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This thesis applies integrative and systemic approaches to gene expression experiments measuring responses to environmental stress. Methods were developed to identify systematic differences in response strength, functional pathway activation, and gene regulatory network structure. Results in three wild killifish populations revealed high population variability at the level of individual genes, consistent with the killifish’s genetic diversity and ability to adapt rapidly to anthropogenic pollution. Despite gene level diversity, modular network structures, patterns of pathway activation, and patterns of gene expression canalization were conserved in the three populations, demonstrating that gene regulatory networks are preserved by selective processes and may constrain killifish adaptation. The presence of arsenic during killifish acclimation to osmotic shock systematically reduced the magnitude of gene expression responses, and reduced coordination between genes that respond to osmotic shock. Results in the water flea suggested that cadmium tolerance is associated with systematically larger gene expression responses to cadmium stress, and greater network coordination among genes that respond to cadmium. In summary, environmentally responsive gene regulatory networks 1) shape the efficacy of biotic and abiotic stress responses, 2) are targeted by toxic effects, and 3) are shaped by selective forces. |
