Abstract
Disclosure: K. Kim: None. I. Park: None. J. Kim: None. J. Kim: None. H. Rhee: None. J. Suh: None.
To facilitate the understanding of metabolic changes associated with aging and disease ...processes we have developed new in vivo tools that enable tissue-specific profiling of subcellular proteomes. First we describe a method to profile in vivo mitochondrial proteomes utilizing transgenic mice expressing mitoAPEX, a peroxidase-based proximity labeling enzyme containing a mitochondrial matrix targeting sequence. Upon label activating conditions, mitoAPEX rapidly (<1 min) catalyzes production of biotin radicals which biotinylate proteins within a 20 nm radius. Mass analysis of biotinylated proteomes from proximity labeled mitoAPEX mouse tissues confirmed specific and efficient labeling of the mitochondrial proteome and revealed tissue-specific patterns of the matrix proteome. The labeled muscle proteomes from young and old mitoAPEX mice revealed significant changes in the quantity and composition of protein species. Of these, RTN4IP1, was shown to be downregulated in muscle tissue of old mice. However, in contrast to previous reports, our analysis of RTN4IP1 shows RTN4IP1 is localized to the mitochondrial matrix and not the outer membrane. In addition to the mitoAPEX mice, we generated another in vivo proximity labeling tool iSLET (in situ Secretory protein Labeling via ER-anchored TurboID) which labels secretory pathway proteins, via proximity labeling activity by ER lumen targeted TurboID, an engineered biotin ligase. We expressed iSLET in the mouse liver and demonstrate efficient labeling of the liver secreted proteome which could be tracked and identified within circulating blood plasma. We expect mitoAPEX and iSLET mice will facilitate our understanding of mitochondrial function and interorgan communication networks in aging and associated disease processes.
Presentation: Saturday, June 17, 2023
This dissertation investigates three important topics related to flowering phenology throughout the United States. First, this work evaluates the utility of herbarium records for estimating ...historical variation in community-level flowering phenology, and evaluate the relationship of such estimates to satellite-derived greenup timing at regional scales. This dissertation then reconstructs historical variations in flowering phenology throughout the spring, summer, and autumn across South Carolina for the years 1951 through 2009. These estimates will then be compared to seasonal temperature variations throughout this period. Finally, this dissertation develops novel herbarium-based methods to separate intraspecific phenological variations over space from changes in flowering time derived from differences in community composition, and evaluate the contributions of compositional differences to spatial variation in community-level flowering times throughout the early, mid, and late portions of the growing season and across a variety of temperate environments within the continental United States. The results of these inquiries demonstrate that phenological information included in digital herbarium archives can produce annual phenological estimates correlated to satellite-derived green wave phenology. Examinations of historical flowering throughout South Carolina also determined that species that flower near the onset of the growing season advanced under increasing mean March temperatures, while late spring through mid-summer flowering exhibited delays in response to higher February temperatures. Thus, although no long-term phenological trends were detected, these findings indicate that flowering synchrony may undergo significant restructuring in response to warming spring temperatures, even in humid subtropical environments. Examinations of composition-derived phenological variation over space determined that, although typically smaller than intraspecific variations, composition-derived shifts in flowering time explained up to 49.3% of overall phenological variation, and were the most responsive to differing climate conditions within xeric regions and among late-flowering species. These results demonstrate that interspecific differences in flowering time play a significant role in determining the composition of the plant community over space. Additionally, these findings indicate that impacts of flowering phenology on community assemblage are most severe within xeric regions and throughout the late-flowering portion of the plant community.
In the face of recent wildfires across the Western United States, it is essential that we understand both the dynamics that drive the spatial distribution of wildfire, and the major obstacles to ...modeling the probability of wildfire over space and time. However, it is well documented that the precise relationships of local vegetation, climate, and ignitions, and how they influence fire dynamics, may vary over space and among local climate, vegetation, and land use regimes. This raises questions not only as to the nature of the potentially nonlinear relationships between local conditions and the fire, but also the possibility that the scale at which such models are developed may be critical to their predictive power and to the apparent relationship of local conditions to wildfire. In this study we demonstrate that both local climate–through limitations posed by fuel dryness (CWD) and availability (AET)–and human activity–through housing density, roads, electrical infrastructure, and agriculture, play important roles in determining the annual probabilities of fire throughout California. We also document the importance of previous burn events as potential barriers to fire in some environments, until enough time has passed for vegetation to regenerate sufficiently to sustain subsequent wildfires. We also demonstrate that long-term and short-term climate variations exhibit different effects on annual fire probability, with short-term climate variations primarily impacting fire probability during periods of extreme climate anomaly. Further, we show that, when using nonlinear modeling techniques, broad-scale fire probability models can outperform localized models at predicting annual fire probability. Finally, this study represents a powerful tool for mapping local fire probability across the state of California under a variety of historical climate regimes, which is essential to avoided emissions modeling, carbon accounting, and hazard severity mapping for the application of fire-resistant building codes across the state of California.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The potential for populations of invasive plants to differ in their response to stressful environmental conditions or in their invasiveness is an underexplored issue in determining introduced ...species’ range limits. Introduced genotypes might differ in their response to freezing temperatures, soil type, or differing biotic factors within their introduced range. We examined the potential of Chinese tallow tree seeds (Triadica sebifera (L.) Small) collected from two genetically distinct areas of its introduced range in the United States (North Carolina and South Carolina) as well as from the northern and southern portions of its native range in China to germinate and for seedlings to survive winter conditions inland of the species’ current coastal distribution in the state of South Carolina. Germination success of seeds from these four source populations was compared between fall plantings that mimic natural dispersal timing and spring plantings after the last frost in areas within (coastal sites) and inland (midland and piedmont areas) of its current distribution in South Carolina. In separate studies, overwinter survival, stem damage, budbreak timing and response to freeze events occurring before and after budbreak were compared among seedlings of the four source populations. Overall, seed germination success was lower in the colder piedmont areas than the warmer coastal sites, and seeds and seedlings from South Carolina genotypes showed greater reduction in germination success by inland winters, greater winter damage and reduced budbreak success in the field, and lower survival after prolonged freeze events than genotypes from North Carolina or China. These results show that genetically determined differences in environmental constraints exist among introduced genotypes of Chinese tallow, and that the North Carolina genotype shows greater potential for inland expansion than the South Carolina one. These population differences must be taken into account when evaluating the potential range expansion of Chinese tallow.
Vegetation phenology is an important indicator of climate change impacts on the seasonal dynamics of the biosphere. However, little is known about the influence of elevation on spring phenological ...sensitivity to temperature in an alpine ecosystem. Based on remotely sensed land surface phenology and temperature data from 2001 to 2010, this study investigated the rate of spring phenological change of the Tibetan Plateau (TP) grasslands in response to interannual temperature variations at different elevations. Results suggest that spring phenology in the TP grasslands exhibits a stronger response to changes in temperature at higher elevations than at lower ones. In particular, spring phenology advanced by 1–2 days in response to a 1 °C increase in May average temperature at elevations from 3,000 to 3,500 m, while the rate was up to 8–9 days/°C at 5,000–5,500 m. Analysis using accumulated growing degree days (AGDD) from January 1 through May 31 showed the same general trend with increased elevation associated with increased sensitivity (as measured by phenological change per unit of AGDD change). Such temperature sensitivity gradients in the TP grasslands could be partly explained by the growth efficiency hypothesis which suggests that vegetation adapted to colder climates likely requires less heat energy for the onset of growing season and vice versa in warmer climates. Furthermore, accumulated growing degree days from January 1 to the greenup date were found to decrease with increasing elevations, which provided evidence to support the applicability of the growth efficiency hypothesis in an alpine grassland ecosystem.
Thesis (M.S.) -- Clemson University, 2009.
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