Precursor structure, distribution and possible functions of pigment-dispersing hormone (PDH) in the terrestrial isopod Armadillidium vulgare (Latreille)

Pigment-dispersing hormone (PDH) is an 18 amino acid neuropeptide that induces pigment migration in Decapoda and serves as a circadian neurotransmitter in the locomotor activity rhythm in Drosophila In this study a cDNA encoding PDH was cloned from adult brains of the pill bug Armadillidium vulgare (Av) The cDNA comprising 529 bp encodes a peptide (AvPDH) that consists of a putative 26 amino acid signal peptide and a 34 amino acid PDH-precursor-related peptide containing an 18 amino acid mature peptide The peptide shows a high sequence identity (55-77%) to crustacean beta-PDHs and insect PDFs The tissue-specific expression pattern was examined by reverse transcription PCR. The transcript is expressed in the brain strongly and ventral nerve cord weakly but the signal was not detected in the intestinal tract A similar expression profile appeared in Western blot analyses Western blot analyses with timed samples showed more Intense expression of PDH-like antigen at night PDH-like immunohistochemical reactivity (PDH-ir) was detected in the optic lobe anteromedian protocerebrum accessory lobe tritocerebrum and suboesophageal ganglion but the reactivity was faint or nil in the pseudofrontal organ (sinus gland) These results were substantiated by in situ hybridization Co-localization using anti-Gryllus bimaculatus (Gb)-PDF anti-Bombyx mori (Bm)-CLK and anti-Bm-CYC showed a co-localization of these antigens in the optic lobe and SOG The results provide the first structural and immunocytochemical identification of PDH neurons in terrestrial isopods and the co-localization of PDH with CLK and CYC supports its possible involvement in circadian clock A day/night rhythm of PDH content is also a new feature (C) 2010 Elsevier Ltd All rights reserved