The mechanisms of segregation distortion in Drosophila

项目摘要 扭曲分离的人是自私的遗传因素，在成熟的人中通过过度表现自己来运作 Gamete池，因此从根本上违反了孟德尔定律。在两国之间引发的进化军备竞赛 长期以来，扭曲基因及其抑制者一直被认为是塑造进化的强大力量 基因组、细胞和物种。尽管种族隔离扭曲者无处不在，也很重要，但我们理解 对这类自私遗传因素的遗传基础和分子机制知之甚少。一把钥匙 理解偏析扭曲机制的障碍在于它们存在于非模型中 缺乏遗传工具的系统，几乎总是与受阻的染色体倒置有关 基因发现的传统遗传学方法。而没有刻画潜在的遗传基础和 分子机制仍然不可能将自私分子引发的军备竞赛直接联系到 减数分裂和性染色体系统进化中的更广泛的现象。 在这里，我们开发了两种独立的方法来绕过染色体带来的传统障碍 基因倒置的发现，与剖析这种自私行为背后的遗传基础密切相关 果蝇物种。在我们的第一个目标中，我们开发了一种突变方法来识别导致性别- 假黑斑潜蝇的比率失真。通过组合测序，在电子互补中，放大- 分离作图和基于CRISPR/Cas9的编辑，我们准备解决复杂的遗传 架构是扭曲的基础，并确定完整的基因集，包括修饰符和 增强子，驱动假黑斑潜蝇性别比染色体的自私行为。我们的第二个目标是， 我们为扭曲的抑制者揭示了物种内部的隐秘变异。在这里，我们的目标是了解 通过鉴定基因和抑制子在畸变子和抑制子之间的分子军备竞赛 偏析扭曲的抑制机制和扭曲抑制因子。在我们的第三个 目的：我们设计了一种人工染色体倒位，以允许性别比扭曲的重组作图。 变态D.这种方法适应了FLP/FRT位点特定的重组工具，以生成完美的 共线非驱动染色体允许在包含所有必要和 有足够的基因导致SR失真。一旦候选基因被绘制、验证并组织成 这两个系统的比较分析将检验SR 机制是唯一的或共享的。总而言之，这项工作将提供最完整的 到目前为止，性别连锁分离扭曲者打开了理解性别连锁分离的分子机制的大门 在两个性别比系统中的失真，并首次明确测试独立或共享的起源和 这些亲缘关系密切的物种的性比扭曲机制。

Project Summary Segregation distorters are selfish genetic elements that operate by over-representing themselves in the mature gamete pool, thus fundamentally violating Mendel’s law. The evolutionary arms races triggered between distorter genes and their suppressors have long been recognized as a powerful force that shapes the evolution of genomes, cells, and species. Despite the ubiquity and importance of segregation distorters, we understand very little about the genetic basis and molecular mechanisms of this class of selfish genetic elements. A key barrier in understanding the mechanisms of segregation distorters is that they are present in non-model systems that lack genetic tools, and are almost always associated with chromosomal inversions that thwart traditional genetic approaches to gene discovery. Without characterizing the underlying genetic basis and molecular mechanisms it remains impossible to directly connect the arms race initiated by selfish elements to broader phenomena in the evolution of meiosis and sex chromosome systems. Here, we develop two independent methods to side-step traditional barriers presented by chromosomal inversions to gene discovery, and dissect the genetic basis underlying this selfish behavior in closely related Drosophila species. In our first aim, we develop a mutagenesis approach to identify the genes causing Sex- Ratio distortion in D. pseudoobscura. Through a combination of sequencing, in silico complementation, bulked- segregant mapping, and CRISPR/ Cas9 based editing, we are poised to resolve the complex genetic architecture that underlies distortion and to identify the complete set of genes, including modifiers and enhancers, that drive the selfish behavior of the D. pseudoobscura Sex-Ratio chromosome. In our second aim, we uncover cryptic variation within species for suppressors of distortion. Here, we aim to understand the molecular arms races between distorters and their suppressors through the identification of the genes and mechanisms of suppression of segregation distortion, and suppressors of suppressors-of-distortion. In our third aim, we engineer a synthetic chromosomal inversion to allow recombination mapping of Sex-Ratio distortion in D. persimilis. This approach adapts the Flp/FRT site-specific recombination tools to generate a perfectly collinear non-driving chromosome to allow free recombination in the region containing all necessary and sufficient genes for SR distortion. Once candidate genes are mapped, validated, and organized into a functional pathway for D. persimilis, a comparative analysis of these two systems will test whether SR mechanisms are unique or shared. Together, this work will provide the most complete genetic architecture of sex-linked segregation distorters to date, open the door to understanding the molecular mechanisms of distortion in two Sex-Ratio systems, and for the first time explicitly test independent or shared origins and mechanisms of Sex-Ratio distortion in these closely related species.