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What regulates our digestion?

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What causes fireflies to light up?

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How will understanding a plant's 24-hour clock aid food production?

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Humans have always measured their existence by outward signs of the passage of time, day and night or sunrise and sunset. Commonly referred to as a 24-hour clock or circadian rhythm in humans, a cluster of cells in the brain regulates our metabolism, digestion and the sleep-wake cycle.

Gaining control of this clock, researchers claim, could produce many benefits, including lowering blood pressure, improving drug metabolism, overcoming jet lag and helping shift workers function more effectively.

But, as often happens in science, key tools that are now making it possible to understand the clock's mechanism came from an unexpected direction.

Early research
Research begun in the early 1950s led to identifying the compound luciferase as the enzyme responsible for the bioluminescent "fire" of fireflies.

Decades later, researchers at the University of California-San Diego isolated and cloned the luciferase gene and subsequently developed a new molecular probe by attaching the luciferase gene to other genes in plants and animals.

This technology allowed scientists to measure activities of specific genes of interest under natural conditions and opened up a whole new way to study how genes regulate life processes.

"Biological clock" genes
More recently, researchers at the NSF Science and Technology Center at the University of Virginia and other locations were able to use the luciferase technology to show periodic cycling as a luminescent glowing when "biological clock" genes turned on and off in living plants and animals. These plants and animals, with well-studied genes, include a mustard plant (Arabidopsis thaliana) and a fruit fly species (Drosophila melanogaster).

This research has allowed new ways to precisely monitor clock gene activity and has increased our understanding of the importance of human beings' internal 24-hour clock and its role in everyone's daily life.

Plant genes and clocks
This kind of modification of plants has generated high interest in the agricultural, energy and environmental communities. Further, it is expected that scientists may soon be able to increase certain plants' value as crops or as renewable resources if they can modify those crops' growing seasons or metabolic cycles to suit seasonal conditions of specific growing areas.

Other research is trying to control the way humans' 24-hour clock synchronizes with other internal clocks (such as women's reproductive cycles) or external clocks (such as the sun) that are on different schedules. This control could be useful for people with sleep disorders or shift workers who need to stay alert while they work through the night.

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