Department of Molecular Biology, Max Planck Institute for Developmental Biology, Tübingen, Germany.
Department of Ecology,Environment, and Plant Sciences, Stockholm University, Stockholm, Sweden.
Elife. 2019 Feb 26;8:e43606. doi: 10.7554/eLife.43606.
Genetic drift is expected to remove polymorphism from populations over long periods of time, with the rate of polymorphism loss being accelerated when species experience strong reductions in population size. Adaptive forces that maintain genetic variation in populations, or balancing selection, might counteract this process. To understand the extent to which natural selection can drive the retention of genetic diversity, we document genomic variability after two parallel species-wide bottlenecks in the genus . We find that ancestral variation preferentially persists at immunity related loci, and that the same collection of alleles has been maintained in different lineages that have been separated for several million years. By reconstructing the evolution of the disease-related locus , we find that divergence between ancient haplotypes can be obscured by referenced based re-sequencing methods, and that trans-specific alleles can encode substantially diverged protein sequences. Our data point to long-term balancing selection as an important factor shaping the genetics of immune systems in plants and as the predominant driver of genomic variability after a population bottleneck.
遗传漂变预计会在长时间内从种群中消除多态性，当物种经历种群规模的强烈减少时，多态性丧失的速度会加快。维持种群遗传变异的适应力，或平衡选择，可能会抵消这一过程。为了了解自然选择在多大程度上可以保留遗传多样性，我们记录了属中的两个平行的全物种瓶颈后基因组的可变性。我们发现，祖先的变异优先在与免疫相关的基因座上保留下来，而且相同的等位基因集合在已经分离了数百万年的不同谱系中得到了维持。通过重建与疾病相关的基因座的进化，我们发现基于参考的重测序方法可能会掩盖古代单倍型之间的分歧，并且跨物种的等位基因可以编码明显不同的蛋白质序列。我们的数据表明，长期的平衡选择是塑造植物免疫系统遗传学的一个重要因素，也是种群瓶颈后基因组可变性的主要驱动因素。
