NFAT5 genes are part of the osmotic regulatory system in Atlantic salmon (Salmo salar)

Abstract

The anadromous Atlantic salmon utilizes both fresh and salt water (FW and SW) habitats during its life cycle. The parr-smolt transformation (PST) is an important developmental transition from a FW adapted juvenile parr to a SW adapted smolt. Physiological changes in osmoregulatory tissues, particularly the gill, are key in maintaining effective ion regulation during PST. Changes are initiated prior to SW exposure (preparative phase), and are com- pleted when smolts enter the sea (activational phase) where osmotic stress may directly stimulate changes in gene expression.In this paper we identify 4 nuclear factor of activated T cells (NFAT5, an osmotic stress transcrip- tion factor) paralogues in Atlantic salmon, which showed strong homology in characterized functional domains with those identi fi ed in other vertebrates. Two of the identi fi ed paralogues (NFAT5b1 and NFAT5b2) showed in- creased expression following transfer from FW to SW. This effect was largest in parr that were maintained under short day photoperiod, and showed the highest increases in chloride ion levels in response to SW exposure. The results of this study suggest that NFAT5 is involved in the osmotic stress response of Atlantic salmon.