Fig. 1

Relative mRNA expression levels of protein-coding mitochondrial genes in brain, liver and kidney of normal temperature 25 °C (A, C, E) and low temperature 8 °C (B, D, F) exposed H. rugulosus (TT frogs) and H. rugulosus (CT frogs). Relative mRNA levels were determined by RT-qPCR with n = 4 independent biological replicates and results are shown as mean ± SE. Mean values for TT frogs were set to 1.0 and values for CT frogs are expressed relative to TT frogs. Relative transcript levels were standardized against β-actin transcript levels as the reference gene. For each sample, the average β-actin Ct value was subtracted from the average target Ct value, obtaining a ΔCt value. Data are shown 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)