Investigation of the role of the homologous proteins PCH1 and PCHL in phytochrome B-mediated light signalling

光敏色素是植物中的光感受器，它调节植物的生长和发育，以应对环境的变化。光的质量和强度控制着从非活性Pr到活性Pfr以及从Pfr到Pr的转化。此外，Pfr到Pr的转化也发生在一个不依赖光的过程中，称为暗还原。光敏色素B （Phytochrome B, phyB）在光生长和成体植物中具有特别重要的作用，在可见光谱的红光范围内起着探测光的作用。我们最近发现PCH1和PCHL是phyB的结合蛋白。过表达PCH1或PCHL的植物对红光有强烈的超敏反应，而缺乏功能性PCH1则导致对红光的反应降低。初步实验表明，PCH1和PCHL抑制了phyB的暗还原，从而维持了较高的Pfr水平。在拟议的项目中，我们希望研究PCH1/ pchl介导的phyB活性调节的分子机制，特别强调PCH1/ pchl依赖的黑暗逆转控制。我们还想研究PCH1/PCHL在phyB和其他信号通路之间的串扰中的潜在作用，这些信号通路可能通过调节PCH1/PCHL来影响phyB的活性。我们自己的数据和文献数据表明，PCH1/PCHL将其他光信号通路与phyb介导的红光信号通路联系起来。此外，PCH1/PCHL可能通过增加吸收种子的光敏感性在种子萌发过程中发挥作用，并在phyB和karrikins之间提供了分子联系，后者是烟雾中促进萌发和幼苗发育的化合物。PhyB暗还原是温度依赖性的，因此PhyB也可能具有温度传感器的功能。考虑到PCH1/PCHL影响暗还原，它们可能在温度传感中发挥作用，我们也想研究这一点。

Phytochromes are photoreceptors in plants that regulate growth and development in response to changes in the environment. Light quality and intensity control the conversion from the inactive Pr to the active Pfr state as well as from Pfr back to Pr. In addition, reversion of Pfr to Pr also occurs in a light-independent process called dark reversion. Phytochrome B (phyB) is of particular importance in light-grown and adult plants and plays a role in detection of light in the red light range of the visible spectrum. We recently identified PCH1 and PCHL as phyB binding proteins. Plants overexpressing PCH1 or PCHL are strongly hypersensitive to red light, while lack of functional PCH1 results in reduced responses to red light. Initial experiments show that PCH1 and PCHL decrease phyB dark reversion and thereby maintain high Pfr levels. In the proposed project, we want to investigate molecular mechanisms underlying PCH1/PCHL-mediated regulation of phyB activity, with particular emphasis on PCH1/PCHL-dependent control of dark reversion. We also want to investigate a potential role of PCH1/PCHL in cross-talk between phyB and other signalling pathways, which could affect the activity of phyB by regulation of PCH1/PCHL. Our own data and data in the literature suggest that PCH1/PCHL link other light signalling pathways to phyB-mediated red light signalling. Moreover, PCH1/PCHL might play a role during seed germination by increasing the light sensitivity of imbibed seeds and provide a molecular link between phyB and karrikins, which are chemical compounds in smoke that promote germination and seedling development. PhyB dark reversion is temperature-dependent and therefore phyB might also have a function as temperature sensor. Given that PCH1/PCHL affect dark reversion, they might play a role in temperature sensing, which we also want to investigate.