REMODELING OF THE SECRETORY PATHWAY AND CELL POLARITY MACHINERY IN DIVIDING AND ENVIRONMENTALLY STRESSED SCHIZOSACCHAROMYCES POMBE CELLS

Abstract

Cellular polarity underlies various aspects of life including morphogenesis, differentiation and proliferation. The fission yeast Schizosaccharomyces pombe is a highly polarized eukaryote that maintains rod-shaped morphology by restricting growth to cell tips and dividing through formation of an equatorial septum. I show that upon heat-stress, cells transiently lose polarity in a process likely regulated at the level of the GTPase Cdc42. I identify a chaperone cascade that modulates the heat-stress-associated transcription to eventually correct the growth pattern in fission yeast adapting to elevated temperatures. Targeting of secretory vesicles promotes polarized growth and cytokinesis but the dynamics of the upstream secretory apparatus remain unexplored. I characterize the spatiotemporal distribution of Schizosaccharomyces pombe secretion machinery and find that it exhibits marked polarization to the division site. The enrichment of the transitional endoplasmic reticulum and Golgi cisternae at the division site require actomyosin ring assembly and function of the EFC-domain protein Cdc15.