Genetic Biochemical Studies of Plant Steroid Signaling

描述(申请人提供)：动物和植物都使用类固醇作为 用于生理和发育调节的信号分子(激素)。 在植物中，油菜素类固醇(BRs)具有促进生长的活性，并且 对正常生长和发育是必不可少的。BR生物合成中的缺陷 和响应性导致戏剧性的发育变化，包括 由于细胞伸长和伸长减少而导致的矮小，男性不育，延迟 的生殖发育和轻度生长形态的发育 一片漆黑。BR是通过细胞表面受体激酶BALL来感知的。BR如何 信号从质膜上的BRI1传递到其他细胞和 核反应仍不得而知。这项提议旨在获得一种分子 模式植物拟南芥中BR信号通路的理解 利用分子遗传学、生物化学和细胞学的方法 生物学。首先，我们发现BRI1受体激酶在一个很大的 蛋白质复合体，我们假设与BRI1相关的其他蛋白质在 受体复合体是受体功能所必需的。我们计划 利用亲和纯化技术鉴定与BRI1相关的蛋白质 利用反向基因和反向遗传技术研究这些蛋白质的功能 分子方法。第二，我们已经分离并进行了初步的 一个新的BR信号突变体BZR1-1D及其相应基因BZR1的研究。 基于这些研究，我们假设BZR1起着积极的作用 在BRI1下游的BR反应途径中的调节子。我们计划进一步 通过鉴定bzr1和bzr1的功能缺失等位基因来鉴定bzr1基因 Bzr2，通过分析BZR1与BR信号转导的其他基因的相互作用 途径，并通过测定BZR1蛋白的生化活性。我们 还计划识别和表征BZR1相互作用的蛋白质并执行 基因内和基因外抑制或增强突变的遗传学研究 BZR1-1D突变表型。最后，我们筛选并隔离了 与BR信号相关的其他突变体。我们已经克隆了这个基因 与其中一个突变体BZR6相对应，BZR6编码一个小蛋白。我们 BZR6可能作为拮抗BR的多肽配体 信令或作为BR响应的辅助信号之一。我们计划 确定BZR6及其同源物BZL1的功能。

DESCRIPTION (provided by applicant): Both animals and plants use steroids as signaling molecules (hormones) for physiological and developmental regulation. In plants, brassinosteroids (BRs) have growth-promoting activity and are essential for normal growth and development. Deficiencies in BR biosynthesis and responsiveness cause dramatic developmental alterations that include dwarfism due to reduced cell elongation and expansion, male sterility, delayed reproductive development, and development of light-grown morphology in the dark. BRs are perceived by the cell surface receptor kinase BAIl. How the BR signal is transduced from BRI1 on the plasma membrane to other cellular and nuclear responses remains unknown. This proposal aims at obtaining a molecular understanding of the BR signaling pathways in the model plant Arabidopsis thaliana, using approaches of molecular genetics, biochemistry, and cell biology. First, we have found that the BRI1 receptor kinase is in a large protein complex, and we hypothesize that other proteins associated with BRI1 in the receptor complex are required for the receptor function. We plan to identify the proteins associated with BRI1 using affinity purification and to characterize the functions of these proteins using reverse-genetic and molecular approaches. Second, we have isolated and carried out preliminary studies of a new BR-signaling mutant bzr1-1 D and the corresponding gene BZR1. Based on these studies, we hypothesize that BZR1 functions as a positive regulator in the BR response pathway downstream of BRI1. We plan to further characterize the BZR1 gene by identifying loss-of-function alleles of bzrl and bzr2, by analyzing the interaction of BZR1 with other genes of the BR signaling pathway, and by determining the biochemical activity of the BZR1 protein. We also plan to identify and characterize BZR1 interacting proteins and perform genetic studies of intragenic and extragenic mutations that suppress or enhance the bzr1 -1 D mutant phenotype. Finally, we have screened and isolated additional mutants associated with BR signaling. We have cloned the gene corresponding to one of these mutants, BZR6, which encodes a small protein. We hypothesize that BZR6 may function as a peptide ligand antagonizing BR signaling or as one of the secondary signals for the BR response. We plan to determine the functions of BZR6 and its homologue BZL1.