Expression and activity of XTH. a. Expression of Nicotiana tabacum xyloglucan endotransglycosylase (XTH, Genbank Acc AB017025.1) in Vvpgip1 lines 37 and 45 relative to the untransformed control (WT). Standard deviation of the mean relative expression of four technical repeats per plant line is shown with error bars. b. Total XTH activity in tobacco leaves determined by a dot-blot enzyme activity assay. Leaves representing leaf position 3 was used for the assay. A two-tailed Student's t-test showed that p < 0.05 for both transgenic lines in comparison to WT. N denotes the number of biological repeats.