Biochemical Characterization of a Fungal Bifunctional Type I Diterpene Synthase Brings a Cryptic Natural Product to Light

We report the identification of the tnd biosynthetic cluster from the marine-derived fungal strain Aspergillus flavipes CNL-338 and in vivo characterization of a cryptic type I diterpene synthase. Heterologous expression of the bifunctional terpene synthase TndC in Saccharomyces cerevisiae led to the discovery of a new diterpene backbone, talarodiene, harboring a benzo[a]cyclopenta[d]cyclooctane tricyclic fused ring system. The cyclization mechanism that converts geranylgeranyl diphosphate to the tricyclic hydrocarbon skeleton was investigated using 13 C-labeling studies and stable isotope tracer experiments showed the biotransformation of talarodiene into talaronoid C.