Genetic control of recombination rate differences between Drosophila species

描述(由申请人提供)： 该项目将确定果蝇物种间基因组重组格局进化差异的分子遗传控制。毛果金龟子的总遗传图谱比黑腹果蝇长约1.7倍，这意味着每个减数分裂的交叉数几乎是前者的两倍，而且着丝粒和端粒对交叉的抑制程度要比黑果蝇小得多。在前期工作中，我们发现一个双顺反子基因mei-217/mei-218具有反复适应性进化的历史，并在遗传图谱长度上调节这种进化的物种差异。在这里，我们建议从三个方面对梅217/梅218进行进一步的研究。首先，我们将使用种间嵌合转基因构建物从功能上剖析mei-217/mei-218基因，以确定哪些功能结构域对重组率的进化变化起作用。Mei-217和Mei-218预测了DNA结合域，并参与了一个推测的微小染色体维持(MCM)蛋白复合体-以及MCM5和REC/MCM8-在减数分裂重组过程中形成和/或稳定异源双链DNA交叉中间体所必需的。因此，我们对mei-217/mei-218的功能解剖可能有助于阐明基因产物如何改变成功交叉形成的概率。其次，我们将使用多路下一代测序来获得和比较转基因黑腹果蝇之间的互换和基因转换的高分辨率基因组图谱，这些转基因黑腹果蝇只携带mei-217/mei-218的黑腹果蝇或毛果果蝇等位基因。有了这些数据，我们将确定交叉事件的频率和分布的物种差异的基础。最后，我们将使用我们的黑腹果蝇系统来测试在mei-217/mei-218中功能差异的影响，以询问这个快速进化的基因中的重复替换是否介导了其他果蝇谱系中重组率的变化。

DESCRIPTION (provided by applicant): The project proposed here will determine the molecular genetic control of evolved differences in the genomic recombination landscape between Drosophila species. The total genetic map of D. mauritiana is ~1.7 times longer than that of D. melanogaster-implying nearly twice as many crossovers per meiosis- and the extent of centromeric and telomeric suppression of crossing over is considerably smaller in D. mauritiana than D. melanogaster. In preliminary work, we showed that a dicistronic gene, mei-217/mei-218, has a history of recurrent adaptive evolution and mediates this evolved species difference in genetic map length. Here we propose to further investigate mei-217/mei-218 in three ways. First, we will functionally dissect the mei- 217/mei-218 gene, using interspecific chimeric transgene constructs, to determine which functional domains contribute to the evolutionary change in recombination rate. MEI-217 and MEI-218 have predicted DNA- binding domains and participate in a putative complex of minichromosome maintenance (MCM) proteins- along with MCM5 and REC/MCM8- required for the formation and/or stabilization of heteroduplex DNA crossover intermediates during meiotic recombination. Our functional dissection of mei-217/mei-218 may therefore shed light on how the gene products alter the probability of successful crossover formation. Second, we will use multiplexed next-generation sequencing to obtain and compare high-resolution genomic maps of crossing over and gene conversion between transgenic D. melanogaster genotypes that differ only in carrying either the D. melanogaster or D. mauritiana allele of mei-217/mei-218. With these data, we will determine the basis of species differences in the rate and distribution of crossover events. Finally, we will use our D. melanogaster system to assay the effects of functional divergence in mei-217/mei-218 to ask if recurrent substitutions in this rapidly evolving gene mediate changes in recombination rate in other Drosophila lineages.