Characterization of genes encoding prolactin and prolactin receptors in starry flounder Platichthys stellatus and their expression upon acclimation to freshwater

• Published in: Fish physiology and biochemistry 2013-04, Vol.39 (2), p.263-275
• Main Authors: Noh, Gyeong Eon, Lim, Han Kyu, Kim, Jong-Myoung
• Format: Article
• Language: English
• Subjects: Acanthopagrus schlegelii; Acclimatization; Acclimatization - genetics; Acclimatization - physiology; Amino acids; Animal Anatomy; Animal Biochemistry; Animal Physiology; Animals; Base Sequence; Biomedical and Life Sciences; Brackish; Chemical analysis; DNA Primers - genetics; Experiments; Fish; Fisheries; Fishing; Flounder - genetics; Fresh Water; Freshwater & Marine Ecology; Gene Expression Regulation - genetics; Gene Expression Regulation - physiology; Genes; Gills - metabolism; Histology; Intestines - metabolism; Kidney - metabolism; Life Sciences; Marine; Molecular Sequence Data; Morphology; Oncorhynchus mykiss; Open Reading Frames - genetics; Oreochromis niloticus; Ovaries; Phylogeny; Pituitary Gland - metabolism; Platichthys stellatus; Pleuronectiformes; Prolactin - genetics; Prolactin - metabolism; Proteins; R&D; Receptors, Prolactin - genetics; Receptors, Prolactin - metabolism; Research & development; Reverse Transcriptase Polymerase Chain Reaction - veterinary; Rivulus; Salinity; Salmon; Seawater; Sequence Analysis, DNA - veterinary; Sequence Homology; Signal transduction; Species Specificity; Takifugu rubripes; Teleostei; Thunnus thynnus; Tilapia; Water analysis; Zoology
• ISSN: 0920-1742; 1573-5168
• DOI: 10.1007/s10695-012-9697-y

This study aims to investigate the genes encoding prolactin (PRL) and prolactin receptors (PRLR) and their tissue-specific expression in starry flounder Platichthys stellatus. Starry flounder PRL gene consisting of five exons encodes an ORF of 212 amino acid residue comprised of a putative signal peptide of 24 amino acids and a mature protein of 188 amino acids. It showed amino acid identities of 73 % with tuna Thunnus thynnus , 71 % with black porgy Acanthopagrus schlegelii , 69 % with Nile tilapia Oreochromis niloticus , 64 % with pufferfish Takifugu rubripes , 63 % with rainbow trout Oncorhynchus mykiss, and 60 % with mangrove rivulus Kryptolebias marmoratus . Phylogenetic analysis of piscine PRLs also demonstrated a similarity between starry flounder and other teleosts but with a broad distinction from non-teleost PRLs. PRLR gene consists of eight exons encoding a protein of 528 amino acid residues. It showed a similarity to the PRLR2 subtype as reflected by amino acid identities of 54 % with A. schlegelii , 48.1 % with K. marmoratus , 46.3 % with tilapia O. mossambicus , and 46.1 % with O. niloticus PRLR2 as compared to PRLR1 isoform having less than 30 % identities. While mRNA transcript corresponding to PRL was detected only from the pituitary, most of PRLR mRNA was detected in the gill, kidney, and intestine, with a small amount in the ovary. The level of PRL transcript progressively increased during 6 days of acclimation to freshwater and then decreased but stayed higher than that of seawater at 60 days of acclimation. An opposite pattern of changes including a decrease at the beginning of the acclimation but a slight increase in the level osmolality was found as adaptation continued. The results support the osmoregulatory role of PRL signaling in starry flounder.