Identification and functional analysis of drosophila mothers against decapentaplegic protein gene 1 (Smad1) from the red swamp crayfish Procambarus clarkii: The first evidence of Smad1 involved in immunity in invertebrates

Smads, part of signaling cascades that represent downstream pathways of the TGF-β super family proteins, are pleiotropic cytokines with important role in mediating cell proliferation, homeostasis, differentiation, apoptosis and immune response. However, the specific functions of Smads remain unknown in crustaceans. In the present study, the drosophila mothers against decapentaplegic protein gene 1 (Smad1) was firstly identified and characterized from the Red Swamp Crayfish Procambarus clarkii. The obtained cDNA sequence of pcSmad1was 2, 503 bp long with a 1, 488 bp open reading fame, which encoded a putative protein of 496 amino acids. Furthermore, pcSmad1 responded to both Aeromonas hydrophila and WSSV challenge, suggesting the involvement of pcSmad1 in innate immune responses. Knockdown of pcSmad1 in vivo dramatically increased the expressions of NF-κB signaling genes and anti-lipopolysaccharide factor genes. Additionally, overexpression of pcSmad1 in HEK293T cells could markedly activate NF-κB signaling. Taken together, these results indicated that pcSmad1 played an immune-regulatory role in crayfish's innate immunity, which may provide a better understanding of TGF-β superfamily members in crustacean.