Identification of a ficolin involved in ovary reproductive immunity in Macrobrachium nipponense

Recent studies have revealed that the ovary plays a crucial role in defending against pathogen infection in crustaceans, yet the underlying molecular mechanisms remain poorly understood. Our previous work identified numerous genes responsive to poly I:C challenge in the ovary of Macrobrachium nipponense, including several members of the fibrinogen-related protein (FREP) family. Here, we characterized a FREP member from M. nipponense and designated as Mnficolin-1. The Mnficolin-1' cDNA was 1086 bp, encoding 361 amino acids with a C-terminal fibrinogen-related domain (FReD). Mnficolin-1 mRNA was ubiquitously expressed across examined tissues, including the ovary. Furthermore, MnFicolin-1 protein was detected in various germ cells and exhibited upregulated expression pattern following challenges with lipopolysaccharide (LPS), peptidoglycan (PGN), and polyinosinic-polycytidylic acid (poly I:C). Recombinant MnFicolin-1 (rMnFicolin-1) displayed direct binding affinity for LPS, PGN, and multiple microorganisms (Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Aeromonas hydrophila, and Vibrio alginolyticus) in vitro. Additionally, rMnFicolin-1 disrupted bacterial cell walls. Overall, these findings confirm the crucial roles of MnFicolin-1 as both a pattern recognition receptor and an immune effector, contributing to reproductive immunity in M. nipponense.