The Role of Brassinosteroid Inactivation in Plant Development

油菜素类固醇是一种促进生长的激素，参与调节植物的发育，以应对环境的变化。利用模式植物拟南芥进行的油菜素类固醇研究大多集中在这些激素的生物合成或受体介导的信号通路上。国际油菜籽研究所之前的研究主要集中在油菜素类固醇失活酶，即细胞色素P734A1和细胞色素P72C1，并证明调节这些激素水平的一种重要方式是通过失活实现的。遗传分析表明，这些酶共同作用，调节植物发育的许多方面。生化分析表明，这两种酶通过不同的机制使油菜素类固醇失活。在这个项目中，将采用一种生化方法来检验这一假设，即CYP734A1以不同的亲和力与多种活性油菜素类固醇结合。类似的方法将被用来检验这一假设，即CYP72C1通过与CYP734A1不同的生化机制来灭活油菜素类固醇。分子遗传学分析将被用来检验这一假设，即CYP734A1和CYP72C1在植物发育中既有重叠又有独特的作用。类似的方法将被用来检验这样的假设，即由CYP734A1和CYP72C1介导的油菜素类固醇失活途径与另一种油菜素类固醇失活酶UCG73C5相互作用。这些研究将有助于揭示油菜素类固醇失活的调节机制，以及这一过程如何影响植物发育的许多方面。该项目的研究结果将影响多个研究领域，包括：植物发育、油菜素类固醇和其他植物激素、酶功能以及协同/冗余遗传相互作用的研究。这些研究将直接有助于博士生、博士后、本科生和高中生的教育。

Brassinosteroids are growth-promoting hormones involved in modulating plant development in response to changes in the environment. Most brassinosteroid investigations using the model plant Arabidopsis have concentrated on either the biosynthesis of these hormones or on the receptor-mediated signaling pathways. Previous research undertaken by the PI has focused on the brassinosteroid-inactivating enzymes, CYP734A1 and CYP72C1 and demonstrated that an important mode of regulating the level of these hormones is achieved through inactivation. Genetic analysis demonstrates that these enzymes act together to regulate many aspects of plant development. Biochemical analysis demonstrates that these two enzymes inactivate brassinosteroids, doing so via different mechanisms. In this project, a biochemical approach will be taken to test the hypothesis that CYP734A1 binds multiple active brassinosteroids, doing so with different affinities. Similar approaches will be used to test the hypothesis that CYP72C1 inactivates brassinosteroids via a different biochemical mechanism than CYP734A1. Molecular-genetic analysis will be used to test the hypothesis that CYP734A1 and CYP72C1 have overlapping as well unique roles in plant development. Similar approaches will be used to test the hypothesis that the CYP734A1- and CYP72C1-mediated brassinosteroid-inactivation pathway interacts with another brassinosteroid-inactivating enzyme, UCG73C5. These studies will help reveal the mechanisms regulating brassinosteroid inactivation and how this process affects many aspects of plant development. Findings from this project will impact multiple areas of research including studies of: plant development, brassinosteroids and other plant hormones, enzyme function, and synergistic/redundant genetic interactions. These studies will contribute directly to the education of a Ph.D. student, a postdoc, undergraduates and high school students.