The Mechanism of Glycine Betaine Mediated Cellular Osmoregulation-Revision 2

皮尔斯9604679这项提案要求资金继续研究调节细胞内渗透调节物质甘氨酸甜菜碱浓度的机制，以应对高盐胁迫。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。虽然人们对盐度诱导的甜菜碱在细菌中的调节知之甚少，但对其在植物中的调节知之甚少，对动物的调节更是知之甚少。PI以前发现，大西洋沿岸的牡蛎(Crassostrea Virgiica)在高盐度胁迫后利用大量的甘氨酸甜菜碱来调节细胞内渗透浓度。切萨皮克湾的同种牡蛎的甘氨酸甜菜碱水平要小得多，这种甜菜碱不会随着盐度胁迫而改变，而且海湾牡蛎对盐度的耐受性也不高。此外，PI以前的工作表明，甘氨酸甜菜碱积累和耐盐性差异的基础在于线粒体中的合成途径。此外，在细菌和植物中，盐度诱导的甘氨酸甜菜碱积累受渗透激活的一系列基因调控。对动物的渗透激活基因几乎一无所知。这个项目中描述的实验计划利用大西洋牡蛎和海湾牡蛎在甘氨酸甜菜碱代谢方面的差异，以开始了解这种重要的、但很少被研究的渗透分子如何在动物细胞中受到调控。此外，由于所有海湾牡蛎都是由单孢子虫寄生虫Perkinsus marinas寄生的，这种寄生虫已经摧毁了海湾牡蛎渔业，初步实验将集中在这种寄生虫导致两个牡蛎种群之间的生化差异的可能性上。这些结果将有助于理解甘氨酸甜菜碱的调节、耐盐机制、细胞渗透调节，并可能揭示该寄生虫对牡蛎代谢的一些生化后果。

Pierce 9604679 This proposal requests funds to continue a study of the mechanisms that regulate the concentration of the intracellular osmolyte, glycine betaine, in response to high salinity 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. The PI had found previously that oysters (Crassostrea virginica) from the Atlantic coast utilize substantial amounts of glycine betaine to regulate intracellular osmotic concentrations following high salinity stress. Conspecific oysters from the Chesapeake Bay have much smaller levels of glycine betaine that do not change following salinity stress and the Bay oysters are not as salinity tolerant. In addition, the PI's previous work has indicated that the basis of this difference in glycine betaine accumulation and salinity tolerance lies within synthetic pathways that reside in the mitochondria. Furthermore, in bacteria and plants, salinity-induced glycine betaine accumulation is regulated by a family of genes that is osmotically-activated. Almost nothing is known about osmotically activated genes in animals. The experiments described in this project propose to exploit the differences between Atlantic and Bay oysters in glycine betaine metabolism to begin to understand how this important, but scarcely studied osmolyte is regulated in animals cells. Further, since all of the Bay oysters are parasitized by the haplosporidian parasite, Perkinsus marinas, which has devastated the Bay oyster fishery, the initial experiments will focus on the possibility that the parasite is causing the biochemical differences between the two oyster groups. The results will contribute a great deal to the understanding of glycine betaine regulation, salinity tolerance mechanis ms, cellular osmoregulation and, perhaps, uncover some of the biochemical consequences of that parasite on oyster metabolism.