Function of a novel C-type lectin with two CRD domains from Macrobrachium rosenbergii in innate immunity

•A novel C-type lectin with two CRD domains was identified from Macrobrachium rosenbergii.•MrCTL was regulated by Vibrio parahaemolyticus and WSSV.•rMrCTL, rMrCRD1 and rMrCRD2 could bind different bacteria.•rMrCTL, rMrCRD1 and rMrCRD2 could agglutinate bacteria in a Ca2+-dependent manner. C-type lectins play crucial roles in innate immunity. In the present study, a novel C-type lectin gene, designated as MrCTL, was identified from Macrobrachium rosenbergii. MrCTL contains 2 carbohydrate-recognition domains (CRDs), namely MrCRD1 and MrCRD2. The MrCRD1 contains a QEP motif and MrCRD2 contains a motif of EPD. MrCTL was mainly expressed in the hepatopancreas. The expression level of MrCTL in hepatopancreas was significantly upregulated after a challenge with Vibrio parahaemolyticus or White spot syndrome virus (WSSV). The recombinant MrCTL, MrCRD1 and MrCRD2 have an ability to agglutinate both Gram-negative (V. parahaemolyticus) and Gram-positive bacteria (Staphylococcus aureus) in a calcium dependent manner. The recombinant MrCTL, MrCRD1 and MrCRD2 bind directly to all tested microorganisms. All these results suggested that MrCTL may have important roles in immune defense against invading pathogens in prawns.