HOW TEMPERATURE-CHANGES RESET A CIRCADIAN OSCILLATOR

Circadian rhythms control many physiological activities. The environme ntal entrainment of rhythms involves the immediate responses of clock components. Levels of the clock protein FRQ were measured in Neurospor a at various temperatures; at higher temperatures, the amount of FRQ o scillated around higher Levels. Absolute FRQ amounts thus identified d ifferent times at different temperatures, so temperature shifts corres ponded to shifts in clock time without immediate synthesis or turnover of components. Moderate temperature changes could dominate Light-to-d ark shifts in the influence of circadian timing. Temperature regulatio n of clock components could explain temperature resetting of rhythms a nd how single transitions can initiate rhythmicity from characteristic circadian phases.