Crucial roles of a novel exoskeletal‐derived lectin in innate immunity of the oriental river prawn, Macrobrachium nipponense

As important pattern recognition receptors (PRRs), C-type lectins play crucial roles in the crustacean innate immune system. In this study, a novel C-type lectin, designated as MnLec1, was obtained from the exoskeleton of the oriental river prawn Macrobrachium nipponense for the first time. The full-length cDNA of MnLec1 was 1329 bp with an open reading frame of 774 bp. The predicted MnLec1 protein contains a single carbohydrate-recognition domain with an EPN/LND motif and one Ca2+ binding site-2. MnLec1 transcripts were widely detected in the tested tissues of M. nipponense and significantly up-regulated after Aeromonas hydrophila challenge. The recombinant MnLec1 protein was found to have a wide spectrum of binding activities towards various microorganisms, agglutinate two kinds of Gram-negative bacteria (Escherichia coli and A. hydrophila) in a Ca2+ -independent manner. What's more, the survivability of prawns was significantly down-regulated after RNAi of MnLec1 when infected with A. hydrophila. Collectively, these findings suggest that MnLec1 from the exoskeleton might function as a PRR and play a crucial role in immune defense against invading pathogens in M. nipponense.