Key Laboratory of Molecular and Cell Biology, College of Life Sciences, Hebei Normal University, Shijiazhuang, 050024, China.
State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, 475004, China.
Plant Cell Rep. 2021 Feb;40(2):421-432. doi: 10.1007/s00299-020-02644-7. Epub 2021 Jan 4.
CCA1α and CCA1β protein variants respond to environmental light and temperature cues, and higher temperature promotes CCA1β protein production and causes its retention detectable in the cytoplasm. CIRCADIAN CLOCK ASSOCIATED1 (CCA1), as the core transcription factor of circadian clock, is involved in the regulation of endogenous circadian rhythm in Arabidopsis. Previous studies have shown that CCA1 consists of two abundant splice variants, fully spliced CCA1α and intron-retaining CCA1β. CCA1β is believed to form a nonfunctional heterodimer with CCA1α and its closed-related homolog LHY. Many studies have established that CCA1β is a transcription product, while how CCA1β protein is produced and how two CCA1 isoforms respond to environmental cues have not been elucidated. In this study, we identified CCA1α and CCA1β protein variants under different photoperiods with warm or cold temperature cycles, respectively. Our results showed that CCA1 protein production is regulated by prolonged light exposure and warm temperature. The protein levels of CCA1α and CCA1β peak in the morning, but the detection of CCA1β is dependent on immunoprecipitation enrichment at 22 °C. Higher temperature of 37 °C promotes CCA1β protein production and causes its retention to be detectable in the cytoplasm. Overall, our results indicate that two splice variants of the CCA1 protein respond to environmental light and temperature signals and may, therefore, maintain the circadian rhythms and give individuals the ability to adapt to environment.
CCA1α 和 CCA1β 蛋白变体对环境光照和温度信号作出响应，较高的温度促进 CCA1β 蛋白的产生，并使其在细胞质中的滞留可被检测到。CCA1（circadian clock associated1，生物钟关联蛋白 1）作为生物钟的核心转录因子，参与拟南芥内源性生物钟的调节。先前的研究表明，CCA1 由两种丰富的剪接变体组成，完全剪接的 CCA1α 和内含子保留的 CCA1β。CCA1β 被认为与 CCA1α 及其封闭相关的同源物 LHY 形成无功能的异二聚体。许多研究已经证实 CCA1β 是一种转录产物，而 CCA1β 蛋白是如何产生的，以及两种 CCA1 同工型如何响应环境线索，尚未阐明。在这项研究中，我们分别在不同的光周期下和温暖或寒冷的温度循环下鉴定了 CCA1α 和 CCA1β 蛋白变体。我们的结果表明，CCA1 蛋白的产生受长光照暴露和温暖温度的调节。CCA1α 和 CCA1β 的蛋白水平在早晨达到峰值，但 CCA1β 的检测依赖于在 22°C 时免疫沉淀富集。37°C 的较高温度促进 CCA1β 蛋白的产生，并使其在细胞质中的滞留可被检测到。总的来说，我们的结果表明，CCA1 蛋白的两种剪接变体对环境光照和温度信号作出响应，因此可能维持生物钟，并使个体具备适应环境的能力。
