The dual-specificity protein phosphatase Yvh1p acts upstream of the protein kinase Mck1p in promoting spore development in Saccharomyces cerevisiae

Diploid Saccharomyces cerevisiae cells induce YVH1 expression and enter the developmental pathway, leading to sporulation when starved for nitrogen. W e show that yvh1 disruption causes a defect in spore maturation; overexpres sion of MCK1 or IME1 suppresses this yvh1 phenotype. While mck1 mutations a re epistatic to those in yvh1 relative to spore maturation, overexpression of MCK1 does not suppress the yvh1 slow-vegetative-growth phenotype. We con clude that (i) Yvh1p. functions earlier than Mck1p and Ime1p in the signal transduction cascade that regulates sporulation and is triggered by nitroge n starvation and (ii) the role of Yvh1p in gametogenesis can be genetically distinguished from its role in vegetative growth.