Biology Theses and Dissertations

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Browsing Biology Theses and Dissertations by Author "Archer, Heather"

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    Evolution of Independent Genetic Pathways for Pathogen Resistance within the Nematode Caenorhabditis remanei
    (University of Oregon, 2013-10-10) Archer, Heather; Guillemin, Karen
    Pathogenic host-microbe interactions can result from continuous evolution of a host's ability to resist infection and a pathogen's ability to survive and replicate. Pseudomonas aeruginosa is a versatile and opportunistic pathogen, ubiquitous in soil, and capable of damaging plants, vertebrates, and invertebrates. Previous studies in nematodes suggest that the pathogenic effects of P. aeruginosa can result from multiple distinct pathways: a toxin-based effect that kills within a few hours and a generalized virulence that kills over the course of multiple days. Using experimental evolution in the highly polymorphic nematode Caenorhabditis remanei, I show that nematode resistance to the two modes of pathogenesis in P. aeruginosa evolves through genetically independent pathways. These results demonstrate that multiple virulence factors in a pathogen can result in multiple responses in the host, and the genetic lines established here create resources for further exploration of the genetic basis for resistance to P. aeruginosa.
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    The Genetic Basis of Natural Variation in the Response to Adult Starvation in Caenorhabditis elegans
    (University of Oregon, 2019-09-18) Archer, Heather; Phillips, Patrick
    Caenorhabditis elegans typically feeds on rotting fruit and plant material in a fluctuating natural habitat, a boom-and-bust lifestyle. Moreover, stage specific developmental responses to low food concentration suggest that starvation-like conditions are a regular occurrence. In order to assess variation in the C. elegans starvation response under precisely controlled conditions and simultaneously phenotype a large number of individuals with high precision, we have developed a microfluidic device that, when combined with image scanning technology, allows for high-throughput assessment at a temporal resolution not previously feasible and applied this to a large mapping panel of fully sequenced intercross lines. Under these conditions worms exhibit a markedly reduced adult lifespan with strain-dependent variation in starvation resistance, ranging from <24 hours to ~120 hours. Genome-wide mapping of the responses of more than 7,855 individuals suggests four loci of large effects. Three of these loci are associated with single genes (ash-2, exc-6, and dpy-28) and the fourth is a ~26 KB region on Chromosome V encompassing several genes. Backcross with selection confirmed the effect of the Chromosome V locus. Overall, there is a clear genetic basis for natural variation in the response to food availability within this species.