Heterologous Production of the Structurally Complex Diterpenoid Forskolin in Synechocystis sp. PCC. 6803

Photosynthetic organisms such as cyanobacteria have the potential for sustainable production of complex organic molecules due to their ability to absorb and use light as an energy source to fix CO2 and assimilate inorganic nutrients. Over the past decade, large efforts have gone into the metabolic engineering of cyanobacteria to produce various compounds such as alcohols, isoprenoids, biopolymers, recombinant proteins, as well as biofuels. Forskolin is a structurally complex labdane-type diterpenoid with eight chiral carbon atoms and is naturally produced in the root cork of the plant Plectranthus barbatus. Forskolin is a potent cAMP activator indicated as a pharmaceutical for a variety of diseases. In the plant, forskolin biosynthesis from geranylgeranyl diphosphate involves six enzymes: two terpene synthases, three cytochrome P450s, and a single acetyltransferase. In this work, we express all six biosynthetic genes from Plectranthus barbatus in Synechocystis sp. PCC. 6803 and demonstrate heterologous production of this complex diterpenoid in a phototroph cyanobacterium. Forskolin titers reached 25.0 ± 4.4 µg/L, all of which was secreted into the media.