title: The iron-responsive element (IRE)/iron-regulatory protein 1 (IRP1)-cytosolic aconitase iron-regulatory switch does not operate in plants.
abstract: Animal cytosolic ACO (aconitase) and bacteria ACO are able to switch to RNA-binding proteins [IRPs (iron-regulatory proteins)], thereby playing a key role in the regulation of iron homoeostasis. In the model plant Arabidopsis thaliana, we have identified three IRP1 homologues, named ACO1-3. To determine whether or not they may encode functional IRP proteins and regulate iron homoeostasis in plants, we have isolated loss-of-function mutants in the three genes. The aco1-1 and aco3-1 mutants show a clear decrease in cytosolic ACO activity. However, none of the mutants is affected in respect of the accumulation of the ferritin transcript or protein in response to iron excess. cis-acting elements potentially able to bind to the IRP have been searched for in silico in the Arabidopsis genome. They appear to be very rare sequences, found in the 5'-UTR (5'-untranslated region) or 3'-UTR of a few genes unrelated to iron metabolism. They are therefore unlikely to play a functional role in the regulation of iron homoeostasis. Taken together, our results demonstrate that, in plants, the cytosolic ACO is not converted into an IRP and does not regulate iron homoeostasis. In contrast with animals, the RNA binding activity of plant ACO, if any, would be more likely to be attributable to a structural element, rather than to a canonical sequence.
authors: Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, UMR 5004 Agro-M/CNRS/INRA/UMII, Bat 7, 2 place Viala, 34060 Montpellier cedex 1, France.
authors: Nicolas
authors: N
authors: Arnaud
authors: Karl
authors: K
authors: Ravet
authors: Andrea
authors: A
authors: Borlotti
authors: Brigitte
authors: B
authors: Touraine
authors: Jossia
authors: J
authors: Boucherez
authors: Cécile
authors: C
authors: Fizames
authors: Jean-François
authors: JF
authors: Briat
authors: Françoise
authors: F
authors: Cellier
authors: Frédéric
authors: F
authors: Gaymard
mesh_terms: D000154:Aconitate Hydratase / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism*; D019295:Computational Biology; D003600:Cytosol / Q000378:metabolism; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant; D007501:Iron / Q000378:metabolism*; D035941:Iron Regulatory Protein 1 / Q000378:metabolism*; D008969:Molecular Sequence Data
chemical_list: D007501:Iron; D000154:Aconitate Hydratase; D035941:Iron Regulatory Protein 1