Neuropeptide-like precursor 4 is uniquely expressed during pupal diapause in the flesh fly

Suppression subtractive hybridization comparing brains from diapausing and nondiapausing pupae of the flesh fly, Sarcophaga crassipalpis, suggested that the gene encoding neuropeptide-like precursor 4 (Nplp4) was uniquely expressed during diapause. We have sequenced the full-length cDNA encoding Nplp4 and used Northern blots to further evaluate linkage to diapause. The open reading frame of this cDNA encodes a 61-amino acid residue precursor protein containing a predicted 18 residue signal peptide, one 22-amino acid and one 2-amino acid propeptides, and a 19-amino acid neuropeptide. The amino acid sequence of the precursor protein shows 64% identity to Drosophila melanogaster Nplp4; homologues of this precursor protein are not known from species other than these two flies. Nplp4 mRNA levels were quite low in nondiapausing (long day) pupae, but in contrast the gene was highly upregulated in diapausing (short day) pupae. Expression increased at the onset of diapause, remained high throughout diapause, and then decreased 2 days after diapause was terminated. Although the function of this precursor protein and the neuropeptide it yields remain unknown, this close association with diapause suggests a potential role for Nplp4 in initiating and maintaining diapause in the flesh fly.