Synthesis of nicotianamine and deoxymugineic acid is regulated by OsIRO2 in Zn excess rice plants

Yasuhiro Ishimaru, Motofumi Suzuki, Yuko Ogo, Michiko Takahashi, Hiromi Nakanishi, Satoshi Mori, Naoko K. Nishizawa

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Zinc (Zn) excess has significant toxicity to biological systems through metal-based cytotoxic reactions. Nicotianamine (NA) and deoxymugineic acid (DMA) are low-molecular-weight, high-affinity transition metal chelators. Studies have shown that NA may have a role in the tolerance of excess Zn. We show that a gene coding the iron (Fe)-regulated DNA-binding transcription factor (OsIRO2) and the downstream genes of OsIRO2, such as NA synthase, DMA synthase and the DMA-Fe3+ transporter, were induced in rice roots by excess Zn. Consistent with the expression of these genes, the amounts of endogenous NA, endogenous DMA and DMA secretion increased in the excess Zn roots. Although the Fe concentration in the excess Zn roots was much higher than that in the control, rice ferritin gene, OsFer1, was downregulated in Zn excess roots. OsIRT1, which is upregulated by Fe deficiency, was not induced in Zn excess roots, suggesting that OsIRO2 may not be induced simply by the Fe deficiency caused by excess Zn. The data indicate that the induction of OsIRO2 by excess Zn is responsible for the production of NA and DMA, which may play a role in maintaining cellular Zn availability.

Original languageEnglish
Pages (from-to)417-423
Number of pages7
JournalSoil Science and Plant Nutrition
Issue number3
Publication statusPublished - 2008 Jun
Externally publishedYes


  • Basic helix-loop-helix
  • Deoxymugineic acid
  • Nicotianamine
  • Transcriptional factor
  • Zinc excess

ASJC Scopus subject areas

  • Soil Science
  • Plant Science


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