GLUCOSE SIGNAL TRANSDUCTION PATHWAY IN PLANTS

本研究计划的长期目标是以拟南芥为模型系统，阐明植物中葡萄糖信号转导通路的分子机制。通过光合作用生产糖是植物中最重要的活动，它支持着地球上所有的生命。我的实验室最近的研究提供了令人信服的证据来支持糖作为中心信号分子调节光合作用基因表达和协调许多重要过程的新概念，包括植物的发芽、幼苗发育、叶和根分化、开花和衰老。通过使用突变体、瞬时表达和转基因植物，我们提供了新的证据，证明葡萄糖信号可以从葡萄糖代谢中解耦，并且至少有一种特异性己糖激酶（AtHXK1）作为植物中主要的葡萄糖传感器/信号传感器具有双重催化和调节作用。拟采用植物模型拟南芥的研究将揭示植物中葡萄糖传感和信号传导的分子机制的非常规和令人兴奋的新见解，并可能对其他真核生物产生影响。结合分子，生化，遗传和细胞的方法将被使用。通过拟南芥AtHXK1敲除突变体和HXK水平改变的转基因植株，将用于鉴定HXK介导的葡萄糖反应靶基因。一套全面的葡萄糖依赖性生物测定将被测试来定义HXK介导的发育活动。葡萄糖磷酸化和积累将被监测。这些实验将建立分析植物糖反应的标准，并将通过遗传手段明确定义特定HXK作为葡萄糖传感器/信号传感器的作用。2)阐明AtHXK1在葡萄糖传感和信号转导中的分子机制，提出综合实验，确定AtHXK1的表达模式和亚细胞定位，建立AtHXK1功能检测，生成和分析AtHXK1突变体，表征AtHXK1蛋白复合物，鉴定AtHXK1信号转导伙伴。葡萄糖信号转导途径中的成分鉴定拟南芥葡萄糖不敏感突变体（gin）将被表型和分子表征。最有趣的突变体gin1的基因将被分离和分析。

The long-term objective of this research proposal is to elucidate the molecular mechanisms underlying the glucose signal transduction pathway in plants using Arabidopsis thaliana as a model system. Sugar production through photosynthesis is the most important activity in plants and supports all life on the planet. Recent studies from my laboratory have provided compelling evidence to support the new concept that sugars are acting as central signaling molecules to modulate photosynthetic gene expression and coordinate many vital processes, including germination, seedling development, leaf and root differentiation, flowering, and senescence in plants. By using mutants, transient expression, and transgenic plants, we have provided new evidence that glucose signaling can be uncoupled from glucose metabolism, and at least one specific hexokinase (AtHXK1) has dual catalytic and regulatory roles as a major glucose sensor/signal transducer in plants. The proposed studies employing a plant model A.thaliana will reveal unconventional and exciting new insights into the molecular mechanisms of glucose sensing and signaling in plants with potential implications in other eukaryotes. A combination of molecular, biochemical, genetic, and cellular approaches will be used. Three specific aims are: 1) Define the glucose responses mediated through AtHXK1 as a sensor/signal transducer An Arabidopsis AtHXK1 knockout mutant and transgenic plants with altered HXK levels will be used to identify HXK- mediated glucose-responsive target genes. A comprehensive sets of glucose-dependent bioassays will be tested to define HXK- mediated developmental activities. Glucose phosphorylation and accumulation will be monitored. These experiments will establish the standards for analyzing sugar responses in plants and will unequivocally define the role of specific HXK as a glucose sensor/signal transducer by genetic means. 2) Elucidate the molecular mechanism of AtHXK1 function in glucose sensing and signaling Comprehensive experiments are proposed to determine the expression patterns and subcellular localization of AtHXK1, establish AtHXK1 functional assays, generate and analyze AtHXK1 mutants, characterize the AtHXK1 protein complex, and identify AtHXK1 signaling partners. 3) Identify the components in the glucose signal transduction pathways The Arabidopsis mutants that are glucose insensitive (gin) will be phenotypically and molecularly characterized. The gene for the most interesting mutant gin1 will be isolated and analyzed.