"Role of fungi in Tree-microbe interactions”

Abstract :

Plant–microbe interactions are central to forest ecosystem functioning, influencing nutrient cycling, plant health, and stress resilience. Our study explores fungal symbioses in poplar (Populus spp.) with a focus on ectomycorrhizal and endophytic fungi.

In our group we have identified and characterised how the triterpene regulates interactions with the ectomycorrhizal fungus Laccaria bicolor and the dark septate endophyte. Transgenic poplars with altered triterpene synthase expression revealed that elevated triterpene levels negatively affect ectomycorrhizal formation. However, high triterpene accumulation significantly inhibited intracellular coil formation by endophytic fungi, suggesting a role in restricting fungal penetration.

In parallel, new emerging Order of Helotiales Within this group, the genus Hyaloscypha (Leotiomycetes) is emerging as an ecologically relevant taxon, especially in extreme environments. Despite their widespread presence, the functional role and colonization dynamics of Hyaloscypha in plant hosts remain poorly understood, particularly with respect to their contribution to nutrient exchange and symbiosis. In this study, we investigated the interaction between Hyaloscypha spp. and Poplar (Populus spp.) to assess their potential involvement in a symbiotic relationship. We focused on the exchange of nutrients, using stable isotope labelling specifically whether Hyaloscypha can facilitate nitrogen (N) acquisition by the host in return for plant-derived carbon.

Together, these findings highlight the complex roles of plant secondary metabolites and fungal endophytes in shaping forest plant–microbe interactions and provide new insights into the ecological significance of ectomycorrhizal and endophytic fungi in nutrient-limited forest ecosystems.