The epidermis controls root torsion and defines plant growth.

A study by researchers at Washington University shows that the epidermis controls the symmetry disruption that leads to root twisting in plants. The research reveals that microscopic alterations in this outer layer are enough to determine whether the root grows straight or in a spiral. The work suggests ways to adjust root architecture and improve plant adaptation to the soil.

The authors analyzed roots of Arabidopsis thaliana with mutations in proteins linked to microtubules. These mutations cause helical growth. The study connected events at multiple scales. The disorganization of cellulose microfibrils occurs at the nanometer level. Then, asymmetrical cell expansion occurs. Next, helical cell files appear in the epidermis. Finally, the entire root begins to grow in a twisted pattern.

Experiments showed that the epidermis dominates the process. Restoring normal microtubule activity in this layer alone restored straight root growth. The effect did not appear when the correction occurred in inner layers. Mechanical modeling explained the result. Torsional stiffness increases with the fourth power of the radius. Therefore, the outermost layer exerts a greater influence.

The environment interferes.

The environment also plays a role. In a homogeneous medium, such as agar, the roots grew straight even with twisted epidermal cells. On the agar surface and in the soil, the imbalance of forces led to curvature. In soil, mutant roots maintained regions of torsion and pronounced curves. This behavior persisted without the involvement of root hairs.

The study evaluated responses to the environment. Twisted roots altered the adjustment to gravity and the reaction to obstacles. In tests with barriers, mutants exhibited directional deviations or reorientation failures. The results indicate a direct impact on soil exploration.

Tissue integrity

The integrity of the epidermal tissue proved essential. Reduced adhesion between the epidermis and cortex suppressed root torsion, even with epidermal cells still helically oriented. This finding reinforces the mechanical role of the epidermis in coordinating growth.

The authors point to applications. Controlling microtubule-associated proteins in the epidermis could allow roots to penetrate compacted soils more efficiently or overcome obstacles. This strategy paves the way for engineering root systems that are better adapted to the physical and chemical stresses of the soil.

Further information at doi.org/10.1038/s41467-025-66029-8