Ever since as children we saw fireflies emitting light at night, we ranked luminescence high in excitement of natural phenomena. We learned later that other kinds of living things, such as bacteria, protists, fungi, insects, and many others, are also capable of emitting light. The magic is only slightly dimmed when we find out that light is produced by a fairly simple biochemical reaction, the oxidation of the organic substrate luciferin (of which there are 9 varieties) by the enzyme luciferase (encoded by 7 gene families). Until now, the biochemistry of only a bacterial system has been described in detail.
A recent paper reports on both function and evolution of a bioluminescent system from a fungus. The investigators further showed that cloning the genes involved into other eukaryotes is sufficient to make them produce light. The fungus, Neonothopanus nambi (previosuly called Panus), is a poisonous mushroom known among mycologists for its bioluminescent properties. Its bioluminescence genes form a cluster that is conserved among three other bioluminescent mushrooms, suggesting that it may have arisen just once.
How is light produced? Luciferase catalyzes a reaction between luciferin and atmospheric oxygen resulting in a high energy luciferin intermediate. This decomposes to yield light and oxyluciferin. In turn, oxyluciferin can be recycled to luciferin and, as long as oxygen is present, the process continues
Luciferase is a popular reporter, so cloning its fungal gene in other organisms is of practical interest. Indeed, the investigators reported light production after cloning it into E. coli, a yeast, Xenopus embryos, and human cells. They also showed that tumors of mouse carcinoma cells endowed with this gene light up as readily as those with the gene from fireflies.
The authors conclude: ‘Reconstitution of fungal bioluminescent pathway in eukaryotic organisms might enable applications where tissues or organisms report changes in their physiological state with autonomous light emission. It might also push forward development of the next generation of organic architecture where genetically modified glowing plants will be integrated into buildings and city infrastructure. Apart from that, with its intriguing evolutionary history, a family of luciferases, and overall simplicity, the fungal bioluminescent system presented here is a molecular playground holding numerous opportunities for basic and applied research. ‘
A lot of work went into this. It required the collaboration of 40 investigators from 9 institutions and 3 continents.