Abstract：
Chromosome inversions are of unique importance in the evolution of genomes and species because when heterozygous with a standard arrangement chromosome, they suppress meiotic crossovers within the inversion. In Drosophila species, heterozygous inversions also cause the interchromosomal effect, whereby the presence of a heterozygous inversion induces a dramatic increase in crossover frequencies in the remainder of the genome within a single meiosis. To date, the interchromosomal effect has been studied exclusively in species that also have high frequencies of inversions in wild populations. We took advantage of a recently developed approach for generating inversions in Drosophila simulans, a species that does not have inversions in wild populations, to ask if there is an interchromosomal effect. We used the existing chromosome 3R balancer and generated a new chromosome 2L balancer to assay for the interchromosomal effect genetically and cytologically. We found no evidence of an interchromosomal effect in D. simulans. To gain insight into the underlying mechanistic reasons, we qualitatively analyzed the relationship between meiotic double-strand break formation and synaptonemal complex assembly. We find that the synaptonemal complex is assembled prior to double-strand break formation as in D. melanogaster; however, we show that the synaptonemal complex is assembled prior to localization of the oocyte determination factor Orb, whereas in D. melanogaster, synaptonemal complex formation does not begin until Orb is localized. Together, our data show no evidence that heterozygous inversions in D. simulans induce an interchromosomal effect and that there are differences in the developmental programming of the early stages of meiosis.
摘要：
染色体倒位在基因组和物种进化中具有独特的重要性，因为当与标准排列染色体杂合时，它们在倒置中抑制减数分裂交叉。在果蝇物种中，杂合倒位也会引起染色体间效应，其中杂合倒位的存在诱导单个减数分裂中基因组其余部分的交叉频率的急剧增加。迄今为止,染色体间效应仅在野生种群中也具有高倒位频率的物种中进行了研究。我们利用了最近开发的一种方法来在果蝇模拟物中产生倒置，一个在野生种群中没有倒置的物种，询问是否有染色体间效应。我们使用了现有的3R染色体平衡器，并产生了一种新的2L染色体平衡器，以在遗传和细胞学上测定染色体间效应。我们在D.simulans中没有发现染色体间效应的证据。为了深入了解潜在的机械原因，我们定性分析了减数分裂双链断裂形成与突触复合体组装之间的关系。我们发现突触复合体在双链断裂形成之前就已经组装好了，就像在黑腹D.我们表明，突触复合体是在卵母细胞决定因子Orb定位之前组装的，而在黑腹D.中，直到Orb被定位，突触复合物才开始形成。一起,我们的数据显示没有证据表明D.simulans中的杂合倒位会诱导染色体间效应，并且减数分裂早期的发育程序存在差异。
