![]() The dynamic expression responses observed suggest a role for the AMPK system in balancing energetic investment into muscle growth according to immunological status in salmonid fishes.ĥ′adenosine monophosphate-activated protein kinase (AMPK) is the primary sensor of cellular energetic status in eukaryotes, including vertebrates 1, 2. Further, immune stimulation caused a decrease in the expression of several AMPK subunit-encoding genes in GH-transgenic fish specifically. These analyses revealed a constitutive up-regulation of several AMPK-α and -γ subunit-encoding genes in GH-transgenic fish achieving accelerated growth. Transcript levels for the fifteen unique salmonid AMPK subunit genes were quantified in skeletal muscle after stimulation with bacterial or viral mimics to alter immune status. Specifically, we compared wild-type and GH-transgenic fish, the latter achieving either enhanced or wild-type growth rate via ration manipulation. ![]() As a model, we studied immune-stimulated coho salmon ( Oncorhynchus kisutch) from three experiment groups sharing the same genetic background, but showing highly-divergent growth rates and nutritional status. We tested the hypothesis that the expanded AMPK gene system of salmonids is transcriptionally regulated by growth and immunological status. This study identified expansions in the AMPK-α, -β and -γ families of salmonid fishes due to a history of genome duplication events, including five novel salmonid-specific AMPK subunit gene paralogue pairs. The findings reported here demonstrate that salmon populations may be locally adapted at small spatial scales and that the fitness consequences resulting from genetic interactions between population pairs can not readily be predicted.5′adenosine monophosphate-activated protein kinase (AMPK) is a master regulator of energy homeostasis in eukaryotes. There was also evidence of intrinsic outbreeding depression for one second-generation hybrid cross in the wild environment. ![]() In the wild environment reciprocal transplant, there was consistent evidence for extrinsic outbreeding depression and inbreeding depression for one river population and there was among-site variability in the responses of the other two river populations examined. In the laboratory common-garden environment, there were no significant differences in fitness-related traits between the crosses. Here, inbred and outbred crosses were generated using three neighbouring endangered Atlantic salmon (Salmo salar) populations. The negative consequences associated with inbreeding depression and the loss of within-population genetic diversity may be similar in scope to those associated with outbreeding depression. ![]() Overall, these results reveal a high degree of phenotypic plasticity in salmon populations that nevertheless differ in their adaptive potential to hypoxia given the distinct reaction norms observed between and within populations. We also detected significant sire × treatment interactions in most populations and a tendency for heritability values to be lower under stressful conditions. We found different hypoxia reaction norms among populations, but almost no population effect in both treatments. Under hypoxic conditions, embryos had a lower survival and hatched later than in normoxic conditions. Embryos were reared under normoxic and hypoxic conditions, and we measured their survival, incubation time and length at the end of embryonic development. We used factorial crossing designs to measure additive genetic variation of early life-history traits in each population. In this study, we used a common garden experiment to compare the responses to hypoxic stress of four genetically differentiated and environmentally contrasted populations. Such hypoxic stress can alter the development and even be lethal for Atlantic salmon (Salmo salar) embryos that spend their early life into gravel beds. For instance, the clogging of bottom substratum by fine sediments is observed in many rivers and usually leads to a decrease in dissolved oxygen concentrations in gravel beds. Aquatic organisms are increasingly exposed to environmental changes linked with human activities in river catchments. Understanding whether populations can adapt to new environmental conditions is a major issue in conservation and evolutionary biology.
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