| Title: | Discovery of a modified tetrapolar sexual cycle in Cryptococcus amylolentus and the evolution of MAT in the Cryptococcus species complex |
| Author(s): | Findley K; Sun S; Fraser JA; Hsueh YP; Averette AF; Li W; Dietrich FS; Heitman J; |
| Address: | "Genetics and Molecular Biology Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland, USA" |
| DOI: | 10.1371/journal.pgen.1002528 |
| ISSN/ISBN: | 1553-7404 (Electronic) 1553-7390 (Print) 1553-7390 (Linking) |
| Abstract: | "Sexual reproduction in fungi is governed by a specialized genomic region called the mating-type locus (MAT). The human fungal pathogenic and basidiomycetous yeast Cryptococcus neoformans has evolved a bipolar mating system (a, alpha) in which the MAT locus is unusually large (>100 kb) and encodes >20 genes including homeodomain (HD) and pheromone/receptor (P/R) genes. To understand how this unique bipolar mating system evolved, we investigated MAT in the closely related species Tsuchiyaea wingfieldii and Cryptococcus amylolentus and discovered two physically unlinked loci encoding the HD and P/R genes. Interestingly, the HD (B) locus sex-specific region is restricted ( approximately 2 kb) and encodes two linked and divergently oriented homeodomain genes in contrast to the solo HD genes (SXI1alpha, SXI2a) of C. neoformans and Cryptococcus gattii. The P/R (A) locus contains the pheromone and pheromone receptor genes but has expanded considerably compared to other outgroup species (Cryptococcus heveanensis) and is linked to many of the genes also found in the MAT locus of the pathogenic Cryptococcus species. Our discovery of a heterothallic sexual cycle for C. amylolentus allowed us to establish the biological roles of the sex-determining regions. Matings between two strains of opposite mating-types (A1B1xA2B2) produced dikaryotic hyphae with fused clamp connections, basidia, and basidiospores. Genotyping progeny using markers linked and unlinked to MAT revealed that meiosis and uniparental mitochondrial inheritance occur during the sexual cycle of C. amylolentus. The sexual cycle is tetrapolar and produces fertile progeny of four mating-types (A1B1, A1B2, A2B1, and A2B2), but a high proportion of progeny are infertile, and fertility is biased towards one parental mating-type (A1B1). Our studies reveal insights into the plasticity and transitions in both mechanisms of sex determination (bipolar versus tetrapolar) and sexual reproduction (outcrossing versus inbreeding) with implications for similar evolutionary transitions and processes in fungi, plants, and animals" |
| Keywords: | "Biological Evolution Cryptococcus/*physiology Fungal Proteins/genetics *Genes, Mating Type, Fungal Receptors, Pheromone Spores, Fungal/genetics;" |
| Notes: | "MedlineFindley, Keisha Sun, Sheng Fraser, James A Hsueh, Yen-Ping Averette, Anna Floyd Li, Wenjun Dietrich, Fred S Heitman, Joseph eng R37 AI039115/AI/NIAID NIH HHS/ R01 AI50113-08/AI/NIAID NIH HHS/ 5R01-AI063443-04/AI/NIAID NIH HHS/ R37 AI39115-14/AI/NIAID NIH HHS/ R01 AI050113/AI/NIAID NIH HHS/ P30 AI064518/AI/NIAID NIH HHS/ R01 AI063443/AI/NIAID NIH HHS/ R01 AI039115/AI/NIAID NIH HHS/ Research Support, N.I.H., Extramural 2012/02/24 PLoS Genet. 2012; 8(2):e1002528. doi: 10.1371/journal.pgen.1002528. Epub 2012 Feb 16" |
