LEAFY, a plant transcription factor as a model for transcriptional activation by ubiquitination

花是开花植物或被子植物中结构最复杂的。花确保被子植物的成功繁殖，是果实和种子发育的基础，是人类和动物的主要食物来源。植物特异性转录因子LEAFY （LFY）是被子植物花发育的主要调控因子。LFY指定了花分生组织身份的出现，因此在从营养阶段（叶和枝）到生殖阶段（花）的发育转换中起着核心作用。最近有研究表明，LFY的活性依赖于与F-box蛋白异花器官（UFO）的相互作用。UFO是一种泛素连接酶，它被认为是参与蛋白质降解。众所周知，LFY可以与UFO一起触发叶子形成花朵，但UFO如何增强LFY活动仍然不清楚。虽然在酵母和哺乳动物中很少有泛素化和转录因子可能降解的转录激活的例子，但这种机制迄今尚未归因于植物。该项目的目的是揭示LFY- ufo相互作用在花发育中的生物学作用，以及LFY活性作为植物中泛素化激活转录的测试案例中泛素化途径的作用。我计划结合泛素系统研究LFY-UFO相互作用的机制，并利用细胞生物学、生物化学、分子生物学、一流成像和蛋白质组学的综合方法分析其对靶基因表达和花发育的分子影响。由于其众所周知的特征和功能（结构、DNA结合特性、相互作用伙伴、靶基因等）以及可用的工具，LFY是研究生物学中这一基本问题的完美模型。从我的研究中获得的知识显然有助于了解植物的花朵发育，特别是在几种开花植物中发现了LFY-UFO相互作用。此外，该项目将解决泛素化如何激活转录的生物学中具有普遍意义的问题，因此对其他模式生物的转录和泛素化感兴趣的社区非常感兴趣。

Flowers are the most complex structure of flowering plants or angiosperms. Flowers ensure successful reproduction of angiosperms and are the basis for fruit and seed development, which are major food source for humans and animals. The plant-specific transcription factor LEAFY (LFY) is the master regulator of flower development in angiosperms. LFY specifies the emergence of the floral meristem identity and therefore, plays a central role in the developmental switch from vegetative stage (leaves and branches) to reproductive stage (flowers). Recently it has been shown that LFY activity is dependent on the interaction with the F-box protein UNUSUAL FLORAL ORGANS (UFO). UFO is an ubiquitin ligase and it is assumed that UFO is involved in protein degradation. It is known that LFY can trigger the formation of flowers from leaves in conjunction with UFO, but how UFO potentiates LFY activity has remained obscure. Although few examples of transcriptional activation by ubiquitination and possible degradation of transcription factors exist in yeast and mammals, this mechanism has so far not been ascribed to plants. The aim of this project is to unravel the biological role of LFY-UFO interaction in flower development and what the role of ubiquitination pathways is in regard of LFY activity as a test case for activation of transcription by ubiquitination in plants. I plan to investigate the mechanism of the LFY-UFO interaction in conjunction with the ubiquitin-system and to analyse the molecular consequences on target gene expression and flower development using an integrated approach using cell biology, biochemistry, molecular biology, top-notch imaging and proteomics. LFY is the perfect model to investigate this fundamental question in biology, due to its well-known characteristics and functions (structure, DNA binding properties, interacting partners, target genes, etc), as well as available tools. The knowledge gained from my studies will clearly benefit to the understanding of flower development in plants, especially since the LFY-UFO interactions was identified in several flowering plants. Besides, this project will tackle a question of general significance in biology regarding how ubiquitination can activate transcription, therefore being of great interest to communities interested in transcription and ubiquitination in other model organisms.