A Tale of Two Clades: The Shared Biosynthesis of Cyclic Diterpenoids between Conifer trees and Peatland Mosses

Authors: Chad K. Papenfuhs, 1 Anita Berg, 1 Ida R. Hipfinger, 1 Amy E. Fraley1 

Affiliations: 1Institute of Pharmaceutical Sciences, Department of Chemistry and Applied Biosciences, Eidgenössische Technische Hochschule (ETH) Zürich, Vladimir-Prelog-Weg 4, CH-8093 Zürich, Switzerland 

Abstract: Sphagnum mosses live semi-submerged in water, growing mere centimeters in height. In contrast, trees of the family Pinaceae, can grow tens of meters high, making them among the tallest living organisms. While differing immensely in size, they coexist in a unique ecosystem called a peat bog. Peatlands are wetland ecosystems principally engineered by Sphagnum mosses. Through acidification of their environment, and the release of secondary metabolites, Sphagnum create a hostile environment, where few plants can thrive. Select species of Spruce (Picea) and Pine (Pinus) trees characteristically line the perimeter of alpine peatlands, with saplings often growing within the Sphagnum itself. Through untargeted metabolomics of wild-collected Sphagnum mosses coupled with parallel experimentation on laboratory-cultivated axenic Sphagnum, we have observed a biosynthetic crosstalk across this vascular-nonvascular plant interface. Our data point to a unidirectional metabolic exchange of abietane diterpenoids from the trees into the waterlogged peatland where they are absorbed and oxidatively modified within the Sphagnum mosses. Here we report a diterpenoid that appears to arise uniquely from this lineage spanning interaction. These findings suggest that, over evolutionary timescales, Sphagnum have developed the biochemical capacity to transform terpenoids from their surrounding aquatic environment, namely conifer-derived natural products, which may represent previously unrecognized regulators of ecological interactions in freshwater wetlands.