Rice OsYSL15 Is an Iron-regulated Iron(III)-Deoxymugineic Acid Transporter Expressed in the Roots and Is Essential for Iron Uptake in Early Growth of the Seedlings

doi:10.1074/jbc.M806042200

Rice OsYSL15 Is an Iron-regulated Iron(III)-Deoxymugineic Acid Transporter Expressed in the Roots and Is Essential for Iron Uptake in Early Growth of the Seedlings*

Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan

3 To whom correspondence should be addressed. Tel./Fax: 81-3-5841-7514; E-mail: annaoko{at}mail.ecc.u-tokyo.ac.jp.

Abstract

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-β-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.

Footnotes

↵4 The abbreviations used are: MA, mugineic acid family phytosiderophore; DMA, 2′-deoxymugineic acid; GFP, green fluorescent protein; GUS, β-glucuronidase; VC, vector control; MS, Murashige and Skoog medium; RT, reverse transcription; ORF, open reading frame; MES, 4-morpholineethanesulfonic acid; NA, nicotianamine; TM, transmembrane domain; IDEF, iron deficiency-responsive element-binding factor; CBS, circadian clock-associated 1-binding site.
↵5 M. Takahashi, K. Usuda, H. Inoue, H. Nakanishi, S. Mori, and N. K. Nishizawa, unpublished results.
↵* This work was supported by a grant-in-aid for scientific research on priority areas from the Ministry of Education, Culture, Sports, Science, and Technology of Japan and Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the DDBJ/GenBank™/EBI Data Bank with accession number(s) AB190923.
↵ The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. S1–S2 and Table S1.
↵1 Both authors contributed equally to this work.
↵2 Present address: Division of Plant Sciences, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan.
- Received August 5, 2008.
- Revision received December 2, 2008.
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