The Hidden Potential of South American Cortinarii

South American Nothofagaceae forests harbor unique, endemic tree species, representing the oldest lineages of Nothofagus evolution. The ectomycorrhizal fungi in mutualistic symbiosis with Nothofagus, such as dermocyboid Cortinarius species (C.), are widely under-explored in these areas. However, it is well known that they usually co-evolve with their associated plant partner. Our previous studies demonstrated that the diversity of unknown dermocyboid C. is high there, as reflected in their pigment diversity. The pigments are mainly (pre)Anthraquinones, which are at the same time one of the most promising classes of natural photosensitizer. A systematic study of the photobiological active pigments in dermocyboid C. species will help to unravel the ecological role of such pigments. The aim of the project is to sample and eventually newly describe South American dermocyboid C., to isolate, identify their pigments, and to test the latter for photo-activity. As a base of the project, the taxonomy of endemic dermocyboid Cortinarii is resolved with extensive fieldwork, molecular network analysis of metabolites, and multi-gene phylogeny. Molecular network analysis is used for the first time here as metabolomic-taxonomical tool. Pigment profiles will be created by coupling thin layer chromatography and mass spectrometry using desorption electrospray ionization. (New) pigments will be isolated and their structure elucidated and tested for their biological activity with a focus on targeted light activation.

As part of the bilateral POSADEC project, funded by the Austrian Science Fund (FWF) and the German Research Foundation (DFG), we investigated the previously largely unknown fungal diversity of South American southern beech forests, discovering unique new pigments that are particularly interesting because their bioactivity can be induced by light. This offers interesting potential applications in medicine and agriculture. In collaboration with colleagues in Chile, Argentina and Germany, we collected over 1,000 fungal specimens from forests dominated by Southern Hemisphere beech trees (Nothofagaceae). The specimens examined comprised a total of 370 species. Most of these fungi belong to the genus Cortinarius, a group that forms mycorrhizal associations with trees. By comparing morphology, DNA and pigments, we were able to resolve long-standing nomenclatural confusion and clearly define 249 known species - now, for the first time, with DNA barcodes and photographs. We also discovered 89 species that are new to science and are now being officially described. All specimens and images are archived not only in Austrian herbaria but also in the countries where they were found, to help safeguard local knowledge and support future research. Furthermore, data such as photographs, GPS data and sequences are made available to the public in accordance with the FAIR principles on databases such as GenBank and GBIF. The high species diversity went hand in hand with chemical diversity in the compounds they contain. Dermocyboid Cortinarius species produce many coloured pigments. We isolated several of these pigments for laboratory testing. Some act as 'photosensitisers' that could be used in photodynamic therapy: they are harmless in the dark but become active when exposed to light and can kill microbes or damage cancer cells. Notably, we have also discovered previously unknown chemical structures acting as photosensitisers, which opens up new avenues for drug development. Our project is distinguished by the way we closely interweave taxonomy (the classification of species), chemistry (the discovery and identification of pigments), pharmacological bioactivity studies (the destruction of cells in combination with light) and modern data tools. We have linked chemical 'fingerprints' to species identities. We also combined very large evolutionary phylogenies with the chemical species profiles and demonstrated how pigment families evolved across continents. We were able to identify species whose chemical properties link South American fungal species to their European and Australian relatives. This provides us with new insights into how these important mycorrhizal fungi colonised new regions over the course of evolution and developed into distinct species across the various continents.