How does the cell wall 'stick' in the mucilage? A detailed microstructural analysis of the seed coat mucilaginous cell wall

•Microstructural organization of mucilaginous cell wall is direct visualized.•Characteristic net-like architecture of the seed mucilage envelope is demonstrated.•Immunolocalizations show the presence of selected hemicelluloses in the mucilage.

The seed mucilage envelope of myxospermatic diaspores is considered as a modified cell wall. Its chemical constitutes are mainly polysaccharide groups typical of the cell wall, however, pectins are very often the main component. A detailed analysis of the mucilaginous cell wall spatial architecture was demonstrated for the first time using a less-invasive CPD + SEM technique, which allowed the preservation of the mucilaginous cell wall structure. The examined pectic (Linum usitatissimum) and cellulose (Neopallasia pectinata) seed mucilage showed the fibrillary character of the components. The second type of mucilage indicated a much more arranged structure than that of the pectic one due to the presence of cellulose microfibrils. We showed cellulose organization in a net-like scaffold on which other mucilage components were spread and shoved how the mucilage was anchored to the seed surface through the cellulose skeleton, preventing it from being lost. Our detailed analysis gave an insight into how the mucilage is spatially arranged and also provided direct microstructural evidence of cell wall polysaccharides structure, distribution and interactions especially for widely-postulated xylan-cellulose linking. We demonstrated that xylan might be represented by long chains covering the surface of cellulose fibrils. The main advantage of the applied technique is its less-invasive character which retains the 3D structure of the components within the intact mucilaginous cell wall. As utilized in our studies, preparation and visualization methods with seed mucilage as a model system can give us new possibilities in structural studies of the (mucilaginous) cell wall.