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Molecular Plant Advance Access originally published online on July 22, 2009
Molecular Plant 2009 2(5):1059-1066; doi:10.1093/mp/ssp051
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© The Author 2009. Published by the Molecular Plant Shanghai Editorial Office in association with Oxford University Press on behalf of CSPP and IPPE, SIBS, CAS.

Rice-Specific Mitochondrial Iron-Regulated Gene (MIR) Plays an Important Role in Iron Homeostasis

Yasuhiro Ishimarua,2, Khurram Bashira,2, Masaru Fujimotoa, Gynheung Anb, Reiko Nakanishi Itaia, Nobuhiro Tsutsumia, Hiromi Nakanishia and Naoko K Nishizawaa,c,1

a Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-Ku, Tokyo 113-8657, Japan
b Department of Life Sciences, Pohang University of Science and Technology, Pohang, 790–784, Republic of Korea
c Research Institute for Bioresources and Biotechnology, Ishikawa Prefectural University, Ishikawa 921-8836, Japan

1 To whom correspondence should be addressed. E-mail annaoko{at}mail.ecc.u-tokyo.ac.jp, fax +81 3 5841 7514, tel. +81 3 5841 7514.

Mitochondria utilize iron (Fe), but the proteins involved in mitochondrial Fe regulation are not characterized in plants. We cloned and characterized a mitochondrial iron-regulated (MIR) gene in rice involved in Fe homeostasis. MIR, when expressed in tobacco BY-2 cells, was localized to the mitochondria. MIR transcripts were greatly increased in response to Fe deficiency in roots and shoot tissue. MIR is not homologous to any known protein, as homologs were not found in the rice or Arabidopsis genome databases, or in the EST database for other organisms. Growth in the MIR T-DNA knockout rice mutant (mir) was significantly impaired compared to wild-type (WT) plants when grown under Fe-deficient or -sufficient conditions. Furthermore, mir plants accumulated more than twice the amount of Fe in shoot and root tissue compared to WT plants when grown under either Fe-sufficient or -deficient conditions. Despite the high accumulation of Fe in roots and shoots, mir plants triggered the expression of Fe-deficiency-inducible genes, indicating that mir may not be able to utilize Fe for physiological functions. These results clearly suggest that MIR is a rice-specific mitochondrial protein, recently evolved, and plays a significant role in Fe homeostasis.

Key Words: Fe-deficiency-regulated gene • Fe homeostasis • mitochondria • Oryza sativa

2 These authors contributed equally to this work.


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