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化。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，收集阳光和繁殖，以及能够感知和应对快速变化的环境条件。早期的植物是如何做到这一点的，在很大程度上仍然未知。小立碗藓是最早出现的陆生植物之一，是研究植物对土地适应性的一个很好的物种。 P. patens还具有多种特性，使其适合科学研究，包括其小尺寸，透明细胞，少量遗传物质，易于在实验室中生长，以及易于使用分子工具进行操作。已经开发出了苔藓品系，其含有突变，导致植物恢复成类似陆地植物的祖先绿色藻类的单细胞生物体。这些植物也能够承受脱水条件比正常苔藓植物更好。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1）开发能够更好地抵御干旱的作物，以及2）开发用于生物燃料生产的藻类品系，这些藻类品系可能更容易收获，通过设计个体藻类细胞，这些细胞在受到提示时会粘在一起。将被检查的苔藓突变体在蛋白质异戊烯化中是有缺陷的，异戊烯化是一种翻译后修饰，其将脂质基团添加到特定的靶蛋白。该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，苔藓中异戊二烯化缺陷导致细胞分裂后缺乏细胞粘附，沿着完全缺乏细胞分化。这些苔藓突变体对脱落酸也更敏感，这导致在脱水条件下的存活率更高。本项目的目标有三个方面：1）产生不同类型蛋白质异戊二烯化缺陷的额外突变体，2）进一步确定异戊二烯化在细胞粘附、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，以及3）鉴定和检查关键异戊二烯化靶蛋白在介导细胞粘附和发育过程中的功能作用。苔藓中异戊二烯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，特别是那些来自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.