Structural and biochemical investigations of the Brassinosteroid (BR) pathway in Arabidopsis thaliana

对粮食、饲料、纤维和燃料的需求使农业成为本世纪重大挑战的中心。在过去的15年中，小分子植物激素调节拟南芥生长的机制已被阐明。其中，油菜素内酯（BR）促生长信号通路是植物中最明确的信号转导通路之一。受体及其信号成分是已知的，但在受体活化过程中蛋白质-蛋白质相互作用的详细描述是缺乏的。受体的活化导致至少2种蛋白质的磷酸化：BSK 1和CDG 1。最近的一项研究表明，BSK 1通过磷酸化激活另一种蛋白质BSU 1。然而，目前还不清楚BSK 1是否是一种真实的激酶，它是否与第三种蛋白质CDG 1一起发挥作用。因此，本文的研究将试图回答以下问题：1. BSKs是蛋白激酶吗？2. CDG、BSK和BSU是否相互直接接触，它们是否需要与激活的BRI 1/BAK 1/BR接触才能发出信号？3. CDG、BSK和CDG 1的蛋白质-蛋白质相互作用结构域是什么？这些问题将主要通过X射线蛋白质晶体学和生物化学方法如激酶活性测定来解决。拟议实验的成功完成将关闭BR信号通路的最终缺口，BR信号通路是决定植物大小的关键通路，其结果对解释植物的表型可塑性具有非常高的影响。对我来说，一个额外的好处是我将学习拟南芥遗传学，并可以将植物技术添加到我的实验室技能中。

The demand for food, feed, fiber, and fuel has placed agriculture at the center of grand challenges for this century. During the past 15 years, the mechanisms by which small molecule phytohormones regulate growth have been elucidated in Arabidopsis. Among them, the growth-promoting brassinosteroid (BR) pathway is one of the best-defined signal transduction pathways in plants. The receptor and its signaling components are known, but a detailed description of protein-protein interactions during receptor activation is lacking.Activation of the receptor leads to phosphorylation of at least 2 proteins: BSK1 and CDG1. A recent study revealed that BSK1 activates a further protein, BSU1, by phosphorylation. However, it remains unclear at the moment if BSK1 is a real kinase, which functions on its own or if it acts together with a third protein, CDG1. Thus, my research will try to answer the following questions:1. Are BSKs protein kinases? 2. Are CDG, BSK and BSU in direct contact with each other and do they require contact with an activated BRI1/BAK1/BR to signal? 3. What are the protein-protein interaction domains of CDG, BSK, and CDG1?These problems will be mainly addressed by means of X-ray protein crystallography and biochemical methods like kinase activity assays. The successful completion of the proposed experiments will close the final gap in the BR signaling pathway, a key pathway that determines the size of plants and the results should have very high impact to explain the phenotypic plasticity of plants. An added bonus in my case is that I will learn Arabidopsis genetics and can add plant techniques to my laboratory skill set.