Project Summary Natural product leads from marine life continue to inspire new drugs, with nine approved for clinical use since 2010. A historical challenge with developing marine organism-derived bioactive chemicals has been one of limited supply. Often, natural drug leads are isolated from rare or environmentally sensitive marine invertebrates and algae, which challenges the pre-clinical evaluation of promising candidates when demands outweigh natural supplies. Some terrestrial plant-derived drugs can now be produced in genetically engineered microbial cell factories, an approach that would be attractive for marine-derived molecules. However, the biosynthetic machinery responsible for the biosynthesis of bioactive natural products in marine animals and algae is largely unknown. Until now. We have discovered and validated the first steps of biosynthetic pathways in corals and algae that lead to over 6,000 terpenoids, including the anti- inflammatory pseudopterosin and anticancer halomon. We propose a multidisciplinary project to investigate the molecular basis of terpenoid diversification in marine eukaryotes that harbor terpenoids with promising biological properties. Significant outcomes of this research project will include a new paradigm for terpenoid biosynthetic logic in marine eukaryotes, and the application of this basic knowledge toward the microbial production of marine animal and algal molecules. We propose three specific aims, namely: 1) To develop a marine eukaryotic genome mining platform for algae and corals; 2) To functionally characterize marine eukaryotic terpene synthases for high yield terpene production; and 3) To discover and characterize terpene tailoring enzymes (halogenation/oxygenation) associated with bioactive coral and algal natural products.