REGULATION OF AUXIN RESPONSE FACTOR ACTIVITY IN ARABIDOPSIS

 描述(申请人提供)：荷尔蒙通过转录因子调节基因激活或抑制是所有生物体的中心。生长素反应因子(ARF)转录因子是植物生长的重要调节因子，为探索激素调控基因的激活和抑制提供了理想的模型。我们最近发现，蛋白质多聚化和蛋白酶体降解是调节ARF活性的两种未知机制。本研究项目的长期目标是确定这些ARF调控机制在拟南芥转录调控中的重要性。阐明ARF调控的分子机制可能会揭示其他转录因子共同的调控过程。抑制-去抑制范式调节ARF的活动。在激素生长素的低浓度下，ARF的转录活性被AUX/IAA抑制蛋白抑制。当生长素浓度增加时，由F-box蛋白(TIR1)和AUX/IAA抑制蛋白组成的共同受体复合体直接与生长素结合。F-box蛋白参与Skp1-cullin-F-box(SCF)E3泛素连接酶，该酶针对AUX/IAA蛋白进行降解。这种降解事件解除了ARF的抑制，从而允许生长素调节的基因转录。虽然这种抑制和去抑制生长素活性的分子模型看起来相对简单，但我们最近的初步数据表明，几个令人兴奋的新的控制成分和翻译后修饰物影响ARF的转录活性和蛋白质积累。本项目旨在通过识别ARF蛋白活性和积累的调节因子来阐明生长素信号的分子机制。为了实现这一目标，我们将结合生化、生物物理、细胞生物学、合成生物学、分子和基因技术来深入了解影响ARF活性的因素。第一个目标是理解 蛋白质多聚体在调节ARF转录活性中的作用。合成酵母生长素反应系统和植物生长素反应系统的研究将被用来测试这一目标的各个方面，包括功能分析和3C分析。第二个目的是了解多聚体在调节ARF局部化中的作用。我们将确定ARF翻译后修饰是否影响ARF细胞定位。我们的第三个目标是建立ARF蛋白酶体依赖的降解在调节生长素反应和植物发育中的ROLS。我们将使用各种遗传、生化和细胞生物学技术来了解调节ARF稳定性的生物学和发育作用。这项拟议的研究是创新的，因为我们的方法强烈关注ARF调控的分子理解，以我们最近关于ARF7的结构数据为指导，它有可能显著改变生长素信号模型。这项拟议的研究具有重要意义，因为它有望促进和扩大对转录因子调控的理解，以ARF因子为模型。

 DESCRIPTION (provided by applicant): Hormone-mediated modulation of gene activation or repression through transcription factors is central to all organisms. Auxin Response Factor (ARF) transcription factors are critical modulators of plant growth and provide an ideal model for exploring hormone control of gene activation and repression. We have recently identified protein multimerization and proteasomal degradation as two previously unknown mechanisms that regulate ARF activity. The long-term goal of this research project is to determine the importance of these ARF regulatory mechanisms in Arabidopsis thaliana transcriptional control. Elucidating the molecular mechanism of ARF regulation likely will uncover control processes common to other transcription factors. A repression-derepression paradigm regulates ARF activity. Under low concentrations of the hormone auxin, ARF transcriptional activity is repressed by Aux/IAA repressor proteins. When auxin concentrations increase, a co-receptor complex, comprised of an F-box protein (TIR1) and an Aux/IAA repressor protein, directly binds auxin. The F-box protein participates in a Skp1-Cullin-F-box (SCF) E3 ubiquitin ligase, which targets the Aux/IAA protein for degradation. This degradation event relieves ARF repression, thereby allowing auxin-regulated gene transcription. Although this molecular model of repression and derepression for auxin activity appears relatively simple, our recent preliminary data suggest several exciting new control components and posttranslational modifiers influence ARF transcriptional activity and protein accumulation. This project aims to elucidate auxin signaling molecular mechanisms by identifying regulators of ARF protein activity and accumulation. To achieve this goal, we will use a combination of biochemical, biophysical, cell biology, synthetic biology, molecular and genetic techniques to gain insight into factors that influence ARF activity. The first aim is to understand the role of protein multimerization in the regulation of ARF transcriptional activity. Studies in both a synthetic yeast auxin response system and in planta will be used to test aspects of this aim, which includes functional assays and 3C analysis. The second aim is understand the role of multimerization in the regulation of ARF localization. We will determine whether ARF posttranslational modification affects ARF cellular localization. Our third aim is to establish rols for ARF proteasome-dependent degradation in regulating auxin response and plant development. We will use a variety of genetic, biochemical, and cell biology techniques to understand the biological and developmental roles for regulated ARF stability. The proposed research is innovative because our approaches focus strongly on the molecular understanding of ARF regulation, guided by our recent structural data on ARF7 and it has the potential to dramatically alter the auxin signaling model. The proposed research is significant because it is expected to advance and expand understanding of transcription factor regulation, using ARF factors as a model.