TOC1 phosphorylation disproportionally enhances chromatin binding at rhythmic gene promoters.

ABSTRACT: Protein phosphorylation is a key regulatory mechanism in circadian systems. TIMING OF CAB EXPRESSION 1 (TOC1) is a core transcriptional repressor in the plant circadian system that is phosphorylated near its N terminus. Phenotype testing of TOC1 phosphosite mutants shows incomplete rescue of the short period toc1 mutant. We establish that TOC1 phosphorylation (particularly at S175) is necessary for optimal interaction with FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and PHYTOCHROME INTERACTING FACTOR 5 (PIF5) at the CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) promoter to down-regulate CCA1 expression. Expression of the closely related LATE ELONGATED HYPOCOTYL (LHY) also requires TOC1 but is independent of TOC1 phosphorylation, suggesting different TOC1-dependent gene repression

SUBMITTER: Yan J 

PROVIDER: S-EPMC12466851 | biostudies-literature | 2025 Sep

REPOSITORIES: biostudies-literature