Research in my group is centered on studies of diterpenoids. These form a large group of natural products, with over 25,000 already known. Notably, many (although certainly not all) of these diterpenoids are found in plants, where the requisite biosynthetic machinery for gibberellin and related phytohormones (GAs), particularly the relevant diterpene cyclases and synthases, provides a biosynthetic reservoir that appears to have been repeatedly drawn upon to evolve new such natural products (1). The biosynthesis of these is characterized by their use of (class II, protonation-initiated) diterpene cyclases, and we have termed them the labdane-related diterpenoids (2). The potent biological activity of the “ancestral” GAs, which has led to the independent evolution of distinct GA biosynthetic pathways in plants, fungi, and bacteria, provides an archetypal example of the selective pressure driving evolution of this large super-family, with over 15,000 already known (3). The observed diversification suggests that the underlying hydrocarbon skeletal structures serve as privileged scaffolds from which biological activity is readily derived. Our studies encompass both investigation of metabolic pathways/networks and the underlying enzymatic mechanisms, along with elucidation of the physiological function of these natural products. The diterpene cyclases and synthases involved in production of the labdane-related diterpenoids are representative of those involved in biosynthesis of all major classes of terpenoids, providing wider significance to our work (4). We have provided several fundamental insights into the intriguing mechanisms of the complex reactions catalyzed by these fascinating enzymes, highlighted by the profound effect that can be exerted by single residue changes on enzymatic activity. Moreover, using rice as a model system we have demonstrated that its arsenal of labdane-related diterpenoids serve manifold roles, ranging from phytoalexins exhibiting antibiotic activity against fungal and bacterial pathogens, along with parasitic nematodes, to allelochemicals secreted into the soil to inhibit the growth of other plant species but also initiate symbiosis with mycorrhizal fungi, as well as shape the microbiome of their rhizosphere. Conversely, we discovered the bacterial operon enabling production of GAs, which are present in both symbiotic rhizobacteria but also phytopathogens, serving disparate roles in consistent with their orthologous plant-microbe interactions. Our work entails use of a wide variety of approaches, ranging from biophysical investigation of enzymatic structure-function relationships to analysis of chemical ecology and metabolic evolution using genome editing to broadly examine the role of labdane-related diterpenoids in plant-plant and plant-microbe interactions. More complete descriptions of our research in these various areas can be found in the 'Projects' pages.
(1) Wang, Z., Nelson, D. R., Zhang, J., Wan, X., and Peters, R. J. (2023) Plant (di)terpenoid evolution: from pigments to hormones and beyond, Nat Prod Rep 40, 452-469.
(2) Peters, R. J. (2010) Two rings in them all: the labdane-related diterpenoids, Nat Prod Rep 27, 1521-1530.
(3) Zi, J., Mafu, S., and Peters, R. J. (2014) To gibberellins and beyond! Surveying the evolution of (di)terpenoid metabolism, Annu Rev Plant Biol 65, 259-286.
(4) Peters, R. J. (2025) Between scents and sterols: Cyclization of labdane-related diterpenes as model systems for enzymatic control of carbocation cascades, J Biol Chem 301, 108142.