Two magnesium transporters in the chloroplast inner envelope essential for thylakoid biogenesis in Arabidopsis
Two magnesium transporters in the chloroplast inner envelope essential for thylakoid biogenesis in Arabidopsis
复制标题
叶绿体内膜中的两个镁转运蛋白对于拟南芥类囊体生物发生至关重要
DOI：
10.1111/nph.18349
复制
发表时间：
2022
期刊：
影响因子：
9.4
通讯作者：
Sheng Luan
中科院分区：
文献类型：
--
作者：
Bin Zhang;Chi Zhang;Renjie Tang;Xiaojiang Zheng;Fugeng Zhao;Aigen Fu;Wenzhi Lan;Sheng Luan
镁(Mg2+)是叶绿体中许多光合酶的辅因子，是Chl分子的中心原子。然而，关于镁离子通过叶绿体被膜运输的分子机制却知之甚少。在这里，我们报道了拟南芥中两种转运蛋白的功能特征：ACDP/CNNM家族的镁释放蛋白8(MGR8)和MGR9，它在进化上在所有生物谱系中都是保守的。MGR8和MGR9基因普遍表达，其编码蛋白定位于叶绿体的内膜。MGR8和MGR9共同突变，但不是单独突变，导致白化胚珠和黄化幼苗。进一步分析发现，该双突变体在类囊体膜生物发生和光合作用复合体组装方面存在严重缺陷。MGR8和MGR9在功能上对缺乏镁吸收能力的鼠伤寒沙门氏菌突变株MM281的生长起到补充作用。Mgr8/mgr9双突变体在胚胎特异的ABI3启动子下表达MGR9，挽救了其胚胎和早期幼苗的缺陷。部分挽救的突变体植株对缺镁条件敏感，叶绿体中的镁离子含量低于野生型植株。综上所述，我们认为MGR8和MGR9作为镁离子转运体参与了叶绿体对镁离子的吸收。
Magnesium (Mg2+ ) serves as a cofactor for a number of photosynthetic enzymes in the chloroplast, and is the central atom of the Chl molecule. However, little is known about the molecular mechanism of Mg2+ transport across the chloroplast envelope. Here, we report the functional characterization of two transport proteins in Arabidopsis: Magnesium Release 8 (MGR8) and MGR9, of the ACDP/CNNM family, which is evolutionarily conserved across all lineages of living organisms. Both MGR8 and MGR9 genes were expressed ubiquitously, and their encoded proteins were localized in the inner envelope of chloroplasts. Mutations of MGR8 and MGR9 together, but neither of them alone, resulted in albino ovules and chlorotic seedlings. Further analysis revealed severe defects in thylakoid biogenesis and assembly of photosynthetic complexes in the double mutant. Both MGR8 and MGR9 functionally complemented the growth of the Salmonella typhimurium mutant strain MM281, which lacks Mg2+ uptake capacity. The embryonic and early seedling defects of the mgr8/mgr9 double mutant were rescued by the expression of MGR9 under the embryo-specific ABI3 promoter. The partially rescued mutant plants were hypersensitive to Mg2+ deficient conditions and contained less Mg2+ in their chloroplasts than wild-type plants. Taken together, we conclude that MGR8 and MGR9 serve as Mg2+ transporters and are responsible for chloroplast Mg2+ uptake.