title: Identification of novel cis-acting elements, IDE1 and IDE2, of the barley IDS2 gene promoter conferring iron-deficiency-inducible, root-specific expression in heterogeneous tobacco plants.
abstract: The molecular mechanisms of plant responses to iron (Fe) deficiency remain largely unknown. To identify the cis-acting elements responsible for Fe-deficiency-inducible expression in higher plants, the barley IDS2 (iron deficiency specific clone no. 2) gene promoter was analyzed using a transgenic tobacco system. Deletion analysis revealed that the sequence between -272 and -91 from the translational start site (-272/-91) was both sufficient and necessary for specific expression in tobacco roots. Further deletion and linker-scanning analysis of this region clearly identified two cis-acting elements: iron-deficiency-responsive element 1 (IDE1) at -153/-136 (ATCAAGCATGCTTCTTGC) and IDE2 at -262/-236 (TTGAACGGCAAGTTTCACGCTGTCACT). The co-existence of IDE1 and IDE2 was essential for specific expression when the -46/+8 region (relative to the transcriptional start site) of the CaMV 35S promoter was used as a minimal promoter. Expression occurred mainly in the root pericycle, endodermis, and cortex. When the -90/+8 region of the CaMV 35S promoter was fused, the -272/-227 region, which consists of IDE2 and an additional 19 bp, could drive Fe-deficiency-inducible expression without IDE1 throughout almost the entire root. The principal modules of IDE1 and IDE2 were homologous. Sequences homologous to IDE1 were also found in many other Fe-deficiency-inducible promoters, including: nicotianamine aminotransferase (HvNAAT)-A, HvNAAT-B, nicotianamine synthase (HvNAS1), HvIDS3, OsNAS1, OsNAS2, OsIRT1, AtIRT1, and AtFRO2, suggesting the conservation of cis-acting elements in various genes and species. The identification of novel cis-acting elements, IDE1 and IDE2, will provide powerful tools to clarify the molecular mechanisms regulating Fe homeostasis in higher plants.
authors.affiliation: Laboratory of Plant Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Takanori
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Yuko
authors.initials: Y
authors.lastname: Nakayama
authors.forename: Reiko Nakanishi
authors.initials: RN
authors.lastname: Itai
authors.forename: Hiromi
authors.initials: H
authors.lastname: Nakanishi
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yoshihara
authors.forename: Satoshi
authors.initials: S
authors.lastname: Mori
authors.forename: Naoko K
authors.initials: NK
authors.lastname: Nishizawa
mesh_terms: D001483:Base Sequence; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D001467:Hordeum / Q000235:genetics*; D000090463:Iron Deficiencies; D006899:Mixed Function Oxygenases / Q000235:genetics*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009838:Oligodeoxyribonucleotides; D010940:Plant Proteins / Q000235:genetics; D018517:Plant Roots / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014026:Nicotiana / Q000235:genetics* / Q000378:metabolism
chemical_list: D009838:Oligodeoxyribonucleotides; D010940:Plant Proteins; D006899:Mixed Function Oxygenases