title: alpha AD alpha hybrids of Cryptococcus neoformans: evidence of same-sex mating in nature and hybrid fitness.
abstract: Cryptococcus neoformans is a ubiquitous human fungal pathogen that causes meningoencephalitis in predominantly immunocompromised hosts. The fungus is typically haploid, and sexual reproduction involves two individuals with opposite mating types/sexes, alpha and a. However, the overwhelming predominance of mating type (MAT) alpha over a in C. neoformans populations limits alpha-a mating in nature. Recently it was discovered that C. neoformans can undergo same-sex mating under laboratory conditions, especially between alpha isolates. Whether same-sex mating occurs in nature and contributes to the current population structure was unknown. In this study, natural alpha AD alpha hybrids that arose by fusion between two alpha cells of different serotypes (A and D) were identified and characterized, providing definitive evidence that same-sex mating occurs naturally. A novel truncated allele of the mating-type-specific cell identity determinant SXI1 alpha was also identified as a genetic factor likely involved in this process. In addition, laboratory-constructed alpha AD alpha strains exhibited hybrid vigor both in vitro and in vivo, providing a plausible explanation for their relative abundance in nature despite the fact that AD hybrids are inefficient in meiosis/sporulation and are trapped in the diploid state. These findings provide insights on the origins, genetic mechanisms, and fitness impact of unisexual hybridization in the Cryptococcus population.
authors.affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Lin
authors.forename: Anastasia P
authors.initials: AP
authors.lastname: Litvintseva
authors.forename: Kirsten
authors.initials: K
authors.lastname: Nielsen
authors.forename: Sweta
authors.initials: S
authors.lastname: Patel
authors.forename: Anna
authors.initials: A
authors.lastname: Floyd
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Mitchell
authors.forename: Joseph
authors.initials: J
authors.lastname: Heitman
mesh_terms: D000483:Alleles; D000818:Animals; D000946:Antigens, Fungal / Q000235:genetics*; D003433:Crosses, Genetic; D003453:Cryptococcosis / Q000382:microbiology*; D003455:Cryptococcus neoformans / Q000235:genetics*; D004171:Diploidy; D049770:Genes, Mating Type, Fungal; D014644:Genetic Variation; D006238:Haploidy; D051379:Mice; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D011110:Polymorphism, Genetic
chemical_list: D000946:Antigens, Fungal