Blue fungus in a new light
Researchers at the University of Jena decipher molecular mechanisms that give the blue bark fungus Terana caerulea its color.
| by Nora Brakhage and Alena Gold
The blue bark fungus Terana caerulea grows on tree trunks and branches of deciduous trees and is characterized by its intense cobalt blue color. The class of substances Corticine from which this blue color is derived is common in many species of fungi. It enables fungi to produce bioactive substances that degrade deadwood and through which they interact with their microbial environment. Researchers from the Balance of the Microverse Cluster of Excellence at Friedrich Schiller University in Jena have now taken a closer look at how the fungus produces this blue substance and found that one factor is crucial: light. The researchers present the results of the study in the journal Microbiology Spectrum.
"In order to analyze the blue color of the fungi more precisely, I prepared a very large quantity of fungal cultures some time ago and placed them in the incubator," reports Dirk Hoffmeister, professor of pharmaceutical microbiology at the University of Jena and associated at Leibniz-HKI. When he examined the cultures a few days later, he was surprised: There was not a single spot of blue color to be seen, all the fungal cultures were white - except for one. It had been forgotten on the windowsill and had not grown in the dark incubator. On this culture plate, the fungus had produced the blue color. "We therefore suspected that the color was only formed when the fungus was exposed to a light source," Hoffmeister explains.
It was already known from previous research findings that fungi can perceive light through receptors and that light affects the metabolism and physiology of fungi. The first author of the study, Stefanie Lawrinowitz, has now approached the phenomenon of blue coloration from a different angle: she analyzed the influence of light on the gene that is centrally responsible for pigment formation. She found out that the gene can only be correctly read and translated into a messenger RNA (mRNA) under the influence of light.
A second mechanism then kicks in, which also requires light to process the mRNA correctly and form proteins. Both processes are regulated by the presence and absence of light. "It is very exciting to see how light regulates the fungus' interaction with the environment," says Dirk Hoffmeister.
Why the fungus forms the unusual blue color is not yet clear. However, Hoffmeister and Erika Kothe and Hans-Dieter Arndt, who are also involved in the study, are certain that the interaction of the fungus with its environment takes place via the molecules that are in turn responsible for the blue coloration.
S. Lawrinowitz, J. M. Wurlitzer, D. Weiss, H.-D. Arndt, E. Kothe, M. Gressler, D. Hoffmeister: “Blue light-dependent pre-mRNA splicing controls pigment biosynthesis in the mushroom Terana caerulea”, Microbiology Spectrum (2022), DOI: https://doi.org/10.1128/spectrum.01065-22