The study presents the first single‑nucleus transcriptome atlas for the CAM plant Mesembryanthemum crystallinum, revealing cell‑type specific transcriptional changes during the C3‑to‑CAM transition. Integrating snRNA‑seq with a 24‑hour bulk RNA‑seq time course identified PPCK1 within a circadian‑enriched co‑expression network, and functional assays showed that the ice‑plant HY5 directly activates PPCK1, a regulatory relationship absent in Arabidopsis thaliana. These findings highlight a rewiring of transcriptional regulation underlying CAM evolution and provide a target for engineering drought‑resilient crops.

The study demonstrates that phosphorylation of the core circadian repressor TOC1, especially at serine 175, is essential for its interaction with FHY3 and PIF5 at the CCA1 promoter, thereby modulating CCA1 repression. While TOC1 phosphorylation is required for CCA1 regulation, LHY expression depends on TOC1 but not on its phosphostate, indicating distinct repression mechanisms. Genome-wide analyses reveal that TOC1’s phosphostate enhances chromatin association and robust rhythmic transcription.

The study demonstrates that dihydroxy B‑ring flavonoids modulate the amplitude of the core circadian clock gene reporter TOC1:LUC in Arabidopsis by affecting cellular H2O2 levels, rather than auxin transport. Reducing reactive oxygen species restored normal TOC1:LUC amplitude in flavonoid‑deficient seedlings, and altered chloroplast Ca2+ levels suggest a retrograde signaling component.