Cloning, Localization and Expression of Prolactin Gene in Discus Fish (Symphysodon aequifasciatus)

Abstract

【Objective】Discus fish (Symphysodon aequifasciatus) has special parental care behavior. In the study, prolactin (PRL) gene from discus fish was cloned and localized and its expression pattern during parental care was analyzed, with an aim to provide a basis for understanding the function of PRL in parental care of discus fish.【Method】A prolactin gene named dfprl was identified by analyzing the whole genome data of the discus fish through BLASTP. The CDS region of dfprl genes were used to design the primer of gene cloing and PCR. The full length of dfprl gene was cloned by RACE technology, and the structure of dfprl gene was analyzed by bioinformatics and its amino acid sequence was analyzed by physicochemical properties and phyletic evolution. Transcriptome sequencing was performed on brain, gonad and skin of discus fish at different rearing stages to explore the expression pattern of dfprl gene during parental care. The dfprl gene in the skin of discus fish was located by paraffin-fluorescence probe-FISH.【Result】The full length of dfprl was 1 282 bp, with 639 bp cDNA sequence encoding 212 amino acids, 309 bp 5'-UTR and 334 bp 3'-UTR. The dfprl protein has the typical domain of PRL family, the Hormone_1 domain. dfprl protein is highly similar to PRL protein of other Cichlidae, and the amino acid sequence homology of dfprl with Archocentrus centrarchus prolactin (AcPRL) was the highest (96.70%). The expression level of dfprl in gonad and skin increased gradually after the parent fish entered the rearing stage, and decreased at the end of the rearing stage. The paraffin-fluorescence probe-FISH results showed that dfprl was expressed in skin mucous cells, and it was coincident with the expression site of prolactin receptor (dfprlr) and was highly expressed in the early stage of parental care.【Conclusion】The dfprl gene is highly conserved and has stable Hormone _1 domain. dfprl gene was highly expressed in the skin during the parental care stage, . and the expression sites of dfprl and dfprlr overlapped in skin mucous cells during the parental care stage of discus fish, suggesting that dfprl might be involved in the occurrence of unique parental care behavior of discus fish.

Keywords

• symphysodon aequifasciatus
• prolactin
• parental care
• skin mucus cell
• gene clone