Tibetan Firefly Luciferase with Low Temperature Adaptation.

Fireflies are widespread all over the world and a numerous numbers of luciferases have been isolated and characterized. In this study, we identified and characterized the luciferase and luciferase-like genes from a Tibetan firefly collected in Shangri-La, China. The altitude of this area is more than 3300 m. We saw this Tibetan firefly flying with strong luminescence after sunset at ~10°C. We analyzed the transcriptome of Tibetan firefly using head, thorax, abdomen (without light organ), and light organ tissue by RNA sequencing. We identified one luciferase gene, which was almost identical to luciferase from fireflies Pyrocoelia species, and expressed specifically in the light organ. Interestingly, the optimal temperature of the Tibetan firefly recombinant luciferase was 10°C. The Km for D-luciferin and ATP of the recombinant luciferase was 23 and 154 μm, respectively. The optimal pH was around 7.0-7.5. The emission peak was 556 nm at pH 8.0, while it shifted to 606 nm at pH 6.0. We also found a luciferase-like gene with 43% identical amino acids to the Tibetan firefly luciferase, which was scarcely expressed in any portion of the adult body. No luciferase activity was detected for this luciferase-like protein.