NITRATE, A NONPHOTIC SIGNAL FOR THE CIRCADIAN SYSTEM

Recent advances in circadian biology have brought insights into the mo lecular mechanisms involved in the generation of circadian rhythmicity . However, Little is known about the relationship between these molecu lar oscillators and the organism's temporal adaptation to complex dail y environmental changes. We have studied the effects of nutrients on t he circadian system of a marine unicellular alga and found that nitrat e influences all three canonical properties of circadian rhythmicity: amplitude, phase, and period. The effects of nitrate are part of a com plex feedback loop involving both circadian input and output. These ne w aspects of circadian nutrient metabolism have important implications for our understanding of the ecological significance of circadian pro grams.