Biological complexity: circadian clock root controls (Introduction)

by David Turell , Monday, April 13, 2020, 19:20 (1685 days ago) @ dhw

As usual a complex protein system:

https://phys.org/news/2020-04-small-protein-synchronizes-circadian-clocks.html

"Five years ago, researchers from the Centre for Research in Agricultural Genomics (CRAG) led by the CSIC Research Professor Paloma Mas made the breakthrough discovery that the circadian clocks in the growing tip of the plant shoot function in a similar way to the clocks in the mammalian brain, which in both cases are able to synchronize the daily rhythms of the cells in distal organs. From that seminal finding, plant researchers have been eager to discover the messenger molecule that could travel from the shoot to the root to orchestrate the rhythms...They have identified a small essential clock protein called ELF4 as the required messenger. Furthermore, through a series of ingenious experiments, the researchers discovered that the movement of this molecule is sensitive to the ambient temperature.

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"In plants, this circadian biological clock is crucial to set up the time for germination, growth and flowering, among other processes. The circadian clock is built of a set of cellular proteins whose amount and activity oscillate daily.

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"The researchers designed grafting experiments with the model plant Arabidopsis thaliana, connecting different shoots into several roots in which the clock was not working properly. These experiments allowed them to identify the clock protein ELF4, an acronym that accounts for "EARLY FLOWERING 4" as the messenger that moves from shoots to roots to convey circadian information.

"Anyone who has ever experienced jet lag, knows that the circadian biological clock is able to reset itself by environmental light cues, allowing the body to adapt to the new time zone within few days. In the same way that the circadian clock can synchronize to environmental light, it can also integrate information about ambient temperature.

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"They discovered that at lower temperatures (12C), ELF4 mobility from shoots to roots was favoured, resulting in a slow-paced root clock. Instead, when the experiments were performed at higher temperatures (28C), they observed less ELF4 movement, which lead to a faster root clock. This newly described mechanism could provide an advantage for optimal root responsiveness to temperature variations."

Comment: A marvelous system that is carefully controlled for both light availability and temperature levels. I would assume, as in all biochemistry of life, there is an sideline feedback loop not yet identified. This complex system must be originally designed or from the beginning plant roots would not have responded properly.