Circadian rhythms are a roughly 24-hour cycle governing biochemical, physiological, or behavioral processes that have been widely observed not only in humans, but other animals, fungi, cyanobacteria and plants. In plants, circadian rhythms help synchronize biological processes with day and night to control photosynthesis, tell the plant what season it is, and the best time to flower to attract insects. Yale University researchers have now identified a key genetic gear that keeps the circadian clock in plants ticking, offering the prospect of engineering plants that can grow all year round and in locations where that's not currently possible.

Scientists have known for some time that plants' circadian clocks operate through the cooperative relationship between "morning" genes and "evening" genes. Proteins encoded by the morning genes suppress evening genes at daybreak, but by nightfall the levels of these proteins drop and evening genes are activated again. These evening genes are actually necessary to turn the morning genes on and complete the 24-hour cycle, but scientists weren't certain of the exact processes involved. By identifying the gene DET1 as crucial in helping to suppress expression of the evening genes in the circadian cycle, the Yale researchers have solved one of the last remaining mysteries in this process.

"Plants that make less DET1 have a faster clock and they take less time to flower," said On Sun Lau, a former Yale graduate student who is now at Stanford University and is lead author of the study that appears in the Sept. 2 issue of the journal Molecular Cell. "Knowing the components of the plant's circadian clock and their roles would assist in the selection or generation of valuable traits in crop and ornamental plants."

"Farmers are limited by the seasons, but by understanding the circadian rhythm of plants, which controls basic functions such as photosynthesis and flowering, we might be able to engineer plants that can grow in different seasons and places than is currently possible," added Xing Wang Deng, the Daniel C. Eaton Professor of Molecular, Cellular, and Developmental Biology at Yale and senior author of the paper.