Characterization of the Grass Carp trpc3 Gene Reveals Its Role in Osmoregulation Under Salinity Stress

This study investigated the role of trpc3 in osmoregulation under salt stress in grass carp (Ctenopharyngodon idella). Tissue expression analysis showed trpc3 was highest in the brain, followed by gills, skin, and muscle. In gills and kidney, its expression increased with salinity. RNA interference using synthesized trpc3-dsRNA (2 μg/g) significantly reduced its expression. Under early salt stress, serum osmolality, Na+, Ca2+, and renal NKA activity were comparable between the interference and non-interference groups. However, gill CaN, NKA, and Ca2+-ATPase, as well as renal CaN and Ca2+-ATPase activities were significantly lower in the interference group. During late salt stress, the interference group exhibited significantly higher serum osmolality, Na+ concentration, and renal NKA activity than the non-interference group. Serum Ca2+ concentration remained unchanged between groups. Conversely, gill CaN, NKA, and Ca2+-ATPase, as well as renal CaN and Ca2+-ATPase activities were significantly lower in the interference group. Gene expression analysis revealed that early plcxd1 was higher, while trpc3, calm1a, aqp3a, nka beta 1b subunit, IL-1β, hsp70, and gill nkcc1 variant X1 were lower in the interference group. Late-stage expression showed nka beta 1b subunit (gills/kidney) and renal trpc3, nkcc1 variant X1 were higher; gill trpc3, plcxd1, aqp3a, nkcc1 variant X1, IL-1β and renal plcxd1, aqp3a, nkcc1 variant X1, hsp70 were comparable; and gill calm1a, hsp70 and renal calm1a, IL-1β remained lower in the interference group. In summary, grass carp trpc3 may mediate Ca2+ influx to regulate ion transport in the gills and kidney, playing a key role in restoring osmotic homeostasis.