Figure 1.

OryzaTPS1s have diverged to produce three different sesquiterpene product spectra. The enzymes were expressed in E. coli, extracted, and incubated with the substrate (E, E)-farnesyl diphosphate. The resulting terpene products were separated by gas chromatography–mass spectrometry (GC-MS). The traces of the MS detector were shown for ObTPS1, a representative (E)-β-caryophyllene synthase (ECS), for OsTPS1, a representative (E)-β-caryophyllene/germacrene A synthase (EGS), and for OrTPS1, the germacrene D & germacrene A synthase (DAS). Products were identified as 1, β-elemene; 2, (E)-β-caryophyllene; 3, α-humulene; 4, germacrene D by comparison of their retention times and mass spectra to those of authentic standards. *Unidentified sesquiterpenoids. The chemical structures of compounds 1, 2 and 4 were shown on the right. Note: β-elemene was produced as a thermal rearrangement product from germacrene A in the GC injector (Additional files 4 and 5).