Mating-Type-Specific Ribosomal Proteins Control Aspects of Sexual Reproduction in .

The locus of has a bipolar organization characterized by an unusually large structure, spanning over 100 kb. genes have been characterized by functional genetics as being involved in sexual reproduction and virulence. However, classical gene replacement failed to achieve mutants for five genes (, , , , and ), indicating that they are likely essential. In the present study, targeted gene replacement was performed in a diploid strain for both the α and alleles of the ribosomal genes and Mendelian analysis of the progeny confirmed that both and are essential for viability. Ectopic integration of the allele of opposite identity in the heterozygous /αΔ or αΔ mutant strains failed to complement their essential phenotype. Evidence suggests that this is due to differential expression of the genes, and an RNAi-dependent mechanism that contributes to control expression. Furthermore, via CRISPR/Cas9 technology, the alleles were exchanged in haploid α and strains of These exchange strains displayed morphological and genetic defects during bilateral mating. These results contribute to elucidating functions of essential mating type genes that may constitute a type of imprinting system to promote inheritance of nuclei of both mating types.