Functional characterization of amyrin synthase involved in ursolic acid biosynthesis in Catharanthus roseus leaf epidermis

► Molecular and biochemical characterization of Catharanthus amyrin synthase (CrAS). ► Expression of CrAS in yeast produces α- and β-amyrin a 5:1 ratio. ► Leaf epidermis expression of the mevalonic and triterpene biosynthesis pathways. ► Ursolic acid accumulation on the leaf surface. ► CrAS expression in early stages of seedling development and in young leaves.