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途径的分子机制。 通过光合作用产生糖是植物中最重要的活动，并支持地球上的所有生命。 我的实验室最近的研究提供了令人信服的证据来支持新的概念，即糖作为中央信号分子来调节光合基因的表达，并协调许多重要的过程，包括发芽，幼苗发育，叶和根分化，开花和植物衰老。 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，葡萄糖信号可以从葡萄糖代谢解耦，至少有一个特定的己糖激酶（AtHXK 1）具有双重催化和调节作用，作为一个主要的葡萄糖传感器/信号转导在植物中。 采用植物模型拟南芥的拟议研究将揭示对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。 将使用分子、生物化学、遗传和细胞方法的组合。 三个具体目标是：1）将AtHXK 1介导的葡萄糖反应定义为传感器/信号转换器将使用拟南芥AtHXK 1敲除突变体和HXK水平改变的转基因植物来鉴定HXK介导的葡萄糖反应靶基因。 将检测一组全面的葡萄糖依赖性生物测定，以确定HXK介导的发育活性。 将监测葡萄糖磷酸化和蓄积。 这些实验将建立分析植物糖反应的标准，并将明确定义特定HXK作为葡萄糖传感器/信号转导器的作用。 2)阐明AtHXK 1在葡萄糖传感和信号传导中的分子机制。提出了确定AtHXK 1的表达模式和亚细胞定位、建立AtHXK 1功能测定、产生和分析AtHXK 1突变体、表征AtHXK 1蛋白复合物以及鉴定AtHXK 1信号传导伙伴的综合实验。 3)确定葡萄糖信号转导途径中的组分将对葡萄糖不敏感的拟南芥突变体（gin）进行表型和分子表征。 将分离和分析最令人感兴趣的突变体gin 1的基因。

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.