Analysis of a MAP kinase in Yeast that is Required for Spore Development

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Winter 9630656 A large amount of signal transduction in eukaryotic cells depends on conserved kinase cascades that activate a family of enzymes called mitogen activated protein (MAP) kinases. MAP kinases are required for adaptive responses to changes in the environment, proliferative responses to mitogens, and differentiative responses to signals that occur during development. SMKI, encodes a developmentally regulated MAP kinase that is required for sporulation in Saccharomyces cerevisiae. Sporulation in yeast represents an excellent model system with which to study developmental processes. Similar to differentiation programs in higher eukaryotic cells, induction is controlled by a combination of cell-type and environmental signals. Once initiated, a precisely controlled, transient expression pattern is observed for sporulation-specific genes that ultimately leads to a cell (or spore) that is both genetically and biochemically distinct from its precursor. Molecular and cytological analysis show that the early sporulation program (including meiosis I and II) occurs normally in homozygous smk1 diploids. However, both microscopic and functional assays show that smk1 asci are defective for executing spore wall morphogenesis and subsequent developmental events. A collection of conditional and partial-function smk1 alleles have already been isolated that display a variety of distinct developmental defects. We will characterize the developmental and morphogenetic defects of different smk1 alleles. The biochemical defects of the corresponding mutant Smk1 pathway using dosage suppression approaches in selected smk1 genetic backgrounds. The high degree of evolutionary conservation in MAP kinase signaling pathways make it likely that this study will provide fundamental insights into the role of these signaling pathways in coordinating developmental processes in a wide variety of organisms.