A novel major facilitator superfamily protein at the tonoplast influences zinc tolerance and accumulation in Arabidopsis
A novel major facilitator superfamily protein at the tonoplast influences zinc tolerance and accumulation in Arabidopsis
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DOI：
10.1104/pp.106.092015
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发表时间：
2007-04-01
期刊：
影响因子：
7.4
通讯作者：
Cobbett, Christopher S.
中科院分区：
文献类型：
--
作者：
Haydon, Michael J.;Cobbett, Christopher S.
锌是所有细胞必需的微量营养素，但过量的锌是有毒的。我们已经鉴定出三个对锌敏感的等位基因突变体。该基因被命名为锌诱导FACILITATOR1(ZIF1)，编码主要的促进剂超家族膜蛋白的成员，该家族在所有生物体中都存在，并运输广泛的小分子有机分子。Zif1突变体的地上部对锌的积累增加，而对其他金属离子的积累没有增加。结合影响锌向根转运的突变，zif1 hma2 hma4三重突变体积累的锌低于野生型，但仍对锌敏感，表明zif1锌敏感表型是锌分布改变所致。Zif1突变体对镉的敏感性也较高，但对镍的敏感性较低。ZIF1启动子-β-葡萄糖醛酸苷酶融合基因在整个植物中都有表达，其中在幼嫩组织中表达最强，在年老组织中主要在维管系统中表达。锌对ZIF1的诱导作用较强，锰对ZIF1的诱导作用较弱。转基因植物中定位于液泡膜的ZIF1-绿色荧光蛋白融合蛋白。MTP1已被鉴定为液泡膜锌转运体，并且Zif1-1mtp1-1双突变体对锌的敏感性高于这两个单一突变体，这表明ZIF1影响锌的动态平衡。在一些高表达ZIF1的转基因株系中，ZIF1的过表达增加了叶片对锌的耐性和叶片脉间失绿。我们认为，ZIF1参与了一种新的锌隔离机制，可能是通过将锌配体或锌配体络合物运输到液泡中。
Zinc (Zn) is an essential micronutrient required by all cells but is toxic in excess. We have identified three allelic Zn-sensitive mutants of Arabidopsis (Arabidopsis thaliana). The gene, designated ZINC-INDUCED FACILITATOR1 (ZIF1), encodes a member of the major facilitator superfamily of membrane proteins, which are found in all organisms and transport a wide range of small, organic molecules. Shoots of zif1 mutants showed increased accumulation of Zn but not other metal ions. In combination with mutations affecting shoot-to-root Zn translocation, zif1 hma2 hma4 triple mutants accumulated less Zn than the wild type but remained Zn sensitive, suggesting that the zif1 Zn-sensitive phenotype is due to altered Zn distribution. zif1 mutants were also more sensitive to cadmium but less sensitive to nickel. ZIF1 promoter-beta-glucuronidase fusions were expressed throughout the plant, with strongest expression in young tissues, and predominantly in the vasculature in older tissues. ZIF1 expression was highly induced by Zn and, to a lesser extent, by manganese. A ZIF1-green fluorescent protein fusion protein localized to the tonoplast in transgenic plants. MTP1 has been identified as a tonoplast Zn transporter and a zif1-1 mtp1-1 double mutant was more sensitive to Zn than either of the single mutants, suggesting ZIF1 influences a distinct mechanism of Zn homeostasis. Overexpression of ZIF1 conferred increased Zn tolerance and interveinal leaf chlorosis in some transgenic lines in which ZIF1 expression was high. We propose that ZIF1 is involved in a novel mechanism of Zn sequestration, possibly by transport of a Zn ligand or a Zn ligand complex into vacuoles.