Abstract
The circadian clock matches various biological processes to diurnal environmental cycles, such as light and temperature. Accumulating evidence shows that chromatin modification is crucial for robust circadian oscillation in plants, although chromatin modifiers involved in regulating core clock gene expression have been limitedly investigated. Here, we report that the Jumonji C domain-containing histone demethylase JMJ29, which belongs to the JHDM2/KDM3 group, shapes rhythmic changes in H3K4me3 histone marks at core clock loci in Arabidopsis. The evening-expressed JMJ29 protein interacts with the Evening Complex (EC) component EARLY FLOWERING 3 (ELF3). The EC recruits JMJ29 to the CCA1 and PRR9 promoters to catalyze the H3K4me3 demethylation at the cognate loci, maintaining a low-level expression during the evening time. Together, our findings demonstrate that interaction of circadian components with chromatin-related proteins underlies diurnal fluctuation of chromatin structures to maintain circadian waveforms in plants.
Highlights
The circadian clock is an internal timekeeping mechanism that generates biological rhythms with a period of ~24 h and synchronizes plant growth and development with environmental cycles
Accumulating evidence has supported that histone demethylase activity is important for the rhythmic oscillation of histone methylation at the core clock promoters [16]
We further explored whether JMJ29 rhythmically bound to the CLOCK–ASSOCIATED 1 (CCA1) and PRR9 promoters
Summary
The circadian clock is an internal timekeeping mechanism that generates biological rhythms with a period of ~24 h and synchronizes plant growth and development with environmental cycles. Multiple transcriptional feedback loops establish the basic architecture of the plant circadian clock. In Arabidopsis, the two morning-expressed single-MYB transcription factors, CIRCADIAN CLOCK–ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY), repress transcription of the evening-expressed TIMING. OF CAB EXPRESSION 1 (TOC1)/PSEUDO RESPONSE REGULATOR 1 (PRR1), that in turn represses CCA1 and LHY expression, forming the central loop [1,2,3,4]. A subset of the PRR family, including PRR7 and PRR9, associate with the CCA1 and LHY promoters to repress expression [5,6], and PRR5 binds to the CCA1 promoter late in the day [7]. Evening-expressed clock components, such as TOC1 and the Evening Complex (EC), contribute to repressing the morning genes [8,9,10]
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