Genetic control of recombination rate differences between Drosophila species

描述（由申请人提供）： 这里提出的项目将确定果蝇物种之间基因组重组景观进化差异的分子遗传控制。构建了D. mauritiana比D.黑腹果蝇的染色体数目是黑腹果蝇的两倍，这意味着每次减数分裂的交换数目几乎是黑腹果蝇的两倍，而着丝粒和端粒对交换的抑制程度在D. mauritiana比D.黑腹菌在初步的工作中，我们发现，双顺反子基因，梅-217/梅-218，有一个经常性的适应性进化的历史，并介导这种进化物种的遗传图谱长度的差异。在这里，我们建议进一步研究mei-217/mei-218在三个方面。首先，我们将功能解剖的梅-217/梅-218基因，使用种间嵌合转基因构建体，以确定哪些功能域有助于重组率的进化变化。MEI-217和MEI-218具有预测的DNA结合结构域并参与微小染色体维持（MCM）蛋白的推定复合物-沿着MCM 5和REC/MCM 8-在减数分裂重组期间形成和/或稳定异源双链DNA交换中间体所需.因此，我们对mei-217/mei-218的功能解剖可能揭示基因产物如何改变成功交叉形成的概率。第二，我们将使用多重下一代测序技术来获得和比较转基因D。melanogaster基因型的差异仅在于携带D. melanogaster或D. mei-217/mei-218的毛里求斯等位基因。有了这些数据，我们将确定交叉事件的发生率和分布的物种差异的基础。最后，我们将使用D。melanogaster系统来分析mei-217/mei-218中功能分歧的影响，以询问在这个快速进化的基因中的经常性替换是否介导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.