Biosynthesis of Xyloglucan by Plant Golgi Membranes

木葡聚糖是一种植物细胞壁基质多糖，由高尔基体细胞膜中的酶合成。木葡聚糖在细胞壁结构和功能中起着核心作用。此外，它还可能在控制植物生长发育过程中起到调节作用。它是一种复杂的多糖，但与某些多糖相比，它相对简单。这项提案描述了一项旨在阐明木葡聚糖合成酶及其产物的活性的研究计划。本项目的总体目标是完善木葡聚糖生物合成系统，作为研究植物细胞壁多糖生物合成和植物高尔基体结构和功能组织的模型。这两个研究课题是密切相关的，完成这项研究将大大增加我们对两者的理解。从悬浮培养的梧桐树细胞中分离出的高尔基膜正在进行细分，这些部分纯化的膜组分被用作木聚糖合成酶的来源。糖基组成分析、甲基化连锁分析和放射性气体比例计数的组合被用来确定所结合的放射性标记残基的身份和它们之间的联系。参与木葡聚糖合成的糖基转移酶正在被提纯，从而最终有可能对植物高尔基体进行亚细胞定位和隔室定位。这项研究的成功完成将使人们更好地了解植物细胞壁的合成过程以及植物器官的结构和功能。植物生物学中有许多基本问题没有得到解答。细胞壁生物发生对植物生长发育的影响就是这样一个问题。这项研究为在这一领域取得进展提供了机会。木葡聚糖在结构和功能上都是植物细胞壁的重要组成部分。它们允许细胞壁保持一定程度的弹性，并与生长素在生长过程中刺激的伸长有关。这项研究是对这些重要细胞壁糖的生物合成的深入研究，并提供了对高尔基体更好的了解，高尔基体产生负责合成它们的酶。

Xyloglucans are plant cell wall matrix polysaccharides that are synthesized by enzymes in the membranes of the Golgi apparatus. Xyloglucan plays a central role in both cell wall structure and function. In addition, it may have a regulatory function in the process of controlling plant growth and development. It is a complex polysaccharide, yet compared to some it is relatively simple. This proposal describes a program of research designed to clarify the activities of xyloglucan synthase enzymes and the products they make. The overall objective of this project is to refine the xyloglucan biosynthesis system for use as a model for the study of both plant cell wall polysaccharide biosynthesis and the structure and functional organization of the plant Golgi apparatus. These two research topics are closely related and completion of this research will significantly increase our understanding of both. Golgi membranes isolated from suspension- cultured Acer pseudoplatanus (sycamore maple) cells are being subfractionated and these partially purified membrane fractions are being used as a source of xyloglucan synthases. Combinations of glycosyl composition analysis, methylation linkage analysis, and radiogas proportional counting are being used to determine identities of incorporated radiolabeled residues and the linkages between them. The glycosyl transferases involved with xyloglucan synthesis is being purified so that eventual subcellular localization and compartment mapping of plant Golgi are possible. Successful completion of this study will result in a greater understanding of the process of plant cell wall synthesis as well as the structure and function of the plant apparatus. There are many unanswered fundamental questions in plant biology. What influence cell wall biogenesis has on plant growth and development is one such question. This research offers an opportunity for progress in this area. Xyloglucans are an important component of plant cell walls both structurally and functionally. They allow the cell wall to maintain a degree of flexibility and are implicated in auxin-stimulated elongation during growth. This research is an in-depth study of the biosynthesis of these important cell wall sugars and provides a better understanding of the Golgi apparatus which produces the enzymes responsible for their synthesis.