Nicotianamine synthase gene expression differs in barley and rice under Fe-deficient conditions
Nicotianamine synthase gene expression differs in barley and rice under Fe-deficient conditions
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DOI：
10.1046/j.1365-313x.2001.00951.x
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发表时间：
2001-01-01
期刊：
影响因子：
7.2
通讯作者：
Mori, S
中科院分区：
文献类型：
--
作者：
Higuchi, K;Watanabe, S;Mori, S
烟碱胺（NA）是mugineic acid family phytosiderophores （MAs）生物合成途径中的一种中间体，是禾本科植物铁获取装置的重要组成部分。在非谷类植物中，NA被认为是金属阳离子平衡的重要螯合剂。因此，NA在所有高等植物的铁代谢和体内平衡中起着关键作用。烟碱胺合成酶（Nicotianamine synthase， NAS, EC 2.5.1.43）催化s -腺苷甲硫氨酸三聚化形成一个NA分子。大麦是一种抗缺铁的植物，分泌大量的MAs，而水稻是一种易受缺铁影响的植物，只分泌少量的MAs。本研究从大麦中分离出含有HvNAS1的基因组片段，从缺铁水稻根系中分离出3个水稻cDNA克隆：osnas1、osnas2和osnas3。我们还分离出含有OsNAS1和OsNAS2的基因组片段。在大麦中，缺铁只诱导NAS基因在根中表达，而在水稻中，缺铁诱导NAS基因在根和褪绿叶中表达。根和叶的内源NA含量均高于大麦。我们利用农杆菌介导的转化，将含有HvNAS1的大麦基因组DNA片段（5'侧区9 kb或2 kb）导入水稻。缺铁诱导转基因水稻根和叶中HvNAS1的表达，与水稻NAS基因一样。对大麦和水稻在适应铁缺乏过程中NAS基因的变化进行了比较。
Nicotianamine (NA) is an intermediate in the biosynthetic pathway of the mugineic acid family phytosiderophores (MAs), which are crucial components of the iron acquisition apparatus of graminaceous plants. In non-graminaceous plants, NA is thought to be an essential chelator for metal cation homeostasis. Thus NA plays a key role in Fe metabolism and homeostasis in all higher plants. Nicotianamine synthase (NAS, EC 2.5.1.43) catalyzes the trimerization of S-adenosylmethionine to form one molecule of NA. Barley, a plant that is resistant to Fe deficiency, secretes large amounts of MAs, whereas rice, a plant that is susceptible to Fe deficiency, secretes only small amounts. In this study we isolated a genomic fragment containing HvNAS1 from barley and three rice cDNA clones, osnas1, osnas2 and osnas3 from Fe-deficient rice roots. We also isolated a genomic fragment containing both OsNAS1 and OsNAS2. In contrast to barley, in which Fe deficiency induces the expression of NAS genes only in roots, Fe deficiency in rice induced NAS gene expression in both roots and chlorotic leaves. The amounts of endogenous NA in both the roots and leaves were higher than in barley. We introduced barley genomic DNA fragments containing HvNAS1 with either 9 or 2 kb of the 5'-flanking region into rice, using Agrobacterium-mediated transformation. Fe deficiency induced HvNAS1 expression in both roots and leaves of the transgenic rice, as occurs with rice NAS genes. Barley and rice NAS genes are compared in a discussion of alteration of the NAS genes during adaptation to Fe deficiency.