Genetic Biochemical Studies of Plant Steroid Signaling

项目描述（申请人提供）：该项目的长期目标是了解油菜素内酯（brassinosteroids， BR）与其他激素和环境信号共同控制植物生长发育的分子网络。类固醇是植物和动物中重要的激素。BR通过从细胞表面受体激酶（BRI1）到核转录因子（BZR1和BZR2/BES1）的信号转导途径，调控植物广泛的发育和生理过程。BR与其他激素和环境信号一起调节植物的发育和生理，并与光和赤霉素（GA）有着密切的关系。我们在了解BR与BRI1结合导致BZR1活化和调控上千个靶基因的分子细节方面取得了很大进展。此外，我们还深入了解了BR信号通路如何与其他通路连接在一起，控制植物的各种功能。对于这一更新提议，我们计划了解BR信号通路如何与气孔受体激酶通路以及光和赤霉素信号通路交叉，以协调细胞分化和植物发育。我们将结合遗传学、蛋白质组学和基因组学的方法来实现以下具体目标：1)我们将研究BR信号如何调节MAP激酶和与ERECTA家族受体激酶的串扰来调节气孔分化。2)通过表征BZR1与光敏色素相互作用因子（pif）调控常见靶基因的相互作用，以及3种BZR1靶转录因子在光调控基因表达和发育中的作用，阐明BR和光信号通路整合的机制。3)我们将研究BR和GA激素协调共同发育过程的分子机制。本研究提出的实验将阐明一个整合了控制植物生长的四种重要信号通路的调控网络。这将极大地促进我们对信号转导的分子机制以及信号通路整合机制的理解。尽管在动物中BR信号通路与核受体介导的类固醇信号通路不同，但BR信号通路使用的许多成分和信号机制是保守的，并且在动物中类固醇调节过程或其他信号通路中发挥重要作用。因此，这项研究不仅对植物生物学和农业具有重要意义，而且还可能帮助我们了解与人类健康相关的类固醇功能和细胞调节的基本机制。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand the molecular network through which brassinosteroid (BR) and other hormonal and environmental signals together control plant growth and development. Steroids are important hormones in both plants and animals. BR regulates a wide range of developmental and physiological processes in plants through a signal transduction pathway from cell- surface receptor kinases (BRI1) to nuclear transcription factors (BZR1 and BZR2/BES1). BR acts together with other hormonal and environmental signals to regulate plant development and physiology, and has particularly intimate relationships with light and gibberellin (GA). We have made great progress in understanding the molecular details of how BR binding to BRI1 leads to activation of BZR1 and regulation of over a thousand target genes. Furthermore, we have gained insights into how the BR signaling pathway is wired together with other pathways to control various functions in plants. For this renewal proposal, we plan to understand how the BR signaling pathway crosstalks with the stomata receptor kinase pathway and the light and gibberellin signaling pathways to coordinate cell differentiation and plant development. We will use a combination of genetic, proteomic, and genomic approaches to achieve the following specific Aims. 1) We will study how BR signaling regulates the MAP kinases and crosstalks with the ERECTA family receptor kinases to regulate stomata differentiation. 2) We will elucidate the mechanism of integration of the BR and light signaling pathways, by characterizing the interaction between BZR1 and the phytochrome- interacting factors (PIFs) in regulating common target genes, and the functions of three BZR1-target transcription factors in light regulation of gene expression and development. 3) We will study the molecular mechanisms by which BR and GA hormones orchestrate common developmental processes. The experiments proposed in this proposal will elucidate a regulatory network that integrates four important signaling pathways controlling plant growth. This will greatly advance our understanding of not only the molecular mechanisms of signal transduction but also the mechanisms of signaling pathway integration. Although the BR signaling pathway is distinct from the nuclear receptor-mediated steroid signaling mechanism in animals, many components and signaling mechanisms used by the BR pathway are conserved and play important roles in either steroid regulated processes or other signaling pathways in animals. Thus, this study not only is important for plant biology and agriculture, but also can potentially help us understand fundamental mechanisms of steroid function and cellular regulation that are relevant to human health. PUBLIC HEALTH RELEVANCE: Steroids are important growth hormones in both animals and plants. The brassinosteroid hormone is major growth promoting hormone that control a wide range of activities in plants. Brassinosteroid signal transduction uses many proteins that are similar to important proteins in humans, and understanding the functional mechanisms of these proteins will lead to not only means for improving crop yield but also knowledge that benefit human health.