Of the more than one hundred thousand described mushroom species, barely seventy-one are capable of emitting their own light — almost all grouped within the order Agaricales, the same order that includes most of the cap mushrooms we know. For more than two thousand years, the function of this green light was a subject of scientific debate. Recent evidence is beginning to answer why they glow.
A biological clock under the bark
A study on Neonothopanus gardneri, one of the brightest known bioluminescent fungi, showed that its light emission is not constant but is controlled by a temperature-compensated circadian clock — regular cycles in the content and activity of luciferase, reductase, and luciferin that make up the mushroom's luminescent system. The existence of regulation necessarily implies an adaptive function behind the light.
Light as a lure
To test this function, researchers constructed artificial mushrooms internally lit with green LEDs that mimicked the wavelength of real bioluminescence. These decoys attracted rove beetles, flies, wasps, and ants in numbers far exceeding those of dark control traps. The resulting hypothesis: the mushroom glows to attract insects that help disperse its spores, a particularly valuable resource under the thick forest canopy, where wind barely circulates.
The molecular circuit of light
In 2018, an international team identified the complete biochemical pathway of fungal bioluminescence: luciferin is synthesized from caffeic acid, a simple and widely distributed metabolite in the fungal kingdom, through a cycle of four key enzymes. By introducing these genes into yeast along with the caffeic acid biosynthesis genes, they achieved a strain capable of glowing autonomously — the first complete luciferin biosynthesis pathway described in a eukaryotic organism.
References
- Oliveira AG, Stevani CV, Waldenmaier HE, et al. Circadian control sheds light on fungal bioluminescence. Curr Biol. 2015;25(7):964-968. PMID: 25802150. DOI: 10.1016/j.cub.2015.02.021
- Kotlobay AA, Sarkisyan KS, Mokrushina YA, et al. Genetically encodable bioluminescent system from fungi. Proc Natl Acad Sci U S A. 2018;115(50):12728-12732. PMID: 30478037. DOI: 10.1073/pnas.1803615115