Abstract
Plants induce iron uptake/utilization system in response to iron deficiency. We have previously identified and characterized cis-acting elements and trans-acting factors involved in iron deficiency response in graminaceous plants, whereas identity of signals that trigger this response remains unknown. The rice transcription factor IDEF1 (Iron Deficiency-responsive Element-binding Factor 1), which specifically binds the IDE1 sequence, confers iron deficiency response and tolerance in rice. IDEF1 expression is constitutively observed in various organs including roots, leaves, flowers and seeds throughout rice life, and is not affected by iron nutritional status. During iron sufficiency and the early stages of iron deficiency, the majority of known iron uptake/utilization-related genes are positively regulated by IDEF1. In subsequent stages of iron deficency, however, IDEF1 partially changes the species of its downstream genes. These observations raise the possibility that IDEF1 may possess the ability to sense iron nutritional status. Identification of putative functional domains involved in this iron sensing will be reported.
