DECAPPING PROTEIN 5 regulates the circadian clock in Arabidopsis
The Arabidopsis transcriptome must be continuously reshaped to integrate endogenous and environmental cues, including the circadian clock and ambient light. This reprogramming relies on the coordinated synthesis and degradation of mRNAs, yet the contribution of RNA decay factors to circadian regulation remains poorly characterized. Here, we show that nearly all core clock genes are high-amplitude clock-controlled genes (HA-CCGs). A meta-analysis of transcriptome-wide mRNA decay datasets revealed that HA-CCGs have consistently shorter half-lives across multiple studies. We further identify the mRNA decapping activator DECAPPING PROTEIN 5 (DCP5) as a key regulator of circadian RNA stability. Using iCLIP, we show that DCP5 binds preferentially to HA-CCG transcripts at AU-rich motifs in their 3' UTRs, thereby modulating their stability. Accordingly, the dcp5 mutant displays an extended circadian period at both physiological and molecular levels. Our findings establish mRNA decay as a post-transcriptional regulatory layer that fine-tunes the decay of multiple key transcripts within the circadian system.