Doctoral Dissertation Improvement: Genetic Transposition of Baboon Endogenous Virus (BaEV) in Hybrid Old World Monkeys (Primates: Papionini)

在《物种起源》发表140多年后，导致新的、一贯独特的种群出现和遗传稳定的过程仍然是最不为人所知的进化过程之一。虽然多种机制可能与遗传隔离有关，但最近的注意力集中在基因组水平的特征上，这些特征既快速进化，又能大大降低其携带者杂交和产生可存活的杂交后代的能力。最近的各种证据表明，转座因子（te）促进了这种生殖隔离。te是很小的（100-10kb碱基对）遗传元件，它们在基因组中保持了移动的能力。对果蝇和小袋鼠等多种生物的研究表明，转座因子活性与株系间杂交种的不育性呈正相关。为了确定te介导的群体间杂交障碍是如何进化的，有必要研究这些元素在可育杂交种及其后代中在自然发生的杂交种区中的行为。该项目的目的是研究TE扩增和杂交之间的关系，通过测试的证据，狒狒内源性病毒（BaEV）转位在旧大陆猴组的分级系列杂交。BaEV是一种内源性逆转录病毒，曾经在个体之间水平传播，但现在已成为许多旧大陆猴垂直遗传基因组的组成部分。逆转录病毒是最复杂的TE形式之一，具有较大的基因组，可以通过内在驱动的逆转录过程产生拷贝。因此，本项目将通过测试具有不同程度杂交血统的木瓜肽杂交种的BaEV扩增来研究TE活性与生殖隔离之间的关系。提出的研究的具体目的是：确定BaEV扩增与杂交不育的相关程度；测定杂交番木瓜素BaEV扩增随亲本类群进化距离的增加而增加的程度；在已知亲缘关系的个体中检测可能归因于特定杂交事件的新型BaEV整合；以及确定野生灵长类动物种群中BaEV序列变异的程度。这些目标将通过对反映不同程度杂交祖先的杂交番木瓜素进行分级取样来实现。这些数据将作为确定TEs对番木瓜素生殖隔离的贡献的第一步。

More than 14 decades after the publication of "On the Origin of Species," the processes leading to the appearance and genetic stabilization of new, consistently distinct populations remains one of the least understood of evolutionary processes. While a variety of mechanisms may be associated with genetic isolation, attention recently has focussed upon genome-level features that are both rapidly-evolving and can drastically reduce the ability of their carriers to interbreed and produce viable hybrid offspring. A variety of recent evidence implicates transposable elements (TEs) in facilitating such reproductive isolation. TEs are small (100-10kb base pairs) genetic elements that have retained their ability to move about within genomes. Investigations conducted on organisms as diverse as fruit flies and wallabies suggest that there is a positive correlation between transposable element activity and sterility in inter-strain hybrids. In order to determine how TE-mediated barriers to inter-population hybridization might evolve, it is necessary to examine the behavior of such elements in fertile hybrids and their progeny in naturally occurring hybrid zones.The goal of this project is to investigate the relationship between TE amplification and hybridity by testing for evidence of baboon endogenous virus (BaEV) transposition in a graded series of Old World Monkey hybrids in the papionin group. BaEV is an endogenous retrovirus that was once transmitted horizontally from individual to individual but now forms an integrated part of the vertically inherited genome of many Old World Monkeys. Retroviruses are one of the most complex TE forms, with large genomes that can generate copies through the intrinsically driven process of reverse transcription. This project will thus investigate the relationship between TE activity and reproductive isolation by testing BaEV amplification in papionin hybrids with varying degrees of hybrid ancestry. The specific aims of the proposed research are: to determine the degree to which BaEV amplification is correlated with hybrid sterility; to determine the degree to which BaEV amplification increases in hybrid papionins with increased evolutionary distance between parental taxa; to detect novel BaEV integrations in individuals with known parentage that may be attributable to specific hybridization events; and to determine the extent of BaEV sequence variation in a wild primate population. These objectives will be accomplished by sampling a graded series of hybrid papionins reflecting different degrees of hybrid ancestry. These data will serve as a first step in determining the contribution of TEs to reproductive isolation in papionins.