Progressive Regulation of Sesquiterpene Biosynthesis in Arabidopsis and Patchouli (Pogostemon cablin) by the miR156-Targeted SPL Transcription Factors.

Plant metabolites vary at different stages of life cycle. Although it is well documented that environmental factors stimulate biosynthesis of secondary metabolites, the regulation by endogenous developmental cues remains poorly understood. The microRNA156 (miR156)-tageted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) factors function as a major age cue in regulating developmental phase transition and flowering. We show here that the miR156-targeted SPL transcription factor plays an important role in the spatiotemporal regulation of sesquiterpene biosynthesis. In Arabidopsis thaliana, the miR156-SPL module regulates the formation of (E)-β-caryophyllene in flowering stage through modulating expression of the sesquiterpene synthase gene TPS21. We demonstrated that SPL9 directly binds to TPS21 promoter and activates its expression. In the perennial fragrant herb Pogostemon cablin, the accumulation of "patchouli oil", largely composed of sesquiterpenes dominated by (-)-patchoulol, is also age-regulated, and the SPL promotes biosynthesis of sesquiterpenes in elder plants by up-regulating patchoulol synthase (PatPTS) gene expression. As miR156-SPLs are highly conserved in plants, our finding not only uncovers a molecular link between developmental timing and sesquiterpene production, but also suggests a new strategy to engineer plant for accelerated growth with enhanced production of terpenoids.