Title: Effects of Elevated Temperature on Gene Expression, Energy Reserves, and Cellular Energy Status in Salmo trutta (brown trout)
Author: Buumba Hampuwo
Supervising Institution: BOKU University
Year: 2024
Abstract:
Global warming poses a significant threat to aquatic ecosystems, especially freshwater habitats. According to the Intergovernmental Panel on Climate Change (IPCC), an increase in global temperature by 1.5°C to 2°C will impact these ecosystems. Salmo trutta is particularly vulnerable due to its sensitivity to temperature changes and narrow tolerance range. This study examined the effects of elevated temperature on gene expression, energy reserves, and cellular energy status in brown trout (Salmo trutta). A total of 250 brown trout were placed in four stream channels with flow-through conditions (0.2 l/sec). Two of these channels were maintained at 10 ± 0.2°C as control groups, while the other two had their temperature gradually increased to 20°C over a 7 day, and then maintained at 20°C for 21 days. Liver samples were collected for gene expression analysis and stored in RNAlater, and those for metabolite analysis were stored in perchloric acid at -20°C. Samples were taken on day seven and day 21 for both control and treatment groups. Additionally, growth and condition indices were measured and calculated at sampling times. Our results revealed an increase in the expression of genes related to cellular stress responses relative to the control (hsp70, hsp90, cat, and casp8) alongside a decrease in the expression of lipid and carbohydrate metabolism genes (d5fad and pfkfb4) respectively. There was also a reduction in energy storage metabolites, such as glycogen and triglycerides, as well as a decline in cellular energy status, indicated by ATP and AEC levels. Furthermore, a decrease in growth was observed in brown trout after 21 days at 20°C water temperature. This study showed that prolonged exposure led to significant trade-offs which ultimately limited brown trout adaptive capacity over the long term. The knowledge gained from this study helps evaluate the species' adaptive capacity and informs the development of effective conservation strategies in a warming world.
Keywords: elevated temperature, gene expression, brown trout, metabolites, energy reserves