Rice plants take up iron as an Fe3+-phytosiderophore and as Fe2+

Yasuhiro Ishimaru, Motofumi Suzuki, Takashi Tsukamoto, Kazumasa Suzuki, Mikio Nakazono, Takanori Kobayashi, Yasuaki Wada, Satoshi Watanabe, Shinpei Matsuhashi, Michiko Takahashi, Hiromi Nakanishi, Satoshi Mori, Naoko K. Nishizawa

Research output: Contribution to journalArticlepeer-review

523 Citations (Scopus)


Only graminaceous monocots possess the Strategy II iron (Fe)-uptake system in which Fe is absorbed by roots as an Fe3+-phytosiderophore. In spite of being a Strategy II plant, however, rice (Oryza sativa) contains the previously identified Fe2+ transporter OsIRT1q3. In this study, we isolated the OsIRT2 gene from rice, which is highly homologous to OsIRT1. Real-time PCR analysis revealed that OsIRT1 and OsIRT2 are expressed predominantly in roots, and these transporters are induced by low-Fe conditions. When expressed in yeast (Saccharomyces cerevisiae) cells, OsIRT2 cDNA reversed the growth defects of a yeast Fe-uptake mutant. This was similar to the effect of OsIRT1 cDNA. OsIRT1- and OsIRT2-green fluorescent protein fusion proteins localized to the plasma membrane when transiently expressed in onion (Allium cepa L.) epidermal cells. OsIRT1 promoter-GUS analysis revealed that OsIRT1 is expressed in the epidermis and exodermis of the elongating zone and in the inner layer of the cortex of the mature zone of Fe-deficient roots. OsIRT1 expression was also detected in the ccompanion cells. Analysis using the positron-emitting tracer imaging system showed that rice plants are able to take up both an Fe3+-phytosiderophore and Fe2+. This result indicates that, in addition to absorbing an Fe3+-phytosiderophore, rice possesses a novel Fe-uptake system that directly absorbs the Fe2+, a strategy that is advantageous for growth in submerged conditions.

Original languageEnglish
Pages (from-to)335-346
Number of pages12
JournalPlant Journal
Issue number3
Publication statusPublished - 2006 Feb
Externally publishedYes


  • FRO2
  • IRT1
  • Iron deficiency
  • Phytosiderophore
  • Rice

ASJC Scopus subject areas

  • Genetics
  • Plant Science
  • Cell Biology


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