Fig. 3

Expression patterns of eight CuCBLs and 17 CuCIPKs in cold-tolerant ‘Guijing2501’ satsuma mandarin under cold stress as determined by qRT‒PCR. Two-year-old healthy and uniform bud-grafting ‘Gujing2501’ satsuma mandarin trees growing in a greenhouse were subjected to low-temperature (4 °C) treatment as described in the Methods section. Three biological replicates were used for measuring gene expression, and the experiment was repeated once with similar results. The relative expression levels of candidate genes were calculated using the 2^−∆∆CT method. The CuEF1α gene was used as an internal reference gene for normalization of the transcript levels of the tested genes. Error bars indicate inferential statistics according to the SE. *indicates statistical significance (*p < 0.05; **p < 0.01; ***p < 0.001; Student’s t test) when compared to the expression level at 0 h/d