Diterpenoid Diversity across Land Plants

ABSTRACT The diverse array of diterpenoid natural products stems from the ease of manipulating the promiscuity of diterpene cyclases. These enzymes are able to generate a vast array of structurally distinct diterpene skeletons from a common precursor, such as geranylgeranyl diphosphate, through subtle modifications in their active sites. Even minor amino acid substitutions can reshape the contour of the active site or alter the stabilization of key carbocation intermediates, leading to the emergence of new product profiles. This capacity for functional plasticity allows diterpene cyclases to rapidly explore chemical space, providing a rich assortment of scaffolds for development and persistence via natural selection. As a result, gene duplication followed by neofunctionalization of diterpene cyclases has driven the expansion of terpenoid repertoires across plant lineages, contributing to ecological diversification and specialized metabolic functions such as defense, communication, and adaptation to environmental stress. Here we will focus on the understudied bryophyte terpenome from structural diversification at the molecular level to regulation of biosynthetic pathways at the macroorganism level.