Identification of biliverdin as a pigment involved in the seasonal variation of green lacewing body colour and the enzymes involved in its metabolism

Abstract

The green lacewing, Chrysoperla nipponensis, is an insect that undergoes complete metamorphosis, and its body colour changes depending on the developmental stage; adults and larvae are greenish and brownish, respectively. In addition, the body colour of some adults changes to brown in winter, suggesting that environmental factors influence pigment biosynthesis in this insect. However, the underlying colour regulation systems remain unknown. In this study, we purified the pigments that produce the body colour of green adult lacewings and identified biliverdin via MS/MS analyses. We therefore elucidated the mRNA and amino acid sequences of biliverdin-related biosynthetic enzymes, such as haem oxygenase (HO) and biliverdin reductase (BR), in C. nipponensis. By expressing recombinant BR in E. coli, we investigated the ability of BR to metabolize biliverdin. In addition, via RNAi techniques, we examined whether the suppression of these enzymes changed body colour. Finally, we quantified the expression levels of the mRNAs encoding these enzymes and compared those in green adults reared under normal conditions with those in brown adults reared under winter-mimicking conditions. The results suggest that not only biliverdin but also other green pigments contribute to the green body colour of adult lacewings.