Is the bioluminescence in many Mycena species overlooked? – A case study from M. crocata in Switzerland

Fungal bioluminescence is mystifying humans since ancient times. Nevertheless, the biosynthetic pathway behind this phenomenon was only very recently resolved. Fungal bioluminescence occurs in five distantly related linages (Omphalotaceae lineage, Armillaria lineage, mycenoid lineage, Lucentipes lineage and Eoscyphella lineage) of the basidiomycete order Agaricales. Recent research suggests fungal bioluminescence has emerged 160 million years ago in the most common ancestor of the mycenoid and marasmioid clade and is maintained since then. Surprisingly, in the mycenoid linage, primarily represented by the genus Mycena, most species are considered non-luminescent, implying that many mycenoid species have lost their bioluminescent ability. Here, we report evidence for bioluminescence in Mycena crocata and show that the genome of this species is fully equipped with the genes associated with fungal bioluminescence. Mycena crocata is a long-known species frequently reported from Europe and Japan, which was considered non-luminescent until now. The low light emission intensity and the restriction of the luminescence to the vegetative mycelium and the base of the basidiome may be reasons why bioluminescence was not perceived earlier. We assume there might be other known Mycena species whose luminescent properties are not yet discovered, and that therefore the number of bioluminescent Mycena species is currently underestimated.