Department of Evolution and Ecology, University of California - Davis, , Davis, CA 95616, USA.
Philos Trans R Soc Lond B Biol Sci. 2010 Apr 27;365(1544):1219-28. doi: 10.1098/rstb.2009.0318.
Transposable elements (TEs) are families of small DNA sequences found in the genomes of virtually all organisms. The sequences typically encode essential components for the replicative transposition sequences of that TE family. Thus, TEs are simply genomic parasites that inflict detrimental mutations on the fitness of their hosts. Several models have been proposed for the containment of TE copy number in outbreeding host populations such as Drosophila. Surveys of the TEs in genomes from natural populations of Drosophila have played a central role in the investigation of TE dynamics. The early surveys indicated that a typical TE insertion is rare in a population, which has been interpreted as evidence that each TE is selected against. The proposed mechanisms of this natural selection are reviewed here. Subsequent and more targeted surveys identify heterogeneity among types of TEs and also highlight the large role of homologous and possibly ectopic crossing over in the dynamics of the Drosophila TEs. The recent discovery of germline-specific RNA interference via the piwi-interacting RNA pathway opens yet another interesting mechanism that may be critical in containing the copy number of TEs in natural populations of Drosophila. The expected flood of Drosophila population genomics is expected to rapidly advance understanding of the dynamics of TEs.
转座元件 (TEs) 是几乎所有生物体基因组中发现的小 DNA 序列家族。这些序列通常编码该 TE 家族复制转座序列的必需成分。因此，TE 是简单的基因组寄生虫，它们对宿主的适应性造成有害突变。已经提出了几种模型来控制像果蝇这样的异交宿主群体中的 TE 拷贝数。对来自果蝇自然种群基因组中的 TEs 的调查在 TE 动力学的研究中起着核心作用。早期的调查表明，典型的 TE 插入在种群中很少见，这被解释为每个 TE 都受到选择的证据。这里回顾了这种自然选择的提出机制。随后的、更有针对性的调查确定了 TE 类型之间的异质性，并强调了同源和可能异位交叉在果蝇 TE 动力学中的重要作用。最近通过 piwi 相互作用 RNA 途径发现生殖细胞特异性 RNA 干扰，开辟了另一个可能在控制果蝇自然种群中 TE 拷贝数方面至关重要的有趣机制。预计果蝇群体基因组学的大量涌现将迅速推进对 TE 动力学的理解。
