Inoue Haruhiko, Kobayashi Takanori, Nozoye Tomoko, Takahashi Michiko, Kakei Yusuke, Suzuki Kazumasa, Nakazono Mikio, Nakanishi Hiromi, Mori Satoshi, Nishizawa Naoko K
Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1 Yayoi, Tokyo 113-8657, Japan.
J Biol Chem. 2009 Feb 6;284(6):3470-9. doi: 10.1074/jbc.M806042200. Epub 2008 Dec 2.
Graminaceous plants take up iron through YS1 (yellow stripe 1) and YS1-like (YSL) transporters using iron-chelating compounds known as mugineic acid family phytosiderophores. We examined the expression of 18 rice (Oryza sativa L.) YSL genes (OsYSL1-18) in the epidermis/exodermis, cortex, and stele of rice roots. Expression of OsYSL15 in root epidermis and stele was induced by iron deficiency and showed daily fluctuation. OsYSL15 restored a yeast mutant defective in iron uptake when supplied with iron(III)-deoxymugineic acid and transported iron(III)-deoxymugineic acid in Xenopus laevis oocytes. An OsYSL15-green fluorescent protein fusion was localized to the plasma membrane when transiently expressed in onion epidermal cells. OsYSL15 promoter-beta-glucuronidase analysis revealed that OsYSL15 expression in roots was dominant in the epidermis/exodermis and phloem cells under conditions of iron deficiency and was detected only in phloem under iron sufficiency. These results strongly suggest that OsYSL15 is the dominant iron(III)-deoxymugineic acid transporter responsible for iron uptake from the rhizosphere and is also responsible for phloem transport of iron. OsYSL15 was also expressed in flowers, developing seeds, and in the embryonic scutellar epithelial cells during seed germination. OsYSL15 knockdown seedlings showed severe arrest in germination and early growth and were rescued by high iron supply. These results demonstrate that rice OsYSL15 plays a crucial role in iron homeostasis during the early stages of growth.
禾本科植物通过YS1（黄条纹1）和类YS1（YSL）转运蛋白，利用被称为 mugineic 酸家族植物铁载体的铁螯合化合物来吸收铁。我们检测了18个水稻（Oryza sativa L.）YSL基因（OsYSL1 - 18）在水稻根表皮/外皮层、皮层和中柱中的表达情况。缺铁诱导了OsYSL15在根表皮和中柱中的表达，并且其表达呈现日波动。当提供铁（III）-脱氧 mugineic 酸时，OsYSL15恢复了铁吸收缺陷的酵母突变体的功能，并且在非洲爪蟾卵母细胞中转运铁（III）-脱氧 mugineic 酸。当在洋葱表皮细胞中瞬时表达时，OsYSL15 -绿色荧光蛋白融合体定位于质膜。OsYSL15启动子 -β-葡萄糖醛酸酶分析表明，在缺铁条件下，OsYSL15在根中的表达在表皮/外皮层和韧皮部细胞中占主导，而在铁充足时仅在韧皮部中检测到。这些结果强烈表明，OsYSL15是负责从根际吸收铁的主要铁（III）-脱氧 mugineic 酸转运蛋白，并且也负责铁在韧皮部中的运输。OsYSL15在花、发育中的种子以及种子萌发期间的胚盾片上皮细胞中也有表达。OsYSL15基因敲低的幼苗在萌发和早期生长中表现出严重停滞，高铁供应可使其恢复。这些结果表明，水稻OsYSL15在生长早期的铁稳态中起关键作用。
