Myosin Function in Root Hairs

所有细胞都表现出某种形式的极性，这种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尚不清楚。本研究项目旨在揭示细胞极性的维持、分泌产物在细胞内特定位置的传递以及细胞结构的动态维持等方面的基本知识。该项目的中心假设是植物肌球蛋白XI运动蛋白在细胞生长和发育的这些关键方面起着至关重要的作用。根毛是一个很好的实验系统来验证这一假设，因为它们只在顶端生长，同时显示出紧密聚焦的极性和强烈的细胞质流。肌球蛋白XI突变体导致根毛伸长减少而不消除细胞质流动，以前已经确定。目前的工作模型假设这些肌凝蛋白负责将特定的细胞器或分子传递到生长尖端，因此参与维持细胞极性。因此，本项目研究了myosin XI运动蛋白在模式植物拟南芥根毛中的特定细胞功能。较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结构的定量细胞生物学分析以及肌球蛋白定位测定，鉴定MYA1和XI-K在根毛伸长中的作用靶点。(2)通过对cargo-binding domain表面残基的特异性修饰和对相互作用蛋白的一般筛选，鉴定cargo附着于MYA1的机制。这个项目的智力价值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，该项目解决了细胞结构的动态维护，细胞骨架马达在建立细胞极性中的作用，以及将分泌产物输送到生长区域。此外，将开发新的定量方法，对模型细胞类型中的肌球蛋白功能进行全面的细胞，遗传和生化分析。这项工作的广泛影响主要在于培养年轻科学家，主要是两名研究生和一名博士后。继续培养有才能的本科生和高中生，希望吸引他们未来从事科学工作。学生和博士后将与田纳西大学的同事合作，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).