A toll receptor is involved in antibacterial defense in the oriental river prawn, Macrobrachium nipponense.

Toll-like receptors (TLRs) play an important role in the activation of innate immune response in animals. In this study, we identified a TLR from the oriental river prawn, Macrobrachium nipponense (MnToll1) and investigated its functions in immunity. The MnToll1 protein shares similar structural characteristics with other known Toll family proteins. MnToll1 transcripts are broadly distributed in all of the examined tissues, and its expression level was significantly up-regulated by bacterial challenge. RNAi-mediated knockdown of MnToll1 significantly impaired the survivability of Vibrio-challenged prawns. RNAi experiments also revealed that the expression of several antimicrobial peptide genes were regulated by MnToll1. Moreover, we found the extracellular region of MnToll1 could directly bind to bacteria and bacterial glycoconjugates. These findings suggest that MnToll1 function as a pattern recognition receptor to recognize invading pathogen and initiate downstream gene expression, to participate in antibacterial defense of M. nipponense.