Cell Adhesion and Fate Determination in Physcomitrella Patens

地球生命史上的一个重要里程碑是植物对陆地的殖民。为了完成这一壮举，植物必须以各种方式适应更加恶劣的陆地环境，包括制造专门的结构来锚定土壤，收集阳光，繁殖，以及能够感知和响应快速变化的环境条件。早期的植物是如何做到这一点的仍不得而知。苔藓是最早出现的陆地植物之一，是研究植物适应陆地环境的一个很好的物种。P. patens还具有多种使其适合科学研究的特性，包括其体积小，细胞透明，遗传物质量少，易于在实验室中生长，易于使用分子工具进行操作。苔藓系已经被开发出来，其中包含突变，导致植物恢复到单细胞生物，类似于绿藻，陆地植物的祖先。这些植物也能比普通的苔藓植物更好地承受脱水条件。对这些突变体的研究将为苔藓的正常发育过程提供线索，也将为早期植物适应陆地的机制提供线索。这些研究也对1)开发更能抵抗干旱的作物，以及2)开发用于生物燃料生产的藻类系，这种生物燃料生产可能更容易收获，通过设计单个藻类细胞，使其在受到刺激时粘在一起。将被检查的苔藓突变体在蛋白质前酰化中存在缺陷，这是一种翻译后修饰，在特定的靶蛋白上添加脂质基团。这种脂质基团在将蛋白质靶向膜和蛋白质-蛋白质相互作用中起作用。先前发现，苔藓中戊酰化缺乏导致细胞分裂后缺乏细胞粘附，同时完全缺乏细胞分化。这些苔藓突变体对脱落酸也更敏感，这使得它们在脱水条件下的存活率更高。目前项目的目标有三个方面：1)产生更多的不同类型的蛋白质烯酰化缺陷突变体；2)进一步确定烯酰化在细胞粘附、细胞命运决定、细胞分化、细胞极性和激素反应中的功能作用；3)鉴定和检查关键的烯酰化靶蛋白在介导细胞粘附和发育过程中的功能作用。对苔藓中戊烯酰化的研究将促进我们对许多具有广泛科学意义的重要植物过程的遗传和分子基础的理解。该项目将提供各种实验技术的培训，并将包括学生的广泛参与，特别是那些在科学领域代表性不足的群体的学生。

One of the key milestones in the history of life on earth was the colonization of land by plants. To accomplish this feat, plants had to adapt to the much harsher terrestrial environment in a variety of ways, including making specialized structures for anchoring in soil, gathering sunlight, and reproducing, as well as being able to sense and respond to rapidly changing environmental conditions. How early plants were able to do this remains largely unknown. The moss Physcomitrella patens is an excellent species in which to study plant adaption to land, since mosses are among the earliest-arising land plants. P. patens also has a variety of properties that make it amenable to scientific study, including its small size, transparent cells, small amount of genetic material, ease of growth in the laboratory, and ease of manipulation using molecular tools. Moss lines have been developed that harbor mutations causing the plants to revert to single-celled organisms resembling green algae, the progenitor of land plants. These plants also are able to withstand dehydrating conditions better than normal moss plants. Studies of these mutants will give clues into how normal development of moss proceeds, but also what mechanisms early plants used to adapt to land. These studies also have implications for 1) developing crops that are better able to withstand drought, and 2) developing algae lines to be used in biofuel production that might be easier to harvest, by engineering individual algae cells that will stick together when prompted. The moss mutants that will be examined are defective in protein prenylation, which is a post-translational modification that adds a lipid group to particular target proteins. This lipid group plays a role in targeting the protein to membranes and in protein-protein interactions. It was previously found that prenylation deficiencies in moss resulted in a lack of cell adhesion after cell division, along with a complete lack of cell differentiation. These moss mutants were also more sensitive to abscisic acid, which resulted in higher survivability under dehydrating conditions. The goals of the current project are threefold: 1) to generate additional mutants defective in various types of protein prenylation, 2) further determine the functional roles of prenylation in cell adhesion, cell fate determination, cell differentiation, cell polarity, and hormone responses, and 3) identify and examine the functional role of key prenylation target proteins in mediating cell adhesion and developmental processes. Studies of prenylation in moss will advance our understanding of the genetic and molecular basis of many important plant processes of broad scientific interest. This project will provide training in a wide variety of experimental techniques, and will include extensive participation by students, especially those from groups underrepresented in the sciences.