New Zealand glowworms use an all-new luciferin

Deep inside New Zealand’s darkest caves and dampest forests lurk astonishing creatures that put on a breathtaking light show. New Zealand’s unique glowworms draw tourists in droves to marvel at the eerie blue-green glow dotting cave roofs and tree branches.

Now, researchers at Otago University, on the country’s southern island, have worked out that a unique molecule makes the worms glow (Sci. Rep. 2018, DOI: 10.1038/s41598-018-21298-w).

Like fireflies and other bioluminescent creatures, the New Zealand glowworms’ (Arachnocampa luminosa’s) glow comes from the oxidation of small molecules called luciferins, a reaction catalyzed by luciferase enzymes. This study concludes, however, that the worms’ luciferin is entirely different from that of other critters.

Identifying the unique luciferin used by the worms wasn’t easy, as biochemist Kurt Krause explains. “The identification of the luciferin precursors and luciferin candidates was very, very challenging and it left me a bit in awe of my chemistry colleagues,” he says. “For starters the number of glowworms that are obtainable is pretty limited and their light organs are tiny. In addition, the bioluminescent material was sensitive to oxygen and time. So it was a race against the clock with tiny amounts of material.”

Nevertheless, the team did scrape together enough material to characterize using chromatography, mass spectrometry, and NMR spectroscopy. From the isolated luciferin, the team discovered that two precursors were responsible for the glow: xanthurenic acid and tyrosine. This combination of precursor hasn’t been seen in other glow worms, Krause says.

With the precursors identified, the team is now working to confirm the luciferin structure they make. They aim to synthesize it in the lab with the goal of exploiting the bioluminescence for applications in disease tracking and identification. Having a newly-identified bioluminescent molecule is exciting, says Marie Heffern, from University of California, Davis, whose group employs these tools regularly. Until recently, she says, firefly and renilla luciferases were the only options for investigating bioluminescence, and the newly identified system will expand the toolbox. “From a chemical standpoint, it will be quite interesting to see any work towards determining the complete structure of the substrate,” she says. “This will provide a new chemical handle for the development of chemoreactive substrates for molecular imaging.”

CORRECTION: The photo caption on this story was updated on March 16, 2018.