Molecular Physiological Evolution: Steroid Hormone Receptors and Antifreeze Proteins

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dc.contributor.advisorCresko, Williamen_US
dc.contributor.authorCziko, Paulen_US
dc.date.accessioned2015-01-14T15:58:34Z
dc.date.issued2015-01-14
dc.description.abstractFor my dissertation research I explored the diversity and functional evolution of steroid hormone receptors (SRs) in animals and the physiological implications of the evolution of antifreeze proteins in Antarctic notothenioid fishes. For the former, I discovered multiple new SRs from the vast and under-sampled swath of animal diversity known as invertebrates. I used the sequences of these and other newly discovered related receptors in combination with genomic data and molecular phylogenetic techniques to revise the understanding of the evolutionary history of this important gene family. While previous studies have suggested that vertebrate SR diversity arose from a gene duplication in an ancestor of all bilaterian animals, my work presents strong evidence that this duplication occurred much later, at the base of the chordates. Furthermore, to determine the implications of added diversity and a revised phylogeny on inferences of the functional evolution of SRs, I functionally characterized heretofore-unknown SRs from hemichordates, an acoelomate flatworm, and a chaetognath and statistically reconstructed and functionally characterized ancestral SRs. My results expand the known sequence and functional repertoire of SRs in animals while reinforcing the previous inference that all SRs evolved from an estrogen-sensitive ancestral receptor. I also explored the consequences of the evolution of antifreeze proteins in Antarctic notothenioid fishes, a crucial adaptation to their icy, polar environment. These special proteins adsorb to ice crystals that enter a fish's body and prevent further growth, thereby averting death. I discovered that, in addition to their lifesaving growth-inhibiting ability, AFPs also prevent the melting of internal ice crystals at temperatures above the expected equilibrium melting point. Together with a decade-long temperature record of one of the coldest fish habitats on earth, my experimental results show that the evolution and expression of antifreeze proteins is accompanied by a potentially detrimental consequence: the lifelong accumulation of ice inside these fishes' bodies. This dissertation includes previously published co-authored material as well as unpublished co-authored material.en_US
dc.description.embargo2017-01-14
dc.identifier.urihttps://hdl.handle.net/1794/18733
dc.language.isoen_USen_US
dc.publisherUniversity of Oregonen_US
dc.rightsAll Rights Reserved.en_US
dc.subjectAntifreeze proteinsen_US
dc.subjectEndocrinologyen_US
dc.subjectMolecular evolutionen_US
dc.subjectPolar marine biologyen_US
dc.subjectProtein evolutionen_US
dc.subjectSteroid hormone receptorsen_US
dc.titleMolecular Physiological Evolution: Steroid Hormone Receptors and Antifreeze Proteinsen_US
dc.typeElectronic Thesis or Dissertationen_US
thesis.degree.disciplineDepartment of Biologyen_US
thesis.degree.grantorUniversity of Oregonen_US
thesis.degree.leveldoctoralen_US
thesis.degree.namePh.D.en_US

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