Glucose Signaling in Plants

描述(申请人提供)：葡萄糖是一种古老的中央信号分子，存在于从大肠杆菌、酵母到植物和人类的广泛生物体中。尽管葡萄糖在基因表达、生理、代谢、细胞增殖和死亡、生长和发育以及人类疾病中发挥着重要作用，但在植物和动物中，葡萄糖信号转导的分子和细胞机制仍然很难理解。我们对模式植物拟南芥的研究提供了令人信服的遗传和生化证据，表明己酮酸酶1(HXK1)是一种进化保守的葡萄糖传感器，它整合了营养和激素信号来调控基因表达和植物对环境提示的生长。代谢酶是如何调节葡萄糖信号的仍然是个谜。我们最近的发现表明，拟南芥HXK1在没有代谢活性的情况下介导葡萄糖信号转导，并与核内的两个非常规伙伴(HUP1：与HXK1、HUP2和转录因子相互作用的支架蛋白；HUP2：与HXK1、HUP1和其他ATPase相互作用的ATPase)相互作用，以控制转录和不同的葡萄糖反应。本研究的目的是阐明拟南芥中核传感器HXK1控制的葡萄糖信号转导机制。拟议的实验旨在利用分子、细胞、遗传学和基因组学方法来阐明HXK1的功能和调控，并分析作用于核HXK1-HUP1/2复合体下游的两组信号调节因子。该项目的重点是利用转基因植物和在葡萄糖传感器HXK1、HXK1信号伙伴HUP1、新的转录因子(MYB、SCL3、ZFP)和ATPase(HUP2/RPT5、RPT2和RPT6)中存在特定缺陷的功能缺失突变株来鉴定和整合8个拟南芥基因在葡萄糖信号转导中的功能。近全基因组芯片和染色质免疫沉淀(ChIP)将用于鉴定HXK1的主要靶基因，并研究它们在体内的调控。该项目对现有的植物和动物基于代谢的葡萄糖反应模式提出了挑战，旨在建立一个新的概念框架，以加强我们对植物向人类发出葡萄糖信号的分子和细胞机制的理解。目的：1.阐明核糖感受器HXK1的功能和调控；2.鉴定HXK1-HUP1/2介导的葡萄糖信号通路中的三种新的转录因子；3.确定三种ATPase在核RPT5/2/6复合体中的功能。与公共健康相关：尽管葡萄糖在基因表达、生理、新陈代谢、细胞增殖和死亡、生长和发育以及人类疾病中发挥着核心作用，但在植物和动物中，葡萄糖信号的分子机制仍然不清楚。我们最近的研究提供了有力的证据表明，在多细胞真核生物中，葡萄糖信号可以与葡萄糖代谢解偶联，而拟南芥己糖激酶1作为一个进化保守的感受器，在核葡萄糖信号中发挥着关键作用。这项拟议的研究将发现新的调节因子并阐明它们在核糖信号中的功能，并为未来改善农业、环境和可再生能源生产以及在治疗葡萄糖信号调节的糖尿病、肥胖症、癌症和衰老方面的人类健康提供创新工具。

DESCRIPTION (provided by applicant): Glucose is an ancient and central signaling molecule in a broad range of organisms from E. coli, yeast to plants and humans. Despite the essential roles of glucose in gene expression, physiology, metabolism, cell proliferation and death, growth and development, and human diseases, the molecular and cellular mechanisms of glucose signaling remain mostly elusive in plants and animals. Our research in the model plant Arabidopsis thaliana has provided compelling genetic and biochemical evidence that hexokinase1 (HXK1) is an evolutionarily conserved glucose sensor that integrates nutrient and hormone signals to govern gene expression and plant growth in response to environmental cues. How the metabolic enzyme mediates glucose signaling remains a mystery. Our recent findings indicate that Arabidopsis HXK1 mediates glucose signaling without its metabolic activity, and interacts with two HXK1 Unconventional Partners (HUP1: a scaffolding protein interacting with HXK1, HUP2 and transcription factors (TFs); HUP2: an ATPase interacting with HXK1, HUP1 and other ATPases) in the nucleus to control transcription and diverse glucose responses. The goal of this research project is to elucidate the mechanisms of glucose signaling controlled by the nuclear sensor HXK1 in Arabidopsis. The proposed experiments aim to use molecular, cellular, genetic, and genomic approaches to elucidate HXK1 functions and regulation, and to analyze two sets of signaling regulators acting downstream of the nuclear HXK1-HUP1/2 complex. The project will focus on characterizing and integrating functions of eight Arabidopsis genes in glucose signaling using transgenic plants and loss-of-function mutants with specific defects in the glucose sensor HXK1, HXK1 signaling partners HUP1, novel transcription factors (MYB, SCL3, ZFP) and ATPases (HUP2/RPT5, RPT2 and RPT6). Near whole-genome microarray and chromatin-immunoprecipitation (ChIP) will be carried out to identify the primary HXK1 target genes and characterize their regulation in vivo. The project challenges the existing paradigm on metabolism-based glucose responses in plants and animals, and aims to build a new conceptual framework to enhance our understanding of the molecular and cellular mechanisms of glucose signaling from plants to humans. Three Specific Aims are: Aim 1. Elucidate the functions and regulation of the nuclear glucose sensor HXK1 Aim 2. Characterize three novel TFs in HXK1-HUP1/2-mediated glucose signaling Aim 3. Define functions of three ATPases in the nuclear RPT5/2/6 complex. PUBLIC HEALTH RELEVANCE: In spite the central roles of glucose in gene expression, physiology, metabolism, cell proliferation and death, growth and development, and human diseases, the molecular mechanisms of glucose signaling remain elusive in plants and animals. Our recent research has provided compelling evidence that glucose signaling can be uncoupled from glucose metabolism in multicellular eukaryotes, and Arabidopsis hexokinase1 acts as an evolutionarily conserved sensor playing a pivotal role in nuclear glucose signaling. The proposed research will discover novel regulators and elucidate their functions in nuclear glucose signaling, and provide innovative tools for future improvement of agriculture, environment and renewable energy production, as well as human health in treating diabetes, obesity, cancer and ageing modulated by glucose signaling.