Molecular cloning of red pigment-concentrating hormone (RPCH) from eyestalks of the whiteleg shrimp (Litopenaeus vannamei): Evaluation of the effects of the hormone on ovarian growth and the influence of serotonin (5-HT) on its expression

A cDNA (Liv-RPCH) encoding a putative red pigment-concentrating hormone was cloned from whiteleg shrimp (Litopenaeus vannamei) eyestalks. The deduced amino acid sequence of this cDNA was 93 residues long and consisted of a 21-residue signal peptide, a 9-residue red pigment-concentrating hormone (RPCH) mature peptide, a dibasic cleavage site, and a 61-residue RPCH precursor-related peptide (RPRP). The Liv-RPCH transcript was detected not only in neural tissues (eyestalks, brain, thoracic ganglia, and abdominal ganglia) but also in non-neural tissues (ovaries and heart). In vivo injection of synthetic RPCH (pELNFSPGW-NH2) caused significant increases in hemolymph vitellogenin (Vg) concentrations, ovarian Vg mRNA levels, and mean oocyte area, suggesting that RPCH has a positive role in promoting ovarian growth in L. vannamei. The effects of 5-HT on the expression of Liv-RPCH transcripts in selected tissues (eyestalks, brain, thoracic ganglia, and ovaries) were examined by using quantitative real-time PCR. Injection of 5-HT (20 μg g−1 body weight) resulted in elevated Liv-RPCH transcript levels in the ovaries 3 and 6 h after injection, but no significant effects were observed in the eyestalks, brain, or thoracic ganglia.