Across climate regions, organisms have developed various mechanisms that adapt them to their local environments. Understanding the adaptive variation and the underlying genetic basis for the variation can greatly improve our understanding of how natural selection works. Organisms are constantly defending against various environmental stressors. These stressors often share some response pathways, although organisms also deploy stress-specific mechanisms. In this dissertation, I chose to work with natural populations of Arabidopsis thaliana across an elevation gradient as a model to explore their variation and local adaptation to various environmental stressors that exist in their local regions. In the first half of my dissertation, I examined the constitutive and induced expression of several key stress response chemicals, camalexin, salicylic acid (SA) and one key heat shock protein (Hsp101), in response to heat stress. Three separate studies were performed using common garden experiments in Arabidopsis thaliana seedlings. These chemicals all showed adaptive variation. In the second half of my dissertation, I explored variation and local adaption in response to heat stress, one of the most important stressors in nature, at three different levels. At the phenotypic level, I found out that high elevation plants adopt greater avoidance strategy while low elevation plants adopt greater tolerance to heat stress. At the transcriptomic level, high elevation populations showed more extensive changes in their gene expression in response to heat stress, both in the numbers of differentially expressed genes and the magnitude of the fold change. Finally, at the genomic level, genome resequencing of 16 populations from our study site also indicated several regions that had undergone selective sweeps, i.e. were genomic targets of strong selection. Summarizing all the studies together, my dissertation provided support of the adaptive divergence in the studied Arabidopsis thaliana plants and also provided a framework for exploring other stressors across climate regions.
|School:||University of Pittsburgh|
|Department:||Arts and Sciences|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 78/04(E), Dissertation Abstracts International|
|Subjects:||Ecology, Plant sciences, Bioinformatics|
|Keywords:||Local adaptation, Natural selection, Stress response, Variation|
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