The Mechanism of Glycine Betaine Mediated Cellular Osmoregulation

这项提案要求资金支持一项关于调节细胞内渗透调节物质甘氨酸甜菜碱浓度以应对高渗透胁迫的机制的研究。甘氨酸甜菜碱是一种极其常见和重要的渗透调节剂，存在于从细菌到动植物的各种物种中。虽然关于盐度诱导甘氨酸甜菜碱在细菌中的调节已知很多，但对其在植物中的调节知之甚少，在动物中的调节更是少之又少。我们发现，大西洋沿岸的牡蛎(Cassostrea Virgiica)在高渗透胁迫后利用大量的甘氨酸甜菜碱来调节细胞内的渗透浓度。切萨皮克湾的同种牡蛎含有的甘氨酸甜菜碱水平要小得多，这种甜菜碱在高盐度胁迫后不会改变，而且海湾牡蛎对盐度的耐受性较差。由于线粒体通常是甘氨酸甜菜碱合成的场所，这些结果表明这两种牡蛎在线粒体水平上是不同的。这项提议包含的实验旨在通过比较盐度诱导海湾牡蛎和大西洋牡蛎合成甘氨酸甜菜碱的机制的几个方面来测试这种可能性。这一结果将有助于理解甘氨酸甜菜碱的调控，此外，还应该解决牡蛎种群之间的差异是基于遗传还是基于环境。

This proposal requests funds to support a study of the mechanisms that regulate the concentration of the intracellular osmolyte, glycine betaine, in response to hyperosmotic stress. Glycine betaine is an extremely common and important osmolyte in a wide variety of species ranging from bacteria to plants and animals. Although a great deal is known about the salinity induced regulation of glycine betaine in bacteria, far less is known about its regulation in plants and even less in animals. We have found that oysters (Cassostrea virginica) from the Atlantic coast utilize substantial amounts of glycine betaine to regulate intracellular osmotic concentrations following hyperosmotic stress. Conspecific oysters from the Chesapeake Bay have much smaller levels of glycine betaine that do not change following high salinity stress, and the Bay oysters are not as salinity tolerant. Since the mitochondrion is usually the site of glycine betaine synthesis, these results suggest that these two populations of oysters differ at the mitochondrial level. This proposal contains experiments designed to test that possibility by comparing several aspects of the mechanism of salinity induced glycine betaine synthesis between the Bay and Atlantic oysters. The results will contribute a great deal to the understanding of glycine betaine regulation and, in addition, should resolve whether the differences between the oyster populations are genetic or environmentally founded.