Synthesis of nicotianamine and deoxymugineic acid is regulated by OsIRO2 in Zn excess rice plants
Synthesis of nicotianamine and deoxymugineic acid is regulated by OsIRO2 in Zn excess rice plants
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DOI：
10.1111/j.1747-0765.2008.00259.x
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发表时间：
2008-06-01
影响因子：
2
通讯作者：
Nishizawa, Naoko K.
中科院分区：
文献类型：
--
作者：
Ishimaru, Yasuhiro;Suzuki, Motofumi;Nishizawa, Naoko K.
锌（Zn）过量通过基于金属的细胞毒性反应对生物系统具有显著毒性。烟酰胺（NA）和脱氧麦根酸（DMA）是低分子量、高亲和力的过渡金属螯合剂。研究表明，NA可能在耐受过量Zn中起作用。结果表明，过量Zn诱导了水稻根中编码铁调控DNA结合转录因子（OsIRO 2）的基因及其下游基因NA合成酶、DMA合成酶和DMA-Fe ~（3+）转运蛋白的表达。与这些基因的表达相一致，在过量Zn根中，内源NA、内源DMA和DMA分泌量增加。虽然过量Zn处理根中Fe浓度远高于对照，但水稻铁蛋白基因OsFer 1在过量Zn处理根中表达下调。OsIRT 1因Fe缺乏而上调，但在Zn过量的根中并未被诱导，这表明OsIRO 2可能不仅仅是由过量Zn引起的Fe缺乏而诱导的。这些数据表明，诱导OsIRO 2过量锌是负责生产NA和DMA，这可能在维持细胞锌的可用性发挥作用。
Zinc (Zn) excess has significant toxicity to biological systems through metal-based cytotoxic reactions. Nicotianamine (NA) and deoxymugineic acid (DMA) are low-molecular-weight, high-affinity transition metal chelators. Studies have shown that NA may have a role in the tolerance of excess Zn. We show that a gene coding the iron (Fe)-regulated DNA-binding transcription factor (OsIRO2) and the downstream genes of OsIRO2, such as NA synthase, DMA synthase and the DMA-Fe3+ transporter, were induced in rice roots by excess Zn. Consistent with the expression of these genes, the amounts of endogenous NA, endogenous DMA and DMA secretion increased in the excess Zn roots. Although the Fe concentration in the excess Zn roots was much higher than that in the control, rice ferritin gene, OsFer1, was downregulated in Zn excess roots. OsIRT1, which is upregulated by Fe deficiency, was not induced in Zn excess roots, suggesting that OsIRO2 may not be induced simply by the Fe deficiency caused by excess Zn. The data indicate that the induction of OsIRO2 by excess Zn is responsible for the production of NA and DMA, which may play a role in maintaining cellular Zn availability.