Biological functions of α2-adrenergic-like octopamine receptor in Drosophila melanogaster.

Octopamine regulates various physiological phenomena including memory, sleep, grooming and aggression in insects. In Drosophila, four types of octopamine receptors have been identified: Oamb, Oct/TyrR, OctßR and Octα2R. Among these receptors, Octα2R was recently discovered and pharmacologically characterized. However, the effects of the receptor on biological functions are still unknown. Here, we showed that Octα2R regulated several behaviors related to octopamine signaling. Octα2R hypomorphic mutant flies showed a significant decrease in locomotor activity. We found that Octα2R expressed in the pars intercerebralis, which is a brain region projected by octopaminergic neurons, is involved in control of the locomotor activity. Besides, Octα2R hypomorphic mutants increased time and frequency of grooming and inhibited starvation-induced hyperactivity. These results indicated that Octα2R expressed in the central nervous system is responsible for the involvement in physiological functions.

Elevenin regulates the body color through a G protein-coupled receptor NlA42 in the brown planthopper Nilaparvata lugens.

The neuropeptide elevenin and similar neuropeptide precursors are common in some invertebrates but their physiological function in most species has not been explored. The brown planthopper, Nilaparvata lugens (Stål) has an elevenin-like peptide and a G protein-coupled receptor (GPCR) NlA42 that is homologous to the elevenin receptor of the annelid Platynereis dumerilii. RNA interference (RNAi)-mediated knockdown of either Nl-elevenin or the NlA42 gene resulted in cuticle melanization. Ion transport peptide (ITP) also induces melanization, but unlike ITP, knockdown of NlElevenin and NlA42 did not have any effect on wing expansion or activity after eclosion. In wild condition macropterous individuals show a darker body color when compared with brachypterous individuals, but RNAi experiments suggest that insulin-signaling and Nl-elevenin signaling regulate wing morph and body color independently. NlElevenin was predominantly expressed in the brain while NlA42 was highly expressed in the abdominal integument and brain. A signal Calcium assays using aequorin indicated that NlA42 heterologously expressed in HEK293 cells exhibited responses to synthetic Nl-elevenin peptide from concentrations as low as 10-9M. These results suggest that neuropeptide Nl-elevenin is involved in the regulation of melanization through its receptor NlA42. This is the first report of a physiological function for elevenin-like peptides in insects.