The Genetic Basis of Cytoplasmic Incompatibility

项目摘要 沃尔巴克氏菌提供了一种不含杀虫剂的替代品来遏制虫媒病毒的传播。目前的试点研究释放感染病毒 蚊子要么使居民种群数量崩溃，要么使蚊子传播的媒介能力降低 当地的人口。这两种努力都依赖沃尔巴克氏菌的适应来导致细胞质不亲和性(CI)-a 在感染的雄性和未感染的雌性之间的杂交中导致胚胎停止的精子修改 (单向CI)或携带不同沃尔巴克氏菌株的男性和女性之间(双向CI)。 然而，感染了相同菌株的雌性病毒挽救了修改精子的过程，使它们具有很大的适应性 与未感染的雌性相比具有优势，进而使沃尔巴克氏菌能够通过宿主种群迅速传播。 尽管40年来对媒介控制进行了密集的研究和目前的应用，但潜在的遗传基础 尚未有CI的报告。然而，我们最近在已公布的 自然感染果蝇的wMel Wolbchia菌株。这些基因在下文中称为 即细胞质不亲和因子A(CIFA)和细胞质不亲和因子B(CIFB)。CIFA和CIFB展品 在感染的宿主睾丸中表达增强，与CI相关基因的预期一样。CIFA和CIFB的表达 在未感染的D黑腹果蝇睾丸中的转基因重现了CI的诱导，而在Wolbachia中的表达- 感染的睾丸增加了野生型CI。重要的是，感染wMel的雌性拯救了与转基因相关的 CI，从而暗示这些候选基因可能是CI基因。系统发育分析表明CIFA和CIFB具有不同的分支 沃尔巴克氏菌菌株之间存在双向不亲和关系的同源基因。另外， 最近的基因组测序和比较揭示了候选的救援基因，这些基因表现出与 CIFA和CIFB的表达及在早期胚胎中的优先表达。因为这些发现代表着潜在的 在寻找CI基因方面的突破，拟议研究的中心假设是候选 修饰和挽救基因决定了单向和双向CI。在目标1中，我们将使用转基因 表达遗传差异的CIFA和CIFB变异体以广泛检测CIF必需基因区域以进行诱导 以及这些基因的现有同源基因是否保留了诱发CI的能力。在目标2中，我们将调查 利用雌性和雄性杂交中的转基因表达从wMEL中获得候选救援基因 与CI诱导的沃尔巴克氏杆菌或转基因CIF同源物。这一目标也将明确地检验这样一种假设 修饰和挽救基因的差异是双向CI的基础。到目前为止，考试还没有取得成果 CI双方的全面遗传进步，以及对部署Wolbchia以遏制 虫媒病毒的传播需要对沃尔巴克氏杆菌的驱动系统进行解释。如果成功，这项研究将 细菌诱导生殖寄生的先驱遗传学研究，告知沃尔巴克氏菌的有效性和交付作为 一种控制各种人畜共患疾病的工具，并为发现 卧底告密者。

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.