Role Of Evolutionarily Conserved Signaling Intermediate In Toll Pathways (ECSIT) In Antibacterial Immunity Of Marsupenaeus Japonicus

With the demanding keeps on increasing, shrimp culture has developed rapidly, However, in the past decade, the emergence of various diseases, caused by bacteria and viruses, has been the main limitation to the progress of this industry. Thus, a deep understanding of shrimp innate immunity system can provide theoretical basis to the shrimp culture industry. The Toll/Toll-like receptor (TLR) signaling pathway plays an important role in the innate immunity of animals. To study the mechanism of shrimp Toll signaling pathway will help us have a complete understanding of invertebrate innate immunity system.ECSIT, an evolutionarily conserved signaling intermediate in Toll pathways, is a protein that not only functions as an adaptor protein for the Toll/TLR and bone morphogenetic protein (BMP) signaling pathways but also acts as a key component in the macrophage bactericidal activity of mammals. However, the function of ECSIT in crustaceans remains unclear. In this paper, we report the cloning and identification of a functional ECSIT homologue, MjEcsit1, from kuruma shrimp Marsupenaeus japonicus. The complementary DNA of MjEcsit1is1486base pairs long, with an open reading frame of1221base pairs encoding a407-residue polypeptide. Transcription level of MjEcsit1was detected in hemocytes, gills, hepatopancreas, stomach, heart, intestines, testes, and ovaries, and was upregulated by Gram-positive bacteria(Staphyloccocus aureus) and Gram-negative bacteria(Vibrio anguillarium) injections. Furthermore, the knockdown of MjEcsit1by double-strand RNA injection increases the sensitivity of M. japonicus to S. aureus challenge and weakens its bacterial clearance ability in vivo. In addition, suppressing MjEcsit1restrains the upregulation of two anti-lipopolysaccharide factors (Alf5and Alf6) by S. aureus injection. Furthermore, knock-down of the two Alfs respectively lead to the weakened ability of bacteria eliminating in vivo. Our results also demonstrated that, the upregulation of MjEcsit1and the two Alf genes (Alf5and Alf6) by S. aureus infection in shrimp were inhibited by.MjTLR3knock-down but not the other TLRs in shrimp M. japonicus, indicating an important role of MjTLR3-MjECSIT1-ALFs singnaling pathway in the anti-gram positive bacteria immunity of shrimp.