Clock and riboswitch control of THIC in tandem are essential for appropriate gauging of TDP levels under light/dark cycles in Arabidopsis

• Published in: iScience Vol. 26; no. 3; p. 106134
• Main Authors: Noordally, Zeenat, Land, Lara, Trichtinger, Celso, Dalvit, Ivan, de Meyer, Mireille, Wang, Kai, Fitzpatrick, Teresa B.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 17.03.2023; Elsevier
• Subjects: Plant biology; Plant genetics; Plant biology; Plant genetics
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2023.106134

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. [Display omitted] •We explore regulation of thiamine diphosphate levels in Arabidopsis•Time-of-day regulation of THIC expression is crucial under light/dark cycles•Temporal separation of TDP biosynthesis and transport allows for riboswitch precision•Coenzyme homeostasis within the well-studied domain of metabolic homeostasis is vital Plant genetics; Plant biology