A Gip1p-Glc7p phosphatase complex regulates septin organization and spore wall formation

Sporulation of Saccharomyces cerevisiae is a developmental process in which a single cell is converted into four haploid spores. GIP1, encoding a deve lopmentally regulated protein phosphatase 1 interacting protein, is require d for spore formation. Here we show that GIP1 and the protein phosphatase 1 encoded by GLC7 play essential roles in spore development. The gip1 Delta mutant undergoes meiosis and prospore membrane formation normally, but is s pecifically defective in spore wall synthesis. We demonstrate that in wild- type cells, distinct layers of the spore wall are deposited in a specific t emporal order, and that gip1 Delta cells display a discrete arrest at the o nset of spore wall deposition. Localization studies revealed that Gip1p and Glc7p colocalize with the septins in structures underlying the growing pro spore membranes. Interestingly, in the gip1 Delta mutant, not only is Glc7p localization altered, but septins are also delocalized. Similar phenotypes were observed in a glc7-136 mutant, which expresses a Glc7p defective in i nteracting with Gip1p. These results indicate that a Gip1p-Glc7p phosphatas e complex is required for proper septin organization and initiation of spor e wall formation during sporulation.