miR-155 Regulates Photoperiod Induced Gonadal Development in Atlantic Salmon (Salmo salar) by Targeting Brain-Derived Neurotrophic Factor

This study was designed to explore the impact of the photoperiod on the gonadal development and somatic growth of Atlantic salmon raised in recirculating aquaculture systems (RASs), with specific focus on the role that microRNA (miR)-155 plays as a regulator in the Atlantic salmon's photoperiodic reproduction. These salmon were reared for 5 months under six different photoperiod regimens, including two with changing photoperiods (LL-SL = 24L:0D-8L:16D and SL-LL = 8L:16D-24L:0D) and four with constant photoperiods (24L:0D, 18L:6D, 12L:12D, and 8L:16D). The longer photoperiod groups (LL-SL and 24L:0D) were ultimately associated with higher gonadosomatic index (GSI) values and an increased proportion of mature fish relative to other exposure groups, indicating that the photoperiod positively impacted the Atlantic salmon's gonadal development in RAS environments. Hypothalamic miR-155 expression in these Atlantic salmon was also found to be influenced by the photoperiod, showing a markedly decreased expression in salmon exposed to a long photoperiod and upregulation following rearing under a short photoperiod. Functionally, miR-155 was found to suppress the expression of gonadal axis-related genes, including FSH and GnRH, through its ability to target the brain-derived neurotrophic factor (BDNF) and to thereby regulate photoperiod reproduction. Overall, these results suggested that the photoperiod could regulate gonad development in Atlantic salmon with miRNA-155 being involved in this process by targeting the BDNF.

Automated summary

This study explores the impact of photoperiod on the gonadal development and somatic growth of Atlantic salmon in recirculating aquaculture systems (RASs), specifically focusing on the role of microRNA-155 as a regulator in photoperiodic reproduction. The results show that longer photoperiods positively affect gonadal development in Atlantic salmon, as indicated by higher gonadosomatic index values and a higher proportion of mature fish. Additionally, the expression of hypothalamic miR-155 is influenced by the photoperiod and is involved in the regulation of photoperiod reproduction through targeting brain-derived neurotrophic factor (BDNF) and suppressing gonadal axis-related genes.