title: A novel NAC transcription factor, IDEF2, that recognizes the iron deficiency-responsive element 2 regulates the genes involved in iron homeostasis in plants.
abstract: Iron is essential for most living organisms, and thus iron deficiency poses a major abiotic stress in crop production. Plants induce iron utilization systems under conditions of low iron availability, but the molecular mechanisms of gene regulation under iron deficiency remain largely unknown. We identified a novel transcription factor of rice and barley, IDEF2, which specifically binds to the iron deficiency-responsive cis-acting element 2 (IDE2) by yeast one-hybrid screening. IDEF2 belongs to an uncharacterized branch of the NAC transcription factor family and exhibits novel properties of sequence recognition. An electrophoretic mobility shift assay and cyclic amplification and selection of targets experiment revealed that IDEF2 predominantly recognized CA(A/C)G(T/C)(T/C/A)(T/C/A) within IDE2 as the core-binding site. IDEF2 transcripts are constitutively present in rice roots and leaves. Repression of the function of IDEF2 by the RNA interference (RNAi) technique and chimeric repressor gene-silencing technology (CRES-T) caused aberrant iron homeostasis in rice. Several genes up-regulated by iron deficiency, including the Fe(II)-nicotianamine transporter gene OsYSL2, were less induced by iron deficiency in the RNAi rice of IDEF2, suggesting that IDEF2 is involved in the regulation of these genes. Many genes with repressed expression in IDEF2 RNAi rice possessed the IDEF2-binding core sites in their promoters, and the flanking sequences were also highly homologous to IDE2. IDEF2 bound to OsYSL2 promoter region containing the binding core site, suggesting direct regulation of OsYSL2 expression. These results reveal novel cis-element/trans-factor interactions functionally associated with iron homeostasis.
authors.affiliation: Graduate School of Agricultural and Life Sciences, the University of Tokyo, 1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ogo
authors.forename: Takanori
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Reiko
authors.initials: R
authors.lastname: Nakanishi Itai
authors.forename: Hiromi
authors.initials: H
authors.lastname: Nakanishi
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kakei
authors.forename: Michiko
authors.initials: M
authors.lastname: Takahashi
authors.forename: Seiichi
authors.initials: S
authors.lastname: Toki
authors.forename: Satoshi
authors.initials: S
authors.lastname: Mori
authors.forename: Naoko K
authors.initials: NK
authors.lastname: Nishizawa
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006706:Homeostasis; D007501:Iron / Q000378:metabolism*; D000090463:Iron Deficiencies; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D034622:RNA Interference; D020218:Response Elements; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D027682:Cation Transport Proteins; D014157:Transcription Factors; D007501:Iron