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.
Laboratoire Plastes et Différenciation Cellulaire, Universite Joseph Fourier Grenoble 1, Centre de Recherche sur les Macromolécules Organisées, BP 53, 38041 Grenoble Cedex 9, France.
J Biol Chem. 2009 Dec 25;284(52):36271-36281. doi: 10.1074/jbc.M109.059873. Epub 2009 Oct 14.
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.
在植物中，铁稳态受到严格调节，以提供足够的金属以促进最佳生长，同时防止过度积累以避免氧化应激。为了鉴定铁稳态的新调节剂，开发了一种基于荧光素酶的遗传筛选方法，使用拟南芥 AtFer1 铁蛋白启动子作为靶标。该筛选鉴定出 TIME FOR COFFEE (TIC) 是 AtFer1 基因表达的调节剂。TIC 先前被描述为生物钟的核调节剂。TIC 基因突变体表现出缺绿表型，通过外源铁添加可得到挽救，并且在发育的早期阶段对铁敏感。我们表明，铁过载反应基因受 TIC 和生物钟的中央振荡器调节。TIC 在低铁条件下抑制它们的表达，并且其活性需要光和光/暗循环。对于 AtFer1，这种抑制作用独立于先前表征的顺式作用元件铁依赖调节序列，该序列已知参与 AtFer1 抑制。这些结果表明，植物中铁稳态的调节是 TIC 和中央振荡器依赖信号通路的主要输出。
