Differential regulation of nramp and irt metal transporter genes in wild type and iron uptake mutants of tomato
Differential regulation of nramp and irt metal transporter genes in wild type and iron uptake mutants of tomato
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DOI：
10.1074/jbc.m301365200
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发表时间：
2003-07-04
影响因子：
4.8
通讯作者：
Bauer, P
中科院分区：
文献类型：
--
作者：
Bereczky, Z;Wang, HY;Bauer, P
受铁调控的金属转运蛋白可转运多种二价金属，表明铁调控对铁转运的特异性很重要。在植物中，铁调控的广谱金属转运体IRT1是根表皮吸收铁所必需的。其他铁调控的植物金属转运蛋白的功能尚未确定。为了推断植物铁转运的新功能，我们研究了四个番茄金属转运基因（nramp和irt家族）在影响铁吸收的环境和遗传因素方面的调控。我们从番茄中分离出Lenramp1和Lenramp3，并证明这些基因在酵母中编码功能性的NRAMP金属转运体，其中它们受铁调控，主要定位于细胞内囊泡。与Leirt2和Lenramp3相比，Lenramp1和Leirt1分别表现出根特异性表达和缺铁上调。在缺乏调节铁吸收的bHLH基因的fer突变体植株的根部，Lenramp1和Leirt1下调，而Lenramp3和Leirt2则不下调。在缺乏合成植物特异性金属螯合物尼古丁胺的功能酶的绿神经突变体植株中，尽管有足够的铁供应，但Leirt1和Lenramp1的表达却上调，而不依赖于功能铁基因。Lenramp1在维管根薄壁组织中表达，其细胞模式与fer基因相似。而在异位表达时，fer基因不足以诱导Lenramp1和Leirt1。基于我们的研究结果，我们提出了NRAMP1在植物缺铁时在维管薄壁组织中调动铁的新功能。我们讨论了铁/烟胺合成酶依赖和不依赖的金属转运蛋白基因调控途径。
Metal transporters regulated by iron can transport a variety of divalent metals, suggesting that iron regulation is important for specificity of iron transport. In plants, the iron-regulated broad-range metal transporter IRT1 is required for uptake of iron into the root epidermis. Functions of other iron-regulated plant metal transporters are not yet established. To deduce novel plant iron transport functions we studied the regulation of four tomato metal transporter genes belonging to the nramp and irt families with respect to environmental and genetic factors influencing iron uptake. We isolated Lenramp1 and Lenramp3 from tomato and demonstrate that these genes encode functional NRAMP metal transporters in yeast, where they were iron-regulated and localized mainly to intracellular vesicles. Lenramp1 and Leirt1 revealed both root-specific expression and up-regulation by iron deficiency, respectively, in contrast to Leirt2 and Lenramp3. Lenramp1 and Leirt1, but not Lenramp3 and Leirt2, were down-regulated in the roots of fer mutant plants deficient in a bHLH gene regulating iron uptake. In chloronerva mutant plants lacking the functional enzyme for synthesis of the plant-specific metal chelator nicotianamine Leirt1 and Lenramp1 were up-regulated despite sufficient iron supply independent of a functional fer gene. Lenramp1 was expressed in the vascular root parenchyma in a similar cellular pattern as the fer gene. However, the fer gene was not sufficient for inducing Lenramp1 and Leirt1 when ectopically expressed. Based on our results, we suggest a novel function for NRAMP1 in mobilizing iron in the vascular parenchyma upon iron deficiency in plants. We discuss fer/nicotianamine synthase-dependent and -independent regulatory pathways for metal transporter gene regulation.