title: The rice transcription factor IDEF1 directly binds to iron and other divalent metals for sensing cellular iron status.
abstract: Iron is essential for most living organisms and its availability often determines survival and proliferation. The Oryza sativa (rice) transcription factor IDEF1 plays a crucial role in regulating iron deficiency-induced genes involved in iron homeostasis. In the present report, we found characteristic histidine-asparagine repeat and proline-rich regions in IDEF1 and its homolog in Hordeum vulgare (barley), HvIDEF1. An immobilized metal ion affinity chromatography assay revealed that IDEF1 and HvIDEF1 bind to various divalent metals, including Fe(2+)  and Ni(2+) . Recombinant IDEF1 protein expressed in Escherichia coli contained mainly Fe and Zn. This metal-binding activity of IDEF1 was almost abolished by deletion of the histidine-asparagine and proline-rich regions, but DNA-binding and trans-activation functions were not impaired by the deletion. Transgenic rice plants constitutively overexpressing IDEF1 without these metal-binding domains failed to cause pleiotropic effects conferred by overexpression of full-length IDEF1, including a low germination rate, impaired seedling growth, tolerance to iron deficiency in hydroponic culture, and enhanced expression of various iron deficiency-inducible genes. Impairment of the transcriptional regulation of IDEF1 by deletion of the metal-binding domains occurred primarily at an early stage of iron deficiency. These results suggest that the histidine-asparagine and proline-rich regions in rice IDEF1 directly bind to divalent metals and sense the cellular metal ion balance caused by changes in iron availability.
authors: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Takanori
authors: T
authors: Kobayashi
authors: Reiko Nakanishi
authors: RN
authors: Itai
authors: May Sann
authors: MS
authors: Aung
authors: Takeshi
authors: T
authors: Senoura
authors: Hiromi
authors: H
authors: Nakanishi
authors: Naoko K
authors: NK
authors: Nishizawa
mesh_terms: D000595:Amino Acid Sequence; D001216:Asparagine / Q000737:chemistry; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D018525:Germination / Q000235:genetics; D006639:Histidine / Q000737:chemistry; D018527:Hydroponics; D007501:Iron / Q000378:metabolism*; D008969:Molecular Sequence Data; D009532:Nickel / Q000378:metabolism; D012275:Oryza / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011392:Proline / Q000737:chemistry; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020449:Repetitive Sequences, Amino Acid; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D006639:Histidine; D001216:Asparagine; D009532:Nickel; D011392:Proline; D007501:Iron; D015032:Zinc