Introgression maintains the genetic integrity of the mating-type determining chromosome of the fungus Neurospora tetrasperma
Introgression maintains the genetic integrity of the mating-type determining chromosome of the fungus Neurospora tetrasperma
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DOI：
10.1101/gr.197244.115
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发表时间：
2016-04-01
期刊：
影响因子：
7
通讯作者：
Johannesson, Hanna
中科院分区：
文献类型：
--
作者：
Corcoran, Padraic;Anderson, Jennifer L.;Johannesson, Hanna
基因组进化是由多种因素复杂的相互作用驱动的，包括选择、重组和基因渗入。决定性别认同的区域是真核生物基因组的特别动态的部分，其易于发生与抑制重组相关的分子变性。在真菌四孢脉孢菌（Neurospora tetrasperma）中，有人提出这种分子退化被来自密切相关物种的非退化DNA的渐渗所抵消。在这项研究中，我们使用了比较和群体基因组分析的92个基因组，从8个遗传和生殖隔离的谱系的N。tetrasperma和它的三个最近的亲戚，研究基因组的进化历史形成的因素。我们发现，抑制重组延伸跨越至少6 Mbp（类似于63%）的交配型（mat）染色体在N。四精子，并与减少遗传多样性，这可能是主要的结果，选择在连锁网站。此外，分子进化的分析显示，在这个区域的突变负荷增加，相对于重组区域。然而，比较基因组和系统发育分析表明，垫染色体暂时再生通过渐渗从姐妹物种;六个血统显示渐渗到他们的垫染色体之一，与多个脉孢菌物种作为供体。渗入的大片已固定在谱系内，这表明它们赋予自然种群的适应性优势，我们的分析支持至少在一个谱系中存在选择性扫描。因此，这些数据强烈支持先前假设的作用，作为一种机制，用于维持交配型决定染色体区域的基因渗入。
Genome evolution is driven by a complex interplay of factors, including selection, recombination, and introgression. The regions determining sexual identity are particularly dynamic parts of eukaryotic genomes that are prone to molecular degeneration associated with suppressed recombination. In the fungus Neurospora tetrasperma, it has been proposed that this molecular degeneration is counteracted by the introgression of nondegenerated DNA from closely related species. In this study, we used comparative and population genomic analyses of 92 genomes from eight phylogenetically and reproductively isolated lineages of N. tetrasperma, and its three closest relatives, to investigate the factors shaping the evolutionary history of the genomes. We found that suppressed recombination extends across at least 6 Mbp (similar to 63%) of the mating-type (mat) chromosome in N. tetrasperma and is associated with decreased genetic diversity, which is likely the result primarily of selection at linked sites. Furthermore, analyses of molecular evolution revealed an increased mutational load in this region, relative to recombining regions. However, comparative genomic and phylogenetic analyses indicate that the mat chromosomes are temporarily regenerated via introgression from sister species; six of eight lineages show introgression into one of their mat chromosomes, with multiple Neurospora species acting as donors. The introgressed tracts have been fixed within lineages, suggesting that they confer an adaptive advantage in natural populations, and our analyses support the presence of selective sweeps in at least one lineage. Thus, these data strongly support the previously hypothesized role of introgression as a mechanism for the maintenance of mating-type determining chromosomal regions.