Overcoming Metabolic Constraints in the MEP-Pathway Enrich Salvia sclarea Hairy Roots in Therapeutic Abietane Diterpenes

Abstract

Abietane diterpenoids (e.g., carnosic acid, aethiopinone, 1-oxoaethiopinone, salvipisone, and ferruginol) synthesized in the roots of several Salvia species have proved to have promising biological activities, but their use on a large scale is limited by the very low content extracted from in vivo roots. In this review, we summarized our efforts and the achieved results aimed at optimizing the synthesis of these diterpenes in Salvia sclarea hairy roots by either elicitation or by modifying the expression of genes encoding enzymes of the MEP-pathway, the biosynthetic route from which they derive. Stable S. sclarea hairy roots (HRs) were treated with methyl jasmonate or coronatine, or genetically engineered, by tuning the expression of genes controlling enzymatic rate-limiting steps (DXS, DXR, GGPPS, CPPS alone or in combination), by silencing of the Ent-CPPS gene, encoding an enzyme acting at gibberellin lateral competitive route or by coordinate up-regulation of biosynthetic genes mediated by transcription factors (WRKY and MYC2). Altogether, these different approaches successfully increased the amount of abietane diterpenes in S. sclarea HRs from to 2 to 30 times over the content found in the control HR line.