Department of Plant Molecular Physiology, Institute of Experimental Biology, Wroclaw University, Kanonia 6/8, 50-328, Wroclaw, Poland.
Department of Genetics and Cell Physiology, Institute of Experimental Biology, Wroclaw University, Kanonia 6/8, 50-328, Wroclaw, Poland.
Plant J. 2018 Sep;95(6):988-1003. doi: 10.1111/tpj.14006. Epub 2018 Jul 17.
The plant metal tolerance protein family (MTP) includes 12 members that have been classified into three phylogenetically different subgroups - Zn-cation diffusion facilitator (CDF), Fe/Zn-CDF and Mn-CDF - based on their putative metal specificity. To date, only members belonging to the Zn-CDF or Mn-CDF group have been characterized functionally. The plant Fe/Zn-CDF subgroup includes two proteins, MTP6 and MTP7, but their function and metal specificity have not been confirmed. In this study we showed that cucumber CsMTP7 is a highly specific mitochondrial Fe importer that is able to confer yeast tolerance to Fe excess through increased accumulation of Fe in the mitochondria. We also demonstrated that CsMTP7 contributes to the increased accumulation of Fe in the mitochondria of Arabidopsis thaliana protoplasts. The transcripts and mitochondrial levels of CsMTP7 and ferritin - the iron-storing protein - are significantly increased in cucumber roots in response to Fe excess. This finding suggests that CsMTP7 and ferritin work in concert to accumulate Fe in plant mitochondria. As genes that encode orthologous proteins have been identified in phylogenetically distant organisms, including Archaea, cyanobacteria, humans and plants, but not in yeast, we concluded that the MTP7-mediated mitochondrial Fe accumulation may be conserved in the species, and express mitochondrial ferritin for mitochondrial Fe storage.
植物金属耐受性蛋白家族（MTP）包括 12 个成员，根据其潜在的金属特异性，可分为三个系统发育上不同的亚组 - Zn 阳离子扩散促进剂（CDF）、Fe/Zn-CDF 和 Mn-CDF。迄今为止，只有属于 Zn-CDF 或 Mn-CDF 组的成员具有功能特征。植物 Fe/Zn-CDF 亚组包括两个蛋白，MTP6 和 MTP7，但它们的功能和金属特异性尚未得到证实。在这项研究中，我们表明，黄瓜 CsMTP7 是一种高度特异性的线粒体铁输入蛋白，能够通过增加线粒体中铁的积累使酵母耐受铁过量。我们还证明，CsMTP7 有助于拟南芥原生质体中线粒体中铁的积累增加。在黄瓜根系中，CsMTP7 和铁蛋白（铁储存蛋白）的转录物和线粒体水平在铁过量时显著增加。这一发现表明，CsMTP7 和铁蛋白协同作用将铁积累在植物的线粒体中。由于在包括古细菌、蓝细菌、人类和植物在内的系统发育较远的生物体中鉴定出编码同源蛋白的基因，但在酵母中没有鉴定出编码同源蛋白的基因，我们得出结论，MTP7 介导的线粒体铁积累可能在物种中保守，并表达线粒体铁蛋白以储存线粒体铁。
