Omics insights into spermatozoa activation induced by Fetal bovine serum in viviparous black rockfish (Sebastes schlegelii).

Black rockfish (Sebastes schlegelii) is an economically important marine species with the characteristics of viviparity. The spermatozoa were transferred into the ovary by mating and stored for several months until fertilization. Little is known about spermatozoa activation and its mechanism in black rockfish. In this study, the suitable medium for spermatozoa activation in vitro was explored, and the underlying mechanism was studied by omics analysis. Fetal bovine serum (FBS) could significantly enhance spermatozoa motility in vitro. Omics analysis showed 559 differentially expressed genes (DEGs) and 1311 differentially methylated genes (DMGs) were identified after FBS treatment. Transcriptome analysis revealed that FBS-induced spermatozoa motility activation is associated with spermatozoa capacitation regulated by the cAMP-SRC-PKA, cGMP-PKG and phospholipase D signaling pathway. Spermatozoa capacitation-related gene hsp90aa1 and chemotaxis-related gene cxcr4 were two of the important DMGs. Methylome analysis further revealed that FBS-induced epigenetic modifications are involved in spermatozoa capacitation and chemotaxis. 36 overlaps were identified between DMGs and DEGs, of which five genes were demonstrated to play a role in spermatozoa physiology, required for flagellum stability and spermatozoa motility. The results could provide new clues for understanding spermatozoa activation's molecular mechanism and help establish activation and/or immobilizing media for improving either artificial fertilization or cryopreservation in black rockfish.