DISSERTATION RESEARCH: Evolutionary strategies for adaptation in Wolbachia, a reproductive symbiont of arthropods.

该项目将研究生活在密切联系中并相互受益的物种的进化过程，即共生。沃尔巴克氏体是一种细菌，通常与昆虫密切相关，它通过昆虫宿主的繁殖来确保自己的传播。沃尔巴克氏体的特定生活方式，以及它操纵昆虫的方式，提供了一个独特的机会：(1)研究共生的进化，(2)开发控制昆虫种群的替代方法，包括传播疾病的蚊子和家庭和作物的常见害虫。然而，沃尔巴克氏体从一个物种成功转移到新的目标昆虫物种已经被证明是困难的，可能是因为沃尔巴克氏体不适应新的昆虫物种，因为它们没有共同进化。该研究项目将使用一种新系统在一种昆虫的基因组中创造变异，这种昆虫已经是沃尔巴克氏体自然共生的一部分。随着沃尔巴克氏体适应宿主体内新产生的遗传变异，昆虫和沃尔巴克氏体的变化将随着时间的推移而被追踪。除了为新的昆虫控制策略的发展提供信息外，阐明沃尔巴克氏体的适应过程可能有助于我们了解其他细菌-宿主相互作用。研究方法是通过制造一系列重组的同雌性寄生蜂赤眼蜂（Trichogramma pretiosum），在寄主昆虫中创造遗传变异，随后跟踪沃尔巴克氏体在每一种寄生蜂中的表现。与原寄主相比，沃尔巴克氏体最初在重组寄主中的表现较差，但能够在短时间内适应新的昆虫。利用该系统，沃尔巴克氏体和前赤眼蜂的变化可用于识别在共生建立早期阶段重要的基因和分子途径。基因组重测序方法将用于确定沃尔巴克氏体基因组的突变。反过来，利用RNA-Seq比较黄蜂在早、晚时间点的转录活性，从而确定昆虫对进化共生体的反应。该系统为研究共生体和宿主在共同进化过程中基因组、生理和表型的变化提供了一个平台。

This project will study the process of evolution of species that live in close association and benefit each other, symbioses. Wolbachia is a bacterium, commonly found in close associations with insects, that co-opts the reproduction of an insect host to ensure its own transmission. The specific lifestyle of Wolbachia, and the ways in which it manipulates insects, provide a unique opportunity to (1) study the evolution of symbiosis, and (2) develop alternative methods for controlling insect populations including disease transmitting mosquitoes and common pests of homes and crops. However, the successful transfer of Wolbachia from one species to new target insect species has proven difficult, likely because Wolbachia is not adapted to the new species of insect since they have not coevolved. The research project will use a novel system to create variation in the genome of an insect species that is already part of a natural symbiosis with Wolbachia. Changes in both the insect and Wolbachia will then be tracked over time, as Wolbachia adapts to the newly created genetic variation present in its host. Beyond informing the development of novel insect control strategies, elucidating the adaptive process in Wolbachia may help us understand other bacteria-host interactions.The research approach is to create genetic variation in a host insect by making a series of recombinant isofemale lines of the parasitic wasp, Trichogramma pretiosum, and subsequently to track the performance of Wolbachia in each of those lines. Compared to the original host, Wolbachia performs poorly in the recombinant hosts initially, but is able to adapt to the new insects in a short time span. Using this system, changes to both Wolbachia and Trichogramma pretiosum can be used to identify genes and molecular pathways that are important in the early stages of symbiont establishment. A genome re-sequencing approach will be used to identify mutations in the Wolbachia genome. Reciprocally, transcriptional activity of the wasps will be compared at early and late time points using RNA-Seq, so as to identify how the insect responds to the evolving symbiont. This system provides a platform with which to study changes to the genomes, physiology, and phenotypes of symbionts and hosts during co-evolution.