Decoding the chemical language ofSuillusfungi: genome mining and untargeted metabolomics uncover terpene chemical diversity

Abstract

Ectomycorrhizal fungi establish mutually beneficial relationships with trees, trading nutrients for carbon.Suillusare ectomycorrhizal fungi that are critical to the health of boreal and temperate forest ecosystems. Comparative genomics has identified a high number of non-ribosomal peptide synthetase and terpene biosynthetic gene clusters (BGC) potentially involved in fungal competition and communication. However, the functionality of these BGCs is not known. This study employed co-culture techniques to activate BGC expression and then used metabolomics to investigate the diversity of metabolic products produced by threeSuillusspecies (S. hirtellusEM16,S. decipiensEM49, andS. cothurnatusVC1858), core members of the Pine microbiome. After 28 days of growth on solid media, liquid chromatography–tandem mass spectrometry identified a diverse range of extracellular metabolites (exometabolites) along the interaction zone betweenSuillusco-cultures. Prenol lipids were among the most abundant chemical classes. Out of the 62 unique terpene BGCs predicted by genome mining, 116 putative terpenes were identified across the threeSuillusspecies using metabolomics. Notably, some terpenes were significantly more abundant in co-culture conditions. For example, we identified a metabolite matching to isomers isopimaric acid, sandaracopimaric acid, and abietic acid, which can be found in pine resin and play important roles in host defense mechanisms andSuillusspore germination. This research highlights the importance of combining genomics and metabolomics to advance our understanding of the chemical diversity underpinning fungal signaling and communication.ImportanceUsing a combination of genomics and metabolomics, this study’s findings offer new insights into the signaling and communication ofSuillusfungi, which serve a critical role in forest ecosystems.

Suillus: an emerging model for the study of ectomycorrhizal ecology and evolution

“…While secondary metabolic clusters likely function in a variety of biological processes in Suillus , the genus‐wide expansion of terpene and nonribosomal peptide synthetase‐like clusters hint at roles in interspecific interactions such as microbial and host communication and are ideal targets for investigating the remarkable partner specificity displayed by the genus. Recently, LC/MS‐based untargeted metabolomic analysis of three genome‐sequenced strains of Suillus identified hundreds of unique secondary metabolites, including 41 terpenes with high‐confidence spectral matches (Mudbhari et al ., 2024). The most abundant terpene classes were identified as terpene lactones, sesquiterpenes, and di‐terpenes, including several compounds induced exclusively when grown in co‐culture with other species of Suillus .…”