Crosstalk between Brassinosteroid and autophagy pathways in the regulation of plant growth and stress responses

项目摘要 这个项目的目标是确定生长、发育和压力反应是如何协调的 拟南芥是一种模式植物，具有丰富的遗传、基因组和蛋白质组资源。这将是 通过详细的机制研究来完成，这些研究将为基础生物学提供见解 在真核生物中保守的过程，类固醇激素信号和自噬。油菜素类固醇 (BRs)是促进生长的植物类固醇激素。自噬在植物和动物中都会发生 降解细胞器和蛋白质，特别是在胁迫条件下。我们的初步工作已经确定 BR和自噬途径之间的几个相互作用点。首先，BES1，一种转录因子 BR反应是通过泛素受体DSK2介导的选择性自噬来降解的。此外， BR信号通路中的负调控因子BIN2使DSK2磷酸化，增加了相互作用 在DSK2和ATG8之间，导致BES1降解。其次，自噬的负调控因子TOR是 BR介导的生长所必需的，BRS可能通过BIN2与TOR的相互作用抑制自噬。我们 假设BR和自噬途径通过多种机制串扰来协调植物 生长和应激反应：(A)被BIN2磷酸化后，DSK2作为一种磷酸化调节因子 因此，BES1的自噬受体和BES1泛素化导致其选择性降解 自噬。这反过来减缓了植物在胁迫条件下的生长；(B)BRs调节TOR以促进 生长并通过BIN2磷酸化TOR抑制自噬。对这些假设进行检验和扩展 我们提出了以下两个具体目标：(1)建立选择性自噬受体的功能 DSK2和E3泛素连接酶BAF1和BAR1通过自噬介导BES1降解； 确定BR通过BIN2调节TOR的机制，以及这种调节对生长和 在正常和应激条件下的自噬。这些研究将利用遗传和基因组资源 并使用尖端蛋白质组学来研究个体的泛素化和磷酸化 蛋白质和蛋白质组水平。这些创新的方法不仅有可能揭示特定的 类固醇信号和蛋白质降解途径之间的串扰机制，但也提供了 关于真核生物生长和胁迫反应整合的变革性概念和信息。 例如，自噬与包括神经退行性疾病在内的许多人类疾病有关。 肌萎缩侧索硬化症、帕金森氏症和亨廷顿氏症)和癌症。此外，BES1的降解 自噬使人联想到β-连环蛋白在WNT信号中的作用，以及HIF2α在缺氧反应中的作用 在动物和人类的生长、发育、应激反应和疾病中发挥重要作用。建议数 因此，研究可以为与人类健康相关的过程提供重要的洞察力。

Project Summary The goal of this project is to determine how growth, development and stress responses are coordinated in Arabidopsis, a model plant with extensive genetic, genomic and proteomic resources. This will be accomplished through detailed mechanistic studies that will provide insights into fundamental biological processes, steroid hormone signaling and autophagy, that are conserved across eukaryotes. Brassinosteroids (BRs) are plant steroid hormones that promote growth. Autophagy occurs in both plants and animals to degrade organelles and proteins, especially under stress conditions. Our preliminary work has established several interaction points between BR and autophagy pathways. First, BES1, a transcription factor mediating BR responses, is degraded by selective autophagy, mediated by the ubiquitin receptor DSK2. Furthermore, phosphorylation of DSK2 by BIN2, a negative regulator in the BR signaling pathway, increases the interaction between DSK2 and ATG8, resulting in BES1 degradation. Second, TOR, a negative regulator of autophagy, is required for BR-mediated growth, and BRs inhibit autophagy likely via BIN2 interaction with TOR. We hypothesize that BR and autophagy pathways crosstalk through multiple mechanisms to coordinate plant growth and stress responses: (a) upon phosphorylation by BIN2, DSK2 acts as a phospho-regulated autophagy receptor for BES1, and BES1 ubiquitination therefore leads to its degradation by selective autophagy. This in turn slows down plant growth under stress conditions; (b) BRs regulate TOR to promote growth and inhibit autophagy through BIN2 phosphorylation of TOR. To test and expand on these hypotheses we propose the following two Specific Aims: (1) To establish the functions of selective autophagy receptor DSK2 and E3 ubiquitin ligases BAF1 and BAR1 in mediating BES1 degradation through autophagy; (2) To determine the mechanism of BR regulation of TOR via BIN2, and the effect of this regulation on growth and autophagy under normal and stress conditions. These studies will leverage the genetic and genomic resources in Arabidopsis and use cutting-edge proteomics to study ubiquitination and phosphorylation at the individual protein and proteome-wide levels. These innovative approaches have the potential not only to reveal specific mechanisms of crosstalk between steroid signaling and protein degradation pathways, but also provide transformative concepts and information on the integration of growth and stress responses across eukaryotes. For example, autophagy is involved in many human diseases including neurodegenerative diseases (e.g. Amyotrophic Lateral Sclerosis, Parkinson's and Huntington's) and cancer. In addition, the degradation of BES1 by autophagy is reminiscent of that of β-catenin in WNT signaling and HIF2α in hypoxia responses, which play essential roles in growth, development, stress responses and disease in animals and humans. The proposed studies can therefore provide important insight into processes related to human health.