Light signaling in the basal land plants Physcomitrella patens and Marchantia polymorpha

在种子植物拟南芥中，E3泛素连接酶COP 1/SPA是在黑暗中抑制光信号所需的关键负调节因子。 它控制整个植物生命周期的生长和发育，包括幼苗黄化、避荫和光周期开花。 COP 1/SPA复合物由COP 1和SPA蛋白组成，它们在黑暗中合作泛素化光信号传导的正调节因子-主要是转录因子。光暴露使COP1/SPA复合物失活，从而使这些转录因子积累并使光信号传导进行。 虽然COP1/SPA功能在拟南芥中得到了很好的表征，但对光信号传导的这些重要中间体的进化一无所知。COP1也存在于动物中，这表明它有着古老的起源。 SPA基因，相反，是特定的绿色谱系，表明COP 1/SPA合作功能已经在绿色谱系中进化，可能是为了将COP 1的活性置于光的控制之下。COP 1和SPA基因的直系同源物存在于小立碗藓和地钱中，这两种模式系统都是早期陆地植物。我们的遗传分析表明，SPA基因的功能立碗藓是不同的，从他们的特点拟南芥同行。此外，光信号在立碗藓似乎是少互连与内源发育程序（如分生组织活动）比种子植物。因此，光信号的比较分析在两个brendrites（立碗藓和地钱）和种子植物将大大推进我们的知识在陆地植物的光环境的适应性反应的演变。我们将分析立碗藓和地钱COP1和SPA样基因的功能，通过遗传和生化方法相结合。 我们将集中在以下主要问题：1）在何种程度上做COP1-和SPA-样蛋白从这些brabrites合作，即需要对方的活动？ 2)COP1和SPA样蛋白在何种程度上与黑暗和光明中的信号相互关联？ 3)什么是转录因子的功能，与brabenteCOP1和/或SPA相互作用，即在何种程度上是brabentes和种子植物之间的保守输出响应。

In the seed plant Arabidopsis, the E3 ubiquitin ligase COP1/SPA is a key negative regulator required to suppress light signaling in darkness. It controls growth and development throughout the plant life cycle, including seedling etiolation, shade avoidance and photoperiodic flowering. The COP1/SPA complex consists of COP1 and SPA proteins which cooperate to ubiquitinate positive regulators of light signaling - mainly transcription factors - in darkness. Light exposure inactivates the COP1/SPA complex, thereby allowing these transcription factors to accumulate and light signaling to proceed. While COP1/SPA function is well characterized in Arabidopsis, nothing is known about the evolution of these essential intermediates of light signaling. COP1 also exists in animals, suggesting an ancient origin. SPA genes, in contrast, are specific to the green lineage, indicating that COP1/SPA cooperative function has evolved in the green lineage, possibly to place the activity of COP1 under the control of light. Orthologs of COP1 and SPA genes are present in the bryophytes Physcomitrella patens and Marchantia polymorpha, both model systems for early land plants. Our genetic analyzes demonstrate that SPA gene functions in Physcomitrella are distinct from those of their well-characterized Arabidopsis counterparts. Also, light signaling in Physcomitrella appears to be less interconnected with endogenous developmental programs (e.g. meristem activity) than in seed plants. Thus, a comparative analysis of light signaling in two bryophytes (Physcomitrella and Marchantia) and seed plants will greatly advance our knowledge on the evolution of adaptive responses to the light environment in land plants. We will analyze the functions of Physcomitrella and Marchantia COP1- and SPA-like genes through a combination of genetic and biochemical approaches. We will focus on the following main questions: 1) To what extent do COP1- and SPA-like proteins from these bryophytes cooperate, i.e. require each other for activity? 2) To what extent are COP1- and SPA-like proteins interconnected with signaling in darkness and in the light? 3) What are the functions of transcription factors interacting with bryophyte COP1 and/or SPA, i.e. to what extent are output responses conserved between bryophytes and seed plants.