Spore shaping in yeast.
Aleksander Benjak, Michael Knop
Cell Biology and Biophysics, EMBL, Meyerhofstr. 1, Heidelberg, 69117, Germany
During meiosis in Saccharomyces cerevisiae four daughter cells, called spores, are formed. All spores in S. cerevisiae have the same round shape, but the mechanism of producing completely round spores is not known, and it is not known whether the shape of the spores is subject to specific regulation. We identified a novel gene with a function required specifically for shaping the yeast spore. The deletion of the gene does not affect spore formation, but the spores acquire random shapes, with high frequency of elongated (banana-like) spores. The protein itself localizes to filaments along the prospore membrane during prospore membrane assembly, and imunoflorescence microscopy of sporulating cells shows that the protein co-localizes with the septins Spr3p and Cdc3p during early stages of spore assembly. In the deletion mutant, septin-filament formation is prevented, and the localization of the septins to the prosporemembrane is affected. In turn, filament formation of the new protein is also abolished in the septin double mutant Δ spr3 Δ spr28. This demonstrates a mutual dependency of septin filament formation on septins and the new protein. Preliminary imunoprecipitaion experiments show an interaction between the new protein and septins and with components of the leading edge protein coat of the prospore membrane. Taken together, we suggest that shaping of spores in yeast meiosis requires proper septin filament formation.