The rice transcription factor IDEF1 directly binds to iron and other divalent metals for sensing cellular iron status

• Published in: The Plant journal : for cell and molecular biology Vol. 69; no. 1; pp. 81 - 91
• Main Authors: Kobayashi, Takanori, Itai, Reiko Nakanishi, Aung, May Sann, Senoura, Takeshi, Nakanishi, Hiromi, Nishizawa, Naoko K.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2012; Blackwell
• Subjects: Affinity chromatography; Amino Acid Sequence; Asparagine - chemistry; Binding Sites; Biological and medical sciences; Cell culture; Cellular biology; Escherichia coli; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Gene expression; Gene Expression Regulation, Plant; Gene regulation; Germination; Germination - genetics; Heavy metals; Histidine - chemistry; Homeostasis; Hordeum vulgare; Hydroponics; IDEF1; Iron; Iron - metabolism; iron deficiency response; iron sensing; metal binding; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Nickel - metabolism; Nutrient deficiency; Oryza - physiology; Oryza sativa; Plant biology; Plant physiology and development; Plant Proteins - genetics; Plant Proteins - metabolism; Plants, Genetically Modified; Proline - chemistry; Proteins; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Repetitive Sequences, Amino Acid; Rice; Seedlings; Sequence Homology, Amino Acid; Transcription factors; Transcription Factors - genetics; Transcription Factors - metabolism; Transcription. Transcription factor. Splicing. Rna processing; transcriptional regulation; Transgenic plants; Zinc; Zinc - metabolism; Binding; Monocotyledones; Transcription; Deficiency; transcriptional regulation; metal binding; Iron; rice; iron deficiency response; iron sensing; Oryza sativa; IDEF1; Regulation(control); Gramineae; Angiospermae; Spermatophyta; Transcription factor
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1111/j.1365-313X.2011.04772.x

Summary 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 Fe2+ and Ni2+. 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.