Increasing expression levels of isoprenoid precursor pathway genes DXS and GGPPS lead to increased CBT-ol production in agro-infiltrated N. benthamiana leaves. (A) CBT-ol content in hexane washes from N. benthamiana leaves co-expressing p19 and NsCBTS2a with SlDXS2 and/or NtGGPPS2 in different combinations. The appropriate Agrobacterium cultures were infiltrated into separate parts of the same N. benthamiana leaf and in two leaves per individual plants. Leaves were harvested five days post-infiltration. Mean CBT-ol values ± SEM are presented (n = 8). Groups indicated by different letters differ significantly from each other regarding their CBT-ol values (P < 0.05, Student’s t-test and one-way ANOVA). ISTD – internal standard sclareol; (B) Full total ion chromatograms demonstrating high CBT-ol peak (dashed lines) when NsCBTS2a was co-expressed with both SlDXS2 and NtGGPPS2. No CBT-ol was detected in leaves agro-infiltrated with the empty T-DNA vector as a control.