The Genetic Basis of Cytoplasmic Incompatibility

项目摘要 沃尔巴克氏体为遏制虫媒病毒传播提供了一种无农药的替代品。目前的试点研究释放感染 蚊子的数量会减少， 当地人口。这两种努力都依赖于沃尔巴克氏体的适应性，以引起细胞质不相容性（CI）- a 在受感染的雄性和未受感染的雌性之间的杂交中导致胚胎停滞的精子修饰 （单向CI）或携带不同沃尔巴克氏体菌株的雄性和雌性之间（双向CI）。 然而，感染相同菌株的雌性挽救精子修改，给他们一个大的健身 这使得沃尔巴克氏体在宿主群体中迅速传播。 尽管经过40年的密集研究和目前在病媒控制方面的应用， CI尚未报道。然而，我们最近在已释放的大肠杆菌中鉴定了两个前噬菌体WO基因候选物。 一种能感染黑腹果蝇的沃尔巴克氏体。这些基因在下文中称为 作为细胞质不相容因子A（cifA）和细胞质不相容因子B（cifB）。cifA和cifB展品 在感染的宿主睾丸中的表达增强，正如对CI中涉及的基因所预期的那样。cifA和cifB的表达 未感染D.黑腹睾丸重演CI的诱导，而在沃尔巴克氏体中的表达， 感染的睾丸增强野生型CI。重要的是，wMel感染的雌性挽救了转基因相关的 CI，从而暗示这些候选人作为可能的CI基因。系统发育详细说明了cifA和cifB的不同分支 在沃尔巴克氏体菌株之间具有双向不亲和关系共变的同源物。此外，本发明还 最近的基因组测序和比较揭示了候选拯救基因，它们表现出平行的同源性， cifA和cifB在早期胚胎中优先表达。因为这些发现代表了 在寻找CI基因方面取得了突破，所提出的研究的中心假设是， 修饰和拯救基因决定单向和双向CI。在目标1中，我们将使用转基因 表达遗传上不同的cifA和cifB变体，以广泛地测试诱导cifA和cifB的必需cif基因区域。 CI和这些基因的现存同源物是否保留诱导CI的能力。在目标2中，我们将研究 在雌性动物和与一系列雄性动物杂交中使用转基因表达的来自wMel的候选拯救基因 用CI诱导的沃尔巴克氏体或转基因cif同源物。这一目标还将明确检验以下假设： 修饰和拯救基因的差异是双向CI的基础。迄今为止， CI双方的全面遗传进展，以及部署Wolbachia以遏制 虫媒病毒的传播需要解释沃尔巴克氏体的驱动系统。如果成功，这项研究将 细菌诱导生殖寄生的先驱遗传研究，告知沃尔巴克氏体的功效和交付， 一种控制多种人畜共患病的工具，并为发现 是CI的基础

Project Summary Wolbachia offer a pesticide-free alternative to curb arbovirus transmission. Current pilot studies release infected mosquitoes to either crash the resident population size or spread mosquitoes with reduced vectorial capacity in the local population. Both efforts rely upon Wolbachia's adaptation to cause cytoplasmic incompatibility (CI) - a sperm modification that causes embryonic arrest in crosses between infected males and uninfected females (unidirectional CI) or between males and females harboring different Wolbachia strains (bidirectional CI). However, infected females with the same strain rescue the sperm modification, giving them a large fitness advantage over uninfected females that in turn enables rapid spread of Wolbachia through host populations. Despite four decades of intense research and current applications to vector control, the underlying genetic basis of CI has not been reported. However, we recently identified two prophage WO gene candidates in the released strain of wMel Wolbachia that natively infects Drosophila melanogaster. These genes are hereafter referred to as cytoplasmic incompatibility factor A (cifA) and cytoplasmic incompatibility factor B (cifB). cifA and cifB exhibit enhanced expression in infected host testes, as expected for genes involved in CI. Expression of cifA and cifB transgenes in uninfected D. melanogaster testes recapitulates induction of CI, while expression in Wolbachia- infected testes enhances the wild type CI. Importantly, wMel-infected females rescue the transgene-associated CI, thereby implicating these candidates as likely CI genes. Phylogenies specify divergent clades of cifA and cifB homologs that covary with bidirectional incompatibility relationships between Wolbachia strains. Additionally, recent genome sequencing and comparisons reveal candidate rescue genes that exhibit parallel phylogenies to those of cifA and cifB and preferential expression in early embryos. As these findings represent a potential breakthrough in the search for CI genes, the central hypothesis of the proposed research is that the candidate modification and rescue genes determine unidirectional and bidirectional CI. In Aim 1, we will use transgenic expression of genetically divergent cifA and cifB variants to broadly test the essential cif gene regions for inducing CI and whether extant homologs of these genes retain the ability to induce CI. In Aim 2, we will investigate candidate rescue genes from wMel using transgenic expression in females and crosses with an array of males with CI-inducing Wolbachia or transgene cif homologs. This aim will also explicitly test the presumption that divergence in modification and rescue genes underlies bidirectional CI. Examinations thus far have yet to yield a comprehensive genetic advance for both sides of CI, and the rising interest in deploying Wolbachia to curb arbovirus transmission necessitates an explanation of Wolbachia's drive system. If successful, this research will pioneer genetic studies of bacteria-induced reproductive parasitism, inform Wolbachia's efficacy and delivery as a tool to control diverse zoonotic diseases, and provide multiple lines of evidence for the discovery of genes that underlie CI.