Browsing by Subject "Angiosperms"
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Item Analysis of an Arabidopsis mutant with altered stress responses(Texas Tech University, 2003-12) Shen, YinPlants face a variety of conditions that cause biotic and abiotic stress. Since plants are sessile, and therefore cannot move to escape stressful conditions, they have evolved complex strategies to survive harsh environments. One such strategy is the ability to quickly alter the expression of genes, which, in effect, acclimates the plant. Glutathione S-transferases (GST) are an example of these genes that are induced under stressful conditions. In order to identify the mechanisms that regulate stress responsive gene expression, I used a genetic strategy to identify stress signaling mutants in which the luciferase (LUC) reporter was expressed under control of the stressresponsive Arabidopsis GST6 promoter. After chemical mutagenesis by ethyl methanesulfonate (EMS), a number of potential mutants that affect the expression of the GST6:LUC reporter gene, and presumably, the stress signaling pathways were isolated. One of the mutants, cdg6 (constitutively down-regulated GST6), is dominant and has altered responses to abscisic acid (ABA), ethylene, and salicylic acid (SA). In addition, physiological studies of cdg6 mutant plants showed that the gene is not involved in the ethylene signaling or synthesis pathways. A transcriptional profile of cdg6 using microarray analysis gave us a genome-wide view of gene expression alterations in mutant plants compared to the wild type plants. This analysis showed that endogenous GST genes are down regulated in cdg6, while a number of defense related genes such as chitinase were up regulated. These data indicate that cdg6 may represent a mutation in a gene that regulates defense responses.Item Applying mathematical and statistical methods to the investigation of complex biological questions(2013-08) Scarpino, Samuel Vincent; Kirkpatrick, Mark, 1956-; Meyers, Lauren AncelThe research presented in this dissertation integrates data and theory to examine three important topics in biology. In the first chapter, I investigate genetic variation at two loci involved in a genetic incompatibility in the genus Xiphophorus. In this genus, hybrids develop a fatal melanoma due to the interaction of an oncogene and its repressor. Using the genetic variation data from each locus, I fit evolutionary models to test for coevolution between the oncogene and the repressor. The results of this study suggest that the evolutionary trajectory of a microsatellite element in the proximal promoter of the repressor locus is affected by the presence of the oncogene. This study significantly advances our understanding of how loci involved in both a genetic incompatibility and a genetically determined cancer evolve. Chapter two addresses the role polyploidy, or whole genome duplication, has played in generating flowering plant diversity. The question of whether polyploidy events facilitate diversification has received considerable attention among plant and evolutionary biologists. To address this question, I estimated the speciation and genome duplication rates for 60 genera of flowering plants. The results suggest that diploids, as opposed to polyploids, generate more species diversity. This study represents the broadest comparative analysis to date of the effect of polyploidy on flowering plant diversity. In the final chapter, I develop a computational method for designing disease surveillance networks. The method is a data-driven, geographic optimization of surveillance sites. Networks constructed using this method are predicted to significantly outperform existing networks, in terms of information quality, efficiency, and robustness. This work involved the coordinated efforts of researchers in biology, epidemiology, and operations research with public health decision makers. Together, the results of this dissertation demonstrate the utility of applying quantitative theory and statistical methods to data in order to address complex, biological processes.