Genetic Approaches to Study Polarity in Plants

在所有细胞中，不对称都与外部信号（如光、重力、邻近细胞等）的梯度有关。这些不对称产生细胞内极性，如具有不同末端的轴，这通常导致后续子细胞的分化。要理解用于解释导致细胞极性变化的环境输入的分子机制，需要一个在细胞、分子和遗传水平上结合实验可追溯性的系统。将普通苔藓植物（如小立Physcomitrella patens）作为探索细胞极性分子基础的优秀模型已经取得了令人印象深刻的进展，主要是因为苔藓是唯一一种同源重组可用于功能遗传学方法的植物系统，即基因敲除和基因替换，可用于确认特定基因在极性过程中的作用。苔藓系统现在是理想的和独特的适合于证实有关蛋白质的性质的假设，例如，分泌系统中的蛋白质和细胞骨架蛋白。以苔藓为模型，我们的主要目标是通过结合分子、细胞和遗传学的方法来识别和证明特定基因在这些极性过程中的功能。在苔藓根尖细胞中，参与极性轴响应重力重新排列的基因将被分离并使用一些随机遗传方法进行鉴定。更有针对性的方法将集中在已经确定的可能在极性中起作用的基因上，例如那些在肌动蛋白细胞骨架动力学中起作用的基因。苔藓系统的特殊特性和本提案中概述的方法将使我们能够识别在生物体最基本的过程之一中发挥重要作用的基因，即细胞不对称如何建立和维持以指导极性发育和模式形成。

0112461QuartranoWithin all cells, asymmetries are found in relation to gradients of external signals such as light, gravity, neighboring cells, etc. These asymmetries generate an intracellular polarity, as axis with different ends, which often results in the differentiation of subsequent daughter cells. To understand the molecular mechanisms used to interpret environmental inputs that bring about changes in cell polarity requires a system that combines experimental tractability at the cellular, molecular and genetic levels. Impressive progress has been made to establish the common moss plant (e.g. Physcomitrella patens) as an excellent model to explore the molecular basis of cellular polarity, primarily because moss is the only plant system in which homologous recombination is available for functional genetic approaches, i.e., gene knockouts and gene replacements, which can be used to confirm the role of a specific gene in polar processes. The moss system is now ideally and uniquely suited to confirm hypotheses concerning the nature of the proteins involved, e.g., proteins in the secretory system and cytoskeletal proteins. Using moss as a model, our main objective is to identify and demonstrate the function of specific genes in these polar processes by a combined molecular, cellular and genetic approach. Genes involved in the realignment of the polar axes in response to gravity in apical cells of moss will be isolated and identified using a number of random genetic approaches. A more targeted approach will focus on genes already identified that are likely to play a role in polarity, e.g. those functioning in actin cytoskeleton dynamics. The particular properties of the moss system and approaches outlined in this proposal will allow us to identify genes that play important roles in one of the most fundamental processes of living organisms, i.e., how cellular asymmetries are established and maintained to direct polar development and pattern formation.