Regulation of iron homeostasis in Arabidopsis thaliana by the clock regulator time for coffee.
In plants, iron homeostasis is tightly regulated to supply sufficient amounts of this metal for an optimal growth while preventing excess accumulation to avoid oxidative stress. To identify new regulators of iron homeostasis, a luciferase-based genetic screen using the Arabidopsis AtFer1 ferritin promoter as a target was developed. This screen identified TIME FOR COFFEE (TIC) as a regulator of AtFer1 gene expression. TIC was previously described as a nuclear regulator of the circadian clock. Mutants in the TIC gene exhibited a chlorotic phenotype rescued by exogenous iron addition and are hypersensitive to iron during the early stages of development. We showed that iron overload-responsive genes are regulated by TIC and by the central oscillator of the circadian clock. TIC represses their expression under low iron conditions, and its activity requires light and light/dark cycles. Regarding AtFer1, this repression is independent of the previously characterized cis-acting element iron-dependent regulatory sequence, known to be involved in AtFer1 repression. These results showed that the regulation of iron homeostasis in plants is a major output of the TIC- and central oscillator-dependent signaling pathways.
Duc
Céline
C
Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, UMR 5004, Agro-M/CNRS/Institut National de la Recherche Agronomique/Université Montpelier II, 34060 Montpellier Cedex 1, France.
Cellier
Françoise
F
Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, UMR 5004, Agro-M/CNRS/Institut National de la Recherche Agronomique/Université Montpelier II, 34060 Montpellier Cedex 1, France.
Lobréaux
Stéphane
S
Laboratoire Plastes et Différenciation Cellulaire, Universite Joseph Fourier Grenoble 1, Centre de Recherche sur les Macromolécules Organisées, BP 53, 38041 Grenoble Cedex 9, France.
Briat
Jean-François
JF
Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, UMR 5004, Agro-M/CNRS/Institut National de la Recherche Agronomique/Université Montpelier II, 34060 Montpellier Cedex 1, France.
Gaymard
Frédéric
F
Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, UMR 5004, Agro-M/CNRS/Institut National de la Recherche Agronomique/Université Montpelier II, 34060 Montpellier Cedex 1, France. Electronic address: gaymard@supagro.inra.fr.
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D005293:Ferritins / Q000096:biosynthesis* / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D006706:Homeostasis / Q000502:physiology*; D007501:Iron / Q000378:metabolism*; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
D029681:Arabidopsis Proteins; D009687:Nuclear Proteins; C523534:TIC protein, Arabidopsis; D005293:Ferritins; D007501:Iron