Building artificial plant cell wall on lipid bilayer by assembling polysaccharides and engineered proteins

The cell wall constitutes a fundamental structural component of plant cells, providing them with mechanical resistance and flexibility. Mimicking that wall is a critical step in the conception of an experimental model of the plant cell. The assembly of cellulose/hemicellulose in the form of cellulose nanocrystals and xyloglucans as a representative model of the plant cell wall has already been mastered, however, those models lacked the pectin component. In this work, we used an engineered chimeric protein designed for bridging pectin to the cellulose/hemicellulose network, therefore achieving the assembly of complete cell wall mimics. We first engineered proteins, i.e. carbohydrate-binding module from Ruminococcus flavefaciens able to bind oligo-galactorunan, resulting in high-affinity polygalacturonan receptors with Kd in the micromolar range. A Janus protein, with cell wall gluing property, was then designed by assembling this CBM with a Ralstonia solanacearum lectin specific for fucosylated xyloglucans. The resulting supramolecular architecture is able to bind fucose-containing xyloglucans and homogalacturonan ensuring high affinity for both. A two-dimension assembly of an artificial plant cell wall was then built first on synthetic polymer and then on supported lipid bilayer. Such artificial cell wall can serve as a basis for the development of plant cell mechanical models and thus deepen the understanding of the principles underlying various aspects of plant cells and tissues. Graphical abstract