Heterologous expression of mating type genes in basidiomycetes

Abstract

Mating type genes in basidiomycetes encode two types of transcription factors (HD1 and HD2) and pheromones and pheromone receptors. Usually, mating type genes are so dissimilar in DNA sequence (allelic genes and genes from different species) that they do not cross-hybridize. In homobasidiomycetes, directly next to the A mating type locus encoding the transcription factors is a highly conserved gene mip that allows positional cloning. A candidate gene for positional cloning of the B mating type genes encoding the pheromone-pheromone receptor system is cla4/ste20. With more and more mating type loci cloned from different species, evolution of these loci and their genes can be addressed by sequence analysis and by function by transformation into other species, here Coprinopsis cinerea. Transformation of cloned mating type genes into heterologous hosts can lead to activation of mating type controlled development. Heterologous expression of mating type genes is especially interesting for species in which no transformation system exists. Since in C. cinerea an A null-mutant is available without functional transcription factor genes, self-compatibility of cloned A genes from homothallic species can also be tested.