Three rice nicotianamine synthase genes, OsNAS1, OsNAS2, and OsNAS3 are expressed in cells involved in long-distance transport of iron and differentially regulated by iron
Three rice nicotianamine synthase genes, OsNAS1, OsNAS2, and OsNAS3 are expressed in cells involved in long-distance transport of iron and differentially regulated by iron
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DOI：
10.1046/j.1365-313x.2003.01878.x
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发表时间：
2003-11-01
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：
Inoue, H;Higuchi, K;Nishizawa, NK
烟酰胺是一种广泛存在于高等植物中的金属螯合剂。在禾本科植物中，NA是植物铁载体的生物合成前体，因此是铁（Fe）获取的关键组分。在这里，我们表明，三个水稻NA合酶（NAS）基因，OsNAS 1，OsNAS 2和OsNAS 3中表达的细胞参与长距离运输的铁和这三个基因的差异调节铁。OsNAS 1和OsNAS 2的转录本检测到铁充足的根，但不是在叶片中，和水平都显着增加，在响应铁缺乏的根和叶。相反，OsNAS 3转录本存在于叶片中，但在铁充足的植物的根中非常低。此外，OsNAS 3表达诱导根，但抑制响应于Fe缺乏在叶中。启动子-GUS分析表明OsNAS 1和OsNAS 2在铁充足的根中表达于与原生木质部相邻的伴细胞和周细胞中。缺铁时，OsNAS 1和OsNAS 2的表达沿着植物铁载体分泌的增加而扩展到所有根细胞。在缺铁植株中，OsNAS 1和OsNAS 2在绿色叶的维管束中表达，并且在表现出严重失绿的叶的所有细胞中表达。OsNAS 3的表达仅限于根的周鞘和伴细胞，以及在叶的伴细胞中，与Fe状态无关。这些结果表明，NAS和NA除了在植物铁载体的分泌中起作用外，还在铁的长距离运输中起重要作用。
Nicotianamine (NA), a chelator of metals, is ubiquitously present in higher plants. In graminaceous plants, NA is a biosynthetic precursor of phytosiderophores and is thus a crucial component for iron (Fe) acquisition. Here, we show that three rice NA synthase (NAS) genes, OsNAS1, OsNAS2, and OsNAS3 are expressed in cells involved in long-distance transport of Fe and that the three genes are differentially regulated by Fe. OsNAS1 and OsNAS2 transcripts were detected in Fe-sufficient roots but not in leaves, and levels of both increased markedly in both roots and leaves in response to Fe deficiency. In contrast, the OsNAS3 transcript was present in leaves but was very low in roots of Fe-sufficient plants. Further, OsNAS3 expression was induced in roots but was suppressed in leaves in response to Fe deficiency. Promoter-GUS analysis revealed that OsNAS1 and OsNAS2 were expressed in Fe-sufficient roots in companion cells and pericycle cells adjacent to the protoxylem. With Fe deficiency, OsNAS1 and OsNAS2 expression extended to all root cells along with an increase in phytosiderophore secretion. In Fe-deficient plants, OsNAS1 and OsNAS2 were expressed in the vascular bundles of green leaves and in all cells of leaves showing severe chlorosis. OsNAS3 expression was restricted to the pericycle and companion cells of the roots, and in companion cells of leaves irrespective of Fe status. These results strongly suggested that NAS and NA play an important role in long-distance transport of Fe in rice plants, in addition to their roles in phytosiderophore secretion from roots.