Molecular Regulation and Transport of Sterols in Plants

植物甾醇是一组复杂的化合物，对植物生长发育的许多方面都是必不可少的，对动物和人类的营养贡献也是相当重要的。因此，人们对甾醇生物合成途径的生物化学和分子生物学进行了深入的研究，这并不令人惊讶。然而，人们对植物中这一生化途径的调控知之甚少。我们对甾醇代谢的长期研究的一个目标一直集中在角鲨烯合成酶的调节上，角鲨烯合成酶是甾醇生物合成酶中的一个关键酶。我们最近的研究结果表明，角鲨烯合成酶基因的表达和酶活性定位于茎分生组织。在试图将这些结果与文献中已经报道的结果相一致时，最合乎逻辑的解释是，固醇生物合成本身局限于这个组织。这一解释表明，甾醇生物合成的调节发生在茎分生组织中，这是一个以前没有被评价过的组织，而且必须存在从顶端分生组织向整个植物移动甾醇的星醇运输系统。我们提出了一些实验来验证这些预测，这些实验包括：1，评估定位于茎分生组织中的固醇生物合成是否受到调控；2，开发一种测试植物中固醇长途运输的方法；3，确定NPC1，一种参与胆固醇吸收和细胞内运输的高度保守的蛋白质，是否在植物中发挥与动物相似的作用。这项拟议的工作将涉及本科生和研究生以及博士后助理，应该为如何利用新兴技术设计这条途径以提高价值提供重要的见解。

Plant sterols represent a complex array of chemical compounds that areessential for many facets of plant growth and development, and are ofconsiderable importance for their nutritional contributions to animals andman. Hence, it is not surprising that the biochemistry and molecularbiology of the sterol biosynthetic pathway has been intensively studied.Nonetheless, very little is actually known about the regulation of thisbiochemical pathway in plants. One goal of our long-term research in sterolmetabolism has been focussed on the regulation of squalene synthase, a keyenzyme in sterol biosynthetic enzyme. Our recent results suggest thatsqualene synthase gene expression and enzyme activity are localized toshoot meristems. In attempting to reconcile these results with thosealready reported in the literature, the most logical interpretation is thatsterol biosynthesis itself is localized to this tissue. This interpretationimplies that regulation of sterol biosynthesis occurs in the shootmeristem, a tissue that has not been evaluated as such before, and that asterol transport system for the movement of sterol from the apical meristemthroughout the plant must exist. Experiments to test these predictions areproposed and include: 1, an evaluation if sterol biosynthesis localized tothe shoot meristem is regulated; 2, the development of a test for longdistance transport of sterol within plants; and 3, a determination if NPC1,a highly conserved protein involved in cholesterol uptake and intracellulartrafficking, plays a similar role in plants as in animals. The proposedwork, which will involve undergraduate and graduate students and apostdoctoral associate, should provide important insights into how thispathway might be engineered for enhanced value using emerging technologies.