Characterization of an Iron-dependent Regulatory Sequence Involved in the Transcriptional Control of AtFer1and ZmFer1 Plant Ferritin Genes by Iron

Abstract

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 ZmFer1iron-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 theAtFer1 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.AF229850 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 ZmFer1iron-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 theAtFer1 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. AF229850 abscisic acid N-acetylcysteine okadaic acid Black Mexican Sweet Murashige and Skoog medium β-glucuronidase iron-responsive element iron-responsive protein iron-dependent regulatory sequence cauliflower mosaic virus base pair(s) polymerase chain reaction soybean homologous sequence Metals are essential for all living organisms but are toxic at high concentrations. Therefore, metal homeostasis requires regulatory circuits to coordinate metal uptake and storage (1Winge D.R. Jensen L.T. Srinivasan C. Curr. Opin. Chem. Biol. 1998; 2: 216-221Crossref PubMed Scopus (49) Google Scholar). Such mechanisms involve metal sensing proteins that transduce the signal within the cell to modulate gene expression. These proteins often act as regulatory factors, binding RNA or DNA cis-elements to promote or repress gene expression (1Winge D.R. Jensen L.T. Srinivasan C. Curr. Opin. Chem. Biol. 1998; 2: 216-221Crossref PubMed Scopus (49) Google Scholar, 2Hentze M.W. Kühn L.C. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 8175-8182Crossref PubMed Scopus (1137) Google Scholar). Among these metals, iron is one of the most abundant and is highly reactive as a pro-oxidant in Haber-Weiss reactions to generate free radicals (3Halliwel B. Gutteridge J. Atlas of Science: Biochemistry. 1988; : 48-51Google Scholar). Furthermore, aerobic organisms have to overcome iron insolubility and then maintain iron in a bioavailable form (4Harrison P.M. Arosio P. Biochim. Biophys. Acta. 1996; 1275: 161-203Crossref PubMed Scopus (2278) Google Scholar). Plants, due to their immobility, need to tightly regulate iron homeostasis to prevent both iron toxicity or deficiency (5Guerinot M.L. Yi Y. Plant Physiol. 1994; 104: 815-820Crossref PubMed Scopus (533) Google Scholar). Recently, genes involved in iron uptake in plants have been cloned: fro2, encoding a root ferric reductase (6Robinson N.J. Procter C.M. Connolly E.L. Guerinot M.L. Nature. 1999; 397: 694-697Crossref PubMed Scopus (966) Google Scholar), andirt1, encoding a putative ferrous transporter (7Eide D. Broderius M. Fett J. Guerinot M.L. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 5624-5628Crossref PubMed Scopus (1083) Google Scholar). Inside the plant cell, a particular class of plastid-localized proteins, the ferritins, are able to store iron in a safe and bioavailable form (8Briat J.F. Lobréaux S. Grignon N. Vansuyt G. Cell. Mol. Life Sci. 1999; 56: 155-166Crossref PubMed Scopus (122) Google Scholar). Ferritins are ubiquitous proteins found in bacteria, animals, and plants, and, upon assembly, able to store up to 4500 iron atoms (4Harrison P.M. Arosio P. Biochim. Biophys. Acta. 1996; 1275: 161-203Crossref PubMed Scopus (2278) Google Scholar). Ferritin gene regulation has become a model to study iron-regulated expression both in the plant and animal kingdoms. In animal cells, ferritin synthesis is mainly regulated at the translational level in response to iron (2Hentze M.W. Kühn L.C. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 8175-8182Crossref PubMed Scopus (1137) Google Scholar), whereas in plants transcriptional control has been demonstrated in soybean cells (9Lescure A.M. Proudhon D. Pesey H. Ragland M. Theil E.C. Briat J.F. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 8222-8226Crossref PubMed Scopus (153) Google Scholar). In maize, iron overload induces accumulation of both ferritin mRNA and protein subunits (10Lobréaux S. Massenet O. Briat J.F. Plant Mol. Biol. 1992; 19: 563-575Crossref PubMed Scopus (137) Google Scholar, 11Lobréaux S. Thoiron S. Briat J.F. Plant J. 1995; 8: 443-449Crossref Scopus (82) Google Scholar). Two nuclear maize ferritin genes have been characterized and namedZmFer1 and 2 (12Fobis-Loisy I. Loridon K. Lobréaux S. Lebrun M. Briat J.F. Eur. J. Biochem. 1995; 231: 609-619Crossref PubMed Scopus (81) Google Scholar). The ZmFer2 gene is regulated by a cellular pathway involving the plant hormone abscisic acid (ABA),1 whereasZmFer1 is regulated by an ABA-independent pathway (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). Using derooted plantlets and maize cell suspension cultures, we have shown that this gene is regulated by both iron and redox signals (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). Indeed, ZmFer1 mRNA increase of abundance is induced by hydrogen peroxide treatments, and the iron-induced accumulation of this transcript is abolished in the presence of N-acetylcysteine (NAC), an antioxidant agent. The accumulation of ZmFer1mRNA induced by both H2O2 and iron treatments were inhibited in the presence of the Ser/Thr phosphatase inhibitors okadaic acid and calyculin A (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar), suggesting the involvement of dephosphorylation events in the transduction pathways regulating ZmFer1 gene expression. To further characterize the regulation of the ZmFer1 maize ferritin gene, we have developed a transient expression assay in maize cells. Using this system, a 2.2-kbp DNA fragment of the ZmFer1 gene was shown to be sufficient to regulate reporter gene expression in response to iron, with the same characteristics as observed for the endogenousZmFer1 gene regulation (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). In this paper, this transient expression assay was used to identify an Iron-Dependent Regulatory Sequence (IDRS) essential for the regulation by iron of the maize ZmFer1 and the Arabidopsis thaliana AtFer1 ferritin genes. Stable transformation of A. thaliana plants was performed to demonstrate the functionality of this element in planta. Maize BMS (Black Mexican Sweet) cells were cultivated as described (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). A. thaliana cells (gift from Dr. Scheel) were cultivated at 24 °C under constant shaking at 170 rpm, in 100 ml of MS medium (14Murashige T. Skoog F. Physiol. Plant. 1962; 15: 473Crossref Scopus (54339) Google Scholar), were 2 ml of cell cell cultures, ml of cell were to ml treatments were performed as described (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). BMS or Arabidopsis cells were by as previously described (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). cells the was to and the to The and were used as as described previously (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). Maize cell nuclear were as described by et al. M. J. Biol. Chem. 1992; Full Text PDF PubMed Google Scholar). used in these are described in B. The DNA was and gel shift were performed as described in et al. P. J. Biol. Chem. 1996; Full Text Full Text PDF PubMed Scopus Google Scholar). AtFer1 F. J. Briat J.F. Biochem. J. 1996; PubMed Scopus (81) Google was used to an A. thaliana A. PubMed Google Scholar). DNA was by J. T. A Scholar), and the DNA fragment was in and the for transient expression were DNA J. T. A and are in the to fragment of ZmFer1 promoter was to of and fragment of was in D. M. M. G. F. S. Grignon C. Plant J. 1996; PubMed Scopus Google to and were by with and previously with used to generate were and for 2 and for and and for To fragment from was in was by from the the sequence from the in Y. C. S. Plant Cell. 1995; PubMed Scopus Google Scholar). mutagenesis was performed to and the in mutagenesis and and of the and were the as described previously O. G. Briat J.F. Biochem. J. 1995; PubMed Scopus Google Scholar). The used were and to generate and to generate and to generate and and to generate promoter were in were with and and in the and for and for and and for To generate DNA fragment with and as was in the the promoter was and with as and in the to and were and and were and in AtFer1 promoter region was and with and and in To generate the a was performed as described O. G. Briat J.F. Biochem. J. 1995; PubMed Scopus Google and and the fragment was in The and were by and a The were 1988; PubMed Scopus Google Scholar). These have been used to A. thaliana the Plant J. 1998; PubMed Google Scholar). were and medium (14Murashige T. Skoog F. Physiol. Plant. 1962; 15: 473Crossref Scopus (54339) Google and was by for 2 at plants were in a under the plantlets were medium for the of the plants were and for 24 medium or were and reporter gene was as previously described (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). was to the Biochem. PubMed Scopus Google Scholar). In a study (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar), we have up a transient expression to maize ferritin gene This to that a 2.2-kbp fragment of the ZmFer1 gene to the β-glucuronidase reporter gene the regulation of the gene. increase of was in response to iron overload in Furthermore, iron-induced expression of the gene was inhibited by the antioxidant and the Ser/Thr phosphatase These are in with by of the ZmFer1 gene expression. The of the promoter sequence and the region from to (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). To involved in the iron-dependent regulation of ferritin gene, we have performed a deletion of the 2.2-kbp ZmFer1 fragment were to a level of expression of the in maize cells (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). This was in with that are essential for the expression of genes from plants M. L.C. Plant Physiol. PubMed Google Scholar). These act mainly by the level of gene expression. it not be that in the a in the iron-dependent regulation of the gene. To this ZmFer1 were by an region of the gene, has been shown to reporter gene expression in a D. B. Mol. 1991; 231: PubMed Scopus Google Scholar). Furthermore, we have previously demonstrated that this gene DNA fragment not iron-regulated (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). This from maize ferritin to in a increase of expression of the in the of iron, the promoter sequence was the same and in of the cells to a increase in This from to of the to be a of the sequence This be in to the of gene expression in the presence of the the expression of the by iron suggesting that essential for this regulation are not within The of the ZmFer1 of this sequence up to the previously transcription (12Fobis-Loisy I. Loridon K. Lobréaux S. Lebrun M. Briat J.F. Eur. J. Biochem. 1995; 231: 609-619Crossref PubMed Scopus (81) Google not the of expression of the not Therefore, a promoter deletion was from the gene promoter sequence of the promoter from to or in a from to in response to iron Such a be to the presence of regulatory to the iron-dependent regulation of ZmFer1 gene. These the level of expression in low iron and demonstrate that essential iron response are of The of promoter from to to a The expression level in low iron to the iron-induced level of the and by iron was A further deletion from to not this of expression. The does not reporter gene expression. Therefore, the region from to to essential regulatory for iron-induced expression of ZmFer1 maize ferritin gene. Furthermore, that this region be involved in the repression expression in low iron conditions. To further and the in this a site-directed mutagenesis was This was performed a the promoter to maintain an iron-induced expression of the gene. This fragment was to as and to the reporter gene. A increase in was in response to iron this was by transient expression in BMS cells This the with the gene as reporter the of ZmFer1 putative regulatory were by sequence for mutagenesis as A sequence was found in the ZmFer1 at to and not in ZmFer2 promoter 2 These sequence in their region (12Fobis-Loisy I. Loridon K. Lobréaux S. Lebrun M. Briat J.F. Eur. J. Biochem. 1995; 231: 609-619Crossref PubMed Scopus (81) Google Scholar), but ZmFer2 is regulated by an pathway and not by the iron-dependent pathway in this (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). sequence mutagenesis to a increase of under low iron and iron of expression was to a increase 2 The ZmFer1 promoter region sequence to the at sequence not the iron-induced regulation of the reporter gene 2 a of and in expression of and of by iron 2 These in the of a functional the sequence for whereas this sequence does not a in the ZmFer1 the sequence were to this putative The region of was of particular in the sequence 2 to a to the 2 This the regulatory region to both and This DNA fragment of to be essential for the ZmFer1 ferritin gene regulation by iron, was Iron-Dependent Regulatory Sequence The ZmFer1 promoter region a sequence in 2 This element has been described as a but be involved in specific Indeed, ferritin gene transcriptional control by in cells is by a element G. B. F. F. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus (81) Google Scholar), and this sequence a in the of genes in response to antioxidant in a cell J. Biol. Chem. 1997; 272: Full Text Full Text PDF Scopus Google Scholar). of the sequence in promoter not the expression of the gene in low or high iron The element 2 is a regulatory sequence in plant gene involved in U. Biochem. Sci. 1995; Full Text PDF PubMed Scopus Google Scholar). of the ZmFer1 promoter this sequence not to be for the iron-dependent regulation of the ZmFer1 maize ferritin gene. regulation of soybean ferritin gene has been demonstrated by nuclear (9Lescure A.M. Proudhon D. Pesey H. Ragland M. Theil E.C. Briat J.F. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 8222-8226Crossref PubMed Scopus (153) Google Scholar). The gene has been cloned D. J. Briat J.F. Theil E.C. J. Mol. 1996; PubMed Scopus Google Scholar), and we have the promoter of this soybean ferritin gene and a conserved region 2 from the IDRS was found in the region of these of this sequence in a transient expression assay that this sequence is not involved gene regulation by iron in maize cells a combined of promoter deletion and site-directed we been able to an essential region for ZmFer1 regulation by iron, we have have previously by and transient expression in maize cells, that the iron-induced expression of ZmFer1 gene is inhibited by or (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). In the presence of the expression was in both and cells, but an increase of was induced by Such that antioxidant the level of expression of this gene, the iron-dependent of ZmFer1 gene. Therefore, it was to these are by the IDRS To that and 2 expression was by transient expression in the presence of or not These that and gene expression are not by the to be specific to the iron Regulatory from the are to mediate the antioxidant at the promoter To further characterize the IDRS were performed to this sequence is sufficient to iron-dependent regulation to a A a promoter sequence to and the reporter gene was The IDRS element was cloned of this the this regulatory sequence and the as in ZmFer1 gene. The IDRS fragment to the ZmFer1 promoter region from to and was cloned in or a level of expression was but iron-dependent regulation was observed not the fragment to to of promoter to the same These that are to the iron regulation or that a specific is essential and not in the gene. To the IDRS element nuclear transcription factors, gel shift were this a to the IDRS was used This was in the presence of nuclear from maize cells or not by iron In both low or high iron one was observed The signal was abundant iron but a signal was iron level was low of iron in the protein from cells, or as a or as an in both the observed not To the of this the reaction was performed in the presence of a of of A of the binding was In in the presence of a of not DNA binding was Therefore, a nuclear or protein the IDRS element in mutagenesis of the ZmFer1 promoter to that base within IDRS the gene regulation in To the binding of nuclear proteins to the IDRS in a was performed in the presence of base with the sequence the binding reaction was performed in the presence of to a of binding was but the was observed and in of binding of nuclear to the IDRS These to the of the the region in in Therefore, in this sequence to a of iron-dependent regulation in and binding in These that the IDRS is by nuclear with its in to regulate reporter gene expression in response to Maize is a plant and with this in iron A uptake of iron by the has been described in this plant whereas it does not in or plants S. Curr. Opin. Plant Biol. 1999; 2: PubMed Scopus Google Scholar). This the of the IDRS element a in iron-regulated expression in plants. To that we have the regulation of gene from A. a has been previously AtFer1 as a in that this gene is regulated by an ABA-independent and iron-induced accumulation mRNA is inhibited in the presence of F. J. Briat J.F. Biochem. J. 1996; PubMed Scopus (81) Google Scholar). These with ZmFer1 gene regulation and that AtFer1 be the A. thaliana ferritin gene to have cloned theAtFer1 ferritin gene encoding the previously This gene an to plant ferritin genes. A sequence the region and ZmFer1 is in A. This of to the is not involved in the iron-dependent regulation gene A region of was to the putative of both The to with high the and to the IDRS This region with IDRS base by gel shift the binding of nuclear proteins to the IDRS To this sequence to a functional IDRS in the AtFer1 gene, a transient expression assay was up transformation of Arabidopsis cell suspension AtFer1 promoter were to the reporter gene and cell The 100 of the AtFer1 promoter and the putative IDRS A increase in was in the transient expression assay in response to a the AtFer1 promoter sequence was from to the an increase of in low iron was and the response to iron was This is to the by the ZmFer1 IDRS Using the site-directed mutagenesis of theAtFer1 IDRS was In the the region of the IDRS was to and in the gel shift The IDRS was in the expression of these a to is observed by the IDRS mutagenesis of the iron-dependent regulation of the not Therefore, the IDRS is essential for the iron-dependent regulation of both AtFer1 ferritin in transient stable transformation of A. thaliana plants is a in to maize we to the IDRS was essential for the of AtFer1 gene expression in thaliana plants. The of thaliana with AtFer1 promoter sequence to the reporter gene, or at the The of the was by the in plants or not with A of the in response to iron was observed in the of the whereas the IDRS in to a of This by the IDRS is due to the in the plants, as reported in transient promoter The by the IDRS in plants with the were by transient assay of the same thaliana cell suspension not Furthermore, as a a of the sequence within the promoter was This the in transgenic plants or in transient cell assay not Therefore, these in stable plants as as in transient cell assays, that the IDRS is a element of the iron regulated expression of the AtFer1 gene. that the IDRS be observed a promoter sequence of or 100 in Using promoter deletion and site-directed mutagenesis analysis, we have a cis-regulatory essential for ZmFer1 maize ferritin gene iron This element does not with regulatory in plant the Regulatory for with from or D. Mol. Cell. Biol. PubMed Scopus Google Scholar). IDRS is for iron-dependent regulation of both ZmFer1 its functionality in the plant kingdom. is to that the IDRS is not essential in transient cell suspension but in stable as transgenic A. thaliana plants to demonstrate that IDRS is sufficient to iron-dependent suggesting that are promoter sequence of AtFer1 ferritin genes to transient expression that IDRS was the conserved sequence essential for iron Furthermore, the of iron transcriptional regulation of a plant ferritin gene was with soybean (9Lescure A.M. Proudhon D. Pesey H. Ragland M. Theil E.C. Briat J.F. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 8222-8226Crossref PubMed Scopus (153) Google Scholar). The gene was cloned D. J. Briat J.F. Theil E.C. J. Mol. 1996; PubMed Scopus Google and an IDRS element within its promoter at to it has been reported that the expression of a reporter gene of this soybean promoter was under low iron in with J. Theil E.C. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). The soybean promoter sequence to be involved in this transcriptional repression is from the IDRS to that this soybean regulatory region is not conserved in AtFer1 and ZmFer1 promoter the by and Theil J. Theil E.C. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google does not a of the soybean IDRS in iron control of ferritin gene expression in this plant that the IDRS element is involved in ferritin gene repression at low iron concentrations. This a specific to IDRS to with the transcription or to the for the IDRS to the promoter to a the IDRS not be In plant and animal cells, a regulatory of ferritin genes by iron is iron repress ferritin at the translational level in (2Hentze M.W. Kühn L.C. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 8175-8182Crossref PubMed Scopus (1137) Google Scholar), and at the transcriptional level in plants. In animals, a in the of ferritin Regulatory iron level is and prevent the of mRNA (2Hentze M.W. Kühn L.C. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 8175-8182Crossref PubMed Scopus (1137) Google Scholar). Two of and have been the of at the iron and the redox of the binding is by iron deficiency or by H2O2 have a the whereas the H2O2 signal a transduction pathway J. K. M.W. J. Biol. Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). have described an of iron and redox signals for ZmFer1 maize ferritin gene regulation (13Savino G. Briat J.F. Lobréaux S. J. Biol. Chem. 1997; 272: 33319-33326Abstract Full Text Full Text PDF PubMed Scopus (48) Google Scholar). In this iron ferritin whereas antioxidant or ferritin in to animal cells for are to the same the redox signal in plants is not by the is specific to the iron These that regulatory in ZmFer1 the antioxidant This of redox and iron signals within the ferritin promoter of the ferritin level and of the cell to the free iron and the redox of the IDRS in the transcriptional regulation of ferritin genes by iron to for this element in gene promoter iron uptake and storage need to be iron-dependent regulatory mechanisms are to modulate gene expression in these In animal cells, the sequence regulating ferritin mRNA is in the of the mRNA (2Hentze M.W. Kühn L.C. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 8175-8182Crossref PubMed Scopus (1137) Google Scholar). In low iron the binding of the the transcript and the synthesis of the Therefore, the same regulatory sequence the of iron storage and iron uptake of the for IDRS in plant sequence and PubMed Scopus Google Scholar, J. Mol. Biol. PubMed Scopus Google Scholar), we have found to IDRS in the promoter of genes that be involved in plant iron (6Robinson N.J. Procter C.M. Connolly E.L. Guerinot M.L. Nature. 1999; 397: 694-697Crossref PubMed Scopus (966) Google Scholar), (7Eide D. Broderius M. Fett J. Guerinot M.L. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 5624-5628Crossref PubMed Scopus (1083) Google Scholar), or the gene C. M. Briat J.F. Biochem. J. PubMed Scopus Google Scholar, S. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). regulate genes in the as or we not the IDRS in these genes. The A. thaliana is and we have found to were not in promoter or were in shift that IDRS is able to nuclear and these with in The of the increase of binding to the IDRS under iron overload to be The of the with the IDRS the of the mechanisms involved in the repression of ferritin synthesis low iron and the by iron, of ZmFer1 ferritin genes. Dr. D. for the A. thaliana cell are to Dr. et for the and are to Dr. for the A. thaliana and Dr. for of this