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

Abstract

AbstractEctomycorrhizal 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.