New understandings of circadian rhythms

July 13, 2011
Science Daily/NIH/National Institute of General Medical Sciences
A tiny plant called Arabidopsis thaliana just helped scientists unearth new clues about the daily cycles of many organisms, including humans. This is the latest in a long line of research, much of it supported by the National Institutes of Health, that uses plants to solve puzzles in human health.

While other model organisms may seem to have more in common with us, greens like Arabidopsis provide an important view into genetics, cell division and especially light sensing, which drives 24-hour behavioral cycles called circadian rhythms.
Some human cells, including cancer cells, divide with a 24-hour rhythm. One of the main human circadian rhythm genes, cryptochrome, has been associated with diabetes and depression. Both of these discoveries grew from work with plants.

Scientists aren't yet certain why night is the best time for stems to grow, but Kay speculates it has to do with using resources efficiently. Plants pick up carbon and nitrogen during the day, then store these essential nutrients as starch and proteins. "In the later night, they can release these resources in a coordinated fashion to provide the building blocks for stem growth," says Kay. "Our understanding of human health and the role of clocks in health and disease can greatly benefit from studying how clocks work in plants," he adds.

How plants like Arabidopsis suppress harmful genes may also help improve HIV therapies. A team of biologists led by Craig Pikaard at Washington University in St. Louis is investigating RNA polymerases, chemicals important in determining which genes get switched on, to learn how plants silence harmful virus-derived genes. Similar silencing pathways could be harnessed for HIV therapies.
http://www.sciencedaily.com/releases/2011/07/110713131642.htm