Identification, characterization and feeding response of peptide YYb (PYYb) gene in grass carp (Ctenopharyngodon idellus)

The peptide YYb (PYYb) is a fish-specific peptide belonging to the neuropeptide Y (NPY) family. In the present study, the full-length cDNA sequence and genomic structure of PYYb (gcPYYb) from Ctenopharyngodon idellus have been isolated and characterized. The gcPYYb gene consists of three exons interspaced by two introns, opposing to the typical architecture of most NPY-family genes as well as its paralogs. Alignment of deduced amino acid sequence indicates that the fish PYYb is more variable compared to NPY and PYY as shown by more residue changes in teleosts lineage, suggesting mild selective pressure imposed on the peptide. Real-time quantitative PCR analysis shows the gcPYYb mRNA in developing larvae is increased during the mixed endo- and exogenous-feeding period and is widely distributed throughout the intestine of fully grown individuals. Following a single meal, the gcPYYb mRNA in foregut is increased at 3 h post-feeding and subsequently decreased before the foregut contents are cleared. These results suggest that the gcPYYb has an important role in the early life stages of grass carp and is involved in food intake by transmitting feeding-related signals.