These plant molecules moonlight as internal thermometers

Daffodils are particularly temperature-sensitive plants(Credit: elenathewise/Depositphotos)

Scientists have long known that molecules known as phytochromes help plants detect light during the day and adjust growth accordingly. Now, thanks to a 12-year study involving researchers from four countries, they have discovered that the very same molecules do double duty at night, switching from light-sensors to temperature detectors. The researchers say the discovery could lead to tougher crops.

Phytochromes are something like internal brakes for plants. When phytochromes are activated by sunlight, they bind to a plant's DNA to slow its growth. That might sound counterintuitive, but when a plant is getting all the sunlight it needs, it doesn't necessarily need to grow faster. But when it's in shade and the phytochromes decouple from the DNA, growth speeds up so that the plant can reach new sources of light.

Till now researchers thought that was the only function of phytochromes and that when the sun set, the molecules simply got deactivated.

The new study says that instead, phytochromes gradually deactivate in direct proportion to the temperature in a process called "dark reversion." If it's cold out, the molecules return to their inactive state more slowly, meaning that the brakes stay on longer and the plant growth is slowed. When it's warmer out, the dark reversion is sped up. The foot (or is that root?) comes off the brake and growth speeds up.

The research was conducted using a mustard plant called Arabidopsis, which is frequently used in scientific studies (and the first plant to have its genome sequenced), but the researchers say that crops have phytochromes as well, and understanding the complete picture of how they work could help us battle difficult growing conditions brought about by climate change.

"It is estimated that agricultural yields will need to double by 2050, but climate change is a major threat to such targets," said lead researcher Dr. Philip Wigge from Cambridge University's Sainsbury Laboratory. "Key crops such as wheat and rice are sensitive to high temperatures. Thermal stress reduces crop yields by around 10 percent for every one degree increase in temperature."

"Discovering the molecules that allow plants to sense temperature has the potential to accelerate the breeding of crops resilient to thermal stress and climate change."

The work of Wigge and his team has been published in the journal Science.

The following video details the findings.

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