Analysis of mating-type genes, pheromones and pheromone receptors
In fungi, sexual reproduction occurs between morphologically indistinguishable partners that are not differentiated into male and female sexes. The term mating type (MAT) is therefore used to differentiate single spore strains of the same species that are sexually compatible. Compatible partners are only distinguished by their mating type (MAT) and the sexual reproduction is controlled by genes that reside in the mating-type locus. Mating-type genes of fungi encode transcription factors which are master regulators of fertilization and sexual development. They often regulate pheromones and pheromone receptors. By reverse genetics approaches we analyze how mating-types pheromone and pheromone receptors contribute to the sexual development of filamentous ascomycetes. In a large number of filamentous ascomycetes, sexual reproduction is supposedly absent. However, mating-type sequences were isolated from several of these fungi by means of heterologous PCR, and the recent sequencing and annotation of complete genomes from more than 180 filamentous fungi and yeasts serves as a rich resource for predicting sexual cycles in species which so far were believed to propagate exclusively asexually Utilizing knowledge of mating-type gene organization we were recently able to describe conditions under which a sexual cycle can be induced in the Penicillin producer Penicillium chrysogenum. The newly identified sexual cycle was used for strain development purposes, generating offspring with novel combinations of traits relevant to penicillin production.