Transcriptional activation of genes belonging to the plastidial MEP-derived
isoprenoid pathway by elicitation with
methyl jasmonate and
coronatine enhanced the content of bioactive
abietane diterpenes in Salvia sclarea hairy roots. We have shown that
aethiopinone, an
abietane diterpene synthesized in Salvia sclarea roots is cytotoxic and induces apoptosis in human
melanoma cells. To develop a production platform for this compound and other
abietane diterpenes, hairy root technology was combined with the elicitation of
methyl jasmonate (MeJA) or the phytotoxin
coronatine (Cor). Both MeJA and Cor induced a significant accumulation of
aethiopinone, but prolonged exposure to MeJA irremediably caused inhibition of hairy root growth, which was unaffected by Cor treatment. Considering together the fold increase in
aethiopinone content and the final hairy root biomass, the best combination was a Cor treatment for 28 days, which allowed to obtain up to 105.34 ± 2.30 mg L-1 of this compound to be obtained, corresponding to a 24-fold increase above the basal content in untreated hairy roots. MeJA or Cor elicitation also enhanced the synthesis of other bioactive
abietane-
quinone diterpenes. The elicitor-dependent steering effect was due to a coordinated transcriptional activation of several biosynthetic genes belonging to the plastidial MEP-derived
isoprenoid pathway. High correlations between
aethiopinone content and MeJA or Cor-elicited level of gene transcripts were found for DXS2 (r 2 = 0.99), DXR (r 2 = 0.99), and GGPPS (r 2 = 0.98), encoding
enzymes acting upstream of GGPP, the common precursor of
diterpenes and other plastidial-derived
terpenes, as well as CPPS (r 2 = 0.99), encoding the
enzyme involved in the first cyclization steps leading to
copalyl-diphosphate, the precursor of
abietane-like
diterpenes. These results point to these genes as possible targets of metabolic engineering approaches to establish a more efficient production platform for such promising anti-proliferative
plant-derived compounds.