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 deletion 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 Sequence (IDRS) is responsible for transcriptional repression of ZmFer1 under low iron supply conditions. The IDRS is specific to the ZmFer1 iron-dependent regulation and does not mediate the antioxidant response that we have previously reported (Savino et al. (1997) J. Biol. Chem. 272, 33319-33326). In addition, we have cloned AtFer1, the Arabidopsis thaliana ZmFer1 orthologue. The IDRS element is conserved in the AtFer1 promoter region and is functional as shown by transient assay in A. thaliana cells and stable transformation in A. thaliana transgenic plants, demonstrating its ubiquity in the plant kingdom.