Scottish scientists discover secrets of good night's cress

IT IS not only people that benefit from a good night's sleep - it seems plants also need rest too.

Scientists from the University of Edinburgh have pinpointed genes that help plants sense when it is dark and time to slow down their growth.

Their findings should help establish which plants grow best in different light conditions, especially as climate change makes it harder for some crops to flourish in altered climes.

The researchers, led by Professor Andrew Millar, used computer models of the networks of genes in a simple cress plant.

Prof Millar, of the University of Edinburgh's School of Biological Sciences, said: "By understanding the various ways in which a simple plant adapts its inner clock to the changing lengths of days in different seasons, we may be able to understand more about why some plants grow better in certain regions of the world and find new varieties to grow in other locations.

"It may also help to understand how native species will cope with climate change."

Prof Millar said, as plants used their inner clock to distinguish the length of days and work out the season, so they knew the right time to flower.

"The duration of the day is characteristic of a particular latitude," he said. "In Scotland, we benefit from these very long summer days. If you take a crop from southern Europe and bring it up here, for example because the climate is warming, its day-length measurement will no longer be appropriate for the season.

"It is expecting a maximum of a 16-hour day and here we get 18 hours. So it is important to understand how the clock is adjusted to the day-night cycle so we can predict which crop varieties might be the most useful to plant under climate change.

"We know that crop varieties are going to have to change because the temperatures go up, but you can't simply take a variety that is well adapted to a more southerly location and plant it in the north and just hope it is going to grow."

The aim was to show that certain genes take effect which allow plants to reduce their activity at night and predict when the sun will rise again.

The main genes found to be playing a part in this effect are called LHY and TOC1.

According to the team, the genes allow plants to make tiny adjustments to their internal clock as light changes.

This process is crucial in helping plants to adapt to different lengths of days and the changing seasons.

The researchers hope the discovery will help bring them a step closer to understanding other daily rhythms that affect plants and people - such as the flowering of staple crops such as wheat, barley and rice, or the patterns of human sleep.Scientists already knew that plant activity - such as growth and flowering - was controlled by an internal rhythm, known as a circadian clock.

Previous studies have shown that even the simplest of plants have a complicated internal clock, with daylight saving time built in. Prof Millar said their findings would also apply to the clocks that control many human rhythms, such as sleep cycles and blood pressure.

The study, which also involved researchers from Nagoya University in Japan, was funded by the Biotechnology and Biological Sciences Research Council and published in the journal Molecular Systems Biology.