Mannose receptor RpMR1 of Manila clam (Ruditapes philippinarum) defense against Vibrio anguillarum infection

Area of Science:

• Immunology
• Marine Biology
• Genomics

Background:

• The mannose receptor (MR) is a C-type lectin and pattern recognition receptor (PRR) crucial for immune responses.
• Understanding mollusk immune mechanisms is vital for aquaculture and marine ecosystem health.

Purpose of the Study:

• To identify and characterize mannose receptor genes in Ruditapes philippinarum.
• To investigate the functional role of RpMR1 in antibacterial immunity against Vibrio anguillarum.

Main Methods:

• Genome-wide identification of MR genes (RpMR1-13) in R. philippinarum.
• Expression profiling post-Vibrio anguillarum challenge.
• Recombinant protein purification and antibacterial assays.
• In vivo challenge experiments and RNA interference (RNAi) for gene silencing.
• qRT-PCR to analyze immune gene expression, including TLR4.

Main Results:

• Thirteen MR genes were identified, with RpMR1-4 showing peak expression at 72h post-infection.
• Recombinant RpMR1 exhibited direct antibacterial activity against Gram-negative Vibrio species.
• RpMR1 injection significantly reduced mortality in R. philippinarum challenged with V. anguillarum.
• RpMR1 knockdown suppressed TLR4 expression, indicating a link between RpMR1 and TLR4 signaling.

Conclusions:

• This study provides the first functional evidence of mannose receptor-mediated immunity in mollusks.
• RpMR1 plays a significant role in the innate immune defense of R. philippinarum against bacterial pathogens.
• RpMR1 interacts with TLR4, highlighting a conserved immune signaling pathway in mollusks.