Scientists Train Mushrooms to Glow in all Colors of the Rainbow
Researchers at the Institute of Bioorganic Chemistry of the Russian Academy of Sciences (IBCh RAS), the Institute of Biophysics of the Krasnoyarsk Scientific Center SB RAS (IBP SB RAS) and the Pirogov Russian National Research Medical University, together with colleagues from Brazil and Japan, have drawn even closer to finally unveiling the secret of the mechanism that mushrooms use to glow. They successfully determined the structure of the molecule of oxyluciferin, a product of the luminescence reaction, from fungi (in this case, mushrooms were used), and also synthesized several artificial replicas of luciferin, which emit light of different colors. This groundbreaking work was funded by a grant from the Russian Science Foundation, RSF, and the results published in the journal Science Advances.
Author: Snezhana Mazhekenova.
“It has long been known that bacteria, worms, fungi and many other organisms can emit light. Aristotle was particularly interested in this phenomenon,” narrates Ilia Yampolsky, D.Sc., Head of the Total Synthesis Lab, IBCh RAS. “However, it was only in the XX century that scientists discovered that the light itself is due to a molecule of luciferin. When translated from Latin, luciferin literally means “bringer of light”. During a bioluminescent reaction, this molecule is oxidized by atmospheric oxygen, accelerated by the enzyme luciferase. This protein-catalyst helps luciferin turn into oxyluciferin, which eventually emits the light.”
The history of the deciphering of the structures of natural luciferins spans more than 60 years. By 1989, molecules of only seven light-emitting biological pigments were known. It took 25 years before scientists could decipher the structure of the new luciferin. This was achieved by a group of scientists at the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences and the Institute of Biophysics Siberian Branch of the Institute of Bioorganic Chemistry of the Russian Academy of Sciences under the supervision of Ilia Yampolsky. Thanks to their work, in 2014, a biological pigment from the Siberian soil worm Fridericia heliota became the “eighth formula of light”, and in 2015, the ninth formula – luciferin of mushrooms, was added to the list.
The same team successfully conducted a new study focused on deciphering the structure of the fungal oxyluciferin and synthesizing luciferin structural analogs. To obtain the product of the bioluminescence reaction, the luciferin from the laboratory was mixed with a natural extract of luciferase from the luminous fungi Neonotopanus nambi, which had been collected from forests in Vietnam, and then the resulting product mixture was separated.
The mechanism of luminescence shall be considered deciphered only when all participants of this complex process are known: the precursor molecule, the enzyme and the product molecule of the reaction. To determine the structure of oxyluciferin, which is formed during fungal luminescence, scientists had to synthesize a large amount of this product. However, oxyluciferin proved to be a very “capricious” and unstable substance, which complicated its accumulation.
Researcher at the IBP SB RAS Konstantin Purtov, Ph.D., shares the details of the work carried out, “We were faced, among other things, with the task of conducting a bioluminescent reaction and determining the conditions under which the product could be preserved for a relatively long time. We were able to pick up such conditions. However, even the oxyluciferin that we had preserved disintegrated, and only a portion of it managed to reach Moscow. Thankfully, even that amount was still enough to be able to determine the general characteristics of the molecule. Nevertheless, it was practically inadequate for conducting structural studies. Afterwards, our colleagues in Moscow working on the NMR spectrometer studied the substances obtained during the decay of the molecule, restored the original structure of oxyluciferin and compared the properties of the resulting molecule with those of the original. The resulting match proved that we had determined the structure of the last link in the mushroom-glow reaction.”
The research was conducted in active collaboration with Brazilian colleagues. Thanks to unique experiments in an atmosphere of labeled oxygen (18О2), it was possible not only to confirm the structure of the reaction product, but also to suggest a mechanism for how mushroom luciferin turns into a light emitting molecule.
Modified molecules of luciferin, which make it possible to obtain a glow of different colors, were the intermediate, but promising, results of the study. “We now have what can be called colored mushrooms,” joke the researchers. It turned out that in mushroom bioluminescence, the emission spectrum depends on the structure of the substrate. While investigating the possibilities of the bioluminescence reaction of mushroom, Moscow chemists managed to synthesize various structural prototypes of luciferin. As a result, the scientists received a number of luciferin prototypes providing a glow in almost all the colors of the rainbow.
“Fungal luciferin consists of two important fragments (pyranone and aromatic rings). We decided to see if the molecule would still “glow” if one of the fragments were changed. It turned out that, of the six synthesized luciferin prototypes, five remained active with luciferase extract, and glowed in different colors. So, firstly, we confirmed the reaction mechanism that we had discovered, and secondly, we proceeded with further investigations aimed at fully understanding how this process can be managed,” narrates Zinaida Osipova, Ph.D., Researcher, Total Synthesis Lab, IBCh RAS.
In addition, during the study, the authors of the article obtained data confirming the hypothesis of there being only a single mechanism for the bioluminescence of fungi. It is important that the basis of the mechanism for the glowing of fungi is such a commonly occurring molecule as caffeic acid, which participates in the metabolism of not only fungi like mushrooms, but also plants. It is possible that in the near future, the bioluminescent system of mushrooms could be used to create luminous trees. Caffeic acid is present in all plants. All that remains is to add a few genes for the synthesis of the enzymes of the bioluminescence reaction, and then they will light up.
The study of bioluminescent organisms is not only an essential work, but also one that carries an importance in terms of its many applications. Deciphering the luminescence system of fungi, obtaining prototypes of luciferin of different structures, and therefore test-systems of different colors, could all be used in bionomics to monitor the quality of the environment, as well as in medicine for clinical trials and in the search for new drugs.
IBCh RAS and IBP SB RAS Joint Press Release.