Fig. 4

Gene expression analysis of the 10 selected genes by RT-qPCR assay. The FPKM values of 9 genes, excluding Potri.001G404100, can be found in Additional file 1: Table S2. The FPKM values of Potri.001G404100 for DAE0, DAE2, DAE4, DAE6, and DAE8 are 23.1, 27.9, 23.6, 23.2 and 13.2, respectively. Because these genes were not classified as differentially expressed genes, their FPKM values are not in Additional file 1: Table S2. Two stars represent the relative expression fold is different between the tested time point and DAE0 under the significant level of P value equal to 0.01; while one star represents the relative expression fold is different between the tested time point and DAE0 under the significant level of P value equal to 0.05