Complex Genetics of D-M Incompatibilities

描述（由申请人提供）：杂种雄性不育因子是理解动物物种形成的关键，也是Haldalle规则的分子基础，即异配子性别的生殖受损是生殖隔离的第一阶段。 生殖隔离起源的Dobzhansky-Muller模型假设分离的同种种群经历独立的基因替换，当这些基因替换在杂种中结合在一起时，导致杂种不育或不存活。事实上，对杂种不亲和因子的遗传或分子基础一无所知。一系列性比减数分裂驱动系统及其抑制因子重塑精子发生已被认为是果蝇杂种雄性不育的一种机制。在这个修正的建议中，我们专注于3号染色体右臂上至少5-6个杂交雄性不育因子的精细遗传作图、定位克隆、测序、分子分析和进化研究。利用存在于D染色体3中许多不同位置的遗传标记的P元件转基因，这些每个都被定位到大约1- 2cM的区域。毛里求斯。这些标记的基因组区域已经渗入到D. simulans和纯合渐渗杂种进行育性测试。在第三染色体上，有19个因子在合适的遗传背景下与杂种雄性不育相关。这些因素之一，表示为tmy，不仅与严重降低杂交雄性育性，但也与性比减数分裂驱动。 使用一种新的遗传作图策略，该策略允许在感兴趣的区域中具有交换的重组体的容易的表型鉴定，tmy基因已经被作图到10 kb或更小的区域。 该相同的作图策略将用于细化其它杂种雄性不育因子的图谱位置，其将具有足够的分辨率以支持定位克隆。 将对每个杂种雄性不育因子进行克隆和测序，并确定其分子结构，如果可行，将用于种系转化拯救。将对tmy系统进行详细的细胞学分析。初步证据表明，第二次分裂Y染色体丢失和碎片的比率很高。其他杂种雄性不育因子的下游功能分析超出了本建议的范围，但当然是一个长期目标。利用系统发育分析、多态性分析和D. melanogaster、黑腹杜父鱼D. simulans和D.毛里求斯，和多态性和单倍型的种群内分析，以寻找最近的选择性扫描的证据。

DESCRIPTION (provided by applicant): Hybrid male sterility factors are the key to understanding speciation in animals and the molecular basis of Haldane's rule that impaired reproduction of the heterogametic sex is the first stage in reproductive isolation. The Dobzhansky-Muller model for the origin of reproductive isolation assumes that separated conspecific populations undergo independent gene substitutions which, when combined together in the hybrid, result in hybrid sterility or inviability. Virtually nothing is known about the genetic or molecular basis of hybrid incompatibility factors. A succession of sex-ratio meiotic drive systems and their suppressors that remodel spermatogenesis has been suggested as one mechanism associated with hybrid male sterility in Drosophila. In this amended proposal, we focus on the refined genetic mapping, positional cloning, sequencing, molecular analysis and evolutionary studies of at least 5-6 hybrid male sterility factors on the right arm of chromosome 3. These have each been mapped to approximately 1-2 cM regions using genetically marked P-element transgenes present at many different locations in chromosome 3 of D. mauritiana. These marked genomic regions have been introgressed into a standard genetic background of D. simulans and the homozygous introgression hybrids tested for fertility. Across the third chromosome, 19 factors are associated with hybrid male sterility in suitable genetic backgrounds. One of these factors, denoted tmy, is associated not only with severely reduced hybrid male fertility but also with sex ratio meiotic drive. Using a novel genetic mapping strategy that allows easy phenotypic identification of recombinants with an exchange in the region of interest, the tmy gene has been mapped to a region of 10 kb or smaller. This same mapping strategy will be used to refine the map positions of the other hybrid male sterility factors, which will have sufficient resolution to support positional cloning. Each hybrid male sterility factor will be cloned and sequenced and its molecular organization determined, and if feasible will be used for germline transformation rescue. The tmy system will be analyzed in detail cytologically. Preliminary evidence suggests a high rate of second-division Y chromosome loss and fragmentation. Downstream functional analysis of the other hybrid male sterility factors is beyond the scope of the present proposal but is of course a long-range goal. Each of the 5-6 hybrid male sterility factors that will be isolated will be subjected to an evolutionary analysis for its rate and pattern of molecular evolution, using phylogenetic analysis, polymorphism and divergence analysis between D. melanogaster, D. simulans and D. mauritiana, and intrapopulation analysis of polymorphisms and haplotypes to look for evidence of recent selective sweeps.