Elucidating structure-function relationship and signaling mechanisms of the novel group III G gamma protein AGG3 in Arabidopsis

由于植物的固位性，植物不断地根据周围环境调整自己的生长、发育和生产力。它们对环境胁迫(如干旱、低温)、各种病原体、营养物质利用率低或高以及与其他生物的相互作用作出反应，通过精确地改变潜在的信号通路。有几种蛋白质，其中许多存在于所有生物体中，已经进化出植物特有的结构特征和功能，以有效地应对这些挑战。异三聚体G蛋白家族就是这样一组蛋白质，虽然它存在于所有真核生物中，但具有某些植物特有的成分和特征。本研究试图发现拟南芥中一种新的、植物特有的G&AMP；伽马蛋白AGG3调节的独特信号通路。这项研究的结果将有助于我们了解植物如何在环境胁迫下保持产量。这些结果将在资源有限的更高产作物的育种或工程中具有潜在的实际应用。这项工作还将涉及多学科领域博士后研究人员的培训和本科生的指导。这项研究将通过一系列动手实验和互动演示，帮助高中生和普通公众加深对植物科学的理解。尽管所有真核生物都具有异源三聚体G蛋白，它们的整体信号机制被广泛保守，但植物已经将其核心G蛋白系统重新连接起来，以满足它们的需求。植物G蛋白系统的一个新成分是新发现的较高植物特异性的III(或C类)G蛋白，在拟南芥中以AGG3为代表。III型G&amp；Gamma；蛋白具有模块化结构，N-末端结构域类似于典型的G&amp；Gamma；结构域，与含有高达35%半胱氨酸(Cys)的大的C-末端延伸部分(长达G&amp；Gamma；结构域的3倍)融合在一起。由于参与植物许多重要的农艺过程的调控，包括种子产量、器官大小调节、依赖于脱落酸(ABA)的信号和胁迫反应以及氮素利用效率，III型G&amp；Gamma；蛋白质目前是研究的热点。这些蛋白的作用方式在很大程度上仍不清楚，一些独立于经典G蛋白周期的独特机制也被提出。因此，本研究旨在确定AGG3的G蛋白依赖和非依赖作用，并阐明其潜在的信号机制，特别是那些在非生物胁迫信号转导中起作用的机制。利用AGG3的特定结构域对单级和高阶突变体进行遗传互补，然后鉴定其蛋白质相互作用网络。这些分析将有助于确定AGG3及其网络元件在非生物胁迫信号通路中的作用，以及它与其控制产量的能力之间的关系。

Due to their sessile nature, plants continuously adjust their growth, development and productivity in accordance with their surroundings. They respond to environmental stresses (e.g. drought, cold temperatures), various pathogens, low or high nutrient availability, and interactions with other organisms by precise modification of underlying signaling pathways. Several proteins, many of which are present in all organisms, have evolved plant-specific structural features and functions to effectively address these challenges. One such group of proteins is the heterotrimeric G-protein family, which although present in all eukaryotes, has certain plant-specific components and features. This research seeks to discover the unique signaling pathways regulated by a novel, plant-specific Gγ protein, AGG3, of Arabidopsis. Results obtained from this research will help us understand how plants maintain their yield against environmental stresses. These results will have potential practical applications in the breeding or engineering of more productive crops with limited resources. The work will also involve the training of a postdoctoral researcher in a multidisciplinary field and mentoring of undergraduate students. The research will help promote an understanding of plant science to the high school students and general public thorough a series of hands on experiments and interactive presentations.Even though all eukaryotes possess heterotrimeric G-proteins and their overall signaling mechanisms are broadly conserved, plants have taken the 'core' G-protein system and rewired it to meet their needs. One novel component of the plant G-protein system is the newly discovered, higher plant-specific, type III (or Class C) Gγ protein, represented by AGG3 in Arabidopsis. Type III Gγ proteins have a modular architecture, with an N-terminal domain similar to canonical Gγ , fused with a large C-terminal extension (up to 3 times the length of Gγ domain) that contains up to 35% cysteine (Cys). The type III Gγ proteins are currently a focus of intense research due to their involvement in regulation of many agronomically important processes in plants, including seed yield, organ size regulation, abscisic acid (ABA)-dependent signaling and stress responses, and nitrogen use efficiency. The mode of action of these proteins remains largely unknown, and some unique mechanisms that are independent of the classic G-protein cycle are also proposed. This research therefore aims to determine the G-protein-dependent and -independent roles of AGG3, and elucidate its underlying signaling mechanisms; especially those operative during abiotic stress signaling. Genetic complementation of single and higher order mutants will be performed using specific domains of AGG3, followed by identification of its protein interaction network. These analyses will help define the role of AGG3 and its network elements in abiotic stress signaling pathways and how it is related to its ability to control yield.