Cloning and molecular characterization of the cDNA for the Brazilian larval click-beetle Pyrearinus termitilluminans luciferase

Abstract

The larval click-beetle Pyrearinus termitilluminans elicits the phenomenon of luminous termite mounds in the central-west region of Brazil. The bioluminescence (BL) spectrum of this larva (lambda max = 534 nm) is one of the most blue-shifted reported among known luminescent Coleoptera. We have isolated mRNA from larval thoracic lanterns and constructed a cDNA library into a lambda ZAP II vector. An expression library was obtained after excision of the pBluescript plasmid. This library was screened by photodetection and one clone that emitted green BL (lambda max = 538 nm) was isolated. The 2.2 kb cDNA insert includes a 543 residue open reading frame showing 82% homology with the luciferase isoenzymes of Pyrophorus plagiophthalamus (Coleoptera: Elateridae). As expected, the region between residues 223 and 247 that contains the putative active site for BL color determination showed a higher degree of homology among click-beetle luciferases that elicit closer BL colors. The in vitro BL spectrum of recombinant P. termitilluminans luciferase also peaks at 538 nm and, as in the case of native enzyme, does not show any bathochromic shift upon decreasing the pH.