Abstract
Diverse organisms possess a circadian clock system that arrows them to coordinate physiological events with environmental day/night cycles. In plants too, the circadian clock has recently been characterized at the molecular level. To extend such studies further, here we employed an established Arabidopsis cell line (named T87). When T87 cells were grown in an appropriate light and dark (LD) cycle, cell autonomous diurnal oscillations of the APRR1/TOC1 quintet genes were observed at the level of transcription, as are in intact plants. These phenomena were verified by monitoring CCA1::LUC and APRRs::LUC bioluminescence activity in transgenic cell lines. We showed that the properties of rhythms in cultured cells consistently fulfilled the diagnostic criteria of the circadian clock, namely, 'free-running', 'entrainment', and 'temperature compensation'. This is the first indication of cell autonomous circadian rhythms in cultured cells, which will provide us with an alternative and advantageous means to characterize the plant biological clock.clock.
