Journal
FRONTIERS IN PHYSIOLOGY
Volume 9, Issue -, Pages -Publisher
FRONTIERS MEDIA SA
DOI: 10.3389/fphys.2018.00100
Keywords
hypoxia; oxidative stress; alternative oxidase; mitochondrial electron transport; anaerobiosis; Diplodon chilensis
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Funding
- European Commission under the 7th Framework Programme through the Action-IMCONet (FP7 IRSES) [318718]
- German Academic Exchange Service (DAAD)
- University of Buenos Aires [UBACYT 20020100100985]
- Consejo Nacional de Investigaciones Cientificas y Tecnicas [CONICET PIP 11220090100492]
- Alexander von Humboldt Foundation [PUD7306A01/2012-2014]
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Hypoxia in freshwater ecosystems is spreading as a consequence of global change, including pollution and eutrophication. In the Patagonian Andes, a decline in precipitation causes reduced lake water volumes and stagnant conditions that limit oxygen transport and exacerbate hypoxia below the upper mixed layer. We analyzed the molecular and biochemical response of the North Patagonian bivalve Diplodon chilensis after 10 days of experimental anoxia (<0.2mg O-2/L), hypoxia (2 mg O-2/L), and normoxia (9 mg O-2/L). Specifically, we investigated the expression of an alternative oxidase (AOX) pathway assumed to shortcut the regular mitochondrial electron transport system (ETS) during metabolic rate depression (MRD) in hypoxia-tolerant invertebrates. Whereas, the AOX system was strongly upregulated during anoxia in gills, ETS activities and energy mobilization decreased [less transcription of glycogen phosphorylase (GlyP) and succinate dehydrogenase (SDH) in gills and mantle]. Accumulation of succinate and induction of malate dehydrogenase (MDH) activity could indicate activation of anaerobic mitochondrial pathways to support anoxic survival in D. chilensis. Oxidative stress [protein carbonylation, glutathione peroxidase (GPx) expression] and apoptotic intensity (caspase 3/7 activity) decreased, whereas an unfolded protein response (HSP90) was induced under anoxia. This is the first clear evidence of the concerted regulation of the AOX and ETS genes in a hypoxia-tolerant freshwater bivalve and yet another example that exposure to hypoxia and anoxia is not necessarily accompanied by oxidative stress in hypoxia-tolerant mollusks.
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