Institute of Biology, Evolutionary Botany, University of Neuchâtel, Neuchâtel, 2000, Switzerland.
Institute of Plant Physiology and Genetics, Laboratory of Genome Dynamics and Stability, Bulgarian Academy of Sciences, Sofia, 1113, Bulgaria.
New Phytol. 2018 Jul;219(2):767-778. doi: 10.1111/nph.15201. Epub 2018 May 14.
Transposable elements (TE) can constitute a large fraction of plant genomes, yet our understanding of their evolution and fitness effect is still limited. Here we tested several models of evolution that make specific predictions about differences in TE abundance between selfing and outcrossing taxa, and between small and large populations. We estimated TE abundance in multiple populations of North American Arabidopsis lyrata differing in mating system and long-term size, using transposon insertion display on several TE families. Selfing populations had higher TE copy numbers per individual and higher TE allele frequencies, supporting models which assume that selection against TEs acts predominantly against heterozygotes via the process of ectopic recombination. In outcrossing populations differing in long-term size, the data supported neither a model of density-regulated transposition nor a model of direct deleterious effect. Instead, the population structure of TEs revealed that outcrossing populations tended to split into western and eastern groups - as previously detected using microsatellite markers - whereas selfing populations from west and east were less differentiated. This, too, agrees with the model of ectopic recombination. Overall, our results suggest that TE elements are nearly neutral except for their deleterious potential to disturb meiosis in the heterozygous state.
转座元件 (TE) 可以构成植物基因组的很大一部分，但我们对它们的进化和适应度效应的理解仍然有限。在这里，我们测试了几个进化模型，这些模型对自交和异交分类群之间 TE 丰度的差异以及小种群和大种群之间的差异做出了具体预测。我们使用几种 TE 家族的转座子插入显示，在北美拟南芥不同的交配系统和长期大小的多个种群中估计了 TE 的丰度。自交种群中每个个体的 TE 拷贝数和 TE 等位基因频率都更高，支持了这样的模型，即认为对 TE 的选择主要通过异位重组过程针对杂合子起作用。在长期大小不同的异交种群中，数据既不支持密度调节转座的模型，也不支持直接有害效应的模型。相反，TE 的种群结构表明，异交种群倾向于分裂成西部和东部群体 - 正如以前使用微卫星标记检测到的那样 - 而来自西部和东部的自交种群则分化程度较低。这也与异位重组模型一致。总的来说，我们的结果表明，TE 元件几乎是中性的，除非它们有潜在的有害性，会在杂合状态下干扰减数分裂。
