Fig. 2

qRT-PCR analysis of genes encoding DNA methyltransferases and demethylases in stems of Populus trichocarpa. Transcript level of the actin gene in P. trichocarpa was used as an endogenous control to normalize expression values of other genes in primary stems (PS), transitional stems (TS), and secondary stems (SS). Bars and standard errors represent the means and standard errors, respectively, of three biological replicates. Each biological replicate was represented by an independent RNA extraction in two technical replicates. The data were analyzed using one-way ANOVA using SPSS 21. Significant differences among different comparisons were determined with Duncan’s multiple range test and significant and highly significant differences are indicated by *(P < 0.05) and **(P < 0.01), respectively