Activity and specificity of the COP1/SPA ubiquitin ligase in Arabidopsis light signaling and photomorphogenesis

植物不断监测周围的光环境，以适应不断变化的光照条件和季节的生长，发育和代谢-以优化光合作用，繁殖，并最终生存和健身的目的。 光敏光感受器（光敏色素和隐花色素）的下游，光敏色素A-105（COP 1/SPA）E3泛素连接酶的组成光形态发生1/供应商，在黑暗中抑制光信号。 它多聚泛素化光信号传导的正调节因子，主要是转录因子，从而靶向那些在26 S蛋白酶体中降解的因子。 在光照下，光敏色素和隐花色素光感受器与COP 1/SPA复合物结合，并通过多种机制抑制其活性。 COP 1也存在于人类中，它作为一种重要的，但不依赖于光的E3连接酶。SPA蛋白，相反，是特定的绿色谱系。 因此，SPA蛋白可能已经进化到将COP 1的活性置于光的控制之下，光是植物的一个重要环境因素。 在这里，我们将机械地定义光感受器，特别是隐花色素和蓝光对COP 1/SPA活性的调节。 此外，我们将研究不同SPA蛋白之间定义功能特异性的分子机制，包括使用邻近标记鉴定COP 1/SPA相互作用伴侣。

Plants constantly monitor the ambient light environment in order to adapt growth, development and metabolism to the changing light conditions and seasons - with the aim of optimizing photosynthesis, reproduction and ultimately survival and fitness. Downstream of the light-sensing photoreceptors (phytochromes and cryptochromes), the CONSTITUTIVELY PHOTOMORPHOGENIC1/SUPPRESSOR OF PHYTOCHROME A-105 (COP1/SPA) E3 ubiquitin ligase acts to suppress light signaling in darkness. It polyubiquitinates positive regulators of light signaling, mainly transcription factors, and thereby targets those for degradation in the 26S proteasome. In the light, the phytochrome and cryptochrome photoreceptors bind to the COP1/SPA complex and inhibit its activity via multiple mechanisms. COP1 also exists in humans where it acts as an important, but light-independent, E3 ligase. SPA proteins, in contrast, are specific to the green lineage. Hence, SPA proteins may have evolved to place the activity of COP1 under the control of light, an essential environmental factor primarily for plants. Here, we will mechanistically define the regulation of the COP1/SPA activity by photoreceptors, in particular by cryptochromes and blue light. Moreover, we will investigate the molecular mechanisms defining functional specificity among the different SPA proteins, including the identification of COP1/SPA interaction partners using proximity labeling.