Promoter analysis of iron-deficiency-inducible barley IDS3 gene in Arabidopsis and tobacco plants.
Under conditions of iron deficiency, graminaceous plants induce the expression of genes involved in the biosynthesis of mugineic acid family phytosiderophores. We previously identified the novel cis-acting elements IDE1 and IDE2 (iron-deficiency-responsive element 1 and 2) through promoter analysis of the barley (Hordeum vulgare L.) iron-deficiency-inducible IDS2 gene in tobacco (Nicotiana tabacum L.). To gain further insight into plant gene regulation under iron deficiency, we analyzed the barley iron-deficiency-inducible IDS3 gene, which encodes mugineic acid synthase. IDS3 promoter fragments were fused to the beta-glucuronidase (GUS) gene, and this construct was introduced into Arabidopsis thaliana L. and tobacco plants. In both Arabidopsis and tobacco, GUS activity driven by the IDS3 promoter showed strongly iron-deficiency-inducible and root-specific expression. Expression occurred mainly in the epidermis of Arabidopsis roots, whereas expression was dominant in the pericycle, endodermis, and cortex of tobacco roots, resembling the expression pattern conferred by IDE1 and IDE2. Deletion analysis revealed that a sequence within -305 nucleotides from the translation start site was sufficient for specific expression in both Arabidopsis and tobacco roots. Gain-of-function analysis revealed functional regions at -305/-169 and -168/-93, whose coexistence was required for the induction activity in Arabidopsis roots. Multiple IDE-like sequences were distributed in the IDS3 promoter and were especially abundant within the functional region at -305/-169. A sequence moderately homologous to that of IDE1 was also present within the -168/-93 region. These IDE-like sequences would be the first candidates for the functional iron-deficiency-responsive elements in the IDS3 promoter.
Kobayashi
Takanori
T
Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
Yoshihara
Toshihiro
T
Itai
Reiko Nakanishi
RN
Nakanishi
Hiromi
H
Takahashi
Michiko
M
Mori
Satoshi
S
Nishizawa
Naoko K
NK
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant; D001467:Hordeum / Q000235:genetics*; D000090463:Iron Deficiencies; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010935:Plant Diseases; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics*; D014026:Nicotiana / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation
D010940:Plant Proteins; D006899:Mixed Function Oxygenases; C417583:Ids3 protein, Hordeum vulgare