Molecular and Computational Analysis of Ghrelin, Growth Hormone Secretagogues Receptor and mRNA Expression of Growth-related Genes after Exogenous Administered Ghrelin Peptide in Labeo rohita.

Ghrelin is a peptide hormone secreted primarily by the stomach and is involved in controlling growth by governing different functions in vertebrates including feed intake and metabolism in vertebrates. This work was aimed to identify sequences of ghrelin gene and growth hormone secretagogue receptor (GHSR) in Labeo rohita. The full-length cDNA sequence of ghrelin is 453 bp including 5'-untranslated region (UTR) of 65 bp, 3'-UTR of 76 bp with a poly-A frame. An open reading frame (ORF) is 312 bp, which encodes a peptide of 103 amino acid residues. A secondary structure of GHSR protein consists of alpha helix 66.0%, 16% disordered and 43% transmembrane helix. Molecular docking and interaction between synthetic ghrelin peptides and GHSR in the contact map revealed 19 amino acid residues closer than 4.5 Å distance. The mRNA expression level of ghrelin, leptin, GHSR, growth hormone releasing hormone (GHRH) and insulin growth factor-I (IGF-1) revealed significant changes (p < 0.05), in the different treatments. The outcome of the present work contributes to understanding the role of ghrelin and its mechanism of action in regulating the expression of growth-related genes and feed intake in fish.