title: Temporal repression of core circadian genes is mediated through EARLY FLOWERING 3 in Arabidopsis.
abstract: The circadian clock provides robust, ∼24 hr biological rhythms throughout the eukaryotes. The clock gene circuit in plants comprises interlocking transcriptional feedback loops, reviewed in [1], whereby the morning-expressed transcription factors CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) repress the expression of evening genes, notably TIMING OF CAB EXPRESSION 1 (TOC1). EARLY FLOWERING 3 (ELF3) has been implicated as a repressor of light signaling to the clock [2, 3] and, paradoxically, as an activator of the light-induced genes CCA1 and LHY [4, 5]. We use cca1-11 lhy-21 elf3-4 plants to separate the repressive function of ELF3 from its downstream targets CCA1 and LHY. We further demonstrate that ELF3 associates physically with the promoter of PSEUDO-RESPONSE REGULATOR 9 (PRR9), a repressor of CCA1 and LHY expression, in a time-dependent fashion. The repressive function of ELF3 is thus consistent with indirect activation of LHY and CCA1, in a double-negative connection via a direct ELF3 target, PRR9. This mechanism reconciles the functions of ELF3 in the clock network during the night and points to further effects of ELF3 during the day.
authors.affiliation: Centre of Systems Biology at Edinburgh, University of Edinburgh, Edinburgh, Midlothian EH9 3JD, UK.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Dixon
authors.forename: Kirsten
authors.initials: K
authors.lastname: Knox
authors.forename: Laszlo
authors.initials: L
authors.lastname: Kozma-Bognar
authors.forename: Megan M
authors.initials: MM
authors.lastname: Southern
authors.forename: Alexandra
authors.initials: A
authors.lastname: Pokhilko
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Millar
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D057906:Circadian Clocks / Q000235:genetics / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D009154:Mutation; D030821:Plants, Genetically Modified; D011485:Protein Binding; D013997:Time Factors; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D014157:Transcription Factors; C432430:At2g25930 protein, Arabidopsis