Project description:The emergence of cyclic hypoxia puts aquatic organisms’ homeostasis under significant strain. Energetic metabolism as well as protein synthesis and folding are particularly altered during hypoxia, while reoxygenation imposes an oxidative challenge. Currently, little is known about how hypoxia-sensitive organisms respond to large oxygen fluctuations. Our previous work on Arctic char revealed that this salmonid, despite being strongly affected by acute hypoxia and reoxygenation (H/R), can successfully reestablish homeostasis, notably through adjustments to hepatic mitochondrial metabolism. However, the mechanisms underlying this acclimation remain poorly understood. We hypothesized that Arctic char remodel their hepatic proteome to optimize energy metabolism, reorganize oxygen-demanding pathways, and maintain cellular homeostasis during repeated H/R cycles. By exposing Arctic char to two or fifteen days of diel cyclic hypoxia, we confirmed this species’ limited capacity to respond to acute H/R. Nevertheless, after fifteen cycles, Fish adjusted their energetic metabolism through coordinated regulation of carbohydrate and lipid pathways and upregulation of amino acid metabolism. Mitochondrial metabolism was strongly reorganized, particularly at the ubiquinone–Complex III interaction level, alongside adjustments in proline utilization and protein processing. Moreover, protein processing and folding pathways were stimulated in both mitochondria and the endoplasmic reticulum. However, chronic cyclic hypoxia may still promote non-mitochondrial ROS production, DNA replication stress, and impaired immune function. This study highlights how a hypoxia-sensitive fish progressively reorganizes its metabolism and oxygen-demanding pathways to establish a phenotype adapted to chronic cyclic hypoxia, while also revealing the physiological costs associated with this acclimation.
Project description:We report here the release of a multi organ transcriptome developped for the Arctic char Salvelinus alpinus. This reference set was obtained using the 454 GS FLX+ technology. A pool of one-year-old, immature offspring of wild, anadromous Arctic charr originating from Lake Varflusjoen, Svalbard (79oN), including both lean and fat individuals, and three-years-old mature offspring of charr originating from Lake Vårflusjøen, North-Norway (70oN) was sampled. In order to maximize the diversity of expressed transcripts, we sampled a variety of organs and tissues; the whole brain, gill and head kidney and pieces of the liver, gonad, abdominal fat and muscle.