Xyloglucan Glucosyltransferase in Plant Golgi Membranes

在植物生物学中，细胞壁生物发生对植物生长发育的影响程度等许多基本问题尚未得到解答。拟议的研究为这一领域的进展提供了机会。木葡聚糖是植物细胞壁的重要组成部分，有证据表明它可能在植物中起到信号分子的作用。增加对木葡聚糖生物合成的酶和基因的了解将大大增加对细胞壁多糖和细胞壁合成过程的理解。此外，所提出的研究将增加对植物高尔基体结构和功能组织的认识。本提案描述了一项旨在完成木葡聚糖葡萄糖基转移酶（XGT）纯化的研究计划。主要目标包括：1。XGT酶的纯化。2. 反应产物表征。3. 受体分子要求。4. XGT表征及酶动力学。在此提议的范围之外，我们计划最终使用纯化的XGT作为确定亚细胞定位模式、时空表达模式和木葡聚糖合成酶系统的分子遗传控制的途径。对植物细胞壁在调节植物生长和发育中的作用有一个基本的了解，对于满足未来植物生物学研究的实际目标是必要的，即转基因农业植物，提高作物产量和生产力，提高抗逆性，提高对病害生物的抵抗力。动物细胞和植物细胞之间的一个根本区别是，每个植物细胞都被一层主要由多糖构成的细胞壁所包围。这些多糖大多是在高尔基体的细胞膜内制造的，然后被包装并分泌到细胞膜外的细胞壁上。目前还没有一种植物细胞壁多糖合成酶被纯化用于详细的生化研究。该项目的目的是纯化木葡聚糖葡萄糖基转移酶（XGT），该酶负责合成多糖木葡聚糖的葡聚糖主干。木葡聚糖是植物细胞壁的重要组成部分，有证据表明它可能在植物中起到信号分子的作用。增加对木葡聚糖生物合成的酶和基因的了解将大大增加对细胞壁多糖和细胞壁合成过程的理解。此外，所提出的研究将增加对植物高尔基体结构和功能组织的认识。更全面地了解细胞壁的合成对了解植物细胞壁在调节植物生长发育中的作用至关重要。

There are many unanswered fundamental questions in plant biology including the extent of influence cell wall biogenesis has over plant growth and development. The proposed research offers an opportunity for progress in this area. Xyloglucans are an important component of plant cell walls and there is evidence they may serve as signaling molecules in plants. Increased knowledge about the enzymes and genes that are responsible for xyloglucan biosynthesis will add significantly to understanding of cell wall polysaccharides and the process of cell wall synthesis. In addition, the proposed research will increase knowledge of the structure and functional organization of the plant Golgi apparatus. This proposal describes a program of research designed to complete purification of xyloglucan glucosyltransferase (XGT). Major objectives include: 1. Purification of XGT enzyme. 2. Reaction product characterization. 3. Accepter molecule requirements. 4. Characterization and enzyme kinetics of XGT. Beyond the scope of this proposal, we plan eventually to use purified XGT as an avenue to determi ne patterns of subcellular localization, spaciotemporal expression patterns, and molecular genetic control of the xyloglucan synthesis enzyme system. A fundamental understanding of the plant cell wall's role in regulating plant growth and development will be necessary to meet the practical goals of future plant biology research, namely, genetically engineered agricultural plants, increased crop yields and productivity, improved stress tolerance, and improved resistance to attack by disease organisms. %%% One of the fundamental differences between animal cells and plant cells is that each plant cell is surrounded by a cell wall made primarily of polysaccharides. Most of these polysaccharides are manufactured inside the cell in the membranes of the Golgi apparatus, and then are packaged and secreted to the wall outside the cell membrane. None of the plant cell wall polysaccharide- synthesizing enzymes has ever been purified for detailed biochemical study. This project has the goal of purifying xyloglucan glucosyltransferase (XGT), the enzyme responsible for synthesis of the glucan backbone of the polysaccharide xyloglucan. Xyloglucans are an important component of plant cell walls and there is evidence they may serve as signaling molecules in plants. Increased knowledge about the enzymes and genes that are responsible for xyloglucan biosynthesis will add significantly to understanding of cell wall polysaccharides and the process of cell wall synthesis. In addition, the proposed research will increase knowledge of the structure and functional organization of the plant Golgi apparatus. A more complete understanding of cell wall synthesis is crucial to an understanding of the plant cell wall's role in regulating plant growth and development.