Luciferase from the Italian firefly Luciola italica: molecular cloning and expression

The cDNA encoding the luciferase from the Italian firefly Luciola italica was cloned using reverse transcriptase-PCR and a gene-specific primer set based on the DNA sequence of Luciola mingrelica. The cDNA sequence of L. italica luciferase was determined to be 1647 base pairs in length with an open reading frame of 548 amino acids. Phylogenetic analysis of the protein sequence demonstrated that this luciferase is closely related to that of other fireflies of the Lampyridae family, particularly within the Luciolinae subfamily, showing 96% homology to luciferases from the fireflies Hotaria unmunsana and Hotaria parvula. The specific activity of the L. italica luciferase was 78% of the North American enzyme, after correction for emission color differences. The bioluminescence emission of the Italian firefly is pH sensitive with maxima at 566 nm and 614 nm at pH 7.8 and 6.0, respectively. Interestingly, the total bioluminescence output was approximately 2-fold greater than that of P. pyralis luciferase due to differences in turnover characteristics evidenced by extended light emission decay kinetics. We expect that this newly discovered luciferase will be suitable for a wide range of bioluminescence applications including in vivo imaging and multiplex assays.