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Plant ‘thermometer’ discovered that triggers springtime budding by measuring night-time heat

last modified Nov 01, 2016 11:02 AM
A photoreceptor molecule in plant cells has been found to moonlight as a thermometer after dark – allowing plants to read seasonal temperature changes. Scientists say the discovery could help breed crops that are more resilient to the temperatures expected to result from climate change.

An international team led by SLCU scientists has discovered a ‘thermometer’ molecule that enables plants to develop according to seasonal temperature changes.

Farmers and gardeners have known for hundreds of years how responsive plants are to temperature: warm winters cause many trees and flowers to bud early, something humans have long used to predict weather and harvest times for the coming year.

The latest research pinpoints for the first time a molecular mechanism in plants that directs developmental changes as a reaction to temperature cues – often triggering the buds of spring we long to see at the end of winter.

The new findings, published today in the journal Science, show that molecules called phytochromes – used by plants cells to detect light during the day – actually change their function in darkness to become cellular temperature gauges that measure the heat of the night.

During the day, light causes the molecules to fluctuate rapidly between active and inactive states – several times a millisecond. In their active state, phytochrome molecules restrict plant growth. Once the sun goes down, these molecules change states, and the pace they change is “directly proportional to temperature” says lead researcher Dr Phil Wigge, who compares it to mercury in a thermometer. The warmer it is, the faster the molecular change – stimulating plant growth. 

The light-sensing function of phytochromes still allows plants to read seasonal changes through the varying length of daylight – and some plants rely on this. Species such as daffodils, however, have greater temperature sensitivity, and can flower months in advance during a warm winter. Wigge believes phytochrome thermo-sensing evolved after light-sensing, and co-opted the biological network already used for light-based growth during the downtime of night.     

The new findings are the culmination of twelve years of research involving scientists from Germany, Argentina and the US, as well as the Cambridge team. The work was done in a model system, a mustard plant called Arabidopsis, but Wigge says the phytochrome genes necessary for temperature sensing are found in crop plants as well.

With weather and temperatures set to become ever more unpredictable due to climate change, researchers say the discovery that this light-sensing molecule moonlights as the internal thermometer in plant cells could help us breed tougher crops.