Golgi Myosin in Higher Plants

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

The secretory system of eukaryotic cells transports macromolecules to the cell surface and lytic compartments of the cell. This transport requires the physical movement of secretory products in membrane-bounded carriers from their site of synthesis to their site of action. In most species, these carriers are small vesicular or tubular transport containers. Plants cells are unique among eukaryotes in that they display rapid, actomyosin-based movements of entire Golgi stacks. This movement raises the possibility that the plant Golgi, a major organelle of the secretory system, also provides long-distance transport functions, in addition to its well-established roles in synthesis, modification, and sorting of secretory products. This project pursues two central goals. The first is to establish the mechanistic basis underlying Golgi stack movements. The second is to test the hypothesis that rapid Golgi stack movements are necessary for proper functioning of the secretory system of plant cells and indirectly play a role in growth and development. The experimental approaches can be broken down into four parts. (1) Identification of myosin motor proteins that localize to Golgi stacks using fusions to fluorescent proteins and isoform-specific antibodies. (2) Isolation of myosin mutants that lack Golgi movements created by reverse genetics, i.e. T-DNA insertion and RNA silencing. (3) Analysis of the phenotype of mutants in Golgi myosin gene(s), particularly the transport efficiency within the secretory system by following marker proteins. (4) Identification of the proteins that mediate cargo attachment for Golgi myosin by both a targeted approach, testing candidate Rab G-proteins, and a general screen using co-immunoprecipitation or the yeast-two hybrid system. Taken together, this project will identify the molecular basis for Golgi stack movement in plant cells as well as test its functional relevance.