Rice plants take up iron as an Fe3+-phytosiderophore and as Fe2+
Rice plants take up iron as an Fe3+-phytosiderophore and as Fe2+
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DOI：
10.1111/j.1365-313x.2005.02624.x
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发表时间：
2006-02-01
期刊：
影响因子：
7.2
通讯作者：
Nishizawa, NK
中科院分区：
文献类型：
--
作者：
Ishimaru, Y;Suzuki, M;Nishizawa, NK
只有禾本科单子叶植物才具有策略 II 铁 (Fe) 吸收系统，其中铁作为 Fe3+-植物铁载体被根部吸收。然而，尽管是策略 II 植物，水稻 (Oryza sativa) 仍含有先前鉴定的 Fe2+ 转运蛋白 OsIRT1。在本研究中，我们从水稻中分离出了OsIRT2基因，该基因与OsIRT1高度同源。实时 PCR 分析表明 OsIRT1 和 OsIRT2 主要在根中表达，并且这些转运蛋白是由低铁条件诱导的。当在酵母（酿酒酵母）细胞中表达时，OsIRT2 cDNA 逆转了酵母铁吸收突变体的生长缺陷。这与 OsIRT1 cDNA 的效果相似。当在洋葱 (Allium cepa L.) 表皮细胞中瞬时表达时，OsIRT1-和 OsIRT2-绿色荧光蛋白融合蛋白定位于质膜。 OsIRT1启动子-GUS分析表明，OsIRT1在缺铁根的伸长区表皮和外皮以及成熟区皮层内层表达。在伴随细胞中也检测到 OsIRT1 表达。使用正电子发射示踪成像系统的分析表明，水稻植株能够吸收 Fe3+ 植物铁载体和 Fe2+。这一结果表明，除了吸收Fe3+-植物铁载体外，水稻还拥有一种直接吸收Fe2+的新型铁吸收系统，这种策略有利于在水下条件下的生长。
Only graminaceous monocots possess the Strategy II iron ( Fe)-uptake system in which Fe is absorbed by roots as an Fe3+-phytosiderophore. In spite of being a Strategy II plant, however, rice ( Oryza sativa) contains the previously identified Fe2+ transporter OsIRT1. In this study, we isolated the OsIRT2 gene from rice, which is highly homologous to OsIRT1. Real-time PCR analysis revealed that OsIRT1 and OsIRT2 are expressed predominantly in roots, and these transporters are induced by low-Fe conditions. When expressed in yeast ( Saccharomyces cerevisiae) cells, OsIRT2 cDNA reversed the growth defects of a yeast Fe-uptake mutant. This was similar to the effect of OsIRT1 cDNA. OsIRT1- and OsIRT2-green fluorescent protein fusion proteins localized to the plasma membrane when transiently expressed in onion ( Allium cepa L.) epidermal cells. OsIRT1 promoter-GUS analysis revealed that OsIRT1 is expressed in the epidermis and exodermis of the elongating zone and in the inner layer of the cortex of the mature zone of Fe-deficient roots. OsIRT1 expression was also detected in the ccompanion cells. Analysis using the positron-emitting tracer imaging system showed that rice plants are able to take up both an Fe3+-phytosiderophore and Fe2+. This result indicates that, in addition to absorbing an Fe3+-phytosiderophore, rice possesses a novel Fe-uptake system that directly absorbs the Fe2+, a strategy that is advantageous for growth in submerged conditions.