In fungi, unisexual reproduction, where sexual development is initiated without the presence of two compatible mating type alleles, has been observed in several species that can also undergo traditional bisexual reproduction, including the important human fungal pathogens Cryptococcus neoformans and Candida albicans . While unisexual reproduction has been well characterized qualitatively, detailed quantifications are still lacking for aspects of this process, such as the frequency of recombination during unisexual reproduction, and how this compares with bisexual reproduction. Here, we analyzed meiotic recombination during α-α unisexual and a -α bisexual reproduction of C. neoformans . We found that meiotic recombination operates in a similar fashion during both modes of sexual reproduction. Specifically, we observed that in α-α unisexual reproduction, the numbers of crossovers along the chromosomes during meiosis, recombination frequencies at specific chromosomal regions, as well as meiotic recombination hot and cold spots, are all similar to those observed during a -α bisexual reproduction. The similarity in meiosis is also reflected by the fact that phenotypic segregation among progeny collected from the two modes of sexual reproduction is also similar, with transgressive segregation being observed in both. Additionally, we found diploid meiotic progeny were also produced at similar frequencies in the two modes of sexual reproduction, and transient chromosomal loss and duplication likely occurs frequently and results in aneuploidy and loss of heterozygosity that can span entire chromosomes. Furthermore, in both α-α unisexual and a -α bisexual reproduction, we observed biased allele inheritance in regions on chromosome 4, suggesting the presence of fragile chromosomal regions that might be vulnerable to mitotic recombination. Interestingly, we also observed a crossover event that occurred within the MAT locus during α-α unisexual reproduction. Our results provide definitive evidence that α-α unisexual reproduction is a meiotic process similar to a -α bisexual reproduction. Author Summary Unisexual reproduction has been reported in several fungal species that have been traditionally thought to undergo bisexual reproduction, including major human fungal pathogens such as Cryptococcus neoformans and Candida albicans . While it has been well characterized qualitatively, quantitative description of unisexual reproduction, and detailed comparisons between unisexual and bisexual reproduction, are lacking. Here, by analyzing meiotic progeny generated from both α-α unisexual and a -α bisexual reproduction in C. neoformans , we find that the progeny collected from the two modes of sexual reproduction show similar phenotypic segregation, with transgressive segregation of several phenotypes being observed in both. Additionally, the two modes of sexual reproduction are similar in all the aspects of meiotic recombination that we have examined, providing definitive evidence that α-α unisexual reproduction is a meiotic process that operates similarly as in a -α bisexual reproduction. The ability to undergo both unisexual and bisexual reproduction may provide evolutionary advantages in environments where suitable mating partners are scarce, or where sexual reproduction is favored over asexual reproduction by mixing genetic materials and producing spores that are more tolerant of harsh environments. We discuss the implications of these findings in the context of the evolution of pathogenesis, mating types, and mating systems.
【초록키워드】 Evolution, Pathogenesis, alleles, Region, comparison, Recombination, phenotype, Pathogens, fungi, quantification, Quantitative, fungal, Evidence, Frequency, Candida albicans, Aneuploidy, similarity, Cryptococcus neoformans, sexual reproduction, mitotic recombination, bisexual reproduction, mating type, sexual development, chromosome 4, mating types, recombination frequencies, asexual reproduction, chromosome, allele, phenotypic, chromosomes, meiotic recombination, spore, spores, meiosis, chromosomal region, heterozygosity, C. neoformans, diploid meiotic progeny, duplication, loss of heterozygosity, MAT locus, meiotic progeny, progeny, while, regions, implication, thought, produced, analyzed, collected, occurred, examined, reported, characterized, undergo, reflected, occur, initiated, chromosomal, producing, Cryptococcus neoforman, fungal pathogen, Candida albican, mitotic, C. neoforman, asexual, meiotic, mixing genetic material, 【제목키워드】 drive, reproduction, Cryptococcus,