Hybridization is increasingly recognized as an important force impacting adaptation and evolution in many lineages of fungi. During hybridization, divergent genomes and alleles are brought together into the same cell, potentiating adaptation by increasing genomic plasticity. Here, we review hybridization in fungi by focusing on two fungal pathogens of animals. Hybridization is common between the basidiomycete yeast species Cryptococcusneoformans × Cryptococcusdeneoformans, and hybrid genotypes are frequently found in both environmental and clinical settings. The two species show 10-15% nucleotide divergence at the genome level, and their hybrids are highly heterozygous. Though largely sterile and unable to mate, these hybrids can propagate asexually and generate diverse genotypes by nondisjunction, aberrant meiosis, mitotic recombination, and gene conversion. Under stress conditions, the rate of such genetic changes can increase, leading to rapid adaptation. Conversely, in hybrids formed between lineages of the chytridiomycete frog pathogen Batrachochytriumdendrobatidis (Bd), the parental genotypes are considerably less diverged (0.2% divergent). Bd hybrids are formed from crosses between lineages that rarely undergo sex. A common theme in both species is that hybrids show genome plasticity via aneuploidy or loss of heterozygosity and leverage these mechanisms as a rapid way to generate genotypic/phenotypic diversity. Some hybrids show greater fitness and survival in both virulence and virulence-associated phenotypes than parental lineages under certain conditions. These studies showcase how experimentation in model species such as Cryptococcus can be a powerful tool in elucidating the genotypic and phenotypic consequences of hybridization.

译文

杂交越来越被认为是影响许多真菌谱系适应和进化的重要力量。在杂交过程中,不同的基因组和等位基因被聚集到同一细胞中,通过增加基因组可塑性来增强适应性。在这里,我们通过关注动物的两种真菌病原体来回顾真菌中的杂交。担子菌酵母物种隐球菌 × 隐球菌之间的杂交很常见,并且在环境和临床环境中经常发现杂交基因型。这两个物种在基因组水平上显示出10-15% 个核苷酸的差异,并且它们的杂种是高度杂合的。尽管这些杂种大部分不育且无法交配,但它们可以无性繁殖,并通过不分离,异常减数分裂,有丝分裂重组和基因转化产生不同的基因型。在压力条件下,这种遗传变化的速度会增加,从而导致快速适应。相反,在凝乳酵母蛙病原体Batrachochytriumdendrobatidis (Bd) 的谱系之间形成的杂种中,亲本基因型的差异要小得多 (0.2% 差异)。Bd杂种是由很少发生性行为的谱系之间的杂交形成的。这两个物种的共同主题是,杂种通过非整倍体或杂合性丧失显示基因组可塑性,并利用这些机制作为产生基因型/表型多样性的快速方法。在某些条件下,某些杂种在毒力和毒力相关表型上都比亲本谱系显示出更高的适应性和存活率。这些研究展示了在模型物种 (如隐球菌) 中的实验如何成为阐明杂交的基因型和表型后果的有力工具。

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