Molecular analysis of hybrid incompatibility genes in Drosophila

描述（由申请人提供）：在跨门的许多分类组内的种间杂交中观察到杂交不相容性（His），包括杂交致死性和不育性。这些表型背后的分子机制目前尚不清楚，但最近在果蝇中发现的一组快速进化的基因提供了一个令人兴奋的机会，以深入了解这一过程。这项计划的目标是详细研究一个这样的基因，杂交雄性拯救（Hmr），它导致果蝇/D的致命性。simulans hybrids Hmr基因编码一种蛋白质，该蛋白质含有保守的DNA结合结构域，但在果蝇属物种中高度分化。这些特征表明HMR在杂交动物中通常作为种特异性转录调节因子发挥作用，并异常结合靶基因导致其死亡。先前的遗传学实验表明，Hmr也可能与另一个杂交致死基因，母体杂交拯救（mhr）相互作用。我将在三个具体目标中检验这些假设。首先，我将通过检测D.黑腹菌将使用多线染色体分析和染色质免疫沉淀（ChIP）来鉴定候选HMR靶基因;将通过测定HMR无效背景中的转录效应以及与HMR的遗传相互作用来检测这些基因。其次，我将使用类似的方法来确定是否HMR结合在杂交中改变。具体来说，我将测试一个子集的候选靶基因的正常HMR结合和异位结合的HMR到整个基因组的不适当的靶位点的测定。将检测单个靶标的转录水平是否改变。第三，我将研究HMR是否与MHR相互作用。为此，我将测定HMR转基因对MHR依赖性杂交致死率的影响，相反，我将测试MHR突变是否影响HMR依赖性杂交致死率。这项工作将是HI基因的第一批分子研究，并将有助于了解HMR的种内功能及其在杂交致死性中的作用之间的关系。 基因组研究已经揭示了在包括人类在内的许多高等真核生物中存在快速进化的基因。虽然这些基因的生物学作用在很大程度上是未知的，但它们可能会影响不同的表型特征，如物种特异性适应和易感性或抗病性。本研究对D.黑腹果蝇将提供一个很好的遗传模型，以了解快速进化的基因的功能，以及它们在人类发育和健康中所扮演的角色。

DESCRIPTION (provided by applicant): Hybrid Incompatibilities (His), including hybrid lethality and sterility, have been observed in interspecies crosses within numerous taxonomic groups across the phyla. The molecular mechanisms underlying these phenotypes are currently not known but a recently identified set of rapidly evolving genes in Drosophila offers an exciting opportunity to gain insight into this process. The goal of this proposal is to examine in detail one such gene, Hybrid male rescue (Hmr), which causes lethality in Drosophila melanogaster/D. simulans hybrids. The Hmr gene encodes a protein that contains conserved DNA-binding domains but is otherwise highly diverged among Drosophila species. These characteristics suggest that HMR normally functions as a species-specific transcriptional regulator and binds target genes abnormally in hybrid animals to cause their death. Previous genetic experiments suggested that Hmr may also interact with another hybrid lethal gene, maternal hybrid rescue (mhr). I will test these hypotheses in three specific aims. First, I will test the putative role of Hmr as a transcriptional regulator by examining the DNA binding pattern of HMR protein in D. melanogaster. Polytene chromosome analysis and chromatin immunoprecipitation (ChIP) will be used to identify candidate HMR target genes; these will be tested by assaying for transcriptional effects in the Hmr-null background and for genetic interactions with Hmr. Second, I will use similar methods to determine whether HMR binding is altered in hybrids. Specifically, I will test a subset of candidate target genes for normal HMR binding and assay for ectopic binding of HMR to inappropriate target sites throughout the genome. Individual targets will be tested for altered transcription levels. Third, I will investigate whether Hmr interacts with mhr. To do this, I will assay for effects of Hmr transgenes on mhr-dependent hybrid lethality and, conversely, I will test if mhr mutations affect Hmr-dependent hybrid lethality. This proposed work will be among the first molecular studies of an HI gene and will help to understand the relationship between the intraspecific function of Hmr and its role in hybrid lethality. Genomic studies have revealed the presence of rapidly evolving genes in a number of higher eukaryotes, including humans. Although the biological roles of these genes are largely unknown, they are likely to influence diverse phenotypic traits such as species-specific adaptations and predisposition or resistance to disease. This study of HI genes in D. melanogaster will provide a good genetic model for understanding the function of rapidly evolving genes and the roles they play in the development and health of humans.