Molecular Specificity of Pheromone/Receptor Interactions for Mating in Schizophyllum

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The overall aim of this research is to understand how a simpleeukaryote distinguishes itself from many other nonselves in regulatingmating and development. A specific objective is to elucidate the molecularmechanism by which the B mating-type genes trigger sexual development inthe wood rotting mushroom Schizophyllum commune. The B genes are in twolinked loci, Ba and Bb, each of which has nine different versions, orspecificities, in the world-wide population. A mating pair must bedifferent at either Ba or Bb to be compatible. Analyses of two specificities ofeach locus has revealed genes for pheromones and pheromone receptors similar to those found in other fungi. Each locus contains a single pheromonereceptor gene and several pheromone genes. This multiplicity of pheromoneand receptor genes appears to be unique to the higher basidiomycete fungi.Molecular analyses to date indicate that as few as one or two aminoacid changes in either a pheromone or receptor molecule can be correlatedwith a switch in mate recognition and signaling of sexual. The proposedresearch is divided into three parts: 1) A comprehensive comparison ofsequence and function for a variety of natural and previously generatedmutant variants of pheromones and receptors to identify amino acid residuesin positions relevant to pheromone/receptor interactions. 2) Test theeffects of substituting various amino acids at specific sites that could berelevant to pheromone/receptor recognition for each type of molecule, usingthe methods of site-directed mutagenesis and DNA-mediated transformation inS. commune. 3) Exploit a recently assembled heterologouspheromone-response reporter system in the yeast Saccharomyces cerevisiae togenerate new mutant variants of S. commune pheromones and receptors andefficiently characterize their effects on ligand/receptor interaction.