Department of Biology, McMaster University, Hamilton, Ontario, Canada.
PLoS One. 2013 May 14;8(5):e62790. doi: 10.1371/journal.pone.0062790. Print 2013.
In the majority of diploid eukaryotes, each meiotic process generates four haploid gametes with each containing a single recombinant nucleus. In some species and/or some meiotic processes, aneuploid or diploid gametes can also be generated due to chromosomal non-disjunction and/or the co-packaging of two of the four haploid nuclei into the same gamete. Here we show that another process is involved in generating genotypes of sexual progeny from a hybrid cross between two divergent lineages of the human fungal pathogen Cryptococcus neoformans. Through micro-dissection of 1358 basidiospores from 194 basidia and genotyping using 33 co-dominant genetic markers, the genotypes of all 230 germinated basidiospores from 94 basidia were obtained. The minimum haploid genotypes required to constitute the observed genotypes from each basidium were then inferred. Our results demonstrated that more than four haploid nuclear genotypes are required to explain the observed genotypes of basidiospores in seven of the 94 basidia. Our results suggest that mitotic recombination within basidia must be involved to produce the observed genotypes in these seven basidia. The mitotic recombination likely includes both chromosomal loss and crossing over. This novel recombination process could play an important role in generating the genotypic and phenotypic diversities of this important human pathogen.
在大多数二倍体真核生物中，每个减数分裂过程都会产生四个含有单个重组核的单倍体配子。在某些物种和/或某些减数分裂过程中，由于染色体不分离和/或四个单倍体核中的两个被包装到同一个配子中，也可以产生非整倍体或二倍体配子。在这里，我们展示了另一种过程，该过程涉及从人类真菌病原体新型隐球菌的两个不同谱系的杂交交叉中产生有性后代的基因型。通过对 194 个担子中的 1358 个担孢子进行微切割，并使用 33 个共显性遗传标记进行基因分型，获得了 94 个担子中所有 230 个萌发担孢子的基因型。然后推断出构成每个担子中观察到的基因型所需的最小单倍体基因型。我们的结果表明，在这 94 个担子中的七个中，需要超过四个单倍体核基因型来解释观察到的担孢子基因型。我们的结果表明，担子内的有丝分裂重组必须参与产生这七个担子中观察到的基因型。有丝分裂重组可能包括染色体丢失和交叉互换。这种新的重组过程可能在产生这种重要人类病原体的基因型和表型多样性方面发挥重要作用。
