Key mechanism on crop improvement unlocked

Chinese scientists have identified a key mechanism that governs the function of plant stem cells — cells that enable plants to continuously generate new leaves, stems and flowers — a finding that could enable the improvement of crop yields, quality and resilience.

The researchers found that the mechanical properties of the plant cell wall play a pivotal role in stem cell regulation. They said that in the future, precise control of cell wall features may allow scientists to "program" stem cell activity to shape ideal plant architectures. Potential benefits, they added, could include larger grains, more tillers and bigger fruits.

Plants maintain an extraordinary ability to produce new organs thanks to stem cells located in growth centers such as the shoot apical meristem and root tips. These cells divide and differentiate to build the plant's structure.

The study, led by a team from the Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences, shows that the cell wall — long viewed as a static scaffold — is in fact dynamically involved in this developmental process.

The researchers found that in the stem cell regions at the tips of plant shoots, pectin, the main component of the cell wall, displays a bimodal distribution. Mature cell walls are stiff, acting like load-bearing beams, while each new wall formed during cell division is initially soft and flexible. The difference is controlled by a simple chemical modification to pectin: stiff walls contain highly methylesterified pectin, while new, soft walls contain de-methylesterified pectin.

To determine how plants ensure that the softening enzyme acts only on new walls, the team identified a key enzyme, PME5, as the central regulator that softens pectin.

"We found a clever trick. The cell keeps the instruction manual for this enzyme — the PME5 messenger RNA — under lock and key inside the nucleus. It is like having a powerful tool stored safely in a toolbox," said Yang Weibing, a researcher at the CAS center.

"Only when a cell is actively dividing does the toolbox open. As the nucleus temporarily disassembles, the PME5 mRNA is released. It is immediately translated into the PME5 enzyme, which is delivered right to the site of the new, forming wall, softening it precisely where and when it is needed. This ensures the mature walls remain stiff and structural, while new walls are flexible enough to be positioned correctly," he said.

The findings, resulting from a decade of work, were published on Friday in the journal Science.

The researchers said the nuclear sequestration mechanism represents a sophisticated form of gene regulation that is not unique to PME5 but shared by several related enzymes. They also found that the bimodal wall pattern occurs across diverse crops, suggesting it is a fundamental feature of plant growth.

The team said the work offers a theoretical foundation and technological pathway for improving crop production and supporting global food security.

zhouwenting@chinadaily.com.cn