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- Genre: Academic theses
- Genre: Masters Thesis
Description
Infections caused by the Hepatitis C Virus (HCV) are very common worldwide, affecting up to 3% of the population. Chronic infection of HCV may develop into liver cirrhosis and liver cancer which is among the top five of the most common cancers. Therefore, vaccines against HCV are under intense study in order to prevent HCV from harming people's health. The envelope protein 2 (E2) of HCV is thought to be a promising vaccine candidate because it can directly bind to a human cell receptor and plays a role in viral entry. However, the E2 protein production in cells is inefficient due to its complicated matured structure. Folding of E2 in the endoplasmic reticulum (ER) is often error-prone, resulting in production of aggregates and misfolded proteins. These incorrect forms of E2 are not functional because they are not able to bind to human cells and stimulate antibody response to inhibit this binding. This study is aimed to overcome the difficulties of HCV E2 production in plant system. Protein folding in the ER requires great assistance from molecular chaperones. Thus, in this study, two molecular chaperones in the ER, calreticulin and calnexin, were transiently overexpressed in plant leaves in order to facilitate E2 folding and production. Both of them showed benefits in increasing the yield of E2 and improving the quality of E2. In addition, poorly folded E2 accumulated in the ER may cause stress in the ER and trigger transcriptional activation of ER molecular chaperones. Therefore, a transcription factor involved in this pathway, named bZIP60, was also overexpressed in plant leaves, aiming at up-regulating a major family of molecular chaperones called BiP to assist protein folding. However, our results showed that BiP mRNA levels were not up-regulated by bZIP60, but they increased in response to E2 expression. The Western blot analysis also showed that overexpression of bZIP60 had a small effect on promoting E2 folding. Overall, this study suggested that increasing the level of specific ER molecular chaperones was an effective way to promote HCV E2 protein production and maturation.
ContributorsHong, Fan (Author) / Mason, Hugh (Thesis advisor) / Gaxiola, Roberto (Committee member) / Chang, Yung (Committee member) / Chen, Qiang (Committee member) / Arizona State University (Publisher)
Created2011
Description
Climate change is making the arid southwestern U.S. (“Southwest”) warmer and drier. Decreases in water availability coupled with increases in episodic heat waves can pose extraordinary challenges for native riparian tree species to persist in their current ranges. However, the morpho-physiological mechanisms that these species deploy to cope with extreme temperature events are not well understood. Specifically, how do these species maintain leaf temperatures within a safe operational threshold in the extreme conditions found across the region? Morpho-physiological mechanisms influencing intraspecific local adaptation to thermal stress were assessed in Populus fremontii using two experimental common gardens. In a common garden located near the mid-point of this species’ thermal distribution, I studied coordinated traits that reflect selection for leaf thermal regulation through the measurement of 28 traits encompassing four different trait spectra: phenology, whole-tree architecture, and the leaf and wood economic spectrum. Also, I assessed how these syndromes resulted in more acquisitive and riskier water-use strategies that explained how warm-adapted populations exhibited lower leaves temperatures than cool-adapted populations. Then, I investigated if different water-use strategies are detectable at inter-annual temporal scales by comparing tree-ring growth, carbon, and oxygen isotopic measurements of cool- versus warm-adapted populations in a common garden located at the extreme hottest edge of P. fremontii’s thermal distribution. I found that P. fremontii’s adaptation to the extreme temperatures is explained by a highly intraspecific specialized trait coordination across multiple trait scales. Furthermore, I found that warmer-adapted populations displayed 39% smaller leaves, 38% higher midday stomatal conductance, reflecting 3.8 °C cooler mean leaf temperature than cool-adapted populations, but with the tradeoff of having 14% lower minimum leaf water potentials. In addition, warm-adapted genotypes at the hot edge of P. fremontii’s distribution had 20% higher radial growth rates, although no differences were detected in either carbon or oxygen isotope ratios indicating that differences in growth may not have reflected seasonal differences in photosynthetic gas exchange. These studies describe the potential effect that extreme climate might have on P. fremontii’s survival, its intraspecific responses to those events, and which traits will be advantageous to cope with those extreme environmental conditions.
ContributorsBlasini, Davis E (Author) / Hultine, Kevin R (Thesis advisor) / Day, Thomas A (Thesis advisor) / Ogle, Kiona (Committee member) / Throop, Heather (Committee member) / Gaxiola, Roberto (Committee member) / Arizona State University (Publisher)
Created2022