Size matters: Non-LTR retrotransposable elements and ectopic recombination in Drosophila
Size matters: Non-LTR retrotransposable elements and ectopic recombination in Drosophila
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DOI：
10.1093/molbev/msg102
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发表时间：
2003-06-01
影响因子：
10.7
通讯作者：
Hirsh, AE
中科院分区：
文献类型：
--
作者：
Petrov, DA;Aminetzach, YT;Hirsh, AE
黑腹果蝇基因组包含大约100个不同的转座因子（te）家族。在基因组的正染色质部分，每个家族都有少量拷贝（5-150份），te的单个拷贝在群体中出现的频率很低。这一模式很可能反映了通过换位而流入的TEs和通过自然选择而移除的TEs之间的平衡。自然选择对te起作用的本质仍然存在争议。我们提供的证据表明，对由异位重组引起的染色体异常的选择限制了一些TEs的传播。我们也首次证明了果蝇常染色质中的一些TE家族似乎只受到净化选择的轻微影响，并且在高种群频率下包含许多拷贝。我们认为，由于全家族的转位率较低，导致TE拷贝数较低，从而降低了作用于单个TE拷贝的选择强度，这些家族中的TE获得了较高的种群频率，甚至达到了固定。在这些家族中，te的固定应该为基因间序列的大小提供上行压力，以平衡通过小缺失导致的快速DNA丢失。由异位重组引起的TE家族拷贝数依赖性选择也可能促进果蝇基因组TE的多样性。
The Drosophila melanogaster genome contains approximately 100 distinct families of transposable elements (TEs). In the euchromatic part of the genome, each family is present in a small number of copies (5-150 copies), with individual copies of TEs often present at very low frequencies in populations. This pattern is likely to reflect a balance between the inflow of TEs by transposition and the removal of TEs by natural selection. The nature of natural selection acting against TEs remains controversial. We provide evidence that selection against chromosome abnormalities caused by ectopic recombination limits the spread of some TEs. We also demonstrate for the first time that some TE families in the Drosophila euchromatin appear to be only marginally affected by purifying selection and contain many copies at high population frequencies. We argue that TEs in these families attain high population frequencies and even reach fixation as a result of low family-wide transposition rates leading to low TE copy numbers and consequently reduced strength of selection acting on individual TE copies. Fixation of TEs in these families should provide an upward pressure on the size of intergenic sequences counterbalancing rapid DNA loss through small deletions. Copy-number-dependent selection on TE families caused by ectopic recombination may also promote diversity among TEs in the Drosophila genome.