Understanding the cellular role of aureochromes, a new type of blue light photoreceptors, in diatoms

硅藻是单细胞光合自养藻类，在浮游和底栖水生群落中非常成功。此外，它们代表了独特的进化嵌合细胞，因为它们是通过将真核生物摄取到另一个真核细胞中而进化的。因此，硅藻具有与绿色藻类和植物不同的遗传背景。硅藻和相关的藻类在组的Straveliles拥有蓝光感光细胞称为aureochromes，只发现在这组。与其他已知的光感受器相比，金色素是具有LOV结构域以及DNA结合bZIP结构域的光激活转录因子。我们最近对硅藻三角褐指藻的研究表明：（i）三角褐指藻具有四种不同的金色素，（ii）金色素对光适应很重要，（iii）敲除单个金色素基因（PtAureo1a）会导致细胞从红光转换为蓝光时转录组调控的急剧和大规模减少。因此，我们假设PtAUREO1a可能是蓝光响应的一个“主开关”。因此，在这个项目中，我们想阐明的功能细胞的作用，金色素在硅藻PtAureo敲除突变体。第一个子项目将研究PtAUREO1c和2个KO突变体在红/蓝光转换后的转录组学反应。在广泛的方法中，我们将研究可用的PtAureo敲除系的生理学，以了解缺乏相应光感受器的具体影响。然后我们将研究不同光照条件的作用，以及限制因素如N剥夺对WT和突变株系竞争力的作用。最后，在代谢组学方法中，我们想研究敲除突变体的竞争力是否受损。在第二个子项目中，我们将尝试通过鉴定金色素结合位点，通过酵母单杂交方法研究PtAureo/启动子结合，金色素二聚体形成以及鉴定共结合因子来解开PTAUREO1a的功能。该项目将基于两个独立研究小组的紧密合作，这两个研究小组开创了硅藻的分子和生理特征领域，并努力更好地了解硅藻如何感知光线以及这些信息如何转化为细胞反应。

Diatoms are unicellular photoautotrophic algae and extremely successful in planktonic and benthic aquatic communities. In addition, they represent peculiar evolutionary chimeric cells, as they evolved by the uptake of a eukaryotic alga into another eukaryotic cell. Accordingly, diatoms have a different genetic background than green algae and plants. Diatoms and related algae within the group of Stramenopiles possess blue light photoreceptors named aureochromes that are found only within this group. In contrast to other know photoreceptors, aureochromes are light-activated transcription factors possessing a LOV domain as well as a DNA-binding bZIP domain. Our recent work on the diatom Phaeodactylum tricornutum demonstrates (i) that this alga possesses four different aureochromes, (ii) that aureochromes are important for photoacclimation, and (iii) that knocking out a single aureochrome gene (PtAureo1a) results in a dramatic and massive reduction of transcriptomic regulation when the cells are transferred from red light to blue light. Therefore, we postulate that PtAUREO1a may be one “master switch” for blue light responses. Accordingly, in this project, we want to elucidate the functional cellular role of Aureochromes in diatoms using PtAureo knockout mutants. The first subproject will study the transcriptomic response of PtAUREO1c and 2 KO mutants after a red/blue light shift. In a broad approach, we will study the physiology of the available PtAureo knockout lines to understand the specific impact of the lack of the respective photoreceptors. Then we will investigate the role of different light conditions, and the role of limiting factors like N deprivation for competitiveness of WT and mutant lines. Finally, in a metabolomics approach, we want to investigate whether in the knockout mutants are impaired in their competitive strength. In the second subproject, we will try to unravel the functionality of PTAUREO1a by identifying aureochrome binding sites, investigating PtAureo/promotor binding via yeast 1-hybrid approaches, aureochrome dimer formation, as well as identification of co-binding factors. This project will be based on a very tight collaboration of two independent research groups that have pioneered the field of molecular and physiological characterization of diatoms, and it strives for a better understanding how diatoms sense light and how this information is converted into a cellular response.