Scientists at the John Innes Centre(JIC), Norwich, UK today report a discovery that explains how plants control the size and development of their cells. Published on-line by the international journal PNAS the report describes how a gene (called RHL1) affects a plant cell’s ability to make multiple copies of its DNA, in turn affecting cell growth and overall plant development.

“Unlike the cells of animals, plant cells typically expand to up to 1,000 times their original size as they develop” says Dr Keiko Sugimoto-Shirasu (project leader at JIC). “We don’t know a lot about how this is controlled but it is often the result of the cell making multiple copies of its DNA (so-called endoreduplication), which then stimulates this massive cell growth. Our discovery has given us an exciting insight into how plant cells actually manage all these extra copies of DNA and shown us that the process is much more sophisticated than we imagined”.

The researchers at JIC were using the common weed Thale Cress (Arabidopsis thaliana) to study the control of cell size and the endoreduplication process. They identified a mutation (called hyp7) that caused seedlings to be dwarf, because their cells did not expand normally. When they compared the damaged gene, which causes the mutation, with known genes they discovered it is a gene that is known to affect root hair production on the roots of plants – hence its name root hairless or rhl.

Hyp7 (or rhl) has similarities to other known genes from animals and bacteria. In this case the genes are known to be important in DNA replication. In fact they have a very specific role in unravelling the DNA double helix to allow it to be copied (replicated). So it seems that the hyp7/rhl gene has a key part in enabling plant cells to make multiple copies of their DNA and so is vital to cell expansion and normal developmen.

Dr Sugimoto-Shirasu concludes, “our discovery is an exciting and important piece in the much larger jigsaw of understanding how plants, which are full of complex tissues and organs, develop from the same relatively simple starting point – the cell. The more we understand about plant development the better placed we are to modify crop plants to be more productive and less dependent on chemical and other inputs”.

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John Innes Centre(JIC), Norwich, UK