Asexuality associated with marked genomic expansion of tandemly repeated rRNA and histone genes

How does asexual reproduction influence genome evolution? While is it clear that genomic structural variation is common and important in natural populations, we know very little about how one of the most fundamental of eukaryotic traits - mode of genomic inheritance - influences genome structure. We address this question with the New Zealand freshwater snail Potamopyrgus antipodarum, which features multiple, separately derived obligately asexual lineages that coexist and compete with otherwise similar sexual lineages. We used whole-genome sequencing reads from a diverse set of sexual and asexual individuals to analyze genomic abundance of a critically important gene family, rDNA (the genes encoding rRNAs), that is notable for dynamic and variable copy number. Our genomic survey of rDNA in P. antipodarum revealed two striking results. First, the core histone and 5S rRNA genes occur between tandem copies of the 18S-5.8S-28S gene cluster, a unique architecture for these crucial gene famili...

无性生殖如何影响基因组进化？尽管我们已明确基因组结构变异（genomic structural variation）在自然种群中普遍存在且至关重要，但对于真核生物最基础的性状之一——基因组遗传模式（mode of genomic inheritance）——如何影响基因组结构，我们仍知之甚少。本研究以新西兰淡水螺*Potamopyrgus antipodarum*为研究对象解答上述问题，该物种拥有多支独立起源的专性无性繁殖谱系，这些谱系可与遗传背景相近的有性繁殖谱系共存并竞争。我们采集了多组有性与无性个体的全基因组测序读段（whole-genome sequencing reads），用以分析一类至关重要的基因家族——核糖体DNA（rDNA，即编码核糖体RNA的基因）——的基因组丰度，该家族以拷贝数动态可变而著称。我们对*Potamopyrgus antipodarum*中核糖体DNA的基因组普查得到了两项引人注目的结果。首先，核心组蛋白基因与5S核糖体RNA（5S rRNA）基因位于18S-5.8S-28S基因簇的串联拷贝之间，这一排版结构对于这类关键基因家族而言是独一无二的……