Thesis (Ph. D.)--University of Florida, 2003. / Title from title page of source document. Includes vita. Includes bibliographical references.

Genotype by environment interaction (GxE) is the tendency of the phenotypic performance of two or more plant genotypes in one environment to not be predictive of their relative performance in another environment. To discover the importance of GxE in this region, a large set of USDA and commercial hybrids were tested in the regions of practical significance to sunflower production in order to produce recommendations regarding mega-environments for yield and oil. Rank changes for oil content occurred among hybrids and two common factors accounted for 68.6% of the total GxE variation. Breeding programs testing pre-commercial hybrids in multiple environments for oil content could be beneficial. Yield covariates for lodging, bird damage, and disease were significant but occurred in different locations with variable severity each year making it difficult to divide the growing region into mega-environments for yield.

Gene expression responds to the environment and can also evolve rapidly in response to altered selection regimes. Little is known, however, about the extent to which evolutionary adaptation to a particular type of stress involves changes in the within-generation ('plastic') responses of gene expression to the stress. We used microarrays to quantify gene expression plasticity in response to ethanol in laboratory populations of Drosophila melanogaster differing in their history of ethanol exposure. Two populations ('R' populations) were maintained on regular medium, two ('E') were maintained on medium supplemented with ethanol, and two ('M') were maintained in a mixed regime in which half of the population was reared on one medium type, and half on the other, each generation. After more than 300 generations, embryos from each population were collected and exposed to either ethanol or water as a control, and RNA was extracted from the larvae shortly after hatching. Nearly 2000 transcripts showed significant within-generation responses to ethanol exposure. Evolutionary history also affected gene expression: the E and M populations were largely indistinguishable in expression, but differed significantly in expression from the R populations for over 100 transcripts, the majority of which did not show plastic responses. Notably, in no case was the interaction between selection regime and ethanol exposure significant after controlling for multiple comparisons, indicating that adaptation to ethanol in the E and M populations did not involve substantial changes in gene expression plasticity. The results give evidence that expression plasticity evolves considerably more slowly than mean expression.

Background: Obesity is now considered to be a global epidemic and gene-environment interaction studies are crucial to understanding the genetic architecture of this disease. The objectives of this research were to (1) review the current evidence of gene-environment interactions in the field of obesity, (2) examine the interactions between obesity predisposing gene variants and physical activity using precise physical activity data and (3) analyze a novel gene-environment interaction between obesity predisposing gene variants and multiple pregnancies. Methods: The data for the gene-environment interaction analyses were collected from the EpiDREAM study: a prospective cohort including participants of six ethnic backgrounds from 21 countries worldwide. A subset of 17 423 participants with complete genotype and phenotype information was included in the analysis. Obesity predisposing single nucleotide polymorphisms were analyzed independently and as a genetic risk score. General linear models were used to analyze all main effects and interactions. Results: Physical activity interacted with FTO rs9939609 to modulate BMI (Pinteraction=0.032) and BAI (Pinteraction=3.26 x 10-4). Increased physical activity attenuated the impact of FTO on obesity. Four SNPs displayed significant associations with physical activity: NTRK2 rs1211166 (P=0.015), BDNF rs6265 (P=0.007), BDNF rs1401635 P=0.003) and NPC1 rs1805081 (P=3.52 x 10-4). Multiple pregnancies was significantly associated with BMI (Pinteraction=1.17 x 10-5) BAI (Pinteraction=3.47 x 10-7) and also interacted with FTO rs9939609 to modulate BMI (Pinteraction=0.014). The impact of FTO on BMI was accentuated by multiple pregnancies in the EpiDREAM cohort. Discussion: Both physical activity and parity have a significant impact on obesity measures and these effects appear to be relevant on a global scale. Our results confirm the physical activity x FTO interaction in a multi-ethnic context and indicate that parity may also interact with FTO polymorphisms. / Thesis / Master of Science (MSc)

Background: Obesity is a multifactorial disease caused by the interplay of environmental and genetic risk factors. With the prevalence of obesity more than doubling since 1980, this disease has become a global epidemic. The objectives of this research were to (1) review the current evidence of gene-environment interactions (GEI) in the field of obesity, (2) investigate novel GEI involving sedentary behaviour, sleep duration and alcohol consumption, (3) assess GEI using a cumulative environmental risk score, and (4) provide an overview of methodological weaknesses in GEI studies and provide suggestions for future directions. Methods: The data for the gene-environment interaction analyses were collected from the EpiDREAM study: a cohort study including participants of six ethnic backgrounds from 17 countries worldwide. A subset of 17 423 participants with complete genotype and phenotype information was included in the analysis. Twenty-three obesity predisposing single nucleotide polymorphisms (SNPs) were analyzed independently and as a genetic risk score (GRS). Linear regression models were used to analyze these interactions. Results: Heritability, monogenic and polygenic obesity studies provide converging evidence that obesity-predisposing genes interact with a variety of environmental exposures including physical activity and diet patterns. In the EpiDREAM cohort, we found that increased sedentary time did not interact with obesity predisposing SNPs or the GRS to modulate BMI. The interaction between sedentary time and physical activity was also not significant. We observed a U-shaped association between sleep duration and BMI and sleep duration did not appear to moderate the impact of the obesity predisposing SNPs or the GRS. However, we did observe an alcohol x FTO rs1421085 interaction, whereby increased alcohol consumption attenuated the impact of FTO rs1421085 variation on BMI. We also found that the combined effect of several environmental risk factors significantly modified the effect of FTO rs3751812 on BMI. Specifically, we found that the effect of the FTO rs3751812 SNP on BMI was over two times greater among those in the highest quartile of environmental risk compared to those in the lowest quartile. The GRS did not interact with any of the exposures tested. Discussion: Our results indicate that sedentary behaviour did not moderate the impact of obesity predisposing genes, while alcohol consumption decreased the impact of variation in FTO rs3751812 on BMI. We also observed that variation in FTO rs3751812 interacted with a cumulative environmental risk score to moderate BMI. The growing body of GEI evidence has provided a deeper understanding of obesity aetiology and may have tremendous applications in the emerging field of personalized medicine and individualized lifestyle recommendations. Although the number of gene-environment interaction analyses has increased rapidly across multiple disciplines, addressing methodological concerns such as statistical modeling, confounding, biological assumptions and measurement precision will be necessary to fully exploit the potential of the GEI field. With the development of new methodological and measurement techniques such as hypothesis-free genome wide interaction studies and deep phenotyping, it may be possible to translate the information from GEI studies into public health policy and personalized medicine for obesity and other complex human diseases. / Thesis / Doctor of Philosophy (PhD)

Doctor of Philosophy / Department of Geography / Lisa M.B. Harrington / The Greater Yellowstone Ecosystem (GYE) is a large, nearly intact ecosystem with significant protection that has often been considered an ideal location to examine coupled human-environment interactions due to the region’s complex mosaic of private and public lands, competing natural resource uses, and rapid population growth. A transition toward sustainability suggests that current societal and economic needs can be met while simultaneously maintaining the planet’s life support systems for future generations. To facilitate sustainability transitions it is imperative that the perceptions and experiences of local communities be documented. The objective of this study was to determine how residents of amenity-driven gateway communities (West Yellowstone and Red Lodge, Montana, and Jackson, Wyoming) surrounding Yellowstone and Grand Teton national parks perceive and experience their transition toward sustainability and the challenges inherent in that transition, how those perceptions inform locally produced and extra-local policies, and how institutions influence sustainability goals. Further, this study determined which factors contribute to these perceptions, and whether they differed spatially and temporally. To meet study objectives, a mixed methods approach was implemented, including the content analysis of local newspapers and key informant interviews. Content analysis of local newspapers was used to investigate decision maker and stakeholder priorities for the local and regional environment, economy, and communities, and to determine what actions had been taken to promote sustainability. A total of 193 articles from West Yellowstone News, 287 articles from Carbon County News, and 333 articles from Jackson Hole News & Guide for the ten year period 2000-2009, were analyzed. Specific focal topics varied among the newspapers/communities, but in general terms the most discussed topics in West Yellowstone during this time were focused on natural resources, economic development, community development, sustainability and conservation, and growth and development. The most discussed topics for Red Lodge were community development, government services, tourism and recreation, and growth and development. The most commonly discussed topics in Jackson were natural resources, growth and development, community development, and government services. A total of 35 semi-structured interviews were conducted with key informants in the three study communities during the summer of 2010 to allow for specific questioning and to gain additional information. Definitions of sustainability differed based on the key informant’s community, role in the community, and length of residence in the community. Overall, definitions of sustainability focused on the environment, the economy, and multi-generational or long-term thinking. The prioritization of the economy, environment, and society also differed based on community; however, there was overall recognition that each community was dependent upon the natural environment for economic vitality. In all three study communities, dependence on tourism and recreation-based industries, the lack of a diversified economy, and continued growth and development have resulted in a disconnect between perceptions, priorities, and goals as they relate to sustainability. In addition, each community was focused on multiple goals that further complicated the fulfillment of sustainability objectives. The multi-goal orientation of study communities is reflected in the multiple visions that various decision makers and stakeholders have for the community and their futures. What is needed most is a hierarchical approach to a sustainability transition, with each community setting its own, as well as ecosystem-wide, goals, objectives, and visions. Findings suggest that a transition toward sustainability is perceived and experienced differently based on local context. In the GYE, that context includes a tourism-based economy that is dependent upon the natural environment, a myriad of local, regional, national, and global stakeholders, and the presence of federal land agencies that are responsible for the sustainability of natural systems, freeing local communities to focus on the societal and economic dimensions of sustainability. A transition toward sustainability will be manifested differently in the Greater Yellowstone Ecosystem, and potentially other communities adjacent to protected lands, than it is other areas because of its unique milieu. While the close proximity of federal lands, including Yellowstone National Park, may complicate the sustainability discourse at times and may, in certain instances, add additional challenges through extra-local control of change, these same federal lands may also favor a transition toward sustainability in amenity-driven gateway communities. In addition, the disparate socio-economic conditions present in study communities, as well as extra-local institutions and agencies, directly influence, and may at times further complicate, a transition toward sustainability. This study is based on the theory that in order to successfully transition toward sustainability, a better understanding of coupled human and natural systems is critical, and because of the close couplings between human and natural systems in the Greater Yellowstone Ecosystem, and because of the unique challenges and conflicts present in the region, the GYE is an ideal location to study human-environment interactions. The use-inspired orientation of sustainability science aims to provide tangible, real-world, and place-based understanding of a transition toward sustainability. The contribution of this study to the field of sustainability science is the understanding that, while sustainability visions, goals, and objectives may be similar across a region, consideration of local contexts affecting goals and perceptions provides valuable insights that may inform sustainability pathways at local scales and, as a result, provide deeper understanding of global sustainability. One of these insights is that communities that seemingly have much in common due to their shared region, physical environmental surroundings, and history, the specific concerns to ensure place-based sustainability can show variability. Another important point from this research is that, while most depictions of sustainability are focused on three elements—the economy, society, and the environment—individuals also key in on multigenerational concerns.

Extensive research has been devoted to evaluating potential genotype-environment interactions. However, plant breeders are still in need of a simple way to describe how genotypes respond to different locations and years. In an environmentally diverse state like Oregon, significant genotype-environment interactions do occur The resulting lack of association between actual and genotypic potential yield performance makes it difficult to select genotypically superior lines. This study was prompted to evaluate the extent of such an interaction and compare various yield stability models. A significant genotype-environment interaction encompassing lines, environments, and years was discovered for each individual year analyzed and for the combined analysis of 1992, 1994 and 1995, and 1989 through 1994. Most lines evaluated during 1992, 1994 and 1995 were adapted to low yielding environments. However, two genotypes (OR880172 and OR880525) exhibited broad adaptation. Stephens and Mac Vicar were less adapted to the relatively high yielding Chambers site than the other genotypes tested during 1992, 1994 and 1995 due to Septoria tritici infections. The most stable genotypes during the combined 1992, 1994 and 1995 and 1989-1994 seasons were OR870831, Madsen and OR8500933H. Gene was the most desirable genotype based on stability and yield for both the combined 1992, 1994 and 1995 and 1989-1994 seasons. Due to an inability to adapt to higher yielding environments, the cultivar Rohde was the least stable genotype during the same combined periods. High and low temperatures and precipitation had minor yet significant effects on yield responses at all three sites during various periods identified. Advanced winter wheat selections and cultivars were grown in three diverse environments and compared over different time periods. Due to trial design and the objective of identifying superior genotypes from a set tested in target environments a combination of two methods, stability variance and a selection index, emerged as the most appropriate techniques. These approaches are considered the most appropriate because they use the mean of the trial as a gauge for measuring stability. / Graduation date: 1997

No description available.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.