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Fish adaptation to changing oxygen levels

Global warming, oxygen limitation and pollution have affected aquatic ecosystems worldwide. European researchers investigated the molecular mechanisms underlying oxygen transport in fish and how they may adapt to environmental change.
Fish adaptation to changing oxygen levels
Globin X (GbX) is an oxygen binder found in fish, reptiles and amphibians that diverged from a common ancestor of mammalian haemoglobin. GbX is involved in oxygen-dependent activation of the sodium/proton exchange in fish red blood cell (RBC) membrane but the exact nature of the mechanism is poorly understood.

The GBX IN FISH RBCS (Expression and function of globin X in nucleated red blood cells of fish) project employed a multidisciplinary approach to elucidate the exact function of GbX. They combined molecular and functional data on this enigmatic molecule with an environmental focus.

The researchers used three different salmonid species – Atlantic salmon, Arctic char and rainbow trout – that differ in temperature and oxygen requirements. They identified conditions (e.g. temperature hike and β-adrenergic stimulation) that increased the transcription rate of GbX in fish RBCs, liver and gill cells. None of the transcripts changed its rate of production in response to environmental change but importantly, the stability of two transcripts was significantly affected.

Still ongoing, the GBX IN FISH RBCS team looked at the effects of hypoxia and reoxygenation. Results showed that only long-term oxygen deficiency affected GbX transcript levels. Overall, however, GbX expression varies highly among individual fish and the precise conditions for its production require further research.

To test the impact of variation in N- and C-terminal extensions of GbX that are unique to the molecule, the team designed several constructs of the rainbow trout GbX coding sequence. Lipid modifications such as palmitoylation localise the protein to cell membranes. Significantly, they found that only the N-terminal determines localisation, not other parts of the molecule.

GBX IN FISH RBCS have accumulated a large amount of new data on gene expression regulation in fish. Analysis of data is still in progress, in particular, whether GbX expression is determined by β-adrenergic stimulation. With a local company, a project microplate reader system was tested that also has wide applications in the life science arena.

Five scientific papers have been submitted for publication and results presented at three international conferences, a reflection of the importance of this research. Applications are very wide in view of the dynamics of the world’s changing ecosystems, many to the detriment of fish species teetering on the brink of survival.

Related information


Fish, oxygen levels, aquatic ecosystem, GbX, GBX IN FISH RBCS
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