31.7:
Cell Adhesion in Plants
Cell adhesion provides organized tissue structure and allows the transmission of molecular signals for cell-cell communication.
In plants, most cell-cell adhesions are mediated by cell wall polysaccharides, such as pectins. During cell division, as a plate forms between the dividing cells, RG II, a pectin polysaccharide, localizes at the plate and helps early-stage adhesion.
As the cells mature, pectins are distributed across the primary cell wall and middle lamella.
Pectins have a negatively charged galactouran backbone that gets cross-linked by calcium ions. The resulting polysaccharide network connects adjacent cells, maintaining tissue integrity.
Though plant cells adhere closely, the thick cell walls prevent the free diffusion of molecules.
Structures called plasmodesmata, functionally similar to gap junctions in animal cells, form continuous channels connecting the cytosol of adjacent cells.
Such channels allow molecules to pass through, aiding cell-cell communication.
31.7:
Cell Adhesion in Plants
Plants have rigid cell walls that are made up of cell wall polysaccharides that mediate cell-cell adhesion. The primary cell walls of plants consist of two independent and interacting polysaccharide networks: a pectin matrix that embeds the second network comprising cellulose and hemicelluloses.
Pectins are complex heteropolymers mainly composed of negatively-charged α-D-glucopyranosyl uronic acid and some neutral glycosyl residues such as α-L-rhamnopyranose, α-L-arabinofuranose, and β-D-galactopyranose. Pectin networks crosslink one cell’s middle lamella to others, thus acting as the most important tool for cell-cell adhesion.
Adjacent cell walls are connected via membrane-lined channels called plasmodesmata (singular plasmodesma). Each plasmodesma allows the transport of molecules via the connected cytoplasm through contact-dependent signaling, like gap junctions in animals. Unlike gap junctions, plasmodesmata are more flexible because they let molecules pass through the cell wall and membrane. The plasmodesmata also allow direct communication from a single cell to many cells, joining the cells in a symplast network.
Other cellular components such as ferulic acids, xyloglucan-like polysaccharides, and proteins such as specialized wall-associated kinases and extensins also regulate cell adhesion during growth and development, although the exact mechanisms remain unknown.
Suggested Reading
- Seymour, G. B., Tucker, G., & Leach, L. A. (2004). Cell adhesion molecules in plants and animals. Biotechnology and Genetic Engineering Reviews, 21(1), 123-132.
- Atakhani, A., Bogdziewiez, L., & Verger, S. (2022). Characterising the mechanics of cell-cell adhesion in plants. Quantitative Plant Biology, 3.