Chemical, biological and evolutionary aspects of beetle bioluminescence

Abstract

This work is dedicated to Prof. Waldemar Adam, an esteemed friend and eminent scientist who, for decades, generously shared knowledge, enthusiasm, and laboratory supplies with many Brazilian investigators, among them G. Cilento and myself. In 1980, Prof. Adam was elected Foreign Member of the Brazilian Academy of Sciences in recognition for his substantial contributions towards the development of Chemistry in Brazil. AbstractThe hypothesis that luciferases evolved from ligases that acquired oxygenase and luminogenic activities, thereby contributing to the antioxidant machinery of bioluminescent organisms, is revisited here. Larvae of click beetle Pyrearinus termitilluminans (Coleoptera: Elateridae) live under conditions close to normoxia into tunnels dug into termite mounds, whereas other elaterid larvae inhabit tunnels in decaying logs, where pO 2 is ~ 2-5%. Interestingly, the catalase and superoxide dismutase (SOD) activities in click beetle larvae were found to respond to the habitat pO 2 and are significantly lower in non-luminescent elaterids. Exposure of larval P. termitilluminans larvae to hyperoxia induced SOD and catalase activities concomitantly with increments in luciferase and luciferin levels mainly in the prothorax, the brightest larval segment. Thoracic luciferase activity is 1000-fold higher than in the abdomen, while SOD activity is 2-fold higher. With larval development, an expected decline in antioxidant enzyme activities was apparently compensated by an increase in luciferase activity (2-3 fold) and in urate (40-fold), a major insect antioxidant. Finally, we found that the ligase-rich fat body of larval Tenebrio molitor, a non-luminescent beetle, contains a primal luciferase-like activity. Altogether, these data strengthen the hypothesis that various bioluminescent systems may have developed from potentially chemiluminescent metabolites and ligases that acquired a dioxygenase and luminogenic function over the course of evolution.

Evaluation of metal toxicity by a modified method based on the fungus Gerronema viridilucens bioluminescence in agar medium

“…This assay is based on the decrease of the intensity of bioluminescence (BL) from globular mycelia cultivated in aqueous medium when exposed to increasing concentrations of metal cations or chlorophenols. Although the mechanism of fungal BL is still controversial [14][15][16], the light emission in all bioluminescent systems has long been known to depend on oxygen consumption, and therefore BL is necessarily connected to the organism's respiratory activity [17]. Hence, light emission is a readily available signal of normal or injured fungal metabolism condition.…”