Phytosiderophore efflux transporters are crucial for iron acquisition in graminaceous plants.
Phytosiderophore efflux transporters are crucial for iron acquisition in graminaceous plants.
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DOI：
10.1074/jbc.m110.180026
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发表时间：
2011-02-18
期刊：
影响因子：
--
通讯作者：
Nishizawa NK
中科院分区：
文献类型：
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作者：
Nozoye T;Nagasaka S;Kobayashi T;Takahashi M;Sato Y;Sato Y;Uozumi N;Nakanishi H;Nishizawa NK
真核生物已经开发出不同的机制来获取铁，这是它们生存所必需的。禾本科植物使用一种螯合策略。它们分泌植物铁载体化合物，使土壤中的铁溶解，然后吸收产生的铁-铁载体复合体。细菌和哺乳动物也会分泌铁载体来获取铁。虽然植物铁载体的分泌对植物的生长至关重要，但其分子机制仍不清楚。在这里，我们证明了脱氧芥酸的外流分别涉及TOM1和HvTOM1基因。脱氧芥酸是水稻和大麦的主要含铁载体。表达TOM1或HvTOM1的非洲爪哇卵母细胞释放~(14)C标记的脱氧烟碱酸，而不释放~(14)C标记的烟胺，这表明TOM1和HvTOM1蛋白是植物铁载体的外排转运体。在缺铁条件下，水稻和大麦根系分别表达高水平的TOM1和HvTOM1，这些基因的过度表达增强了水稻对缺铁的耐性。在水稻根中，TOM1的过度表达提高了脱氧芥酸的分泌效率，而其抑制则降低了其分泌效率，为TOM1编码脱氧芥酸的外排转运体提供了进一步证据。我们还鉴定了两个编码烟胺外流转运蛋白的基因，ENA1和ENA2。我们对植物含铁载体外排转运体的鉴定揭示了禾本科植物获取铁的分子机制中的最后一块。
Eukaryotic organisms have developed diverse mechanisms for the acquisition of iron, which is required for their survival. Graminaceous plants use a chelation strategy. They secrete phytosiderophore compounds, which solubilize iron in the soil, and then take up the resulting iron-phytosiderophore complexes. Bacteria and mammals also secrete siderophores to acquire iron. Although phytosiderophore secretion is crucial for plant growth, its molecular mechanism remains unknown. Here, we show that the efflux of deoxymugineic acid, the primary phytosiderophore from rice and barley, involves the TOM1 and HvTOM1 genes, respectively. Xenopus laevis oocytes expressing TOM1 or HvTOM1 released 14C-labeled deoxymugineic acid but not 14C-labeled nicotianamine, a structural analog and biosynthetic precursor of deoxymugineic acid, indicating that the TOM1 and HvTOM1 proteins are the phytosiderophore efflux transporters. Under conditions of iron deficiency, rice and barley roots express high levels of TOM1 and HvTOM1, respectively, and the overexpression of these genes increased tolerance to iron deficiency. In rice roots, the efficiency of deoxymugineic acid secretion was enhanced by overexpression of TOM1 and decreased by its repression, providing further evidence that TOM1 encodes the efflux transporter of deoxymugineic acid. We have also identified two genes encoding efflux transporters of nicotianamine, ENA1 and ENA2. Our identification of phytosiderophore efflux transporters has revealed the final piece in the molecular machinery of iron acquisition in graminaceous plants.