Burleigh Stephen H, Kristensen Brian K, Bechmann Iben Ellegaard
Plant Research Department, Riø National Laboratory, 4000 Roskilde, Denmark.
Plant Mol Biol. 2003 Jul;52(5):1077-88. doi: 10.1023/a:1025479701246.
Here we present a Zn transporter cDNA named MtZIP2 from the model legume Medicago truncatula. MtZIP2 encodes a putative 37 kDa protein with 8-membrane spanning domains and has moderate amino acid identity with the Arabidopsis thaliana Zn transporter AtZIP2p. MtZIP2 complemented a Zn-uptake mutant of yeast implying that the protein encoded by this gene can transport Zn across the yeast's plasma membrane. The product of a MtZIP2-GFP fusion construct introduced into onion cells by particle bombardment likewise localized to the plasma membrane. The MtZIP2 gene was expressed in roots and stems, but not in leaves of M. truncatula and, in contrast to all other plant Zn transporters characterized thus far, MtZIP2 was up-regulated in roots by Zn fertilization. Expression was highest in roots exposed to a toxic level of Zn. MtZIP2 expression was also examined in the roots of M. truncatula when colonized by the obligate plant symbiont, arbuscular mycorrhizal (AM) fungi, since AM fungi are renowned for their ability to supply plants with mineral nutrients, including Zn. Expression was down-regulated in the roots of the mycorrhizal plants and was associated with a reduced level of Zn within the host plant tissues.
在此，我们展示了来自模式豆科植物蒺藜苜蓿的一个名为MtZIP2的锌转运体cDNA。MtZIP2编码一种推定的37 kDa蛋白，具有8个跨膜结构域，与拟南芥锌转运体AtZIP2p具有中等程度的氨基酸同源性。MtZIP2弥补了酵母的一个锌吸收突变体，这意味着该基因编码的蛋白能够跨酵母质膜转运锌。通过粒子轰击导入洋葱细胞的MtZIP2 - GFP融合构建体的产物同样定位于质膜。MtZIP2基因在蒺藜苜蓿的根和茎中表达，但在叶中不表达，并且与迄今为止所鉴定的所有其他植物锌转运体不同，MtZIP2在锌施肥条件下根中表达上调。在暴露于有毒水平锌的根中表达最高。当被专性植物共生体丛枝菌根（AM）真菌定殖时，我们也检测了蒺藜苜蓿根中MtZIP2的表达，因为AM真菌以其为植物提供包括锌在内的矿质营养的能力而闻名。在菌根植物的根中表达下调，并且与宿主植物组织内锌水平的降低相关。
