Abstract
Polarized intracellular trafficking of vesicles and organelles plays a key role in the establishment and maintenance of cell polarity. Saccharomyces cerevisiae has long been an ideal model system for studying polarity establishment because of its amenability to genetics and live imaging. In yeast, the myosin motor protein Myo2 transports Golgi-derived secretory vesicles and organelles along polarized actin cables, moving them from the mother cell to the daughter cell (or bud). However, the details of how organelles such as the Golgi are distributed between the mother and daughter cells have remained unclear. In this thesis work, I studied the spatiotemporal relationship of actin cables and Golgi in the mother cell to understand how cells coordinate actin cable and Golgi dynamics to orchestrate polarized secretion and organelle positioning and movement. I used live-cell imaging and super-resolution fixed cell microscopy to characterize the spatial and temporal relationship between Golgi and actin cables. I found that Golgi are fairly evenly dispersed within mother cells, and that the great majority of Golgi (80%) are in close proximity (within 100 nm) to actin cables. However, most Golgi movements are random (diffusional), interspersed with less frequent, highly directed movements (presumably along actin cables). These observations provide new insights into the relationship between Golgi and actin cables, and raise several new questions for future studies to address.