Plant cells absolutely have microtubules, and they rely on them for some of the most essential processes in plant life, from building the cell wall to dividing into new cells. These hollow protein tubes, about 24 nanometers in diameter, are a core part of the plant cell’s internal skeleton. What makes them especially interesting is how differently they behave compared to microtubules in animal cells.
What Plant Microtubules Are Made Of
Plant microtubules are built from the same basic materials as animal microtubules. Each tube is assembled from repeating pairs of two proteins called alpha-tubulin and beta-tubulin, stacked end to end into long chains called protofilaments. Thirteen of these chains line up side by side and curl into a hollow cylinder. The structure is polar, meaning the two ends are chemically different: one end (the “plus” end) grows faster, while the other (the “minus” end) grows more slowly. This polarity lets the cell control where and how microtubules extend.
Plant and animal tubulins share over 88% of their amino acid sequence, making them among the most conserved proteins across all complex life. But the differences, small as they are, matter. Plant tubulins respond differently to various drugs that target microtubules, which is why herbicides that destroy plant microtubules don’t affect human cells in the same way. Plants also carry more tubulin genes than animals. Poplar trees, for example, have 8 alpha-tubulin and 20 beta-tubulin genes, compared to just 7 of each in humans. This larger toolkit likely helps plants fine-tune microtubule behavior across different tissues, particularly in wood-forming cells where precise wall construction is critical.
No Centrosomes, No Problem
One of the biggest differences between plant and animal microtubule systems is where they originate. Animal cells organize their microtubules from a structure called the centrosome, a dedicated hub near the nucleus that contains a pair of barrel-shaped centrioles. Higher plants have no centrosomes and no centrioles at all.
Instead, plant cells nucleate microtubules from the surface of the nucleus, from the inner face of the plasma membrane, and from the smooth endoplasmic reticulum. In some cases, new microtubules sprout directly off existing ones. This decentralized system means plant microtubules aren’t anchored to a single organizing point. They can form arrays across the entire cell surface, which turns out to be exactly what plants need to build their cell walls.
Guiding Cell Wall Construction
This is arguably the most important job microtubules do in plants, and it has no equivalent in animal cells. Just beneath the plasma membrane, plant cells maintain a dense network of microtubules called cortical microtubules. These sit right against the inner surface of the membrane and act as guide rails for the enzyme complexes that manufacture cellulose, the main structural fiber in plant cell walls.
The cellulose-making machinery sits embedded in the plasma membrane and moves along it like a train on tracks, spinning out cellulose fibers as it goes. Cortical microtubules determine where these enzyme complexes are inserted into the membrane, guide their direction of travel during synthesis, and even help regulate when they’re pulled back inside the cell. The result is that cellulose fibers end up aligned in the same direction as the microtubules beneath them.
This alignment has a direct effect on how cells grow. In actively growing tissues, cortical microtubules typically run perpendicular to the direction the cell needs to elongate. The cellulose fibers deposited in that orientation act like hoops around a barrel, resisting widening while allowing the cell to stretch lengthwise. Change the microtubule orientation, and you change the shape of the cell.
Plant-Specific Roles in Cell Division
When a plant cell divides, microtubules form several structures that don’t exist in animal cells. The first is the preprophase band, a tight ring of microtubules that appears just before division begins. This band wraps around the cell’s midsection and marks exactly where the cell will eventually split in two. It’s a temporary structure that disappears before division is complete, but the positional information it leaves behind persists, guiding the final step of division to the correct location.
The second unique structure is the phragmoplast, which forms at the end of division. Animal cells pinch in half from the outside using a contractile ring. Plant cells can’t do this because their rigid cell walls won’t allow pinching. Instead, the phragmoplast, a barrel-shaped array of microtubules, assembles between the two new nuclei and directs the construction of a brand-new wall (the cell plate) from the inside out. Vesicles carrying wall materials travel along these microtubules to the center, where they fuse together and gradually expand outward until the cell plate reaches the edges of the cell, completing division at the precise site the preprophase band marked earlier.
Recent work in Arabidopsis has shown that this guidance system involves a collaboration between microtubule-based motors and the actin filament network. The preprophase band recruits a myosin motor protein to the future division site, where it joins other microtubule-associated proteins to form a ring of cytoskeletal assemblies that receive and steer the expanding phragmoplast.
Motor Proteins on Plant Microtubules
In animal cells, two major families of motor proteins walk along microtubules: kinesins and dyneins. Plants have lost dynein entirely. Their genomes contain no dynein genes, which is a striking evolutionary departure. Instead, plants rely on a large and diverse family of kinesins to handle microtubule-based transport.
Most long-distance cargo movement in plant cells actually happens along actin filaments, powered by myosin motors. But kinesins handle important short-distance and specialized tasks. Different kinesins move the nucleus into position before cell division, transport mitochondria in pollen tubes, shift chloroplasts in response to light, disperse Golgi stacks throughout the cell, and carry cell wall materials along cortical microtubules. One kinesin in Arabidopsis, called FRA1, is exceptionally good at sustained movement along microtubules and transports materials needed for proper cellulose patterning in the wall.
Responding to Gravity and Other Signals
Plant microtubules don’t just maintain static structures. They actively reorganize in response to environmental conditions, including gravity, light, and temperature. This reorganization directly influences how cells grow.
Gravity is a particularly clear example. In plant stems grown under normal Earth gravity, cells in actively elongating regions have transverse cortical microtubules (running around the cell like belts), which promotes lengthwise growth. As gravitational force increases, cells shift their microtubules to a longitudinal orientation, which favors lateral expansion instead. Experiments on the International Space Station have shown that under microgravity conditions, the normal transition from transverse to longitudinal microtubules is suppressed, keeping microtubules in the transverse orientation longer and stimulating extra cell elongation. This is one reason plant stems grow differently in space.
These responses highlight something fundamental about plant microtubules: because plants can’t move to escape unfavorable conditions, they use microtubule reorganization as a way to reshape their growth in real time. The same basic protein tubes found in every animal cell have been repurposed in plants into a remarkably flexible system for building walls, dividing without centrosomes, and adapting growth to whatever environment the plant finds itself in.