Each plant cell type displays a unique wall architecture, and the spatial organization and remodeling of wall components within specific microdomains contribute to functional specialization. Arabidopsis thaliana seed mucilage-secretory cells (MSCs) provide an excellent model to study these dynamics. During development, MSCs sequentially form a primary cell wall, a mucilage layer, and an inner secondary wall called the columella. Upon seed imbibition, previously weakened regions rupture, releasing a polysaccharide-rich mucilaginous hydrogel that controls germination and mediates seed–environment interactions.

Homogalacturonans (HGs), the major pectic components of the wall, are central to these processes. Their degree of methylesterification, regulated by pectin methylesterases (PMEs) and their inhibitors (PMEIs), modulates wall mechanical properties. These modifications may also generate specific pectic anchoring platforms for class III peroxidases (PRXs), enzymes able to locally loosen or reinforce the wall though extensins (EXT) cross-linking. Recent studies identified a molecular module involving PMEI6, and PRX36 promoting local radial primary wall microdomain loosening. The current work focusses on an opposite candidate module involving PME16, PRX56 and EXT21 to promote reinforcement of an adjacent wall microdomain. Demonstrating this dual mechanism would provide the first evidence of two PRXs acting antagonistically in two distinct microdomains of the same cell type.