TGF-β/Smad signaling pathway responding to photoperiod for participation in regulation of zebrafish ovarian development

To study the role of TGF-β/Smad signaling pathway in zebrafish (Danio rerio) ovary under different photoperiod conditions, we detected the relative expression of relevant genes in TGF-β/Smad signaling pathway of zebrafish ovary under continuous dark (0 L∶24 D, DD), natural photoperiod (14 L∶10 D, LD) and continuous light (24 L∶0 D, LL) using quantitative real-time PCR. The location of p-Smad2 in zebrafish ovary was detected by immunohistochemical technology. The results show that the expression patterns of genes involved in TGF-β/Smad signaling pathway were different in zebrafish ovary under different photoperiod conditions, and the expression profiles of ligand (tgfb3), receptor (tgfbr2a, tgfbr2b and tgfbr1b) and downstream protein kinase (smad2 and smad3a) were consistent. The relative expression levels of the above six genes were the highest in DD group and the lowest in LL group after 3-day treatment of different photoperiods, and an opposite trend was observed after 7 d. The p-Smad2 protein signal was detected in the development of zebrafish oocytes from previtellogenic stage (PV) to full-grown immature stage (FG). Photoperiod treatment did not affect the localization of p-Samd2 in zebrafish ovary. The results suggest that change of photoperiod might affect the ovarian development of zebrafish by changing the expression pattern of genes of tgfb3/receptor/protein kinase.