Fig. 2

Relative mRNA expression levels of protein-coding mitochondrial genes in brain, liver and kidney before and after low temperature 8 °C stress in H. rugulosus (CT frogs) (A, C, E) and H. rugulosus (TT frogs) (B, D, F). Relative mRNA levels were determined with RT-qPCR with n = 4 independent biological replicates and results are shown as mean ± SE. Mean values for controls were set to 1.0 and values for low-temperature groups are expressed relative to controls. Relative transcript levels were standardized against β-actin transcript levels as a reference gene. For each sample, the average β-actin Ct value was subtracted from the average target Ct value, obtaining a ΔCt value. Expression is represented as relative expression, calculated as 2^-ΔΔCt. Statistical significance was assessed with a two-tailed Student’s t-test, asterisks indicate significantly different expression (*, P < 0.05) and (**, P < 0.01)