What Role Might Non-Mating Receptors Play in ?

The mating-type locus of the tetrapolar basidiomycete encodes pheromones and pheromone receptors in multiple allelic specificities. This work adds substantial new evidence into the organization of the mating-type loci of distantly related strains showing a high level of synteny in gene order and neighboring genes. Four pheromone receptor-like genes were found in the genome of with and located at the mating-type locus, whereas is located separately. Expression analysis of genes in different developmental stages indicates a function in filamentous growth and mating. Based on the extensive sequence analysis and functional characterization of -overexpression mutants, a function of Brl1 in mating is proposed, while Brl3, Brl4 and Brl2 (to a lower extent) have a role in vegetative growth, possible determination of growth direction. The and overexpression mutants had a dikaryon-like, irregular and feathery phenotype, and they avoided the formation of same-clone colonies on solid medium, which points towards enhanced detection of self-signals. These data are supported by localization of Brl fusion proteins in tips, at septa and in not-yet-fused clamps of a dikaryon, confirming their importance for growth and development in .