Characterization of an iron-dependent regulatory sequence involved in the transcriptional control of AtFer1 and ZmFer1 plant ferritin genes by iron

In eukaryotic cells, ferritin synthesis is controlled by the intracellular iron status. In mammalian cells, iron derepresses ferritin mRNA translation , whereas it induces ferritin gene transcription in plants. Promoter deleti on and site-directed mutagenesis analysis, combined with gel shift assays, has allowed identification of a new cis-regulatory element in the promoter region of the ZmFer1 maize ferritin gene. This Iron-Dependent Regulatory Se quence (IDRS) is responsible for transcriptional repression of ZmFer1 under low iron supply conditions. The IDRS is specific to the ZmFer1 iron-depend ent regulation and does not mediate the antioxidant response that we have p reviously reported (Savino et al. (1997) J. Biol. Chem. 272, 33319-33326), In addition, we have cloned AtFer1, the Arabidopsis thaliana ZmFerl ortholo gue. The IDRS element is conserved in the AtFer1 promoter region and is fun ctional as shown by transient assay in A thaliana cells and stable transfor mation in A. thaliana transgenic plants, demonstrating its ubiquity in the plant kingdom.