The Pathway Through Inositol is the Pathway to Stress Tolerance

本研究的重点是植物基因和蛋白质在所有生物体中催化肌醇（MI）的生物合成。MI- ip合成酶将葡萄糖6-磷酸转化为肌醇1-磷酸，而磷酸酶则产生MI。该途径的两种产物在提供信号分子、膜生物发生和（在植物中）磷酸盐储存、低聚糖的生产中起着核心和必不可少的作用。植物性碳水化合物的储存，以及树胶和粘液的产生。肌醇甲基化途径是肌醇甲基化途径的延伸，它产生许多单甲基化或二甲基化的肌醇。甲基化肌醇可能在胁迫条件下光呼吸增加后提供甲基的渗透调节功能。甲基化肌醇存在于耐受高盐度或干旱条件的物种中。具有主要或完全不耐旱的糖生物种的家族似乎缺乏导致从MI扩展到D- pinitol的感觉。为了解决这个问题，dr。Bohnert和Jensen提出了MI生物合成的比较分子，生化和生理学分析以及d -蒎醇途径的延伸。首先，我们将分析糖植物、水稻和盐生植物、冰草中葡萄糖6-磷酸碳分配途径酶的生化特性、通量和通量控制。MI的生物合成局限于细胞质和叶绿体。因此，一项分析将是测量通过任一途径的相对通量的控制，以及应激条件下每种途径中心肌细胞生物合成对外部因素的稳定性或敏感性。此外，还有关于该途径的遗传学和基因的问题。这条通路的基因组成是什么？每种途径中有多少种不同的酶，在发育过程中该途径是如何控制的，在哪些组织和细胞中？在无胁迫和有胁迫的情况下，在区分糖生植物和盐生植物的控制上有区别吗？

9507375 Bohnert This research focuses on the genes and proteins in plants catalyzing an essential pathway in all organisms, the biosynthesis of myo-inositol, MI. The enzyme MI-IP synthase converts glucose 6-phosphate to myo-inositol 1-phosphate and a phosphatase produces MI. The two products of the pathway play a central and essential role in providing signalling molecules, in membrane biogenesis and - in plants - phosphate storage, the production of oligosaccharides, vegetative carbohydrate storage, and the production of gums and mucilages. An extension of the pathway beyond MI is the inositol methylation pathway which produces a number of mono- or di- methylated inositols. The methylated inositols may have a function in osmotic adjustment with the methyl groups provided follwing an increase in photorespiration under stress conditions. Methylated inositols are found in species that tolerate high salinity or drought conditions. Families with predominantly or exclusively glycophytic species that are not drought tolerant seem to lack gense that lead to an extension from MI to, for example, D- pinitol. To address this point, Drs. Bohnert and Jensen propose a comparative molecular, biochemical and physiological analysis of MI biosynthesis and the extension of the pathway to D-pinitol. First, the biochemical characteristics of the pathway enzymes, flux and flux control for carbon partitioning from glucose 6-phosphate will be anlyzed in the glycophyte, rice, and in a halophyte, ice plant. MI biosynthesis is localized to the cytosol and chlorophlasts. Thus, one analysis will be to gauge the control of relative fluxes through either pathway, and, also, on the stability or sensitivity of MI biosynthesis to external factors in each pathway under stress conditions. Additionally, there are questions about the genetics and genes of the pathway. What is the genetic makeup of the pathway? How many - different - gense are there for the enzymes in each pathway, and how is the pathway controlled during development and in which tissues and cells? Is there a difference in control distinguishing the glycophyte and the halophyte during stress-free growth and under stress?