Myosin Function in Root Hairs

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

Project Summary All 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).