Genome-enabled biology provides a foundation for understanding the genetic basis of organism-environment interactions. . The research project links gene expression, genome methylation, and metabolic rates to assess the mechanisms of environmental adaptation (temperature) across multiple generations in a polar, and closely related temperate, polychaete. By comparing these two species, the research will assess how a polar environment shapes responses to environmental stress. This work will produce: 1) a database of full transcriptome (gene specific) profiling data for the polar polychaete cultured at two temperatures; 2) the contribution of genome methylation to the suppression of gene transcription activities; 3) the linkage between shifts in mRNA pools and total cellular activities (as ATP consumption via respiration); 4) an assessment of the inheritance of patterns of gene expression and metabolic activities across three generations; and 5) a simple demographic model of the polar polychaete population dynamics under normal and 'global-warming' temperature scenarios. Broader impacts include two outreach activities. The first is a mentoring program, where African-American undergraduate students spend 1.5 years working on a research project with a UD faculty member (2 summers plus their senior academic year). The second is a children's display activity at UD?s School of Marine Science "Coast Day".
The emergent field of environmental epigenetics broadly encompasses all heritable changes in gene function and expression that are not associated with a change in underlying genomic DNA sequences. The epigenome itself represents a dynamic system of chemical controls that impact gene expression at a molecular level. DNA methylation is a primary component of the epigenome and involves the covalent bonding of a methyl group to the carbon 5 position of a cytosine ring, which forms 5-methyl-cytosine, and makes the DNA around behave differently in terms of biochemical activities. Unlike the underlying genome which remains largely static across cell types and throughout the course of an individual's lifespan, the chemical layer of methylated bases (methylome) is a dynamic system that is influenced by both intrinsic and external environmental signals. Epigenetic modifications of DNA represent an important mechanism through which organisms are able to quickly adjust gene expression in response to changes in environmental conditions including thermal stress. Due to the innate plasticity of DNA methylation of cytosine bases, environmental cues can induce epigenetic shifts in the timing and intensity of gene expression that may contribute to a physiological acclimation response. Here we identify shifts in methyl-cytosine composition within the genomes of Antarctic marine worms in response to an increase in seawater temperature. The high latitude of McMurdo Sound, Antarctica, (77 deg S), makes this polar sea stenothermal at -1.86 C, the freezing point of seawater. A few days each year seawater temperatures may rise above -1.0 C, with -0.5 C being the seasonal high water temperature of recent record in McMurdo Sound. As global sea surface temperatures rise, polar regions are projected to evidence some of the largest changes in ecosystem structure because of their long stable and cold history. Understanding mechanisms and capacities for surviving increasing temperatures is important in a global context of climate change in polar seas. We conclusively show in our work that an epigenetic response system involving cytosine methylation is very active to facilitate the acclimation of these cold water worms to slightly warmer (+ 4 C) seawater temperatures. Understanding how marine animals may be impacted by global warming trends is important for us to predict changes in Antarctic ecosystem structure and function in the future.
