BAHD news from Euphorbia peplus : identification of acyltransferase enzymes involved in ingenane diterpenoid biosynthesis

The plant family Euphorbiaceae are an abundant source of structurally complex diterpenoids, many of which have reported anti-cancer, anti-HIV, and anti-inflammatory activities. Among these, ingenol-3-angelate ( 1a ; tradename: Picato ^® ), isolated from Euphorbia peplus , has potent anti-tumour activity.

Here we report the discovery and characterization of the first genes linked to the committed steps of ingenol-3-angelate ( 1a ) biosynthesis in Euphorbia peplus . We identified two genes, the products of which catalyse the addition of angelyl-CoA ( 9a ) to the ingenol ( 5 ) scaffold to produce ingenol-3-angelate ( 1a ).

We demonstrate using VIGS that just one of these genes, EpBAHD-08 , is essential for this angeloylation in E. peplus . VIGS of the second gene, EpBAHD-06 , has a significant effect on jatrophanes rather than ingenanes in E. peplus .

We also identified three genes whose products can catalyse acetylation of ingenol-3-angelate ( 1a ) to ingenol-3-angelate-20-acetate ( 2 ). In this case VIGS indicates considerable functional redundancy in the E. peplus genome of genes encoding this enzymatic step.

This work paves the way for increasing ingenol-3-angelate ( 1a ) levels in planta and provides a foundation for the discovery of the remaining genes in the biosynthetic pathway of these important molecules.