Temporal orchestration of PRRs fine-tunes circadian pacing and anticipates environmental cues

🥈 Top 2% JournalJan 8, 2026Cell reports

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Abstract

PRR9, PRR5, and TOC1 play interchangeable roles in determining circadian pace.

Pseudo-response regulators (PRRs) in Arabidopsis are critical for regulating the circadian clock.
PRRs form both homodimers and heterodimers, with rhythmic interactions lasting about 12 hours.
Key domains, including the pseudo-receiver and CCT domains, are necessary for dimer formation.
High protein levels during specific periods are crucial for maintaining 24-hour circadian rhythms.
PRRs may quickly adapt to environmental changes, influencing transcription and protein assembly.

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The five pseudo-response regulators (PRRs) in Arabidopsis are key transcriptional repressors in regulating the circadian clock, yet the mechanisms by which they cooperate to maintain circadian homeostasis and adapt to environmental changes remains unclear. We show that PRR9, PRR5, and TOC1 have interchangeable roles in determining circadian pace through promoter swapping and chromatin immunoprecipitation assays. PRRs form homodimers and heterodimers with sequential rhythms lasting approximately 12 h, with the pseudo-receiver (PR), ethylene-responsive element-binding factor-associated amphiphilic repression motif (EAR), and C-terminal CONSTANS, CONSTANS-like, and TOC1 motif (CCT) domains being essential for dimer formation. These interactions coincide with extended periods of high protein abundance and are essential for sustaining the 24-h circadian oscillation. Based on these dynamics, we propose a "PRR escapement" model that explains the diverse circadian periods of prr mutants. Additionally, PRRs rapidly respond to environmental cues, such as light and temperature, adjusting transcription and protein-complex assembly to align growth with environmental changes.

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