31.5:
Role of Microtubules in Cell Wall Deposition
During plant cell division, the thin cell plate formed during cytokinesis is restructured into the cell walls of daughter cells.
As the young cell grows, more and more cellulose is added to the cell wall.
Cellulose synthase or CESA is a multimeric enzyme that uses cytosolic UDP-glucose to spin out cellulose chains on the ECM face of the plasma membrane.
CESA moves on microtubule-defined channels just under the plasma membrane, to orient the newly deposited cellulose chains.
The nascent cellulose chains self-assemble to form microfibrils.
The distal ends of the stiff microfibrils integrate into the cell wall while the elongating proximal ends push CESA along microtubule tracks.
As the cell expands, the microtubules rearrange to control the orientation of new cellulose microfibrils and determine cell shape.
31.5:
Role of Microtubules in Cell Wall Deposition
Microtubules are small hollow tubes in eukaryotic cells. The cell wall microtubules are polymerized dimers of two globular proteins, α-tubulin and β-tubulin, two globular proteins. With a diameter of about 25 nm, microtubules are the widest components of the cytoskeleton. They help the cell resist compression and provide a track along which vesicles move through the cell or pull replicated chromosomes to opposite ends of a dividing cell. Microtubules go through quick cycles of disassembly and reassembly.
In plant cells, cortical microtubules are known to play a role in depositing cellulose in the cell wall. They influence cellulose deposition by either moving microtubules or directly changing the orientation of newly synthesized cellulose microfibrils. Microfibrils stabilize the boundaries of specialized plasma membrane domains that force nascent cellulose chains into a parallel alignment through glucan chain polymerization and chain crystallization. The glucose monomers form hydrogen bonds, thus holding the cellulose chains firmly together, forming oriented microfibrils. This imparts rigidity in the cell wall during cellulose deposition.
Adapted from section 4.5 cytoskeleton, openstax AP biology, section 6.4 Prokaryotic cell division, Openstax concepts of biology, section 3.2 Carbohydrates, Openstax biology 2 e.
Suggested Reading
- Roberts, A. W., Frost, A. O., Roberts, E. M., & Haigler, C. H. (2004). Roles of microtubules and cellulose microfibril assembly in the localization of secondary-cell-wall deposition in developing tracheary elements. Protoplasma, 224(3), 217-229.
- Marchant, H. J., & Hines, E. R. (1979). The role of microtubules and cell-wall deposition in elongation of regenerating protoplasts of Mougeotia. Planta, 146(1), 41-48.