Fig 1. Deletion mutants in the P/R locus.

A. Organization of the P/R locus of strain CBS 6938 depicting gene clusters P/R1 (blue) and P/R2 (orange). B. Pheromones and pheromone receptors as are expected to be expressed the wild type cells. C. P/R locus genes expressed and sporulation phenotypes of mutants in which one or more P/R locus genes have been deleted. Plus signs (dark green) indicate that formation of basidia and basidiospores was observed, while minus (red) signs denote complete failure of the mutant to sporulate. D. Light microscopy photographs showing an example of positive and negative sporulation phenotypes, as indicated. Letters b and bs denote basidium and basidiospore, respectively. E. and F. Mean number of basidia observed per plate in sporulation proficient mutants after 10 days of incubation in sporulation medium at 18°C. Error bars represent standard deviations from the mean for the three biological replicates. No significant differences were observed between the WT and the sporulation proficient mutants (Student’s T test).