PUB - Publikationen an der Universität Bielefeld

Endophytic fungi have been recognized as prolific producers of chemically diverse secondary metabolites. In this work, we describe a new representative of the order Helotiales isolated from the medicinal plant Bergenia pacumbis. Several bioactive secondary metabolites were produced by this Helotiales sp. BL 73 isolate grown on rice medium, including cochlioquinones and isofusidienols. Sequencing and analysis of the approx. 59 Mb genome revealed at least 77 secondary metabolite biosynthesis gene clusters, several of which could be associated with detected compounds or linked to previously reported molecules. Four terpene synthase genes identified in the BL73 genome were codon-optimized and expressed, together with farnesyl-, geranyl- and geranylgeranyl-pyrophosphate synthases, in Streptomyces spp. Analysis of recombinant strains revealed production of linalool and its oxidized form, terpenoids typically associated with plants, as well as a yet unidentified terpenoid. This study demonstrates the importance of a complex approach to the investigation of the biosynthetic potential of endophytic fungi using both conventional methods and genome mining. Importance Endophytic fungi represent as yet underexplored source of secondary metabolites, some of which may have industrial and medical applications. We isolated a slow-growing fungus belonging to the order Helotiales from the traditional medicinal plant Bergenia pacumbis and characterized its potential to biosynthesize secondary metabolites. We used both cultivation of the isolate with subsequent analysis of compounds produced, bioinformatics-based mining of the genome, and heterologous expression of several terpene synthase genes. Our study revealed enormous potential of this Helotiales isolate to produce structurally diverse natural products, including polyketides, non-ribosomally synthesized peptides, terpenoids and RiPPs. Identification of meroterpenoids and xanthones, along with establishing a link between these molecules and their putative biosynthetic genes sets a stage for investigation of the respective biosynthetic pathways. Heterologous production of terpenoids suggests that this approach can be used for the discovery of new compounds belonging to this chemical class using Streptomyces bacteria as hosts.