高Ca²⁺环境对许多植物的生长不利, 因此研究植物对高Ca²⁺环境的适应机制非常重要。研究发现, 拟南芥(Ara- bidopsis thaliana)镁转运体MGT7功能缺失突变体mgt7-1和mgt7-2具有高Ca²⁺敏感表型: 在高Ca²⁺培养基上, 相对于野生型Col-0, 突变体叶鲜重显著下降, 但根长无显著差异。高Ca²⁺对MGT7启动子活性和包括MGT7在内的镁转运体基因表达无显著调节作用。Col-0与mgt7突变体之间, 在外加Ca²⁺诱导细胞质Ca²⁺瞬时升高和Ca²⁺含量方面无显著差异; 但是, 在正常和高Ca²⁺培养基上, mgt7突变体的Mg含量均显著低于Col-0。高Ca²⁺显著抑制Col-0和mgt7突变体内Mg的积累。因此我们假设, mgt7突变体的高Ca²⁺敏感表型是由于其体内Mg含量下降导致的。进一步的研究证实, 只有增加培养基中Mg²⁺的含量, 而不是N、P、K和S, 才可以使突变体的高Ca²⁺敏感表型得到恢复。

A high Ca environment has negative effects on plant growth and development, so the adaptation of plants to high Ca²⁺ level is important to study. We found that the Arabidopsis Mg²⁺ transporter MGT7 loss-of-function mutants mgt7-1 and mgt7-2 showed a high Ca²⁺-sensitive phenotype: under high Ca²⁺ medium, the leaf fresh weight but not root length decreased significantly compared to the wild type Col-0. The high Ca²⁺ content had no effect on MGT7 promoter activity and the expression of other Mg²⁺ transporter genes including MGT7. The mgt7 mutant and the wild type did not differ in extracellular Ca²⁺-induced cytosolic Ca²⁺ level and Ca and Mg content. However, with both normal and high Ca²⁺ media, the Mg content was lower in mgt7 than the wild type. High Ca²⁺ treatment inhibited Mg²⁺ accumulation in both mgt7 and the wild type. The mutant’s high Ca²⁺-sensitive phenotype may be due to decreased Mg content. Increasing the Mg content but not N, P, K or S in the medium fully rescued the high Ca²⁺-sensitive phenotype.