Understanding of nitrogen cycling in lichens of the genus Cladonia by NMR metabolomics

Understanding nitrogen dynamics in lichens, while providing insights into lichen physiology and symbiosis, can also be important in assessing the impact of human footprint on ecosystems. In this work, we studied four species of Cladonia Hill. ( C. foliacea, C. polycarpoides , C. rangiformis , C. rei ), a genus of fruticose lichens with cosmopolitan distribution which provide relevant biomass and ecosystem services in rare and endangered habitats [ 1 ] [ 2 ]. Using NMR metabolomics, we found out metabolic markers of seasonal variation common to the four species, providing a key to understanding how nitrogen and carbon are mobilized across seasons. The developed OPLS model, with y =temperature gradient over the year (dT), showed that as dT decreases, glutamine and the sugar alcohol arabinitol increase, whereas as dT increases, there is an increase in threonine, glucose, sucrose, and trehalose, together with another sugar alcohol found for the first time in lichens. This key and rare metabolite was identified (by 2D NMR and ToF-MS) as β glucopyranose(1→2)mannitol. It is reasonable to hypothesize that nitrogen is assimilated into glutamine during winter and released in spring-summer, favoring lichen catabolism and reproductive activity. The observed decrease in glutamine, coupled with threonine accumulation, suggests a selective channeling of nitrogen resources toward threonine biosynthesis, possibly due to regulatory shifts. The observed seasonal cycle – from glutamine and arabinitol accumulation to peaks in threonine and β -glucopyranose(1→2)mannitol, followed by a winter reset – suggests a highly integrated nitrogen-carbon regulatory mechanism that is likely tuned to environmental changes, with β -glucopyranose(1→2)mannitol as the most important carbon vehicle. Publication History Article published online: 05 March 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany