The lack of recombination drives the fixation of transposable elements on the fourth chromosome of Drosophila melanogaster
The lack of recombination drives the fixation of transposable elements on the fourth chromosome of Drosophila melanogaster
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DOI：
10.1017/s0016672304006755
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发表时间：
2004-04-01
影响因子：
1.5
通讯作者：
Maside, X
中科院分区：
文献类型：
--
作者：
Bartolomé, C;Maside, X
在重组被抑制的区域，在去除轻微有害突变的选择效率较低的地方，转座因子（TE）插入应该更有可能漂移到更高的频率，甚至达到固定。在没有切除事件的情况下，一旦TE固定，它就不能从种群中消除，因此元素的积累应该成为一个不可逆的过程。从长远来看，这可能会导致基因组中大量非重组部分的退化。黑腹果蝇的4号染色体的重组水平非常低，如果有的话，这可能会导致它的退化。在这里，我们报告了基于pcr的分析结果，分析了来自三个非洲自然种群的样本中TE插入的种群频率。我们研究了来自12个TE家族的27个插入，这些插入位于受抑制或自由重组的区域。我们的结果表明，TE插入倾向于固定在非重组区域，特别是在第4染色体上。我们还发现，这涉及到所有类型的元件，并且固定插入比样品中分离的插入明显更短，更偏离标准序列（标准序列长度的28.1% vs 86.3%，平均核苷酸差异（D-XY）分别= 0.082 vs 0.008）。最后，基于dna的元件似乎比反转录转座子更容易达到固定。讨论了这些发现对TEs种群动态的影响，以及在重组减少区域形成遗传变异模式的进化力量。
In regions of suppressed recombination, where selection is expected to be less efficient in removing slightly deleterious mutations, transposable element (TE) insertions should be more likely to drift to higher frequencies, and even to reach fixation. In the absence of excision events, once a TE is fixed it cannot be eliminated from the population, and accumulation of elements thus should become an irreversible process. In the long term, this can drive the degeneration of large non-recombining fractions of the genomes. Chromosome 4 of Drosophila melanogaster has very low levels of recombination, if any, and this could be causing its degeneration. Here we report the results of a PCR-based analysis of the population frequencies of TE insertions in a sample from three African natural populations. We investigated 27 insertions from 12 TE families, located in regions of either suppressed or free recombination. Our results suggest that TE insertions tend to be fixed in the non-recombining regions, particularly on the fourth chromosome. We have also found that this involves all types of elements, and that fixed insertions are significantly shorter and more divergent from the canonical sequence than those segregating in the sample (28.1% vs 86.3% of the canonical length, and average nucleotide divergence (D-XY) = 0.082 vs 0.008, respectively). Finally, DNA-based elements seem to show a greater tendency to reach fixation than retrotransposons. Implications of these findings for the population dynamics of TEs, and the evolutionary forces that shape the patterns of genetic variation in regions of reduced recombination, are discussed.