Mechanism opening doors for crop production, food security

Chinese scientists have unveiled a crucial mechanism that governs the function of plant stem cells, which allow plants to continuously generate new leaves, stems, and flowers throughout their lifecycle, offering potential pathways for enhancing crop yields, quality, and resilience.

As they discovered that the mechanical properties of plant cell wall play a pivotal role in stem cell regulation, they said it is expected that in the future, precise regulation of cell walls could be used to optimize crop stem cell activity, much like programming, to shape ideal plant architectures. This could lead to larger grains, more tillers, and bigger fruits.

Plants possess an extraordinary ability to continuously generate new organs owing to these specialized cells known as stem cells. They reside in growth centers like the shoot apical meristem and root tips, where they meticulously divide and differentiate to construct the plant's architecture.

The study by a team of researchers from the Chinese Academy of Sciences Center for Excellence in Molecular Plant Sciences reveals that the cell wall, often considered a static scaffold, is dynamically involved in this process.

In their research, they discovered that the stem cell regions at the tip of plant shoots, the main component of the cell wall, pectin, exhibits a bimodal distribution pattern.

The old, mature walls are stiff, acting like the load-bearing beams of a building. Meanwhile, each time a cell divides to create two new cells, the new wall that forms between is initially soft and flexible. This difference in stiffness is controlled by a simple chemical tweak to a gel-like component in the wall called pectin. Stiff walls have highly "methylesterified" pectin, while soft, new walls have "de-methylesterified" pectin.

To answer the query of how the plant ensures that the softening enzyme only works on new walls, the team then pinpointed a key enzyme, PME5, which is the master player 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.

A paper about the research, a decade's effort, was published in the journal Science on Friday.

Researchers said that such a nuclear sequestration mechanism is a sophisticated form of gene regulation, which is not unique to PME5 but used by several related enzymes. Furthermore, their research discovered that this bimodal wall pattern was found in diverse crops, including corn, soybean and tomato, indicating that it is a conserved, fundamental principle of plant growth.

This research provides a theoretical framework and technological pathway for improving crop production and supporting food security, according to the team.

"Key crop traits, such as the number of tillers, the length of panicles, and the number of seeds, are all determined by stem cell activity. By learning this cell wall code, scientists could one day engineer crops with improved architecture and higher yields," said Yang, who is also the corresponding author of the paper.