Myosin Function in Root Hairs

所有细胞都显示出某种形式的极性，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然不清楚。该研究项目旨在揭示细胞极性维持的基础知识，将分泌产物输送到细胞内的特定位置，以及细胞结构的动态维持。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起着至关重要的作用。根毛是一个很好的实验系统，以测试这一假设，因为他们只生长在他们的尖端，同时显示紧密集中的极性和强大的细胞质流。先前已经鉴定了导致根毛伸长减少而不消除细胞质流的肌球蛋白Xi突变体。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递送到生长尖端，因此参与细胞极性的维持。因此，本研究以拟南芥为模式植物，探讨其根毛中肌球蛋白Xi马达蛋白的细胞功能。这个较大的项目福尔斯大致分为两个具体目标。(1)通过定量细胞生物学分析细胞器运动性和根毛结构以及肌球蛋白定位确定MYA 1和XI-K在根毛伸长中的靶点。(2)通过对货物结合域表面残基的特异性修饰和对相互作用蛋白质的一般筛选，鉴定货物附着于MYA 1的机制。该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，以及分泌产物向生长区域的输送。此外，将开发新的定量方法，用于模型细胞类型中肌球蛋白功能的全面细胞、遗传和生化分析。这项工作的更广泛影响主要在于培训年轻科学家，主要是两名研究生和一名博士后助理。将继续培养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审的期刊上，并在实验室网站（http：//www.bio.utk.edu/cellbiol）上提供给更广泛的受众。

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).