Abstract
Plants induce iron utilization systems under iron deficiency, but the underlying molecular mechanisms remain largely unknown. We identified the rice transcription factor IDEF1 (IDE-binding factor 1), which specifically binds the iron deficiency-responsive cis-acting element IDE1. IDEF1 belongs to an uncharacterized branch of the plant-specific transcription factor family ABI3/VP1, and exhibits the novel sequence recognition property of efficiently binding to the CATGC sequence within IDE1. IDEF1 transcripts are constitutively present in rice roots and leaves. Transgenic tobacco plants constitutively overexpressing IDEF1 transactivate IDE1-mediated expression only in iron-deficient roots. Transgenic rice plants expressing an introduced IDEF1 exhibit substantial tolerance to iron deficiency in both hydroponic culture and calcareous soil. IDEF1 overexpression leads to the enhanced expression of the iron deficiency-induced transcription factor gene OsIRO2, suggesting the presence of a sequential gene regulatory network. These findings reveal novel cis element/trans factor interactions functionally linked to the iron deficiency response.
