Doctor of Philosophy, Miami University, 2010, Zoology

The demands of winter can be especially onerous to organisms inhabiting temperate and polar regions. In addition to contending with low relative humidity, organisms often experience subzero temperatures and risk freezing of their body fluids. A small group of frogs, turtles, and invertebrates tolerate freezing, during which they rapidly redistribute water and cryoprotectants across their cell membranes to prevent osmotic damage. Despite the importance of water and cryoprotectant movement, the mechanisms underlying redistribution of these molecules are not fully known. Recent evidence suggests that transmembrane, water-permeable proteins called aquaporins play a role in protecting cells during osmotic stress. This dissertation describes two studies that characterized the physiological role of aquaporins during desiccation and freezing in the goldenrod gall fly, Eurosta solidaginis. During autumn, E. solidaginis larvae prepare for winter by accumulating high levels of cryoprotectants (e.g. glycerol) and developing freeze tolerance. In the first study, I examined the abundance of aquaporin-like proteins from July through January to determine whether it is correlated to seasonal cold-hardening. Immunoblots of proteins from larvae collected during this period demonstrated a significant seasonal increase in the abundance of two aquaporin-homologues. Additionally, one of these homologues was regulated in response to short-term acclimation. These results support the hypothesis that aquaporins are closely tied to the seasonal acquisition of freeze and desiccation tolerance. In the second study, I sought to clone and functionally characterize an AQP from E. solidaginis and understand how it promotes tolerance of environmental stresses. We identified EsAQP1, described its molecular structure and predicted its phylogenetic relationship to other known aquaporins. Permeability measurements with a Xenopus laevis oocyte swelling assay determined that EsAQP1 was permeable to water (open full item for complete abstract)

Committee: Richard Lee PhD (Committee Chair); Jon Costanzo PhD (Committee Member); Paul James PhD (Committee Member); Michael Robinson PhD (Committee Member); Gary Lorigan PhD (Committee Member) Subjects: Biology; Zoology