The Mechanism of Glycine Betaine Mediated Cellular Osmoregulation-Revision 2

该提案要求资金继续研究在高盐度胁迫下调节细胞内渗透物甘氨酸甜菜碱浓度的机制。甜菜碱是一种极其常见和重要的渗透物，存在于从细菌到植物和动物的各种物种中。虽然我们对细菌中盐诱导的甜菜碱调节已经了解得很多，但对其在植物中的调节知之甚少，对动物的调节就更少了。PI先前发现，大西洋沿岸的牡蛎（Crassostrea virginica）在高盐度胁迫下利用大量的甘氨酸甜菜碱来调节细胞内渗透浓度。来自切萨皮克湾的同种牡蛎的甘氨酸甜菜碱含量要低得多，在盐度胁迫下不会改变，而且海湾牡蛎的耐盐性也不高。此外，PI先前的工作表明，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，盐诱导的甜菜碱积累是由一个渗透激活的基因家族调节的。我们对动物体内的渗透激活基因几乎一无所知。本项目中描述的实验建议利用大西洋和海湾牡蛎在甘氨酸甜菜碱代谢方面的差异，开始了解这种重要但很少研究的渗透物是如何在动物细胞中调节的。此外，由于所有的海湾牡蛎都寄生于单孢子虫，Perkinsus marinas，这种寄生虫摧毁了海湾牡蛎渔业，最初的实验将集中在寄生虫导致两种牡蛎种群之间生化差异的可能性上。该结果将有助于理解甜菜碱调节、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.