Fig. 1

The transcript comparison in H. tuberosus QY1 and QY3, with purple and white tuber epidermis. a The phenotype of tubers of QY1 and QY3. ‘QY1’ and ‘QY3’ are H. tuberosus cultivars bred by Qinghai Academy of Agricultural and Forestry Sciences (Xining 810,000, China). The tuber epidermis of ‘QY1’ is red, whereas that of ‘QY3’ is white. b The volcano distribution map of differentially expressed genes in the tuber epidermis of QY1 and QY3 on RNA-seq experiments. The genes were classified into three classes. Red genes are up-regulated if gene expression in the tuber epidermis of QY1 was larger than QY3. Blue genes are down-regulated that gene expression of QY3 was larger than QY1. Gray genes are not differentially expressed. The X-axis represents Log2(Fold change). The Y-axis represents the value of -log10 (Padj). c The expression differences of structural genes in the anthocyanin biosynthesis pathway based on RNA-seq experiment. Arrow showed the metabolic stream, abbreviation left or upward arrows represent the genes catalyzing the progress, the number represent the average log2foldchange of the transcript level in the tuber epidermis of QY1 against QY3. d Relative transcript level of the structural genes of anthocyanin biosynthesis in the tuber epidermis of QY1 compared with QY3 based on qPCR. The Unigene33222_All, CL2784.Contig1_All, CL9203.Contig4_All, CL13771.Contig2_All, CL13771.Contig1_All, CL9517.Contig40_All, CL13383.Contig1_All were selected to design primer for qPCR experiment of CHS, CHI, F3H, F3’H, F3’5’H, DFR and ANS