Project description:The goals of these studies are to explore the mechanisms that enable extreme physiological plasticity and that may account for evolutionary divergence of adaptive osmotic physiologies among taxa that occupy different osmotic niches. In a common-garden environment, we track physiological and genome expression responses to hypo-osmotic (freshwater) challenge during a time-course of acclimation, and contrast these responses within and between species. We seek to identify mechanisms that facilitate osmotic acclimation that are evolutionarily conserved between basal and derived physiologies, and identify mechanisms that are uniquely derived to enable the extreme osmotic plasticity exhibited by F. heteroclitus. Importantly, previous studies using a comparable experimental design have identified physiological changes and genome expression responses that are adaptive for populations of F. heteroclitus that live in fresh water. As such, this enables us to test whether mechanisms of adaptive micro-evolutionary divergence across osmotic gradients within F. heteroclitus are shared with the mechanisms that account for patterns of macro-evolutionary divergence between F. heteroclitus and F. majalis that we identify in this study. That is, are the targets of micro-evolutionary fine-tuning the same or different as the targets of macro-evolutionary divergence across osmotic boundaries? Population comparisons include between populations from Chesapeake Bay (CB), coastal Virginia (VA), and coastal Georgia (GA).
Project description:Three-spined stickleback (Gasterosteus aculeatus) represents a convenient model to study microevolution - adaptation to freshwater environment. While genetic adaptations to freshwater are well-studied, epigenetic adaptations attracted little attention. In this work, we investigated the role of DNA methylation in the adaptation of marine stickleback population to freshwater conditions. DNA methylation profiling was performed in marine and freshwater populations of sticklebacks, as well as in marine sticklebacks placed into freshwater environment and freshwater sticklebacks placed into seawater. For the first time, we demonstrated that genes encoding ion channels kcnd3, cacna1fb, gja3 are differentially methylated between marine and freshwater populations. We also showed that after placing marine stickleback into fresh water, its DNA methylation profile partially converges to the one of a freshwater stickleback. This suggests that immediate epigenetic response to freshwater conditions can be maintained in freshwater population. Interestingly, we observed enhanced epigenetic plasticity in freshwater sticklebacks that may serve as a compensatory regulatory mechanism for the lack of genetic variation in the freshwater population. Some of the regions that were reported previously to be under selection in freshwater populations also show differential methylation. Thus, epigenetic changes might represent a parallel mechanism of adaptation along with genetic selection in freshwater environment.
Project description:Three-spined stickleback (Gasterosteus aculeatus) represents a convenient model to study microevolution - adaptation to freshwater environment. While genetic adaptations to freshwater are well-studied, epigenetic adaptations attracted little attention. In this work, we investigated the role of DNA methylation in the adaptation of marine stickleback population to freshwater conditions. DNA methylation profiling was performed in marine and freshwater populations of sticklebacks, as well as in marine sticklebacks placed into freshwater environment and freshwater sticklebacks placed into seawater. For the first time, we demonstrated that genes encoding ion channels kcnd3, cacna1fb, gja3 are differentially methylated between marine and freshwater populations. We also showed that after placing marine stickleback into fresh water, its DNA methylation profile partially converges to the one of a freshwater stickleback. This suggests that immediate epigenetic response to freshwater conditions can be maintained in freshwater population. Interestingly, we observed enhanced epigenetic plasticity in freshwater sticklebacks that may serve as a compensatory regulatory mechanism for the lack of genetic variation in the freshwater population. Some of the regions that were reported previously to be under selection in freshwater populations also show differential methylation. Thus, epigenetic changes might represent a parallel mechanism of adaptation along with genetic selection in freshwater environment. This is the RNA-seq experiment, DNA methylation data (bisulfite-seq) is provided under accession number GSE82310.
Project description:Imprinted macro ncRNAs such as Airn play an important role in silencing protein-coding genes in cis, macro ncRNAs could be a common feature in all imprinted gene clusters. By applying the RNA Expression on Tiling Array (RETA) technique, macro ncRNAs were found to be abundant in 26 known mouse genomic regions containing imprinted genes were detected. All well-known imprinted macro ncRNAs were up-regulated upon depletion of DNA methylation.