Myosin Function in Root Hairs

项目摘要所有细胞都表现出某种形式的极性，表现为特定分子或细胞器的不对称分布，但驱动细胞极性的机制仍不清楚。这项研究项目旨在揭示关于维持细胞极性、将分泌产物输送到细胞内特定位置以及动态维持细胞结构的基本知识。该项目的中心假设是，植物肌球蛋白XI马达蛋白在细胞生长和发育的这些关键方面发挥着关键作用。根毛是检验这一假说的一个很好的实验系统，因为它们只在根尖生长，同时显示出紧密聚焦的极性和强烈的细胞质流动。肌球蛋白XI突变体可以在不消除细胞质流动的情况下导致根毛发伸长减少，此前已经被发现。目前的工作模型假设，这些肌球蛋白负责将特定的细胞器或分子输送到生长的顶端，因此参与了细胞极性的维持。因此，本项目研究模式植物拟南芥根毛中肌球蛋白XI马达蛋白的特定细胞功能。这个更大的项目大致分为两个具体目标。(1)通过细胞器运动和根毛构型的定量细胞生物学分析以及肌球蛋白定位的测定，确定MYA1和XI-K在根毛伸长中的靶标。(2)通过对货物结合区表面残基的特定修饰和蛋白质相互作用的一般筛选来鉴定货物与MYA1的结合机制。该项目的智力优势在于对基本细胞生物学过程的新见解，这将是研究的结果。特别是，该项目涉及细胞结构的动态维持、细胞骨架马达在确定细胞极性中的作用以及将分泌产物运送到生长区域。此外，还将开发新的定量方法，用于在模型细胞类型中对肌球蛋白功能进行全面的细胞、遗传和生化分析。这项工作的更广泛影响主要在于对年轻科学家的培训，主要是两名研究生和一名博士后助理。将继续培训有才华的本科生和高中生，希望吸引他们走向科学的未来。学生和博士后将与田纳西大学的同事合作，并在全国会议上展示他们的发现。这项工作的结果将发表在同行评议的期刊上，并在实验室网站(http://www.bio.utk.edu/cellbiol).)上向更广泛的受众提供

Project SummaryAll cells display some form of polarity which manifests itself in an asymmetric distribution of specific molecules or organelles, yet the mechanisms driving cell polarity remain obscure. This research project seeks to reveal fundamental knowledge surrounding the maintenance of cell polarity, the delivery of secretory products to specific locations within the cell, and the dynamic maintenance of cell architecture. The central hypothesis of this project is that plant myosin XI motor proteins play a crucial role in these critical aspects of cell growth and development. Root hairs are an excellent experimental system to test this hypothesis since they grow only at their tip and simultaneously display tightly focused polarity and strong cytoplasmic streaming. Myosin XI mutants that lead to reduced root hair elongation without eliminating cytoplasmic streaming have been identified previously. A current working model assumes that these myosins are responsible for the delivery of specific organelles or molecules to the growing tip and are therefore involved in maintenance of cell polarity. Thus, this project investigates the specific cellular functions of myosin XI motor proteins in root hairs of the model plant Arabidopsis thaliana. The larger project falls broadly into two Specific Aims. (1) Identification of the targets of MYA1 and XI-K in root hair elongation by quantitative cell biological analysis of organelle motility and root hair architecture as well as determination of myosin localization. (2) Identification of the mechanism of cargo attachment to MYA1 by specific modification of surface residues of the cargo-binding domain and by a general screen for interacting proteins.The intellectual merit of this project lies in the new insights into fundamental cell biological processes that will be obtained as a result of the research. In particular, this project addresses the dynamic maintenance of cell architecture, the role of cytoskeletal motors in establishing cell polarity, and the delivery of secretory products to regions of growth. In addition, novel quantitative methods for the comprehensive cellular, genetic, and biochemical analysis of myosin function in a model cell type will be developed. The broader impact of the work rests predominantly on the training of young scientists, primarily two graduate students and a postdoctoral associate. The training of talented under-graduate students as well as high school students will be continued in hopes of attracting them to a future in science. Students and postdocs will collaborate with colleagues here at the University of Tennessee and present their findings at national meetings. The results of this work will be published in peer-reviewed journals and made available to a broader audience on the lab web site (http://www.bio.utk.edu/cellbiol).