Production of 3-geranyl-4-hydroxybenzoate acid in yeast， an important intermediate of shikonin biosynthesis pathway.

Shikonin and its derivatives are the main active components in the medicinal plant Arnebia euchroma and possess extensive pharmaceutical properties. In this study， we developed an optimized yeast system to obtain high-level production of 3-geranyl-4-hydroxybenzoate acid (GBA)， an important intermediate involved in shikonin biosynthesis pathway. For host selection， recombinant expression of p-hydroxybenzoate:geranyltransferase (PGT) derived from A. euchroma was performed in Saccharomyces cerevisiae WAT11U strain and high yield monoterpene strain. In shake flask culture with 1 mM p-hydroxybenzoate acid (PHBA)， they could yield GBA at 0.1567 and 20.8624 mg L-1， respectively. Additionally， AePGT6 showed higher enzymatic activity than its homologs. Moreover， by combining improvement in the homologous mevalonate pathway with reconstruction in the heterologous shikimic pathway， a de novo GBA synthesis pathway was constructed in StHP6tHC with co-overexpressed SctHMG1， optimized EcUbiC and AePGT6. A high titer of 179.29 mg L-1 GBA was achieved in StHP6tHC under shake flask fermentation with 1 mM PHBA. These results suggest that yeast could be engineered systematically to enable an efficient monoterpene-quinone or naphthoquinone production.