Involvement of a TNF homologue in balancing the host immune system of Macrobrachium nipponense

In vertebrates, tumor necrosis factors (TNFs) are well-known cytokines involved in a diversity of physiological and pathological events. In the present work we identified a novel TNF-like gene (MnTNF) from Macrobrachium nipponense, which codes for a protein sharing detectable sequence identify (26-27%) to the mammalian TNFSF members, TWEAK and EDA. Tissue distribution analysis indicated that MnTNF was predominantly expressed in nervous tissue, and at relatively high level in haemocytes, gill, intestine and muscle, whereas was almost undetectable in hepatopancreas. In gill, MnTNF was significantly up-regulated at both mRNA as well protein levels upon Aeromonas veronii challenge. RNA interference (RNAi) mediated MnTNF silencing led to a significant overexpression of the antimicrobial peptide (AMP) gene crustin, but a non-significant overexpression of another AMP gene anti-lipopolysaccharide factor (ALF), and inhibited the activation of phenoloxidase (PO) significantly following bacterial challenge. Meanwhile, the expression of NF-κB-like factor gene relish was increased while that of dorsal and STAT was uninfluenced in MnTNF-depleted prawn. We suppose that MnTNF be involved in regulating the expression of AMP genes and the capacity of PO by coordinating with the Imd pathway.