The AMPK system of salmonid fishes was expanded through genome duplication and is regulated by growth and immune status in muscle

Abstract

5'adenosine monophosphate-activated protein kinase (AMPK) is a master regulator of energy homeostasis in eukaryotes. 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. We tested the hypothesis that the expanded AMPK gene system of salmonids is transcriptionally regulated by growth and immunological status. 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. Specifically, we compared wild-type and GH-transgenic fish, the latter achieving either enhanced or wild-type growth rate via ration manipulation. 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. These analyses revealed a constitutive up-regulation of several AMPK-α and -γ subunit-encoding genes in GH-transgenic fish achieving accelerated growth. Further, immune stimulation caused a decrease in the expression of several AMPK subunit-encoding genes in GH-transgenic fish specifically. 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.

Figure 1

Maximum likelihood phylogenetic analysis of AMPK-α subunit sequences from: human Homo sapiens (“Hs”), Chinese softshell turtle Pelodiscus sinensis (“Ps”), western clawed frog Xenopus tropicalis (“Xt”), West Indian Ocean coelacanth Latimeria chalumnae (“Lc”), spotted gar Lepisosteus oculatus (“Lo”, sister lineage to teleosts that did not undergo tsWGD), zebrafish Danio rerio (“Dr”), Japanese rice fish Oryzias latipes (“Ol”), tilapia Oreochromis niloticus (“On”), northern pike Esox lucius (“El”, a sister lineage to salmonids that did not undergo ssWGD, Arctic charr Salvelinus alpinus (“Sa”), Atlantic salmon Salmo salar (“Ss”), rainbow trout Oncorhynchus mykiss (“Om”), Chinook salmon Oncorhynchus tshawytscha (“Ot”) and coho salmon Oncorhynchus kisutch (“Ok”). The tree is annotated to show WGD events in the teleost (“TsWGD”) and salmonid ancestor (“SsWGD”). Bootstrap branch support values are shown as circles on each node. Chromosomal locations for salmonid genes are provided when available. Accessions numbers are provided for all sequences.

Figure 2

Maximum likelihood phylogenetic analysis of the AMPK-β subunit. Details of species abbreviations and other annotations as in Fig. 1 legend.

Figure 3

Maximum likelihood phylogenetic analysis of the AMPK-γ subunit. Details of species abbreviations and other annotations as in Fig. 1 legend.