Elucidation and engineering of two distinct plant terpene alkaloid biosynthetic pathways

Numerous monoterpene indole alkaloids (MIAs) and steroidal glycoalkaloids (SGAs) are highly valuable due to their beneficial bioactivities. For example, vinblastine is an MIA produced by the plant Catharanthus roseus that is used as an anti-cancer agent, serpentine is a topoisomerase inhibitor also produced by C. rosesus and mitragynine is an MIA from Mitragyna speciosa that is used to treat pain. Triterpenoid lipid cholesterol-derived SGAs, exemplified by α-tomatine, are produced in various plants within the Solanum genus, and have also been shown to display diverse pharmacologically important activities. However, the SGAs also act as anti-nutritional agents in Solanum food crops. The manipulation of MIA and SGA pathways within biological systems, aimed at either establishing efficient production platforms for pharmacologically useful compounds or altering the content of toxic metabolites in food crops, requires in-depth understanding of the biosynthetic processes. Although the bioactivities displayed by both compound classes are well-studied, many steps of their production remain cryptic. This thesis describes the characterization of multiple steps within the MIA and SGA biosynthetic pathways. Additionally, cutting-edge metabolic engineering strategies for refactoring of both pathways within biological systems are used. Overall, the work presented in this thesis contributes to a deeper understanding of terpene alkaloid biosynthesis and demonstrates how state-of-art plant metabolic engineering strategies can be used to refactor metabolic pathways in biological systems.