<i>Cryptococcus neoformans</i> Mating and Genetic Crosses

Sun, Sheng; Priest, Shelby; Heitman, Joseph

doi:10.1002/cpmc.75

Cited by 34 publications

(39 citation statements)

References 52 publications

(59 reference statements)

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“…uxs1Δ single mutants and ugd1Δ uxs1Δ double mutants were generated via a genetic cross 51 . First, the KN99α uxs1Δ mutant from the Hiten Madhani deletion collection was mated with the wild-type KN99a laboratory strain.…”

Section: Methodsmentioning

confidence: 99%

5-fluorocytosine resistance is associated with hypermutation and alterations in capsule biosynthesis in Cryptococcus

Billmyre

Clancey

et al. 2020

Nat Commun

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Patients infected with the fungal pathogen Cryptococcus are most effectively treated with a combination of 5-fluorocytosine (5FC) and amphotericin B. 5FC acts as a prodrug, which is converted into toxic 5-fluorouracil (5FU) upon uptake into fungal cells. However, the pathogen frequently develops resistance through unclear mechanisms. Here we show that resistance to 5FC in Cryptococcus deuterogattii is acquired more frequently in isolates with defects in DNA mismatch repair that confer an elevated mutation rate. We use whole genome sequencing of 16 independent isolates to identify mutations associated with 5FC resistance in vitro. We find mutations in known resistance genes (FUR1 and FCY2) and in a gene UXS1, previously shown to encode an enzyme that converts UDP-glucuronic acid to UDP-xylose for capsule biosynthesis, but not known to play a role in 5FC metabolism. Mutations in UXS1 lead to accumulation of UDP-glucuronic acid and alterations in nucleotide metabolism, which appear to suppress toxicity of both 5FC and its toxic derivative 5FU.

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Section: Methodsmentioning

confidence: 99%

5-fluorocytosine resistance is associated with hypermutation and alterations in capsule biosynthesis in Cryptococcus

Billmyre

Clancey

et al. 2020

Nat Commun

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“…Plates of V8 (pH = 5) mating medium [77] were inoculated with suspensions of yeast cells in water. For each pair-wise cross, 10 µL of each strain was pipetted onto the same spot of medium.…”

Section: Mating Crosses Spore Dissection and Genotypingmentioning

confidence: 99%

Genetic and genomic analyses reveal boundaries between species closely related to Cryptococcus pathogens

Passer

Coelho

Billmyre

et al. 2019

Preprint

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Speciation is a central mechanism of biological diversification. While speciation is well studied in plants and animals, in comparison, relatively little is known about speciation in fungi.One fungal model is the Cryptococcus genus, which is best known for the pathogenic Cryptococcus neoformans/Cryptococcus gattii species complex that causes over 200,000 new infections in humans annually. The closest non-human pathogenic relatives are the sibling species, Cryptococcus amylolentus and Tsuchiyaea wingfieldii. However, because relatively few isolates of each species are available, it is unclear whether they represent divergent lineages of the same species or different biological species. The recent isolation of an additional strain, preliminarily identified as T. wingfieldii, prompted us to reexamine this group as it may inform about the evolutionary processes underlying the diversification of both non-pathogenic and pathogenic Cryptococcus lineages. Using genomic data, we reappraised the phylogenetic relationship of the four available strains and confirmed the genetic separation of C. amylolentus and T. wingfieldii (now Cryptococcus wingfieldii), and revealed an additional cryptic species, for which the name Cryptococcus floricola is proposed. Comparison of full-length chromosome assemblies revealed approximately 6% pairwise sequence divergence between the three species, and identified significant genomic changes, including inversions as well as a reciprocal translocation that involved inter-centromeric ectopic recombination, which together likely impose significant barriers to genetic exchange. Using genetic crosses, we show that while C.wingfieldii cannot interbreed with any of the other strains, C. floricola can undergo sexual reproduction with C. amylolentus. However, most of the spores resulting from this cross were inviable, and many were sterile, indicating that the two species are genetically isolated through intrinsic post-zygotic barriers and possibly due to niche differentiation. Genome sequencing and analysis of the progeny demonstrated decreased recombination frequency during meiosis in heterospecific crosses compared to C. amylolentus conspecific crosses. This study advances our understanding of speciation in fungi and highlights the power of genomics in assisting our ability to correctly identify and discriminate fungal species. Author SummaryThe idea of species as discrete natural units seems rather intuitive for most people, just as cells are the basic units of life. However, when observing variation across a species range, boundaries can become blurred making it less than obvious when different populations evolve into separate species. Additionally, separate species can still interbreed, such as lions breeding with tigers to produce a liger or a tigon (depending on the paternal and maternal species of origin), but the resulting offspring is usually inviable or sterile, which in turn is evidence that the parents involved are distinct species. Therefore, what species are and how they originate is st...

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“…To study this, the two shuffled strains were crossed with the wild-type strain, KN99 a , which is congenic with the parental strain H99α. During Cryptococcus sexual reproduction, cells of two opposite mating types fuse and then produce hyphae, basidia, and long chains of spores over a two-week course of incubation 26 . In the basidium, the two parental haploid nuclei fuse and undergo meiosis producing four haploid nuclei.…”

Section: Resultsmentioning

confidence: 99%

“…Strains were grown in YPD media for all experiments at 30°C unless stated otherwise, and G418 was added at a final concentration of 200 µg/ml for selection of transformants. MS media was used for all the mating assays, which were performed as described previously 26 . Basidia specific spore dissections were performed after two weeks of mating, and the spore germination rate was scored after four days of dissection.…”

Section: Methodsmentioning

confidence: 99%

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Centromere scission drives chromosome shuffling and reproductive isolation

Yadav

Sun

Coelho

et al. 2019

Preprint

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AbstractA fundamental characteristic of eukaryotic organisms is the generation of genetic variation via sexual reproduction. Conversely, significant large-scale genome structure variations could hamper sexual reproduction, causing reproductive isolation and promote speciation. The underlying processes behind large-scale genome rearrangements are not well understood and include chromosome translocations involving centromeres. Recent genomic studies in the Cryptococcus species complex revealed that chromosome translocations generated via centromere recombination have reshaped the genomes of different species. In this study, multiple DNA double-strand breaks (DSBs) were generated via the CRISPR/Cas9 system at centromere-specific retrotransposons in the human fungal pathogen Cryptococcus neoformans. The resulting DSBs were repaired in a complex manner, leading to the formation of multiple inter-chromosomal rearrangements and new telomeres, similar to chromothripsis-like events. The newly generated strains harboring chromosome translocations exhibited normal vegetative growth but failed to undergo successful sexual reproduction with the parental wild-type strain. One of these strains failed to produce any spores, while another produced ∼3% viable progeny. The germinated progeny exhibited aneuploidy for multiple chromosomes and showed improved fertility with both parents. All chromosome translocation events were accompanied without any detectable change in gene sequences and thus, suggest that chromosomal translocations alone may play an underappreciated role in the onset of reproductive isolation and speciation.

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Cryptococcus neoformans Mating and Genetic Crosses

Cited by 34 publications

References 52 publications

5-fluorocytosine resistance is associated with hypermutation and alterations in capsule biosynthesis in Cryptococcus

5-fluorocytosine resistance is associated with hypermutation and alterations in capsule biosynthesis in Cryptococcus

Genetic and genomic analyses reveal boundaries between species closely related to Cryptococcus pathogens

Centromere scission drives chromosome shuffling and reproductive isolation

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