Fig. 4

Relative mRNA expression levels of protein-coding mitochondrial genes in kidney, brain, and liver of H. rugulosus (CT frogs) and H. rugulosus (TT frogs) under normal conditions (24 h at 25 °C) (A, C) and low-temperature exposure (24 h at 8 °C) (B, D) Mitochondrial gene expression levels in each tissue were standardized relative to β-actin transcript levels. Statistical significance was assessed with a two-tailed Student’s t-test, “a” indicates significantly different expression between brain and liver (a*, P < 0.05) and (a**, P < 0.01); “b” indicates significantly different expression between liver and kidney (b*, P < 0.05) and (b**, P < 0.01); and “c” indicates significantly different expression between brain and kidney (c*, P < 0.05) and (c**, P < 0.01)