Medicinal plants produce many secondary metabolites, particularly alkaloids, which have potent biological activities. Plant derived alkaloids are a potent source of medicinal compounds. For example, more than 4000 alkaloids were identified in traditional Chinese medicine, and 50 of these compounds are used as pharmaceuticals clinically. However, the capacity to harness plant alkaloids is hindered by the fact that these compounds are often produced in low levels, or by plants that are challenging to cultivate. Understanding the biosynthesis of these compounds will pave the way to better production strategies for these compounds, as well as analogues of these compounds that may have improved or modified biological activity. In this proposal, we will uncover the biosynthetic pathways of several medicinally active alkaloids.