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

University Of California-Riverside, Riverside CA

Investigators

Abstract

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.