Science - August 18, 2011

EU millions for stem cell research on plants

'The timing couldn't have been better', says Dolf Weijers. At five thirty on the Friday afternoon before he left on holiday, he received the news that he had been awarded the European Research Council's Starting Grant, worth 1.5 million euros.

Microscopic image of an Arabidopsis embryo. Stem cells for vein tissue (green), connective tissue (yellow) and the organizing cell (purple) are shown in colour.
Weijers, who works at the Laboratory for Biochemistry, is going to use this prestigious grant to find out how plants grow. He will focus chiefly on the stem cells which are responsible for growth in plants. In order to study this, he will monitor the very first cells of the new embryos of the mouse-ear cress plant. 'Leaves, flowers and stems are complex parts of the plant containing may different types of cell. If you want to know how they are made you have to go back to the very beginning of the plant's life, to the embryo that contains the seed', explains Weijers.
A clump of stem cells
The initial plant embryo starts from the division of a single cell. Once there is a clump of about fifty cells, a few cells change identity and become stem cells. The stem cells then grow into the undifferentiated cells or meristems which continue to divide actively throughout the life of the plant. This enables plants, unlike animals, to go on making new organs all their lives: leaves, flowers and stems for instance. 'It fascinates me that a little clump of stem cells that is only formed once ends up making the entire plant and staying active for years', says Weijers. 'In some trees, such as sequoias, that can mean thousands of years.'
These special growth cells are at the heart of the research. 'First of all we want to know what differentiates the embryonic cells that get promoted to stem cells from all the other cells: what makes these cells unique and why do they and not the other cells become stem cells?' asks Weijers. In order to find out, one of the things he will be looking at is the difference in gene activity between stem cells and the other cells.
Growth processes
Weijers is also keen to know exactly what needs to change in the cell for it to remain a stem cell and not grow into a specialized plant cell. 'We know that the cell we call the organizer cell plays a crucial role in this', explains Weijers. 'This cell makes sure that the stem cell remains a stem cell even after division.' This will only work if the organizer cell is positioned right next to the stem cell, and Weijers wants to know how the embryo ensures that the cells are all in the right places.
This is fundamental research at the micro scale, but according to Weijers, it is of great relevance to agriculture. After all, increasing crop yields or improving root growth have a lot to do with changing the way a plant grows. And it is exactly here that stem cells and the meristem have the lead roles. 'Once you understand the how and why of plant growth through stem cells, you have got to the bottom of the growth process', says Weijers. 'Then you've got the fundamental knowledge with which to influence it at your fingertips.'

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