Molecular cloning, characterization, and evolution analysis of the luciferase genes from three sympatric sibling fireflies (Lampyridae: Lampyrinae, Diaphanes).

ABSTRACT

Firefly adult bioluminescence functions as signal communication between sexes. How sympatric sibling species with similar glow pattern recognize their conspecific mates remains largely unknown. To better understand the role of the luciferases of sympatric fireflies in recognizing mates, we cloned the luciferase genes of three sympatric forest dwelling fireflies (Diaphanes nubilus, Diaphanes pectinealis, and Diaphanes sp2) and evaluated their enzyme characteristics. Our data show that the amino acid (AA) sequences of all three luciferases are highly conserved, including the identities (D. nubilus vs D. pectinealis 99%; D. nubilus vs Diaphanes sp2 98.5%; D. pectinealis vs Diaphanes sp2 99.4%) and the protein structures. Three recombinant luciferases produced in vitro all possess significant luminescence activity at pH 7.8, and similar maximum emission spectrum (D. nubilus 562 nm; D. pectinealis and Diaphanes sp2 564 nm). They show the highest activity at 10 °C (D. pectinealis, Diaphanes sp2) and 15 °C (D. nubilus), and completely inactivation at 45 °C. Their KM for D-luciferin and ATP were 2.7 µM and 92 µM (D. nubilus), 3.7 µM and 49 µM (D. pectinealis), 3.5 µM and 46 µM (Diaphanes sp2). Phylogenetic analyses support that D. nubilus is sister to D. pectinealis with Diaphanes sp2 at their base, which further cluster with Pyrocoelia. All combined data indicate that sympatric Diaphanes species have similar luciferase characteristics, suggesting that other strategies (e.g., pheromone, active time, etc.) may be adopted to recognize mates. Our data provide new insights into Diaphanes luciferases and their evolution.