Proteomic Profiling Reveals Region-Specific Brain Responses During Acclimation to Elevated Water Temperature in Atlantic Salmon (Salmo salar L.)

Background: Increasing summer seawater temperatures pose challenges for Atlantic salmon aquaculture, while brain region-specific responses to elevated temperature remain poorly understood. Methods: Atlantic salmon in the warm treatment (WT) underwent thermal ramping from 15 °C to 19 °C, with mortality observed at the end of week 4 (15.78%). The WT temperature was subsequently reduced to 18 °C in week 5, while the control treatment (CT) was adjusted from 15 °C to 14 °C, and the WT (18 °C) and CT (14 °C) conditions were maintained thereafter. At the end of the trial (week 10), six brain regions, including the cerebellum (CBE), hypothalamus (HYP), medulla oblongata (MED), optic tectum (OPT), pituitary gland (PIT), and telencephalon (TEL), were analysed using data-independent acquisition mass spectrometry-based proteomics. Results: Over 9000 protein groups were identified per brain region, and exploratory differential abundance analysis revealed predominantly region-specific protein abundance changes. Increased SERPINH1 (HSP47) abundance was observed in HYP, PIT, and TEL, suggesting roles in protein-folding and stress regulation. Functional enrichment analyses indicated differential regulation of translation, transcription, energy metabolism, and metabolic pathways across brain regions in the WT group. Conclusions: This study provides a brain region-specific proteomic resource for Atlantic salmon and advances understanding of molecular responses associated with recovery from a temperature reduction (19 °C to 18 °C) and subsequent thermal adjustment at 18 °C.