How do plant cells know in which direction to divide?

Wageningen University & Research scientists have found an answer to a fundamental question botanists have been asking for over a century: how do plant cells know in which direction to divide? “We finally understand for the first time how the mechanism may work,” says development biologist Ben Scheres. “This fundamental knowledge about plant development can help us steer the architecture of plant tissue, which is important for the improvement of crops.”

Scientists have occupied themselves for more than a hundred years with the regular patterns in which plant cells arrange themselves. In all the growth points of plants – the places where stems and leaves appear – as well as in the embryo formed by the seedling, cell divisions proceed in specific directions.

A collaboration between Wageningen cell biologists and development biologists has now led to the first explanation of how cells ‘know’ in which direction to divide during the earliest stages of a seedling’s development.

Advanced computer simulations
“A number of geometric rules have been observed over time which more or less predict the division orientation of plant cells,” explains Ben Scheres, who leads the research team together with theoretical biophysicist Bela Mulder. “Until now, those rules had not been linked to an understanding of the underlying processes in plant cells, which is exactly what this study does.”

Left: Arabidopsis plant with flowers. Seeds containing the embryonic seedling are developing in the pollinated flowers. Middle: two-cell embryo. Right: computer simulation of the orientation of the cell skeleton in the embryo (in green) predicts the direction of the division plane (in purple).

Previous work – including by the Mulder group at AMOLF (a research institute of NWO, the Netherlands Organisation for Scientific Research) – has shown that a plant cell’s skeleton can organise itself spontaneously. Wageningen PhD student Bandan Chakrabortty used advanced computer simulations to discover that this organising depends on the shape of the cells, and that a plant growth hormone and a protein in the cell corners help the process.

Visualisation cell structure
The scientists have since tested the predictions of the model in the earliest stages of the plant’s development. They also used state-of-the-art techniques developed in Dolf Weijers’s biochemistry group to create a visualisation of the cell structure. This enabled the scientists to also test other predictions of the computer models together.

Possibilities to improve plants
The knowledge acquired can now be used by scientists to devise ways to adapt the arrangement of plant cells. “World population growth means that global agriculture is in constant search for possibilities to improve plants,” Scheres continues. “Managing the architecture of plant tissue can be of great help in this context. In the future we might, for instance, say that we want a given plant to be more efficient at absorbing nutrients or to have a double layer of cells on the inside so as to make it more resistant to drought.”

The study was published in leading biology journal Current Biology.

Source: Wageningen University & Research

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