Regulation of Water-Stress Protein Synthesis

褐藻是一种固氮光合蓝藻，具有耐干燥能力。这种微生物以单丝（连续生长）或聚集体的形式自由生长，其中细胞的丝状组织不明显（无纺丝生长）。无菌体类型的细胞对极端的水分胁迫表现出明显的耐受性，当它们受到反复的干燥和再水化循环时，会积累大量的一类可溶性酸性蛋白质。其中一种水分胁迫蛋白是糖蛋白，另外两种与碳水化合物密切相关。该项目的目的是纯化和生化表征Wsp蛋白和相关碳水化合物，了解蛋白质的合成如何受到水分胁迫的控制，并发现Wsp蛋白在干燥耐受性中的作用。本研究中使用的技术包括细胞在发酵罐中的半连续和同步生长，细胞在惰性固体载体上的固定和生长，蛋白质纯化，蛋白质a金免疫标记，以及固氮实验，包括在水分胁迫下细胞中检测nifH mRNA。关于导致植物生长受水分胁迫抑制的事件顺序，目前还没有一致的意见。这项工作的目的是促进我们对干燥耐受性的理解。因此，鉴于缺水对管理农业成功的影响程度以及水在基因表达中的基本重要性，这项工作具有重要意义。

Nostoc commune is a nitrogen-fixing photosynthetic cyanobacterium with the capacity for desiccation-tolerance. This microorganism grows freely as single filaments (seriate growth) or in aggregates where filamentous organization of the cells is indistinct (aseriate growth). Cells of the aseriate type express a pronounced tolerance to extremes of water stress and accumulate massive amounts of a class of soluble acidic proteins when they are subjected to repeated cycles of drying and rehydration. One of these water stress (Wsp) proteins is a glycoprotein, two others are intimately associated with carbohydrate(s). The aims of this project are to purify and characterize biochemically the Wsp proteins and associated carbohydrates, understand how the synthesis of the proteins is controlled by water stress, and to discover the role of Wsp proteins in desiccation tolerance. Techniques used in this study involve semi-continuous and synchronized growth of cells in a fermenter, immobilization and growth of cells on inert solid supports, protein purification, protein A-gold immunolabelling, and assays for nitrogen fixation including the detection of nifH mRNA in cells subjected to water stress. There is no consensus of opinion on the sequence of events that leads to the suppression of plant growth by waterstress. The objective of this work is to contribute to our understanidng of desiccation tolerance. Consequently, the work is significant in view of the extent to which water deficits impinge upon the success of managed agriculture as well as the fundamental importance of water in gene expression.