Abstract
The molecular mechanisms of plant responses to iron deficiency remain largely unknown. To identify the cis-acting elements responsible for iron-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 and linker-scanning analysis clearly identified two cis-acting elements: IDE1 (iron-deficiency-responsive element 1) at -153/-136 (relative to the translational start site) and IDE2 at -262/-236. IDE1 and IDE2 synergistically conferred the iron-deficiency-inducible and root-specific expression. Expression occurred mainly in the root pericycle, endodermis, and cortex. The principal modules of IDE1 and IDE2 were homologous. Sequences homologous to IDE1 were also found in many other promoters of barley, rice, and Arabidopsis iron-deficiency-inducible genes, suggesting the conservation of cis-acting elements in various genes and species. This is the first report identifying cis-acting elements responsible for micronutrient-deficiency-inducible expression in higher plants.
