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Internal clock regulates plants' key hormone

Scientists may be able to better understand how plants respond to changes and environmental stresses, now that researchers have discovered a link between a plant's internal time-keeper, called a circadian clock, and a hormone that is key to its survival.
/ Source: Reuters

Scientists may be able to better understand how plants respond to changes and environmental stresses, now that researchers have discovered a link between a plant's internal time-keeper, called a circadian clock, and a hormone that is key to its survival.

Researchers at the University of California-Davis found that a plant's sensitivity to the hormone auxin varied depending on the time of day, with the plant most susceptible at night.

Auxin is vital to a plant's longevity. It helps regulate a plant's growth and development, all the while aiding responses to changes in light, gravity, and water. It also assists the plant in producing fruit and dropping leaves.

The study determined the circadian clock regulates genes that oversee the production, transportation and activation of auxin in the plant.

Michael Covington, lead author of the study, said while only 10 percent of a plant's overall genome is regulated by a circadian clock, a quarter of auxin genes are guided by the clock, which is a 24-hour cycle of physiological processes.

"You already have the clock regulating a lot of different processes, but then you have it regulating auxin, which is essential to the survival of the plant, and bringing the two together is really impressive," Covington said in an interview.

In short, combining the two could allow a farmer to pick when processes happen at the best time of the day to produce a desired outcome such as enhanced growth of the plant.

Almost all living creatures follow circadian clocks, also called circadian rhythms, and plants use them to anticipate daily changes in light and temperature.

Gail McLean, who works with grant programs for plant research at USDA's Cooperative State Research, Education, and Extension Service, said the impact of the circadian clock on auxin could have an wide impact on plants.

"It's pretty surprising at how connected they are and how strong a role the clock is playing in the role of the hormone and regulating processes," said McLean. "This could have a huge implication of how we look at breeding plants."

It could help researchers develop and grow plants, know which conditions to change to help optimize production and how the plant responds to environmental changes such as drought and changes in carbon dioxide in the atmosphere, she said.

The study was partially funded by the U.S. Agriculture Department. It was published in the August issue of the journal Public Library of Science Biology.