Although most cells contain a similar set of organelles, the internal architecture of a particular cell type can be highly distinctive and reflect the specific properties of the cell. How do cells build and organize their internal structures appropriately? Sporulating cells of the yeast Saccharomyces cerevisiae are a particularly amenable model system in which to study this question. During sporulation, a yeast cell undergoes a dramatic remodeling of its internal architecture to develop from a single diploid cell into an ascus containing four separate haploid spores. This process can be easily induced in the laboratory and takes less than 24 hours to complete. Sporulation occurs in diploid cells upon nutritional starvation and involves meiosis followed by spore morphogenesis. Spore morphogenesis involves the de novo synthesis of a double-layered prospore membrane that grows to surround each of the meiotic products, followed by deposition of the four-layered spore wall into the lumen of the prospore membrane. This project will use S. cerevisiae to examine how cellular organization is regulated by signal transduction systems. The long-term goal is to understand how cells regulate their internal architecture. This research seeks to understand the signaling mechanisms that regulate the dramatic reorganization of cellular architecture that occurs as yeast cells sporulate. This project will investigate how the MAP kinase Smk1 and the STE20-family kinase Ste20 regulate spore morphogenesis. Preliminary studies suggest Smk1 regulates spore morphogenesis by acting as a negative regulator of Gsc2, a component of 1,3-beta-glucan synthase, an enzyme important for spore wall synthesis. These will further examine regulation of 1,3-beta-glucan synthase during spore morphogenesis by using molecular genetic techniques to probe the mechanism by which Smk1 negatively regulates Gsc2. The potential role of inositol phosphates in Sps1 signaling will be investigated by examining the function of a regulator of inositol phosphate metabolism that preliminary studies suggest may interact with Sps1. These experiments should both provide information about the organization of spore morphogenesis and contribute insights as to how signaling mechanisms are utilized to regulate cellular architecture. Broader impact of this work: The University of Massachusetts Boston is the only public university in the Boston metropolitan area. The students at this campus are the most diverse university student population in New England, and include a high percentage of underrepresented minority students (approximately 35%, which is higher than any other four year institution in the New England area) as well as non-traditional students (the average age of our undergraduates is 27 years old). This project is designed with the intent to provide training for the diverse and talented pool of both undergraduate and graduate students at the University of Massachusetts Boston.
