Arabidopsis Mg²⁺ Transporter MGT7 Mediates Plants Adapt To High Calcium Environment

High calcium environment has detrimental influence on many plants, so it is important to study the mechanism that how plants adapt to high calcium environment. This study found that Arabidopsis thaliana magnesium transporter MGT7 mutant mgt7-1 and mgt7-2 show high calcium sensitive phenotype on fresh weight, but no phenotype on root. The reasons that mgt7 show high calcium sensitive phenotype may be:(1) high calcium environmental affects MGT7 promoter activity;(2)high calcium environmental affects calcium absorption; (3)high calcium environmental affects magnesium absorption. MGT7 promoter activity has no obvious differences by GUS histochemical staining, so high calcium does not affect the expression of MGT7 gene. Through atomic absorption spectrometry to measure the total content of Ca2+ and total Mg2+, through Luminol method to measure [Ca2+]cyt, we found that on the condition of high calcium, mgt7 and Col-0 have similar total Ca2+ content, have similar [Ca2+]cyt in roots and leaves. It shows that high calcium does not affect Ca2+ absorption of mgt7. However, we found that mgt7 have less total Mg2+ content than Col-O, which indicates that high calcium sensitive phenotype is caused by high calcium inhibiting mgt7 Mg2+ absorption, mgt7 show wild type phenotype after add 2 mM Mg2+ to high calcium medium. In a word, MGT7 mediates plants adapt to high calcium environment.