Genetic Analysis of a Hybrid Cross between Cryptococcus neoformans and Cryptococcus deneoformans

Abstract

Cryptococcus neoformans is a deadly human fungal pathogen that primarily affects immunocompromised individuals. Matings with the closely related species Crypto- coccus deneoformans produce viable, yet atypical offspring. Previous research has demonstrated that the hybrids are aneuploid or diploid, and have low germination rates and suppressed recombination. In addition, numerous large-scale genomic re- arrangements have been identified between C. deneoformans and C. neoformans. We conducted a cross between CDC15, a clinical drug-resistant isolate of C. neoformans and JEC20, a laboratory derived strain of C. deneoformans. We collected 230 hy- brid progeny and determined their genotypes using codominant PCR-RFLP markers. Three separate analyses were conducted in order to better understand the genet- ics of these hybrids. These revealed that there is mitotic recombination during the production of the hybrids, that there are genetic incompatibilities between C. neofor- mans and C. deneoformans, and that differences between the two species in virulence- related traits are controlled by multiple quantitative genetic loci. The results not only improve our understanding of the hybrid progeny themselves, but also of Cryptococcus in general.