αADα hybrids of Cryptococcus neoformans: Evidence of same-sex mating in nature and hybrid fitness

Xiaorong Lin, Anastasia P. Litvintseva, Kirsten Nielsen, Sweta Patel, Anna Floyd, Thomas G. Mitchell, Joseph Heitman

Research output: Contribution to journalArticlepeer-review

112 Scopus citations

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, α and a. However, the overwhelming predominance of mating type (MAT) α over a in C. neoformans populations limits α-a mating in nature. Recently it was discovered that C. neoformans can undergo samesex 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.

Original languageEnglish (US)
Pages (from-to)1975-1990
Number of pages16
JournalPLoS genetics
Volume3
Issue number10
DOIs
StatePublished - Oct 2007
Externally publishedYes

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