Abstract：
Plant cells harbor two membrane-bound organelles containing their own genetic material-plastids and mitochondria. Although the two organelles coexist and coevolve within the same plant cells, they differ in genome copy number, intracellular organization, and mode of segregation. How these attributes affect the time to fixation or, conversely, loss of neutral alleles is currently unresolved. Here, we show that mitochondria and plastids share the same mutation rate, yet plastid alleles remain in a heteroplasmic state significantly longer compared with mitochondrial alleles. By analyzing genetic variants across populations of the marine flowering plant Zostera marina and simulating organelle allele dynamics, we examine the determinants of allele segregation and allele fixation. Our results suggest that the bottlenecks on the cell population, e.g. during branching or seeding, and stratification of the meristematic tissue are important determinants of mitochondrial allele dynamics. Furthermore, we suggest that the prolonged plastid allele dynamics are due to a yet unknown active plastid partition mechanism. The dissimilarity between plastid and mitochondrial novel allele fixation at different levels of organization may manifest in differences in adaptation processes. Our study uncovers fundamental principles of organelle population genetics that are essential for further investigations of long-term evolution and molecular dating of divergence events.
摘要：
植物细胞拥有两个膜结合的细胞器，它们含有自己的遗传物质-质体和线粒体。尽管这两个细胞器在同一植物细胞内共存并共同进化，它们的基因组拷贝数不同，细胞内组织，和隔离模式。这些属性如何影响固定时间，或者相反，中性等位基因的丢失目前尚未解决。在这里，我们表明线粒体和质体共享相同的突变率，但与线粒体等位基因相比，质体等位基因保持在异质状态的时间明显更长。通过分析海洋开花植物Zosteramarina种群的遗传变异并模拟细胞器等位基因动态，我们研究了等位基因分离和等位基因固定的决定因素。我们的结果表明，细胞群体的瓶颈，例如，在分枝或播种期间，和分生组织的分层，是线粒体等位基因动力学的重要决定因素。此外，我们认为，延长质体等位基因动力学是由于一个未知的活性质体分配机制。质体和线粒体新等位基因固定在不同组织水平上的差异可能表现为适应过程的差异。我们的研究揭示了细胞器种群遗传学的基本原理，这些原理对于进一步研究分歧事件的长期进化和分子年代至关重要。
