A fungal clock protein exerts extra-circadian roles in nitrogen metabolism and mitochondrial function

Protein moonlighting refers to functions in polypeptides exceeding those considered canonical roles. While this vision is changing our understanding of cellular signaling integration, in timekeeping proteins this duality, if any, remains mostly unexplored. Circadian clocks are widespread cellular machineries that converge on shared architectural principles, built around negative feedback loops involving the activity of pacemaker proteins. In fungi, FREQUENCY (FRQ) is the defining timeteller, but whether it has roles outside the clock is unknown. Here, we show that the FRQ protein of the fungal phytopathogen Botrytis cinerea also operates as a clock-independent metabolic hub. Loss of FRQ results in the inability to release Nitrogen Catabolite Repression, while the loss-of-function mutant accumulates elevated reactive oxygen species and exhibits sensitivity to mitochondria-targeting fungicides. Secondary metabolite profiles are also largely altered. Together, our findings establish that a core clock protein moonlights as a metabolic integrator, independent of its clock function, raising the question of whether metabolic scaffolding represents an underappreciated role of circadian pacemaker proteins.