College of Pharmacy and Life Science, Jiujiang University, 332000, Jiujiang, China.
UMR CNRS 7267 Ecologie et Biologie des Interactions, Equipe Ecologie Evolution Symbiose, Université de Poitiers, 86073, Poitiers, France.
Nat Commun. 2020 Mar 13;11(1):1362. doi: 10.1038/s41467-020-15149-4.
Horizontal transfer of transposable elements (HTT) is an important process shaping eukaryote genomes, yet very few studies have quantified this phenomenon on a large scale or have evaluated the selective constraints acting on transposable elements (TEs) during vertical and horizontal transmission. Here we screen 307 vertebrate genomes and infer a minimum of 975 independent HTT events between lineages that diverged more than 120 million years ago. HTT distribution greatly differs from null expectations, with 93.7% of these transfers involving ray-finned fishes and less than 3% involving mammals and birds. HTT incurs purifying selection (conserved protein evolution) on all TEs, confirming that producing functional transposition proteins is required for a TE to invade new genomes. In the absence of HTT, DNA transposons appear to evolve neutrally within genomes, unlike most retrotransposons, which evolve under purifying selection. This selection regime indicates that proteins of most retrotransposon families tend to process their own encoding RNA (cis-preference), which helps retrotransposons to persist within host lineages over long time periods.
转座元件（TEs）的水平转移是塑造真核生物基因组的一个重要过程，但很少有研究大规模地量化这一现象，也很少有研究评估垂直和水平传播过程中 TEs 所受到的选择压力。在这里，我们筛选了 307 个脊椎动物基因组，并推断出 1.2 亿多年前分化的谱系之间至少发生了 975 次独立的水平转移事件。HTT 的分布与零假设有很大的不同，其中 93.7%的转移涉及射线鳍鱼类，而涉及哺乳动物和鸟类的不到 3%。HTT 对所有 TEs 都存在纯化选择（保守的蛋白质进化），这证实了产生功能性转座蛋白是 TE 入侵新基因组所必需的。在没有 HTT 的情况下，DNA 转座子似乎在基因组内呈中性进化，而大多数逆转座子则受到纯化选择的影响。这种选择机制表明，大多数逆转座子家族的蛋白倾向于处理自身编码的 RNA（顺式偏好），这有助于逆转座子在宿主谱系中长时间存在。
