Two pheromone precursor genes are transcriptionally expressed in the homothallic ascomycete Sordaria macrospora

In order to analyze the involvement of pheromones in cell recognition and m ating in a homothallic fungus, two putative pheromone precursor genes, name d ppg1 and ppg2, were isolated from a genomic library of Sordaria macrospor a. The ppg1 gene is predicted to encode a precursor pheromone that is proce ssed by a Kex2-like protease to yield a pheromone that is structurally simi lar to the alpha-factor of the yeast Saccharomyces cerevisiae. The ppg2 gen e encodes a 24-amino-acid polypeptide that contains a putative farnesylated and carboxy methylated C-terminal cysteine residue. The sequences of the p redicted pheromones display strong structural similarity to those encoded b y putative pheromones of heterothallic filamentous ascomycetes. Both genes are expressed during the life cycle of S. macrospora. This is the first des cription of pheromone precursor genes encoded by a homothallic fungus. Sout hern-hybridization experiments indicated that ppg1 and ppg2 homologues are also present in other homothallic ascomycetes.