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TOC1 clock protein phosphorylation controls complex formation with NF-YB/C to repress hypocotyl growth

ABSTRACT: Plant photoperiodic growth is coordinated by interactions between circadian clock and light signaling networks. How post-translational modifications of clock proteins affect these interactions to mediate rhythmic growth remains unclear. Here, we identify five phosphorylation sites in the Arabidopsis core clock protein TIMING OF CAB EXPRESSION 1 (TOC1) which when mutated to alanine eliminate detectable phosphorylation. The TOC1 phospho-mutant fails to fully rescue the clock, growth and flowering phenotypes of the toc1 mutant. Further, the TOC1 phospho-mutant shows advanced phase, a faster degradation rate, reduced interactions with PHYTOCHROME INTERACTING FACTOR3 (PIF3) and HISTONE DEACETYLASE 15 (HDA15), and poor binding at pre-dawn hypocotyl-growth-related genes (PHGs), leading to a net de-repression of hypocotyl growth. NUCLEAR FACTOR Y subunits B and C (NF-YB/C) stabilize TOC1 at target promoters and this novel trimeric complex (NF-TOC1) acts as a transcriptional co-repressor with HDA15 to inhibit PIF-mediated hypocotyl elongation. Collectively, we identify a molecular mechanism suggesting how phosphorylation of TOC1 alters its phase, stability and physical interactions with co-regulators to precisely phase PHG expression to control photoperiodic hypocotyl growth.

SUBMITTER: Dr. David, Edward Somers

PROVIDER: S-SCDT-EMBOJ-2021-108684 | biostudies-other |

REPOSITORIES: biostudies-other

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