How plants know the difference between night and day

In a new study, Yale researchers shed new light on how plants use specialized photoreceptor proteins as biochemical light switches.
Soybean plants at sunset


Plants are extremely sensitive to lengths of nights and days and use the information to keep track of seasons, information crucial to their life cycles. Yale researchers shed new light on how plants use their photoreceptors as biochemical light switches in a new study published Aug. 21 in the journal Nature Communications.

In order to sense dusk, plants use photoreceptor proteins that act like light switches. In the dark, these photoreceptors turn on and degrade proteins active during daylight. However, it was unknown how these photoreceptors are turned off to restore those key proteins after sunrise.

The Yale team discovered that the same protein complex that that contains photoreceptors that degrade the proteins also contains an enzyme that functions in the exact opposite manner, stabilizing proteins. This allows the plants to carefully control the stability of important circadian clock proteins in the light and dark and provide precise information about the timing of dusk. “By carefully tracking dusk, this mechanism helps the plant determine the length of the day and thus communicates the season,” said Joshua Gendron, senior author of the paper. Gendron said the enzyme that stabilizes proteins in the light is conserved in animal species and communicates environmental information that regulates circadian rhythms in animals, a rare conservation of function.  In the future, it may be possible to use this information to engineer plants precisely attuned to the environment and better able respond to changes in climate.

Yale’s Chim-Mei Lee is first author of the paper. The work was primarily funded by the National Science Foundation and the National Institutes of Health.

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