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Bioluminescent organisms ranging from plants Arabidopsis
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Bioluminescent organisms ranging from plants (Arabidopsis thaliana) to flies

June 2, 2010
Bioluminescent organisms ranging from plants (Arabidopsis thaliana) to flies (Drosophila) are powerful tools for studying circadian rhythms. A circadian rhythm is the daily rhythmic activity cycle, based on 24-hour intervals, that is exhibited by many organisms. [See Related Image.]

More about this Image Dr. Steve A. Kay, a National Science Foundation (NSF)-supported researcher from the Scripps Research Institute, is studying the circadian biology of a wide range of organisms--from humans to fruit flies to plants.

Bioluminescence from a firefly is created by an enzymatic reaction that takes place in its abdomen. The enzyme responsible for this light-producing reaction is called luciferase. Luciferase uses oxygen, ATP and luciferin to generate light. The firefly's DNA contains the genetic information (gene) for the enzyme luciferase. The luciferase gene is the blueprint that an organism uses to make the luciferase protein. The DNA encoding the luciferase gene can be introduced into the genetic makeup of the other organisms. For example, Dr. Kay has introduced the gene into fruit flies, plants and bacteria. Once these genetically altered organisms contain the gene for luciferase, they can glow in the dark.

Organisms regulate their behavior and metabolism in a circadian (or 24 hour) cycle. Examples of this are a human's sleep/wake cycle or a flower's open/close cycle. The cycles are controlled by an internal circadian clock that resides within our cells. Dr. Kay's laboratory utilizes luciferase bioluminescence technology to observe what happens inside these clocks. Scientists introduce the Luciferase gene into fruit flies and plants under the direct control of the circadian clock and then, using ultra sensitive cameras, the team follows the circadian pattern of bioluminescence over time.

Dr. Kay's team introduced the Luciferase gene into fruit flies and plants under the direct control of the circadian clock. Using ultra sensitive cameras, they followed the circadian pattern of bioluminescence over time. Monitoring of circadian rhythms in fruit flies has allowed researchers to better understand how circadian clocks function in regulating biological processes. Four genes work together to form the basis of the circadian clock inside a fruit fly cell. Since we have identified the genes responsible for the circadian clock in flies, we have been able to identify these same genes in humans. A better understanding of how the clock works in animals provides the opportunity for scientists to develop treatments for clock-related disorders in humans, such as Sleep Disorders and Seasonal Affective Disorder (SADS). Understanding the clock also allows researchers to improve treatments by delivering medications at the most effective time of day. For example, giving cancer chemotherapy at the proper time of day when cancer cells are likely to divide will make a more effective cancer treatment.

This work was supported by NSF grant MCB 96-96255. The support from this grant allowed Dr. Kay to develop a sophisticated assay for defining which photoreceptors are important to signaling the circadian clock in Arabidopsis. (Year of image: 1999)


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