How Does Stress Impact the Circadian Clock?

If you never time up with your partner when to have sex, this means that your inner clocks are not synchronized. Many of us tune our activities after a social schedule: we wake up, work, eat, have fun, make love following the social rhythm, which many times does not correspond to our inner clocks. Inner rhythms are determined by the sunlight and by hormones. Our biological cycles impact our capacities, emotional state, intellectual efficiency and sex drive. Interferences in these rhythms perturb our character and mood.

Now, a team at the University of Cambridge has discovered a molecule that may dictate how the plants' circadian clock react to external changes. A signaling molecule involved in reaction to environmental stress proved to control also plants' circadian clock, perhaps by bringing information about environmental stress into the biological clock controlling the plant physiology.

In both plants and animals, the circadian clock means a variation of gene activity (turn on and off) in cycles that last 24 hours. But in this case, it was not a gene (or its protein product) involved, but a small cellular signaling molecule: the cyclic adenosine diphosphate ribose (cADPR).

Circadian clocks seem to be more than patterns of gene expressions, but cell signaling networks. The right functioning of the plant circadian clock can double plant productivity by boosting photosynthesis. In plants, the circadian clock also controls the seasonal flowering and seed production.

The manipulation of cADPR signaling impaired the circadian clock. Without cADPR, the clock functioned slower. Environmental stress factors, such as drought and salinity, affected the clock through the signals transmitted by cADPR. This way, the cells adjusted their circadian clock, permitting them to survive the stress.

"The biological clock is thought to be essential for plant life and so it is essential to discover how it works. In our study we have identified a new type of circadian clock component that alters the concept of circadian clock architecture", said Dr. Antony Dodd from the Department of Plant Sciences, at Cambridge University.