Aureochromes (AUREOs) are both blue light photoreceptors and transcription factors found in diatoms and related algal groups that play a critical role in regulating gene and cell physiology. One of the AUREOs in the diatom Phaeodactylum tricornutum, PtAUREO1a, has been demonstrated to significantly influence global cellular transcription upon blue light exposure. PtAUREO1a itself is highly regulated on the gene transcription level, depending on the light conditions. However, little is known about the proteostasis of PtAUREO1a in vivo. In this study, we used quantitative immunoblot analysis to examine PtAUREO1a levels under different light conditions as well as in the presence of inhibitors for translation and proteolysis. Our results demonstrate that PtAUREO1a is rapidly degraded in response to blue light exposure after red light acclimation, while the protein has an extended protein half-life in white light conditions. Moreover, the data provide the first in vivo evidence for a functional ubiquitin-proteasome system in the model diatom P. tricornutum. Our findings provide a theoretical basis for studies on protein degradation mechanisms and the regulation of PtAUREO1a, suggesting that changing light conditions can have an impact on the PtAUREO1a protein amount by directly affecting its protein stability.

金色素 (AUREO) 是硅藻和相关藻类中发现的蓝光光感受器和转录因子，在调节基因和细胞生理学中发挥着关键作用。硅藻三角褐指藻中的 AUREO 之一 PtAUREO1a 已被证明在蓝光照射下显着影响整体细胞转录。 PtAUREO1a 本身在基因转录水平上受到高度调控，具体取决于光照条件。然而，人们对 PtAUREO1a 体内蛋白质稳态知之甚少。在本研究中，我们使用定量免疫印迹分析来检查不同光照条件下以及翻译和蛋白水解抑制剂存在下的 PtAUREO1a 水平。我们的结果表明，在红光适应后，PtAUREO1a 会因蓝光暴露而迅速降解，而该蛋白质在白光条件下具有延长的蛋白质半衰期。此外，这些数据为三角角硅藻模型中具有功能性泛素-蛋白酶体系统提供了第一个体内证据。我们的研究结果为蛋白质降解机制和 PtAUREO1a 调控的研究提供了理论基础，表明改变光照条件可以通过直接影响其蛋白质稳定性来影响 PtAUREO1a 蛋白质的量。