On the trail of fungal defense strategies – Employing a special workflow to spot photoactivity
20 December 2019 (online)
Sunlight is not only a key factor for photosynthesis – the process enabling plants to convert solar energy into chemical energy  – but can also provide the basis for a winning defense strategy. Some plants, which are generally unable to actively flee from threats, use photons to fend off predators . In detail, light-activated defense is based on the ability of certain pigments/photosensitizers, to produce reactive oxygen species (e.g. 1O2) after being exposed to light of a specific wavelength . This led to the following hypothesis that fungi – another kingdom with “immobile” reproducing structures – might also possess highly photoactive compounds. To test this hypothesis, a previously established workflow  was used to rank the PDT-activity of several basidiomycetes.
While fungal extracts with pigments derived from the shikimate-chorismate pathway or the mevalonate pathway exhibited no significant activity, those containing dyes from the acetate-malonate pathway and nitrogen heterocycles were characterized by promising 1O2-producing activities. Nevertheless, the obtained results pointed out that not all photoactive pigments are able to induce a photo-activated cytotoxic effect in vitro.
The hypothesis of a photochemical defense mechanism in the kingdom Fungi was tested. By investigating a set of diverse basidiomycetes, we were able to highlight the fact that pigments derived from the acetate-malonate pathway are promising photosensitizers.
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