Clock and riboswitch control of THIC in tandem are essential for appropriate gauging of TDP levels under light/dark cycles in Arabidopsis
Zeenat Noordally,
Lara Land,
Celso Trichtinger,
Ivan Dalvit,
Mireille de Meyer,
Kai Wang,
Teresa B. Fitzpatrick
Affiliations
Zeenat Noordally
Vitamins and Environmental Stress Responses in Plants, Department of Plant Sciences, University of Geneva, 1211 Geneva, Switzerland
Lara Land
Vitamins and Environmental Stress Responses in Plants, Department of Plant Sciences, University of Geneva, 1211 Geneva, Switzerland
Celso Trichtinger
Vitamins and Environmental Stress Responses in Plants, Department of Plant Sciences, University of Geneva, 1211 Geneva, Switzerland
Ivan Dalvit
Vitamins and Environmental Stress Responses in Plants, Department of Plant Sciences, University of Geneva, 1211 Geneva, Switzerland
Mireille de Meyer
Vitamins and Environmental Stress Responses in Plants, Department of Plant Sciences, University of Geneva, 1211 Geneva, Switzerland
Kai Wang
Vitamins and Environmental Stress Responses in Plants, Department of Plant Sciences, University of Geneva, 1211 Geneva, Switzerland
Teresa B. Fitzpatrick
Vitamins and Environmental Stress Responses in Plants, Department of Plant Sciences, University of Geneva, 1211 Geneva, Switzerland; Corresponding author
Summary: Metabolic homeostasis is regulated by enzyme activities, but the importance of regulating their corresponding coenzyme levels is unexplored. The organic coenzyme thiamine diphosphate (TDP) is suggested to be supplied as needed and controlled by a riboswitch-sensing mechanism in plants through the circadian-regulated THIC gene. Riboswitch disruption negatively impacts plant fitness. A comparison of riboswitch-disrupted lines to those engineered for enhanced TDP levels suggests that time-of-day regulation of THIC expression particularly under light/dark cycles is crucial. Altering the phase of THIC expression to be synchronous with TDP transporters disrupts the precision of the riboswitch implying that temporal separation of these processes by the circadian clock is important for gauging its response. All defects are bypassed by growing plants under continuous light conditions, highlighting the need to control levels of this coenzyme under light/dark cycles. Thus, consideration of coenzyme homeostasis within the well-studied domain of metabolic homeostasis is highlighted.
