Photochemical defense as trait of fungi from Cortinarius subgenus Dermocybe

Photoantimicrobial anthraquinones in Australian fungi of the genus Cortinarius

Dermocyboid Cortinarius species of both hemispheres are usually intensely colored and known to contain anthraquinones. Australian dermocyboid fungi have distinct evolutionary histories which are clearly different from Northern Hemisphere species of similar appearance. Allopatric speciation often results in different metabolic adaptations. We were especially interested in the diversity of anthraquinonic pigments and in their photoantimicrobial potential. In this study 33 dried samples from eighteen Australian dermocyboid Cortinarius taxa were extracted with methanol and analyzed via HPLC-DAD-MS. The 9,10-dimethylanthracene (DMA) assay was used to measure the extracts' ability to produce singlet oxygen after irradiation. Furthermore, a photoantimicrobial screening method based on the protocols of Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility (EUCAST), employing the common human pathogens Candida albicans, Escherichia coli, and Staphylococcus aureus was used to identify photoantimicrobials. Based on chromatography, mass spectrometry, and UV/Vis data, peaks were annotated according to literature and in-house data. A chemotaxonomic pigment analysis was established to cluster the species according to their major anthraquinones and to allow identification of the groups by a minimum number of pigments. In agreement with the recorded pigment pattern of the photoactive anthraquinones, nine Cortinarius species (C. alienatus, C. atropurpureus, C. austrovenetus, C. basirubescens, C. canarius, C. clelandii 2, C. globuliformis, C. persplendidus 1, C. sp. "honey pileus 1") showed at least 70 % inhibition of Staphylococcus aureus (Gram-positive bacteria) growth under light irradiation (λ = 428 / 478 nm, H = 30 J/cm2, c = 50 μg/mL, pre-illumination time (tPI) = 60 min) in the photoantimicrobial screening. The extracts of three species (C. alienatus, C. austrovenetus, and C. clelandii 2) showed additional photoactivity against Candida albicans (yeast) under the same conditions. Several relevant (photo)antimicrobials were identified: Emodin, dermocybin, skyrin, physcion (synonym: parietin), 7,7'-biphyscion, and hypericin; From the photoactive extracts, that were not reported to contain photoactive compounds before, austrocortinin and xanthorin were isolated and used for further testing. For austrocortinin a singlet oxygen yield of 0.03 (reference: [Ru(bpy3)Cl2], d4-MeOH) was detected. Accordingly, the anthraquinone did not show activity in the photoantimicrobial assay. Xanthorin, with a singlet oxygen yield of 0.10, led to an inhibition of growth of 78.1 % against Staphylococcus aureus (4.00 μg/mL, λ = 428 nm, 30 J/cm2, tPI = 60 min).

Discovery of Cortinarius O-methyltransferases for the heterologous production of dermolutein and physcion

BACKGROUND

Anthraquinones in the emodin family are produced by bacteria, fungi, and plants. They display various biological activities exploited, e.g., for crop protection, and may also be utilized as sustainable, bio-based colorants for the textile, paints, electronics, and cosmetic industries. Anthraquinone pigments from Cortinarius mushrooms have been used for artisan dyeing because they are stable, colorfast, and compatible with various dyeing methods. However, their chemical synthesis is complex and uneconomical, and harvesting wild mushrooms from forests in commercial quantities is not feasible.

RESULTS

Here, we use genomics, transcriptomics, and synthetic biology to uncover the biosynthesis of the anthraquinone scaffold compounds emodin and endocrocin, and their methylation to the yellow pigments physcion and dermolutein in Cortinarius semisanguineus and C. sp. KIS-3. Both the nonreducing polyketide synthases (nrPKSs), and the regiospecific, fastidious O-methyltransferases (OMTs) are non-orthologous to their Ascomycete counterparts, suggesting a parallel evolutionary origin for the pathway in Basidiomycetes. The genes for the nrPKS and the OMTs are not all clustered in Cortinarius, revealing metabolic crosstalk among paralogous nrPKS biosynthetic gene clusters.

CONCLUSIONS

Heterologous biosynthesis of physcion and dermolutein in Saccharomyces cerevisiae opens the way to produce specific Cortinarius anthraquinones, and to modify these scaffolds to tune their chemistry towards their various applications.

Revised taxon definition in European Cortinarius subgenus Dermocybe based on phylogeny, chemotaxonomy, and morphology

Cortinarius (Fr.) Fr. is one of the most species-rich genera in the Agaricales (Basidiomycota). Cortinarius subgen. Dermocybe (Fr.) Trog includes brightly coloured Cortinarii with anthraquinone pigments. The chemotaxonomic approach has always been as important as classical methods for species definition of Dermocybe and helped to improve overall species concepts. However, some species concepts within this group remain unclear. We therefore address this topic based on a combined phylogenetic, morphological, and pigment-chemical approach. For this, sequence data, HPLC-MS pigment profiles and spore sizes were included were included to obtain a better resolution of taxa. The study was based on 173 recent collections and 12 type specimens. A total of 117 rDNA ITS sequences were produced from the collections in this study, 102 sequences were retrieved from databases. We could detect and clearly delimit 19 Dermocybe species occurring in central European habitats, from which 16 are discussed in detail. Additionally, we grouped the detected anthraquinone pigments into four groups. This detailed analysis of dermocyboid Cortinarius species occurring in a restricted number of habitat types confirmed our hypothesis that species diversity is much higher than currently assumed. This high diversity is blurred by too wide and incorrect species concepts of several classical species like C. croceus and C. cinnamomeus. Molecular and chemotaxonomical studies carried out together with careful phenotypical analyses resulted in a good differentiation of species. A key is presented for these taxa to allow a better identification of Cortinarius subgenus Dermocybe spp. occurring in Central Europe mainly in the alpine range.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11557-024-01959-z.

A guide to mycetisms: A toxicological and preventive overview

Fungi are often considered a delicacy and are primarily cultivated and harvested, although numerous species are responsible for intoxication due to toxin content. Foodborne diseases are a significant public health concern, causing approximately 420 000 deaths and 600 million morbidities yearly, of which mushroom poisoning is one of the leading causes. Epidemiological data on non-cultivated mushroom poisoning in individual countries are often unrepresentative, as intoxication rarely requires emergency intervention. On the other hand, the lack of specialist knowledge among medical personnel about the toxicological manifestations of mushroom consumption may result in ineffective therapeutic interventions. This work aims to provide an easy-to-consult and wide-ranging tool useful for better understanding the variability of mushroom intoxications, the associated symptoms, and the main treatments for the most severe cases, given the absence of a complete species mapping tool toxic. Moreover, we establish an effective collection network that describes the incidence of mushroom poisonings by reporting the species and associated toxicological manifestations for each case. In conclusion, we highlight the need to establish appropriate primary prevention interventions, such as training the affected population and increasing consultancy relationships between mycological experts and specialised healthcare personnel.