conditions. Further analysis indicated that MGT6 was localized in the plasma membrane and played a key role in Mg(2+) uptake by roots under Mg(2+) limitation. We conclude that MGT6 mediates Mg(2+) uptake in roots and is required for plant adaptation to a low-Mg(2+) environment.