Identification And Immune Function Research Of Transforming Growth Factor-β Type Ⅲ Receptor (TβR3) Gene In Mud Crab Scylla Paramamosain

The mud crab,Scylla paramamosain,is one of the most important mariculture species in China.However,with the rapid development of intensive crab culture systems,various disease-driven mass mortality of farmed crab stocks has been frequently reported and caused large economic losses.Accordingly,investigations on the development and growth as well as the innate immunity in mud crab might contribute to design better strategies for crab aquaculture production.Transforming growth factor-β type Ⅲ receptor(TβR3),as a co-receptor of TGF-βsuperfamily,plays critical roles in development and growth as well as some disease pathogeneses by presenting ligands to other receptors in vertebrates.However,the identification and functional characterization of TβR3 had not been reported yet in invertebratesIn the present study,TβR3 was first identified and characterized in mud crab Scylla paramamosain.The obtained cDNA length of SpTβR3 was 2,424 bp with a 1,854 bp open reading frame,which encoded a putative peptide of 617 amino acids containing a typical transmembrane region and a Zona pellucida(ZP)domain.Real-time PCR results showed that SpTβR3 was predominantly expressed at early embryonic development stage and early postmolt stage,suggesting its participation in development and growth.We report,for the first time in invertebrates,the challenge of both Vibro alginolyticus and Poly(I:C)could alter the expression patterns of SpTβR3.Notably,the expression levels of SpIKK,two NF-κB members(SpRelish and SpDorsal),and five antimicrobial peptide genes(SpCrustin and SpALF1-4)were significantly suppressed when SpTβR3 was interfered in vivo.Secondly,the overexpression of SpTβR3 in vitro could activate NF-κB signaling through the dual-luciferase reporter assays Furthermore,the bacterial clearance assay after SpTβR3 was silenced in vivo highlighted the potential of SpTβR3 in activating the innate immune responses.These results implied the involvement of SpTβR3 in the innate immune responses by regulating the NF-κB pathway.This study first indicated that TβR3 was present in invertebrate,and it participated in not only the development and growth but also the innate immunity of S.paramamosain.It also provided new insights into the origin or evolution of TGF-β receptors in crustacean species and even in invertebrates.