Accurate timekeeping is controlled by a cycling activator in Arabidopsis

Hsu, Polly Yingshan; Devisetty, Upendra Kumar; Harmer, Stacey L.

doi:10.7554/elife.00473

Cited by 186 publications

(270 citation statements)

References 61 publications

(136 reference statements)

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“…That EEs have more than one function was suggested previously based on analysis of mutant oligomerized EEs (Harmer and Kay, 2005). Also, REV8 was shown to promote transcription of genes late in the day through binding to EEs (Rawat et al, 2011;Hsu et al, 2013). Our results indicate that the EEs in CRM2 of the GI promoter are used at least twice in the circadian cycle to repress expression in the morning and to activate expression later in the day, presumably through the activity of different MYB-like transcription factors such as REV8.…”

Section: Combinatorial Activity Of Abrels and Ees In Gi Transcriptionmentioning

confidence: 94%

Evening Expression of Arabidopsis GIGANTEA Is Controlled by Combinatorial Interactions among Evolutionarily Conserved Regulatory Motifs

et al. 2014

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Section: Combinatorial Activity Of Abrels and Ees In Gi Transcriptionmentioning

confidence: 94%

Evening Expression of Arabidopsis GIGANTEA Is Controlled by Combinatorial Interactions among Evolutionarily Conserved Regulatory Motifs

et al. 2014

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“…RVE8 overexpression and mutation affect not only circadian gene expression but other clock-regulated processes such as hypocotyl elongation and the photoperiodic regulation of flowering time (15,17). Analysis of lossof-function mutants of rve8 and its close homologs (rve4/rve6/rve8 triple mutants) showed a significant lengthening of the circadian period most likely through the decreased expression of eveningphased clock genes (18). These results assigned an important activating function for the RVE protein family at the core of the clock.…”

mentioning

confidence: 84%

Time-dependent sequestration of RVE8 by LNK proteins shapes the diurnal oscillation of anthocyanin biosynthesis

Pérez-García

Yanovsky

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Circadian clocks sustain 24-h rhythms in physiology and metabolism that are synchronized with the day/night cycle. In plants, the regulatory network responsible for the generation of rhythms has been broadly investigated over the past years. However, little is known about the intersecting pathways that link the environmental signals with rhythms in cellular metabolism. Here, we examine the role of the circadian components REVEILLE8/LHY-CCA1-LIKE5 (RVE8/LCL5) and NIGHT LIGHT-INDUCIBLE AND CLOCK-REGU-LATED genes (LNK) shaping the diurnal oscillation of the anthocyanin metabolic pathway. Around dawn, RVE8 up-regulates anthocyanin gene expression by directly associating to the promoters of a subset of anthocyanin biosynthetic genes. The upregulation is overcome at midday by the repressing activity of LNK proteins, as inferred by the increased anthocyanin gene expression in lnk1/lnk2 double mutant plants. Chromatin immunoprecipitation assays using LNK and RVE8 misexpressing plants show that RVE8 binding to target promoters is precluded in LNK overexpressing plants and conversely, binding is enhanced in the absence of functional LNKs, which provides a mechanism by which LNKs antagonize RVE8 function in the regulation of anthocyanin accumulation. Based on their previously described transcriptional coactivating function, our study defines a switch in the regulatory activity of RVE8-LNK interaction, from a synergic coactivating role of eveningexpressed clock genes to a repressive antagonistic function modulating anthocyanin biosynthesis around midday.circadian clock | anthocyanin accumulation | transcriptional regulation | protein-protein interaction | Arabidopsis thaliana C ircadian clocks are broadly present in nature and allow organisms to anticipate and prepare for the predictable changes that occur during the day/night cycles (1). Synchronization by the environmental signals ensures proper coordination of metabolism and physiology in many organisms, including plants (2). In Arabidopsis, the molecular architecture depends on a complex regulatory network, in which the morning-expressed single Myb-like transcription factors, CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) (3) and LATE ELONGATED HYPOCOTYL (LHY) (4) repress the expression (5) of the evening-phased pseudoresponse regulator, TIMING OF CAB EXPRESSION 1 (TOC1/ PRR1) (6, 7). TOC1 in turn represses CCA1 and LHY (8, 9) as well as the other members of the PRR family (PRR9, 7, and 5) (10) that in turn act as repressors of CCA1 and LHY expression (11). TOC1 also represses LUX ARRHYTHMO (LUX) and EARLY FLOWERING 4 (ELF4) (9), whose protein products interact with EARLY FLOWERING 3 (ELF3) to form the socalled Evening Complex (EC) (12).Chromatin changes at the promoters of the core oscillator genes also play an important role modulating clock gene expression and function (13,14). The single Myb-like transcription factor REVEILLE8/LHY-CCA1-LIKE5 (RVE8/LCL5) (15) antagonizes CCA1 repressing function in the regulation of Histone3 acetylation at TOC1 promoter (16). RVE8 overexpressio...

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“…In the early afternoon, RVE8 directly activates transcription of PRR5, TOC1, and likely other evening phased genes (Farinas and Más, 2011;Rawat et al, 2011;Nakamichi et al, 2012;Hsu et al, 2013). RVEs are close homologs of CCA1/LHY and share Evening Element binding sites (Hsu et al, 2013). RVE8 physically interacts with NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED GENES1 (LNK1) and LNK2 during the day in a circadian manner .…”

Section: A Molecular Framework Of the Circadian Oscillatormentioning

confidence: 99%

Circadian Clock and Photoperiodic Flowering in Arabidopsis: CONSTANS Is a Hub for Signal Integration

2016

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Plants sense changes in day length (= photoperiod) as a reliable seasonal cue to regulate important developmental transitions such as flowering. Integration of various external light information into the circadian clock-controlled mechanisms enables plants to precisely measure photoperiod changes in the surrounding environment. The core mechanism of photoperiodic measurement is regulation of CONSTANS (CO) activity, which takes place in phloem companion cells in leaves. Until recently, it remained unclear whether plants possess specific variations of the clock for this regulation. Now it is known that a specific circadian timing mechanism in the vascular tissue is essential for photoperiodic flowering. In addition to spatial tissue-specific regulation, temporal regulation of CO activity is also important. The identification and characterization of multiple regulators that physically interact with CO and influence its function in the morning in long days are two recent advances in photoperiodic regulation of flowering time. It seems that CO acts as a network hub to integrate various external and internal signals into the photoperiodic flowering pathway. CO regulates the amount of FLOWERING LOCUS T (FT) transcripts and FT protein moves from companion cells of leaf phloem to the shoot apical meristem. The protein that helps long-distance transport of FT protein was also identified recently. Here, we introduce recent advances in tissue-specific variations of the circadian clock and the emerging picture of the intricate connections of transcriptional regulators through CO in the morning, which all facilitate plants knowing when to flower.Properly timing the floral transition is crucial for reproductive success. It can also influence the early development of offspring. To optimize this timing, plants constantly monitor changes in the surrounding environment. Among various environmental factors, observing changes in day length (= photoperiod) is the most reliable way for many organisms to know the specific time of year. Therefore, photoperiodic regulation is one of the major flowering time mechanisms and it has been studied since it was first reported in 1920 (Song et al., 2015). Arabidopsis (Arabidopsis thaliana), as it flowers mainly in spring, can sense lengthening days to induce flowering and became a suitable model to study photoperiodic flowering regulation. (Andrés and Coupland, 2012;Song et al., 2013;Pajoro et al., 2014;Shim and Imaizumi, 2015).In principle, photoperiodic flowering mechanisms can be divided into three parts: light input, circadian clock, and output. Light information is integrated into innate photoperiodic timing mechanisms governed by the circadian clock to induce genes that trigger flowering.

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Accurate timekeeping is controlled by a cycling activator in Arabidopsis

Cited by 186 publications

References 61 publications

Evening Expression of Arabidopsis GIGANTEA Is Controlled by Combinatorial Interactions among Evolutionarily Conserved Regulatory Motifs

Evening Expression of Arabidopsis GIGANTEA Is Controlled by Combinatorial Interactions among Evolutionarily Conserved Regulatory Motifs

Time-dependent sequestration of RVE8 by LNK proteins shapes the diurnal oscillation of anthocyanin biosynthesis

Circadian Clock and Photoperiodic Flowering in Arabidopsis: CONSTANS Is a Hub for Signal Integration

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