In vitro enzymatic assays of recombinant MsTPSs. GST-tagged MsTPS recombinant enzymes were purified by glutathione-based affinity chromatography and used for in vitro assays with GPP or FPP as substrate. The final products were analysed by GC-MS. The peaks marked with an arrow in the GC traces were compared with the reference of the mass spectra library. Mass spectra for the peaks formed with FPP are shown at bottom of figure. m/z, mass-to-charge ratio, (A) Left panel, β-caryophyllene formation by GST-MsTPS1 with FPP; Right panel, the control GC-MS analyses of GST with GPP or FPP. (B) Left panel, β-cubebene/Germacrene D or β-copaene formation by GST-MsTPS2 with FPP; Right panel, the control GC-MS analyses of GST with GPP or FPP.