Biointerfacial Underwater Adhesion of Seagrass <i>Phyllospadix japonicus</i> Mediated by Chitin-Binding Proteins and GlcNAc-Rich Macromolecular Scaffolds

Chitin is a ubiquitous marine biopolymer, yet its role as a functional biointerface in higher plants remains poorly understood. This study elucidates the molecular mechanisms driving the robust underwater adhesion of the surfgrass Phyllospadix japonicus in high-energy rocky intertidal zones. Unlike sediment-rooting species, P. japonicus secretes a hierarchical adhesive matrix comprising fibrous extracellular matrices (ECMs) and granular mucilage matrix (GMM) microparticles. Histochemical and proteomic analyses identify the GMM as a specialized filler characterized by peripheral enrichment of N -acetyl- d -glucosamine (GlcNAc). This architecture is integrated through high-affinity molecular docking with cognate chitin-binding proteins (CBPs) identified within the root cell wall. These findings reveal a previously unrecognized CBP-based underwater adhesion strategy. This mechanism provides a promising biomimetic template for chitin-based underwater adhesives and marine reforestation technologies to enhance blue carbon sequestration.