Cell Adhesion and Fate Determination in Physcomitrella Patens

地球上生命历史上的一个关键里程碑是植物对土地的殖民。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，包括制作专门的结构来固定在土壤中，收集阳光和繁殖，以及能够感知和响应快速变化的环境条件。早期植物是如何做到这一点的，目前在很大程度上尚不清楚。由于苔藓是最早出现的陆地植物之一，因此苔藓是研究植物对陆地适应的极佳物种。P.patens还具有许多使其适合科学研究的特性，包括其体积小、透明的细胞、少量的遗传物质、易于在实验室生长，以及易于使用分子工具进行操作。已经开发出含有突变的苔藓系，使植物恢复到类似于陆地植物祖先绿藻的单细胞有机体。这些植物也比普通的苔藓植物更能承受脱水条件。对这些突变体的研究将为苔藓的正常发育提供线索，也将为早期植物适应土地的机制提供线索。这些研究还对以下方面有影响：1)开发更能抵御干旱的作物，2)开发用于生物燃料生产的藻类品系，这种生产可能更容易收获，方法是设计单个藻类细胞，在受到提示时，它们会粘连在一起。将被检查的苔藓突变体在蛋白质预烯基化方面存在缺陷，这是一种翻译后修饰，将一个脂基添加到特定的目标蛋白质上。这种类脂基团在将蛋白质定向到膜上和蛋白质-蛋白质相互作用中发挥作用。以往的研究发现，苔藓中的苯丙基化缺陷会导致细胞分裂后缺乏细胞黏附，并导致细胞完全缺乏分化。这些苔藓突变体对脱落酸也更敏感，这导致了在脱水条件下更高的生存能力。本项目的目标有三个：1)产生更多在各种类型的蛋白质预烯基化中有缺陷的突变体，2)进一步确定预烯基化在细胞黏附、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，以及3)识别和研究关键的预烯基化靶蛋白在调节细胞黏附和发育过程中的功能作用。苔藓中烯丙基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方面的培训，并将包括学生的广泛参与，特别是那些在科学界代表性不足的群体的参与。

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.