Mechanisms that determine the size of plants have fascinated plant scientists of all times, however they are far from understood. An international research team led by plant scientists from VIB and Ghent University last week reported on an important breakthrough in research which they said could lead to breeding crops for better productivity.

The researchers identified a protein complex that controls the transition from cell division to cell specialization. By extending the activity of the complex during leaf growth, more cells divide, giving rise to larger leaves. The scientists said their insights can now be used to guide plant breeding initiatives towards higher plant productivity.

More dividing cells, larger leaves

Cell division is essential for growth and development of all multicellular organisms. In plants, leaf growth consists of two different phases. A first phase is characterized by intense cell division, which leads to the formation of many new cells. During the second phase, cell division activity declines, the cells elongate and acquire a certain expertise. In a small leaf that just initiated from the stem, almost all cells are in the active division phase. Later on, when the leaf matures, cells at the top of the leaf switch to the specialization phase.

The more time cells stay in the first phase, the more cells are being formed and the bigger the ultimate leaf size will be. It was already known that a protein, ANGUSTIFOLIA3 (AN3), fulfils an important role in determining the timing and activity of cell division in the leaf. However, the precise mode of action of AN3 was not fully understood until the Ghent researchers and their colleagues chose it for their study.

State-of-the-art techniques

To unravel the mysteries of this biological process on a molecular level, the scientists studied "aberrant" plants in which some genetic functions were switched ‘on’ or ‘off.’ The scientists demonstrated that the genetic process by which AN3 governs cell division functions is a 'chromatin remodelling' process, meaning the protein makes certain specific parts of DNA available from a condensed structure within the cell, called the chromatin.

The scientists stated that, as long as AN3 is active and keeps the chromatin remodelling process going, cells will retain their division activity, resulting in plant organs with increased size. The AN3 protein complex regulates the length of the cell division phase in the leaf and hence the transition from cell division towards cell specialization.

The research was performed in collaboration with the University of Pennsylvania (USA), the French Institut de Biologie des Plantes, the Polish University of Warsaw and the Polish Academy of Sciences.

Researchers from the Ghent team said, "The obtained insights can now be used to orchestrate plant breeding activities more efficiently, for example towards higher plant productivity."