Role of Cellulose and Protein in the Dictyostelium Spore Coat

9316897西网柄菌孢子皮含有约一半的多糖，包括纤维素和半乳糖，以及约一半的蛋白质，包括至少7种不同的蛋白质。大衣分两个阶段组装。首先，预制的外壳蛋白和半乳糖被分泌出来，在细胞表面形成一层。大多数蛋白质在相邻孢子之间交换，表明组装在分泌后发生在细胞外。一种蛋白质。是独一无二的，因为它不会交换，就像它锚定或启动涂层组装一样。在第二阶段，纤维素积累，蛋白质进一步组织。传统上，纤维素被认为是结构和功能的主要决定因素。PI提出了两个假设来研究蛋白质和多糖的相对贡献。假说II表明，在没有纤维素的情况下，仍将形成显微镜下可检测和可沉淀的蛋白质伪涂层。孢子衣和其他细胞外基质保护封闭的细胞免受不利环境的影响。虽然其中一些矩阵的组成部分是已知的，但关于这些部分如何组合在一起、它们的比例如何受到监管以及保护如何发生的知识在很大程度上是通过猜测得出的。被毛的结构和功能。这项研究的结果将增进我们对植物和真菌细胞壁组装的了解。***

9316897 West Dictyostelium spore coats contain about one -half polysaccharide, including cellulose and galuronan, and about one half protein, including at least 7 different protein species. The coat is assembled in two phases. First, preformed coat proteins and the galuran are secreted, forming a layer at the cell surface. Most of the proteins exchange between neighboring spores, indicating that assembly occurs extracellularly after secretion. One protein. is unique in that it is not exchanged, as if it anchors or initiates coat assembly. During the second phase cellulose accumulates, and the proteins organize further. Cellulose has traditionally been considered to be the primary determinant of structure and function. The PI proposes two hypotheses to investigate the relative contribution of proteins and polysaccharides. Hypothesis I suggests that proteins play a critical role in initiating assembly of the coat so that the absence of essential groups of proteins such as SP86, the protein part of the coat will not assemble or will not be attached to the plasma membrane, and what accumulates will not be positioned correctly. Hypothesis II suggests that in the absence of cellulose, a microscopically detectable and sedimentable protein pseudocoat will still form.. The proposal has three aims: 1) To disrupt the gene for the spore coat protein SP87; 2) To isolate the gene for the spore coat protein SP86 and disrupt it; and 3) To disrupt the gene for UDPGPP2, and to investigate the effect of this gene on coat structure. %%% Spore coats and other extracellular matrices protect enclosed cells from unfavorable environments. Although the constituents of a number of these matrices is partially known, knowledge of how this parts fit together, how their proportions are regulated, and how protection occurs is largely derived by speculation. The spore coat of the cellular slime mold Dictyostelium is a good system to study matrices at a molecular level, becaus e it is simple it can be isolated in bulk and in high purity, the genes for a number of its proteins and enzymes for polysaccharide synthesis have been cloned and can be disrupted, and good assays exist for the composition. structure and function of the coat. The results of this investigation will enhance our knowledge about the assembly of walls in plant and fungal cells. ***