Evolution of linear triterpenoid biosynthesis within the Euphorbia genus

Terpenoids are among the largest classes of plant natural products. Squalene, a high value commodity in the cosmetic, food and pharmaceutical industries, is a common linear precursor for the biosynthesis of C30 triterpenes and sterols across plant, animal and fungal kingdoms. The anti-fungal compound peplusol is another linear C30 triterpene, but has only been reported in the genus Euphorbia. Here, we show that peplusol production has evolved due to duplication of a sterol synthase gene with one copy acquiring peplusol synthase activity and the original gene retaining the ancestral function. We identify a number of key amino acid residues that can convert the squalene synthase enzyme into peplusol synthase and vice versa. The PEPLUSOL SYNTHASE gene from E. peplus is able to drive significant levels of peplusol production in alternate host production platforms including Nicotiana benthamiana (over 2.5% leaf dry weight) and Saccharomyces cerevisiae (30 mg/L culture).