Abstract
Plants induce iron uptake/utilization system in response to iron deficiency. Recently, we identified the rice transcription factor IDEF1 (IDE-binding Factor 1), which specifically binds the iron deficiency-responsive cis-acting element IDE1. We analyzed the regulation mechanism of IDEF1 in response to iron deficiency using transgenic rice plants with induced or repressed IDEF1 expression. During the early stages of iron deficiency, the majority of known iron uptake/utilization-related genes were positively regulated by IDEF1. In subsequent stages, IDEF1-mediated regulation of these iron uptake/utilization-related genes became less obvious. In turn, expression of several iron deficiency-induced genes encoding late embryogenesis abundant proteins was increasingly regulated by IDEF1 at the subsequent stages. We propose a dual function of IDEF1 for iron deficiency response, namely, (i) the coordinated transactivation of iron utilization-related genes via CATGC-containing IDE1-like elements, especially at the early stage, and (ii) the transactivation of seed maturation-related genes via RY elements, especially during the subsequent stages of iron deficiency.
