Inducing the Alternative Oxidase Forms Part of the Molecular Strategy of Anoxic Survival in Freshwater Bivalves.

YUSSEPPONE, M.S.; ROCCHETTA, I.; SABATINI, S.; LUQUET, C.M.; RIOS DE MOLINA, M.C.; HELD, C.; ABELE, D.

FRONTIERS IN PHYSIOLOGY

FRONTIERS

Año: 2018

Hypoxia in freshwater ecosystems is spreading as a consequence of global change,including pollution and eutrophication. In the Patagonian Andes, a decline in precipitationcauses reduced lake water volumes and stagnant conditions that limit oxygen transportand exacerbate hypoxia below the upper mixed layer. We analyzed the molecularand biochemical response of the North Patagonian bivalve Diplodon chilensis after10 days of experimental anoxia (<0.2mg O2/L), hypoxia (2mg O2/L), and normoxia(9mg O2/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 andenergy mobilization decreased [less transcription of glycogen phosphorylase (GlyP) andsuccinate dehydrogenase (SDH) in gills and mantle]. Accumulation of succinate andinduction of malate dehydrogenase (MDH) activity could indicate activation of anaerobicmitochondrial 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) wasinduced under anoxia. This is the first clear evidence of the concerted regulation of theAOX and ETS genes in a hypoxia-tolerant freshwater bivalve and yet another examplethat exposition to hypoxia and anoxia is not necessarily accompanied by oxidative stressin hypoxia-tolerant mollusks.