Fig. 2
Overexpression of PttVAP27-17 in greenhouse-grown hybrid aspen trees. a The expression of PttVAP27-12, -13, -14, -15, -16 and -17 genes in stem tissues of three transgenic P. tremula × tremuloides lines (1–3) carrying the 35S::PttVAP27-17 construct. The expression data were derived from the transcriptomic analysis of secondary xylem tissues collected from the basal part of 2-months-old greenhouse-grown trees. The log2 fold-change indicates log ratio of PttVAP27-17 expression in each transgenic line compared to WT. The figure also shows relative expression of PttVAP27-17 by qPCR (b), stem height (c), stem diameter (d), wood density (e), and total stem biomass (f) in the three transgenic P. tremula × tremuloides lines carrying the 35S::PttVAP27-17 construct and the WT grown for two months in the greenhouse. Stem volume was estimated using the formula: volume = π × radius2 × height/3. n = 5 for transgenic line 1 and 2, n = 3 for transgenic line 3 and n = 7 for the WT where “n” indicates number of biological replicates. Vertical bars (in a, b) indicate ± SD. The box plots show the median (horizontal line) with the outer limits at the 25th and 75th percentiles, the 1.5 inter-quartile ranges (whiskers) and the outliers (gray spots). Asterisks indicate statistically significant differences compared to WT: p ≤ 5% (*), p ≤ 0.1% (**), using Student’s t-test (b, c, f) and differential expression analysis DESeq2 (a). Percentages indicate increase (+) or decrease (−) of corresponding data values for lines overexpressing PttVAP27-17 compared to WT