Cryptococcus neoformans is a major cause of fungal meningitis in predominantly immunocomprised individuals.
Recently it was discovered that C. neoformans can undergo same-sex mating under laboratory conditions, especially between α isolates. Whether same-sex mating occurs in nature and contributes to the current population structure was unknown.
In this study, natural αADα hybrids that arose by fusion between two α 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 SXI1α was also identified as a genetic factor likely involved in this process.
In addition, laboratory-constructed αADα 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.
This study provides the first evidence of this and sheds light on the genetic and environmental factors that play important roles in the evolution of the current population structure of this pathogenic fungus.
Lin X, Litvintseva AP, Nielsen K, Patel S, Floyd A, et al. (2007) áADá hybrids of Cryptococcus neoformans: Evidence of same-sex mating in nature and hybrid fitness. PLoS Genet 3(10): e186. doi:10.1371/journal.pgen.0030186