Plants set their circadian clock in the evening to make sure they have enough energy to make it through the night, according to a new study from the University of York. The experts identified a metabolic signal that the plants use to set their “bedtime alarm.”
The researchers believe that the newly identified metabolic signal informs the plant on how much sugar is available at dusk so the plant can adjust its metabolism to survive the night.
Plants use sunlight to produce sugar through photosynthesis, and the sugar is stored up for energy during nighttime hours. It is critical for plants to be able to anticipate the duration of these dark hours so that they do not run out of energy.
Predicting sunrise and estimating the duration of the night depends on the circadian rhythm, which is a 24-hour cycle that is part of the body’s internal clock.
“We think this metabolic signal is acting rather like setting an alarm clock before bedtime to ensure the plant’s survival,” said Dr. Mike Haydon.
“Plants must coordinate photosynthetic metabolism with the daily environment and adapt rhythmic physiology and development to match carbon availability.”
To investigate how sugars alter the circadian clock, the researchers modified the sugar supply of some seedlings and measured their gene expression. They zeroed in on a set of genes regulated by the chemical compound superoxide, which is associated with metabolic activity.
Most of these genes are active in the evening, including those that regulate the circadian clock. When the experts inhibited the production of superoxide, the evening effects of sugar on the circadian clock genes were also inhibited.
“Distinguishing the effects of light and sugars in photosynthetic cells is challenging,” said Professor Ian Graham. “Our data suggest a new role for superoxide as a rhythmic sugar-related signal which acts in the evening and affects circadian gene expression and growth.”
The study is published in the journal Proceedings of the National Academy of Sciences.