Overexpression of Ptxt PL1-27 in developing wood of aspen. Relative PtxtPL1-27 transcript level determined by RT-qPCR and calibrated to 18S RNA (A) and PEL activity in wall-bound and soluble protein fractions (B, C) in developing xylem in the most highly expressing independent transgenic lines carrying 35S: Ptxt PL1-27 (1051, 1002) and wild-type (WT). Means of two experiments, each with three biological replicates. WT1 and WT2 represent two sets of randomly selected WT trees. Bars represent standard error.