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Unisexual reproduction drives meiotic recombination and phenotypic and karyotypic plasticity in Cryptococcus neoformans.

Sun S, Billmyre RB, Mieczkowski PA, Heitman J - PLoS Genet. (2014)

Bottom Line: We found that meiotic recombination operates in a similar fashion during both modes of sexual reproduction.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.Our results provide definitive evidence that α-α unisexual reproduction is a meiotic process similar to a-α bisexual reproduction.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.

ABSTRACT
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.

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Transient aneuploid and persistent diploid progeny are generated from α-α unisexual reproduction.A) The three panels show the read depths of all chromosomes in the three parental strains: 431α, XL280αSS, and XL280a. For each panel, the x-axis indicates the 14 chromosomes and the y-axis indicates the read depth from the Illumina sequencing. These strains had only one copy of chromosome 4, as no heterozygosity was detected for any marker from chromosome 4 that was analyzed, and thus, all are haploid. This was also consistent with results from the FACS analyses (S1 Figure). B) The six panels show the read depths of all chromosomes in strains derived from three meiotic progeny from α-α unisexual reproduction between strains 431α and XL280αSS. For each panel, the x-axis indicates the 14 chromosomes and the y-axis indicates the read depth from the Illumina sequencing. All of these strains showed heterozygosity at multiple markers along chromosome 4 (Fig. 6), indicating they had at least two copies of chromosome 4. FACS analyses indicated that these strains were likely diploid (S1 Figure), which was consistent with the sequencing results shown here suggesting all of the meiotic progeny had two copies for the majority of the chromosomes (including chromosome 4). The two panels within each of the three dashed-lined rectangles are sequencing results of small and large colonies, respectively, that were derived from the same meiotic progeny. C) The distribution of SNPs along chromosome 14 in the small and large colonies of the progeny SSB309, as well as the two parental strains 431α and XL280αSS. The genome sequence of each isolate was mapped against the published genome sequence of strain JEC21. The light blue bars indicate SNPs compared to JEC21, dark blue bars indicate heterozygous sites, while grey areas indicate regions that are identical to JEC21. The centromeric region of chromosome 14 is highlighted by the green rectangle.
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pgen-1004849-g007: Transient aneuploid and persistent diploid progeny are generated from α-α unisexual reproduction.A) The three panels show the read depths of all chromosomes in the three parental strains: 431α, XL280αSS, and XL280a. For each panel, the x-axis indicates the 14 chromosomes and the y-axis indicates the read depth from the Illumina sequencing. These strains had only one copy of chromosome 4, as no heterozygosity was detected for any marker from chromosome 4 that was analyzed, and thus, all are haploid. This was also consistent with results from the FACS analyses (S1 Figure). B) The six panels show the read depths of all chromosomes in strains derived from three meiotic progeny from α-α unisexual reproduction between strains 431α and XL280αSS. For each panel, the x-axis indicates the 14 chromosomes and the y-axis indicates the read depth from the Illumina sequencing. All of these strains showed heterozygosity at multiple markers along chromosome 4 (Fig. 6), indicating they had at least two copies of chromosome 4. FACS analyses indicated that these strains were likely diploid (S1 Figure), which was consistent with the sequencing results shown here suggesting all of the meiotic progeny had two copies for the majority of the chromosomes (including chromosome 4). The two panels within each of the three dashed-lined rectangles are sequencing results of small and large colonies, respectively, that were derived from the same meiotic progeny. C) The distribution of SNPs along chromosome 14 in the small and large colonies of the progeny SSB309, as well as the two parental strains 431α and XL280αSS. The genome sequence of each isolate was mapped against the published genome sequence of strain JEC21. The light blue bars indicate SNPs compared to JEC21, dark blue bars indicate heterozygous sites, while grey areas indicate regions that are identical to JEC21. The centromeric region of chromosome 14 is highlighted by the green rectangle.

Mentions: Because all of the progeny with two copies of chromosome 4 were shown to be diploid (or aneuploid) based on FACS analysis, we assigned the copy number of chromosome 4 as two for each of the progeny. Accordingly, we found that for the two meiotic progeny from a-α bisexual reproduction, the copy numbers of each of their chromosomes were the same as that of chromosome 4. Thus they were diploid and euploid (Fig. 7 and S2 Figure). For the 12 meiotic progeny from α-α unisexual reproduction, we found 5 of the 7 progeny that did not produce large and small colonies were diploid and euploid, while the other two, SSB571 and SSB620, were aneuploid. Specifically, progeny SSB571 had two copies of all chromosomes except chromosome 14, which was trisomic with three copies (2N+1; S2i Figure). Progeny SSB620 had two copies of all chromosomes except chromosome 3, which was trisomic (three copies) for the majority of chromosome 3, and disomic (two copies) and tetrasomic (four copies) for the two ends of chromosome 3, respectively (S2j Figure).


Unisexual reproduction drives meiotic recombination and phenotypic and karyotypic plasticity in Cryptococcus neoformans.

Sun S, Billmyre RB, Mieczkowski PA, Heitman J - PLoS Genet. (2014)

Transient aneuploid and persistent diploid progeny are generated from α-α unisexual reproduction.A) The three panels show the read depths of all chromosomes in the three parental strains: 431α, XL280αSS, and XL280a. For each panel, the x-axis indicates the 14 chromosomes and the y-axis indicates the read depth from the Illumina sequencing. These strains had only one copy of chromosome 4, as no heterozygosity was detected for any marker from chromosome 4 that was analyzed, and thus, all are haploid. This was also consistent with results from the FACS analyses (S1 Figure). B) The six panels show the read depths of all chromosomes in strains derived from three meiotic progeny from α-α unisexual reproduction between strains 431α and XL280αSS. For each panel, the x-axis indicates the 14 chromosomes and the y-axis indicates the read depth from the Illumina sequencing. All of these strains showed heterozygosity at multiple markers along chromosome 4 (Fig. 6), indicating they had at least two copies of chromosome 4. FACS analyses indicated that these strains were likely diploid (S1 Figure), which was consistent with the sequencing results shown here suggesting all of the meiotic progeny had two copies for the majority of the chromosomes (including chromosome 4). The two panels within each of the three dashed-lined rectangles are sequencing results of small and large colonies, respectively, that were derived from the same meiotic progeny. C) The distribution of SNPs along chromosome 14 in the small and large colonies of the progeny SSB309, as well as the two parental strains 431α and XL280αSS. The genome sequence of each isolate was mapped against the published genome sequence of strain JEC21. The light blue bars indicate SNPs compared to JEC21, dark blue bars indicate heterozygous sites, while grey areas indicate regions that are identical to JEC21. The centromeric region of chromosome 14 is highlighted by the green rectangle.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4263396&req=5

pgen-1004849-g007: Transient aneuploid and persistent diploid progeny are generated from α-α unisexual reproduction.A) The three panels show the read depths of all chromosomes in the three parental strains: 431α, XL280αSS, and XL280a. For each panel, the x-axis indicates the 14 chromosomes and the y-axis indicates the read depth from the Illumina sequencing. These strains had only one copy of chromosome 4, as no heterozygosity was detected for any marker from chromosome 4 that was analyzed, and thus, all are haploid. This was also consistent with results from the FACS analyses (S1 Figure). B) The six panels show the read depths of all chromosomes in strains derived from three meiotic progeny from α-α unisexual reproduction between strains 431α and XL280αSS. For each panel, the x-axis indicates the 14 chromosomes and the y-axis indicates the read depth from the Illumina sequencing. All of these strains showed heterozygosity at multiple markers along chromosome 4 (Fig. 6), indicating they had at least two copies of chromosome 4. FACS analyses indicated that these strains were likely diploid (S1 Figure), which was consistent with the sequencing results shown here suggesting all of the meiotic progeny had two copies for the majority of the chromosomes (including chromosome 4). The two panels within each of the three dashed-lined rectangles are sequencing results of small and large colonies, respectively, that were derived from the same meiotic progeny. C) The distribution of SNPs along chromosome 14 in the small and large colonies of the progeny SSB309, as well as the two parental strains 431α and XL280αSS. The genome sequence of each isolate was mapped against the published genome sequence of strain JEC21. The light blue bars indicate SNPs compared to JEC21, dark blue bars indicate heterozygous sites, while grey areas indicate regions that are identical to JEC21. The centromeric region of chromosome 14 is highlighted by the green rectangle.
Mentions: Because all of the progeny with two copies of chromosome 4 were shown to be diploid (or aneuploid) based on FACS analysis, we assigned the copy number of chromosome 4 as two for each of the progeny. Accordingly, we found that for the two meiotic progeny from a-α bisexual reproduction, the copy numbers of each of their chromosomes were the same as that of chromosome 4. Thus they were diploid and euploid (Fig. 7 and S2 Figure). For the 12 meiotic progeny from α-α unisexual reproduction, we found 5 of the 7 progeny that did not produce large and small colonies were diploid and euploid, while the other two, SSB571 and SSB620, were aneuploid. Specifically, progeny SSB571 had two copies of all chromosomes except chromosome 14, which was trisomic with three copies (2N+1; S2i Figure). Progeny SSB620 had two copies of all chromosomes except chromosome 3, which was trisomic (three copies) for the majority of chromosome 3, and disomic (two copies) and tetrasomic (four copies) for the two ends of chromosome 3, respectively (S2j Figure).

Bottom Line: We found that meiotic recombination operates in a similar fashion during both modes of sexual reproduction.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.Our results provide definitive evidence that α-α unisexual reproduction is a meiotic process similar to a-α bisexual reproduction.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus