tdrd1 is a germline-specific and sexually dimorphically expressed gene in Paralichthys olivaceus

Tudor domain containing protein 1 (tdrd1) is a member of the Tudor family and has shown essential functions during embryogenesis and gametogenesis. In this study, we cloned the full length cDNA of Paralichthys olivaceus tdrd1 (Potdrd1). PoTDRD1 is a multidomain protein with an N-terminal MYND zinc finger domain, followed by four tandem extended Tudor domains. Sequence comparison, genomic structure, phylogenetic analyses and synteny analyses showed that Potdrd1 was homologous to those of other teleosts. In adult individuals, the expression of Potdrd1 was higher in testis than in ovary, demonstrating a sexually dimorphic gene expression pattern. In situ hybridization (ISH) showed that Potdrd1 mRNA was detected in oogonia and oocytes of ovary as well as in spermatogonia and spermatocytes of testis. In juveniles during gonad differentiation its expression level increased rapidly from 30 dph to 100 dph and showed obvious sexual dimorphism that was in accordance with the expression of anti-Mullerian hormone (amh). Potdrd1 mRNA was consistently detected during embryogenesis, and its level was higher from unfertilzed eggs to the blastula stage and subsequently decreased until hatching. When chimeric RNA containing green fluorescent protein (GFP) and 3' untranslated regions (UTR) of Potdrd1 was microinjected into zebrafish fertilized eggs, the green fluorescence could be visualized only in putative PGCs. These results indicated that Potdrd1 is a germline specific and sexually dimorphic factor that potentially functionate in germline development and gametogenesis in Japanese flounder.