Thermal acclimation of rainbow trout myotomal muscle, can trout acclimate to a warming environment?

Climate change is a looming threat to the planet. Cold-water aquatic species will face significant physiological challenges due to elevated summer temperatures. Salmonids, such as rainbow trout (Oncorhynchus mykiss) maintain fidelity to native streams, limiting their ability to mitigate the impact of climate change through migration. We examined how rainbow trout swimming performance and muscle function were shaped by the thermal environment. We hypothesized that trout would show slower muscle contractile properties and slower swimming performance with long-term exposure to warmer water. For fish held at either 10 °C or 20 °C, maximum steady swimming speed (Ucrit) was determined, and contractile properties of both fast-twitch (white) and slow-twitch (red) myotomal muscle were examined. In addition, immunohistochemistry and quantitative PCR were used to assess changes in myosin content of the myotomal muscle in response to holding temperature. Rainbow trout exposed to warm water for six weeks displayed relatively limited thermal acclimation response. When tested at a common temperature (10 °C), 20 °C acclimated fish had modestly slower muscle performance compared to 10 °C acclimated fish. Significant differences in swimming performance and muscle contractile properties were primarily at colder test temperatures (e.g. 2 °C for muscle mechanics). Shifts in myosin heavy chain protein composition and myosin heavy chain gene expression in the swimming muscle were observed in white but not red muscle. Our results suggest that rainbow trout will have a limited ability to mitigate elevated environmental temperature through thermal acclimation of their myotomal or swimming muscle.

Characterization of the manganese-containing superoxide dismutase and its gene regulation in stress response of Schizosaccharomyces pombe.

Fission yeast Schizosaccharomyces pombe contains two superoxide dismutases (SODs), one in the cytosol and the other in mitochondria. The sod2+ gene encoding putative mitochondrial superoxide dismutase containing manganese (MnSOD) has been isolated. Purification and analysis of the sod2+ gene product revealed that it contained only manganese as a cofactor, thus verified to be a genuine MnSOD. It was localized in mitochondria as expected. Its N-terminal amino acid sequence indicated that the mitochondrial targeting sequence of 21 amino acids was removed. The native form consisted of two identical subunits. The sod2+ expression was induced by external stresses, such as treatments with superoxide generators, high osmolarity, and heat. The induction by these stress treatments depended on Wis1-Spc1 MAPK signal transduction pathway being independent of transcription factors Atf1 or Pap1. The sod2 disruption rendered cells sensitive to various superoxide-generators, heat, and high osmolarity, suggesting that the mitochondrial MnSOD acts as a general defense agent against multiple stresses.