Genetic Dissection of Wolbachia Infection in Drosophila Melanogaster

收缩沃尔巴克氏杆菌是已知分布最广泛的内共生微生物之一。它最初是在库蚊复合体的蚊子中发现的，后来在用于遗传学研究的超过20%的昆虫物种和大约25%的黑腹果蝇中发现了它。沃尔巴克氏菌擅长操纵寄主繁殖。在果蝇中，沃尔巴克氏菌主要导致细胞质不相容(CI)，这是生殖隔离的一种形式。CI的表达使受感染的雄性在与未感染的雌性交配时无法成为后代的父亲。当受感染的雄性正常交配、转移精子并使卵子受精时，卵子无法完成核受精并死亡。未受感染的雄性和受感染的雌性之间的反向杂交是可行的，但由于沃尔巴克氏菌通过雌性垂直传播，因此所有产生的后代都会受到感染。该研究项目将试图了解沃尔巴克氏菌在果蝇睾丸中分布的遗传基础，以及由此产生的对CI的影响。缺失作图将确定对黑腹果蝇睾丸内沃尔巴克氏菌分布和密度有较大影响的基因座。将对短缺库存进行筛查，以确定是否存在沃尔巴克氏菌。那些具有不同沃尔巴克氏菌分布模式的菌株将被进一步研究它们引起CI的能力(或不能)以及不同细菌分布的宿主遗传基础。在通过缺失作图确定重要候选基因座后，将研究不同外显率的等位基因对细菌分布和CI的影响。确定沃尔巴克氏菌分布模式所涉及的基因和生化途径的识别将促进对沃尔巴克氏菌如何操纵果蝇寄主繁殖和精子发生的理解。它还可能提供线索，说明当沃尔巴克氏菌感染更远亲的昆虫，特别是导致人类疾病的害虫(例如，通过蚊子传播的疟疾)时，哪些途径被操纵。这些知识还将有助于利用沃尔巴克氏菌设计有效的虫害管理计划。

Wolbachia pipientis is one of the most widespread endosymbiotic microorganisms known. First characterized in mosquitoes of the Culex pipiens complex, it has since been found in greater than 20% of insect species and about 25% of Drosophila melanogaster used in genetic research. Wolbachia has specialized in the manipulation of host reproduction. In Drosophila, Wolbachia primarily causes cytoplasmic incompatability (CI), a form of reproductive isolation. The expression of CI renders infected males unable to father offspring when mated to uninfected females. While infected males mate normally, transfer sperm and the sperm fertilize the egg, the egg fails to complete karyogamy and dies. Reciprocal crosses between uninfected males and infected females are viable, but since Wolbachia are transmitted vertically through the female, all resulting progeny are infected. The research project will attempt to understand the genetic basis of Wolbachia distribution in Drosophila melanogaster testes and the resulting effects on CI. Deficiency mapping will identify loci with large effects on Wolbachia distribution and density within D. melanogaster testes. Deficiency stocks will be screened for the presence of Wolbachia. Those strains with dissimilar patterns of Wolbachia distribution will be studied further for their ability (or inability) to cause CI as well as the for the host genetic basis of differential bacterial distribution. Following identification of important candidate loci through deficiency mapping, alleles with different levels of penetrance will be studied for their impact on bacterial distribution and CI. The identification of genes and biochemical pathways involved in determining Wolbachia distribution patterns will advance the understanding of how Wolbachia manipulate host reproduction in Drosophila and spermatogenesis in general. It may also provide clues as to what pathways are manipulated when Wolbachia infect more distantly related insects, particularly insect pests that cause human diseases (for example, malarial diseases transmitted by mosquitoes. Such knowledge will also aid in the design of effective pest management programs utilizing Wolbachia.