Abstract
Plants induce iron utilization systems under 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. To investigate the precise function of IDEF1, we analyzed the response to iron deficiency in transgenic rice plants with induced or repressed IDEF1 expression. Iron deficiency treatment in hydroponic culture revealed that IDEF1 knockdown plants are susceptible to early stage of iron deficiency in contrast to IDEF1-induced plants. Time-course expression analysis by microarray and quantitative RT-PCR revealed that expression of various iron utilization-related genes is positively regulated by IDEF1 just after onset of iron starvation, with overrepresentation of IDEF1-binding core sequences within proximal promoter regions. These results indicate the existence of early and subsequent response to iron deficiency in rice, among which the former requires IDEF1 more rigidly.
