Seminar of the Insitute of Microbiology
From Defense to Therapy: The Dual Role of Fungal Phototoxic Pigments
Bianka Siewert – Priv.-Doz. Dr. - UIBK – Pharmazie/Pharmakognosie
05.12.2024, 11:00 - Hybrid
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- or in presence: Seminarraum 1 - ICT Gebäude (Technikerstraße 21a)
Abstract
When insects feed on the fruiting bodies of Cortinarius austrovenetus, the bite site undergoes a remarkable transformation, rapidly turning reddish. This phenomenon arises from a simple yet fascinating chemical reaction: the fungal pigment austrovenetin oxidizes to hypericin upon tissue damage. Inspired by this observation, we conducted a systematic investigation into fungal phototoxicity. Employing photocytotoxicity assays and feature-based molecular networking (FBMN), we screened over 100 fungal species, identifying pigments derived from the polyketide pathway as particularly noteworthy. Furthermore, our findings revealed that phototoxicity is a conserved trait among dermocyboid Cortinarii.
Photoactivity-guided isolation led to the discovery of several potent photosensitizers in fungal fruiting bodies. For instance, 7,7’-biphyscion, isolated from Cortinarius uliginosus, exhibited nanomolar-range photocytotoxicity, inducing apoptosis in cancer cells upon irradiation. We also identified several monomeric anthraquinones with remarkable photoantimicrobial activity against various pathogenic bacteria and fungi, demonstrating high selectivity towards microbial targets.
In addition to their pharmaceutical potential, we explored the ecological role of these photoactive pigments. Guided by the optimal defense hypothesis, we postulated that phototoxic compounds would be predominantly localized in the gills, the most exposed and vulnerable part of the fruiting body. Statistical analyses of over 40 individual fruiting bodies confirmed this enrichment, with compounds like emodin showing significant accumulation.
This work highlights the ecological and pharmaceutical significance of photoactivated defense strategies in fungi, offering fresh perspectives from an often-overlooked kingdom.