Unravelling the biosynthetic pathway genes of olive (Olea europaea, L.) triterpenoids

Olive triterpenoids (Olea europaea, L.), such as oleanolic and maslinic acids, are metabolites exerting numerous valuable proprieties. They contribute to the healthy effects of olive oil and can be used as bioactive components of pharmaceuticals and cosmetics. Despite olive is among the species accumulating the highest amount of these compounds, only a few genes underpinning their biosynthesis have been identified. We searched for terpene synthases and cytochromes P450 involved in the biosynthesis of olive triterpenoids. Candidate genes have been cloned and functionally characterized in yeast (Saccharomyces cerevisiae) and/or plant (Nicotiana benthamiana) host systems. Putative ?-amyrin synthase, a multifunctional ?-amyrin synthase and two candidate CYP450s were co-expressed in N. benthamiana leaves with a feedback-insensitive version of the upstream mevalonate pathway gene 3-hydroxy,3-methylglutaryl-CoA reductase (tHMGR). GC-MS assays have been performed on plant extracts. The analysis of the enzymatic products allowed to functionally characterize the target genes defining their role in triterpenoid biosynthesis. Our results will be applied for the development of molecular markers for health-related traits and to produce high amount of valuable compounds by metabolic engineering.