Paternally inherited P-element copy number affects the magnitude of hybrid dysgenesis in Drosophila simulans and D. melanogaster

Transposable elements (TEs) are repetitive regions of DNA that are able to self-replicate and reinsert themselves throughout host genomes. TEs rapidly propagate throughout populations once introduced, despite the potentially deleterious nature of their spread. Since the discovery of TEs, one of the questions that has been posed is what determines when TEs affect the fitness of their hosts and whether copy number is a cause. P elements (PEs) in Drosophila provide an ideal system through which to study whether the number of PEs, and TEs generally, are an important factor in determining phenotypic defects that within-species F1s suffer. We address this question by inferring the number of PEs in individual isofemale line genomes and measuring whether there is an effect of the P-element copy number on multiple phenotypes associated with the hybrid dysgenesis (HD) syndrome in two species of Drosophila. Consistent with previous reports, we find strong evidence for this effect and a significant increase in fitness defects in F1 females and males as the number of P-element copies in the genome increases. Nonetheless, the effect of the copy number is modulated by temperature and the identity of the species.

转座因子（Transposable elements, TEs）是一类能够自主复制并在宿主基因组中重新插入的DNA重复序列。TEs一旦被引入种群，便会快速扩散，尽管其扩散过程本身存在潜在的有害性。自TEs被发现以来，学界长期关注的核心问题之一是：何种因素决定了TEs何时会对宿主的适合度产生影响，以及拷贝数是否为该影响的关键诱因。果蝇属（Drosophila）中的P因子（P elements, PEs）为研究PEs乃至一般TEs的数量是否为决定种内F1子代所出现的表型缺陷的重要因素，提供了理想的实验模型。本研究通过推断单只同雌系个体基因组中的PEs数量，并检测P因子拷贝数是否对两种果蝇的杂种劣育综合征（hybrid dysgenesis, HD）相关的多种表型存在影响，以此解答上述问题。与既往研究报道一致，我们发现了该效应的强有力证据：随着基因组中P因子拷贝数的增加，F1代雌雄个体的适合度缺陷均显著升高。尽管如此，拷贝数所带来的效应会受到温度以及物种类别的调控。