Piwil1 gene is regulated by hypothalamic-pituitary-gonadal axis in turbot (Scophthalmus maximus): A different effect in ovaries and testes.

As constituent factors of Piwi-interacting RNA (piRNA) pathways, Piwi proteins are essential for germline maintenance and gonadal development. Previous studies show that Piwi-piRNA pathways could be regulated by hypothalamic-pituitary-gonadal (HPG) axis, however, related studies have not been reported in marine species. Here we reported the identification of turbot (Scophthalmus maximus) piwil1 gene, which was abundantly expressed in testis and ovary in a tissue-specific manner. Phylogenetic and genomic structure analyses revealed that piwil1 was conserved in its sequence and function during vertebrate evolution. We also investigated the effects of HPG axis hormones, including human chorionic gonadotropin (hCG), estradiol-17β (E2) and 17α-methyltestosterone (MT), on gonadal piwil1 expression via in vivo and in vitro approaches. In ovary, hCG and E2 suppressed piwil1 expression both in vivo and in vitro, and MT increased piwil1 expression in vivo. In testis, hCG had upregulating effects on piwil1 expression in vivo and in vitro, and MT also increased piwil1 expression in vitro. In addition, E2 suppressed expression of piwil1 in vivo. These results indicated that the decreased or increased expression of piwil1 regulated by hormones might play a crucial role during gonadal differentiation and development in S. maximus.