A loss-of-function mutation in AtYSL1 reveals its role in iron and nicotianamine seed loading
A loss-of-function mutation in AtYSL1 reveals its role in iron and nicotianamine seed loading
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DOI：
10.1111/j.1365-313x.2005.02569.x
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发表时间：
2005-12-01
期刊：
影响因子：
7.2
通讯作者：
Curie, C
中科院分区：
文献类型：
--
作者：
Le Jean, M;Schikora, A;Curie, C
拟南芥类黄条蛋白1（YSL）与玉米类黄条蛋白1（YS 1）具有同源性，玉米类黄条蛋白1（YS 1）在缺铁胁迫下参与根吸收铁-植物铁载体（PS）。虽然双子叶植物不合成PS，但它们确实合成PS前体烟酰胺，烟酰胺是维持铁稳态和铜转运所必需的强金属螯合剂。此外，ZmYS 1和水稻（Oryza sativa）蛋白OsYSL 2在异源表达系统中具有金属烟酰胺转运活性。在这项工作中，我们的特点AtYSL 1在植物的功能。两个插入功能丧失的拟南芥ysl 1突变体被发现表现出增加烟酰胺积累的芽。更重要的是，两种ysl 1基因敲除的种子比野生型种子含有更少的铁和烟酰胺，即使是在过量铁的存在下生长的植物。这种表型可以通过在ysl 1植物中表达野生型AtYSL 1基因来逆转。ysl 1种子发芽缓慢，但这一缺陷被铁供应所挽救。AtYSL 1在叶的木质部薄壁组织中表达，在那里它被上调，在响应铁过剩，以及在花粉和年轻的角果部分。这种模式与铁和烟酰胺的长距离循环及其向种子的传递是一致的。总之，我们的工作提供了强有力的生理证据，证明种子中的铁和烟酰胺水平部分依赖于AtYSL 1功能。
The Arabidopsis Yellow Stripe 1-Like (YSL) proteins have been identified by homology with the maize (Zea mays) Yellow Stripe 1 (YS1) transporter which is responsible for iron-phytosiderophore (PS) uptake by roots in response to iron shortage. Although dicotyledonous plants do not synthesize PS, they do synthesize the PS precursor nicotianamine, a strong metal chelator essential for maintenance of iron homeostasis and copper translocation. Furthermore, ZmYS1 and the rice (Oryza sativa) protein OsYSL2 have metal-nicotianamine transport activities in heterologous expression systems. In this work, we have characterized the function of AtYSL1 in planta. Two insertional loss-of-function ysl1 mutants of Arabidopsis were found to exhibit increased nicotianamine accumulation in shoots. More importantly, seeds of both ysl1 knockouts contained less iron and nicotianamine than wild-type seeds, even when produced by plants grown in the presence of an excess of iron. This phenotype could be reverted by expressing the wild-type AtYSL1 gene in ysl1 plants. ysl1 seeds germinated slowly, but this defect was rescued by an iron supply. AtYSL1 was expressed in the xylem parenchyma of leaves, where it was upregulated in response to iron excess, as well as in pollen and in young silique parts. This pattern is consistent with long-distance circulation of iron and nicotianamine and their delivery to the seed. Taken together, our work provides strong physiological evidence that iron and nicotianamine levels in seeds rely in part on AtYSL1 function.