title: Rice-specific mitochondrial iron-regulated gene (MIR) plays an important role in iron homeostasis.
abstract: 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.
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-Ku, Tokyo 113-8657, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Ishimaru
authors.forename: Khurram
authors.initials: K
authors.lastname: Bashir
authors.forename: Masaru
authors.initials: M
authors.lastname: Fujimoto
authors.forename: Gynheung
authors.initials: G
authors.lastname: An
authors.forename: Reiko Nakanishi
authors.initials: RN
authors.lastname: Itai
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Tsutsumi
authors.forename: Hiromi
authors.initials: H
authors.lastname: Nakanishi
authors.forename: Naoko K
authors.initials: NK
authors.lastname: Nishizawa
mesh_terms: D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D006706:Homeostasis / Q000235:genetics / Q000502:physiology*; D007501:Iron / Q000378:metabolism*; D000090463:Iron Deficiencies; D020411:Oligonucleotide Array Sequence Analysis; D012275:Oryza / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D010940:Plant Proteins; D007501:Iron