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

Plant J. 2006 Feb;45(3):335-46. doi: 10.1111/j.1365-313X.2005.02624.x.


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 OsIRT1. 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.

MeSH terms

  • Amino Acid Sequence
  • Cation Transport Proteins / metabolism*
  • Cell Membrane / metabolism
  • FMN Reductase / genetics
  • Genes, Plant / physiology
  • Green Fluorescent Proteins / analysis
  • Iron / metabolism*
  • Molecular Sequence Data
  • Oryza / anatomy & histology
  • Oryza / genetics
  • Oryza / metabolism*
  • Phylogeny
  • Plant Proteins / metabolism*
  • Plant Proteins / physiology
  • Plant Roots / metabolism
  • Plant Stems / metabolism
  • RNA, Plant / metabolism
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / growth & development
  • Sequence Alignment
  • Up-Regulation


  • Cation Transport Proteins
  • Plant Proteins
  • RNA, Plant
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Iron
  • FMN Reductase
  • ferric citrate iron reductase

Associated data

  • GENBANK/AB126084
  • GENBANK/AB126085
  • GENBANK/AB126086