Expression of the IRT1 metal transporter is controlled by metals at the levels of transcript and protein accumulation
Expression of the IRT1 metal transporter is controlled by metals at the levels of transcript and protein accumulation
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DOI：
10.1105/tpc.001263
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发表时间：
2002-06-01
期刊：
影响因子：
11.6
通讯作者：
Guerinot, ML
中科院分区：
文献类型：
--
作者：
Connolly, EL;Fett, JP;Guerinot, ML
铁是一种必需的营养物质，由于其溶解度低，植物不易利用。此外，铁的毒性过大，会催化羟基自由基的形成，从而破坏细胞成分。因此，植物必须小心地调节铁的吸收，以维持铁的动态平衡。拟南芥IRT1基因是从土壤中高亲和力铁吸收的主要转运体。在这里，我们发现在缺铁条件下转移植物后24小时内，IRT1mRNA的稳定表达水平被诱导，而蛋白水平在转移后72小时达到峰值。在植物恢复到铁充足的条件下，12小时后检测不到IRT1的mRNA和蛋白。过表达IRT1并不能显著提高金属摄取的功能增益。对35S-IRT1转基因植株的分析表明，虽然IRT1在这些植株中有结构性表达，但当铁限制时，IRT1蛋白只在根中存在。在这些条件下，高表达IRT1的植物积累了比野生型植物更高水平的镉和锌，表明IRT1负责这些金属的吸收，并且IRT1蛋白水平确实在这些植物中增加。我们的结果表明，IRT1的表达受两种不同的机制控制，这两种机制提供了一种有效的手段来调节金属运输，以响应不断变化的环境条件。
Iron, an essential nutrient, is not readily available to plants because of its low solubility. In addition, iron is toxic in excess, catalyzing the formation of hydroxyl radicals that can damage cellular constituents. Consequently, plants must carefully regulate iron uptake so that iron homeostasis is maintained. The Arabidopsis IRT1 gene is the major transporter responsible for high-affinity iron uptake from the soil. Here, we show that the steady state level of IRT1 mRNA was induced within 24 h after transfer of plants to iron-deficient conditions, with protein levels peaking 72 h after transfer. IRT1 mRNA and protein were undetectable 12 h after plants were shifted back to iron-sufficient conditions. Overexpression of IRT1 did not confer dominant gain-of-function enhancement of metal uptake. Analysis of 35S-IRT1 transgenic plants revealed that although IRT1 mRNA was expressed constitutively in these plants, IRT1 protein was present only in the roots when iron is limiting. Under these conditions, plants that overexpressed IRT1 accumulated higher levels of cadmium and zinc than wild-type plants, indicating that IRT1 is responsible for the uptake of these metals and that IRT1 protein levels are indeed increased in these plants. Our results suggest that the expression of IRT1 is controlled by two distinct mechanisms that provide an effective means of regulating metal transport in response to changing environmental conditions.