Metabolite-mediated TOR signaling regulates the circadian clock in Arabidopsis

Circadian clocks usually run with a period close to 24 h, but are also plastic and can be entrained by external environmental conditions and internal physiological cues. Two key nutrient metabolites, glucose and vitamin B3 (nicotinamide), can influence the circadian period in both mammals and plants; however, the underlying molecular mechanism is still largely unclear. We reveal that the target of rapamycin (TOR) kinase, a conserved central growth regulator, is essential for glucose- and nicotinamide-mediated control of the circadian period in Arabidopsis. Nicotinamide affects the cytosolic adenosine triphosphate concentration, and blocks the effect of glucose-TOR energy signaling on period length adjustment, meristem activation, and root growth. Together, our results uncover a missing link between cellular metabolites, energy status, and circadian period adjustment, and identify TOR kinase as an essential energy sensor to coordinate circadian clock and plant growth.