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Chimeric activators and repressors define HY5 activity and a feedback control mechanism in Arabidopsis (HY5_ChIPseq)

ABSTRACT: Transcription regulation requires many protein interactions on chromatin, and only a subset of transcription factors have well-defined activation or repression domains. The Arabidopsis transcription factor HY5 controls critical growth-related gene expression programs during plant development, but it’s primary activity in regulating transcription remains unclear. To address this question, we generated constitutive repressor and activator HY5 fusion proteins to direct the expression of HY5 target genes. We used RNA-seq, ChIP-seq, and multiple phenotypes to demonstrate that HY5 depends on accessory factors to promote transcription and identify high confidence direct targets of HY5. We suggest that this strategy can be used broadly to define the transcription regulation activity and direct targets of transcription factors. Interestingly, this approach also revealed a mechanism by which HY5 promotes the accumulation of its own negative regulators. We show that HY5 directly regulates components of the COP1 E3-ubiquitin ligase complex, and by uncoupling this feedback loop we can induce partial de-etiolation in the dark. This provides a system by which plants can quickly repress growth upon light exposure. Lastly, we show that modulating this system can generate significant phenotypic diversity and provide proof of concept that these fusion proteins can modulate growth in tomato, opening a novel path toward selecting desirable traits in crop species.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE132860 | GEO | 2020/04/20

REPOSITORIES: GEO

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Chimeric activators and repressors define HY5 activity and a feedback control mechanism in Arabidopsis (HY5_RNAseq)

Project description:Transcription regulation requires many protein interactions on chromatin, and only a subset of transcription factors have well-defined activation or repression domains. The Arabidopsis transcription factor HY5 controls critical growth-related gene expression programs during plant development, but it’s primary activity in regulating transcription remains unclear. To address this question, we generated constitutive repressor and activator HY5 fusion proteins to direct the expression of HY5 target genes. We used RNA-seq, ChIP-seq, and multiple phenotypes to demonstrate that HY5 depends on accessory factors to promote transcription and identify high confidence direct targets of HY5. We suggest that this strategy can be used broadly to define the transcription regulation activity and direct targets of transcription factors. Interestingly, this approach also revealed a mechanism by which HY5 promotes the accumulation of its own negative regulators. We show that HY5 directly regulates components of the COP1 E3-ubiquitin ligase complex, and by uncoupling this feedback loop we can induce partial de-etiolation in the dark. This provides a system by which plants can quickly repress growth upon light exposure. Lastly, we show that modulating this system can generate significant phenotypic diversity and provide proof of concept that these fusion proteins can modulate growth in tomato, opening a novel path toward selecting desirable traits in crop species.

2020-04-20 | GSE132859 | GEO

DET1-mediated COP1 regulation avoids HY5 activity over second-site targets to tune plant photomorphogenesis

Project description:DE-ETIOLATED1 (DET1) is a negative regulator of plant photomorphogenesis acting as a component of the C3D complex, which can further associate to CULLIN4 to form a CRL4C3D E3 ubiquitin ligase. CRL4C3D is thought to act together with CRL4COP1SPA ubiquitin ligase, to promote the ubiquitin-mediated degradation of the master regulatory transcription factor ELONGATED HYPOCOTYL5 (HY5), thereby controlling photomorphogenic gene regulatory networks. Yet, functional links between COP1 and DET1 have long remained elusive. Here, upon mass spectrometry identification of DET1 and COP1-associated proteins, we provide in vivo evidence that DET1 associates with COP1 to promote its destabilization, a process necessary to dampen HY5 protein abundance. By regulating HY5 over-accumulation, DET1 is critical to avoid its association to second-site loci, including many PIF3 target genes. Accordingly, excessive HY5 levels result in an increased HY5 repressive activity and are sufficient to trigger fusca-like phenotypes otherwise observed typically in COP1 and COP9 signalosome mutant seedlings. This study therefore identifies that DET1-mediated regulation of COP1 stability tunes down HY5 cistrome and avoids hyper-photomorphogenic responses that might compromise plant viability.

2021-09-09 | GSE155147 | GEO

Identification of BBX proteins as rate-limiting co-factors of HY5

Project description:As a source of both energy and environmental information, the importance for plants to monitor the incoming light is evidenced by the highly integrated nature of the light signal transduction pathway with numerous other pathways throughout plant development. One of these signal integrators is the bZIP transcription factor HY5 which holds a key role as a positive regulator of light signalling in plants. Although HY5 is described to act as a DNA-binding transcriptional regulator, the lack of any apparent transactivation domain makes it unclear how HY5 is able to accomplish its many functions. We describe the identification of three B-box containing proteins (BBX20, 21 and 22) as essential partners for HY5 dependent modulation of hypocotyl elongation, anthocyanin accumulation and transcriptional regulation. The bbx202122 triple mutant mimics the phenotypes of hy5 in the light and its strong suppression of the cop1 phenotype in darkness. Furthermore, RNA-seq experiments show that 84% of genes differentially regulated in bbx202122 are also HY5 regulated, consistent with the B-box proteins and HY5 acting interdependently.

2020-07-01 | GSE137147 | GEO

Genomic evidence reveals SPA-regulated developmental and metabolic pathways in dark-grown Arabidopsis seedlings

Project description:Background: Photomorphogenesis is repressed in the dark mainly by an E3 ubiquitin ligase complex comprising CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and four homologous proteins called SUPPRESSOR OF PHYA-105 (SPA1-SPA4) in Arabidopsis. This complex induces the ubiquitination and subsequent degradation of positively acting transcription factors (e.g., HY5, HFR1, PAP1 and others) in the dark to repress photomorphogenesis. Genomic evidence showed a large number of genes regulated by COP1 in the dark, of which many are direct targets of HY5. However, the genomic bases for the constitutive photomorphogenic phenotypes of spaQ remain unknown. Results: Here, we show that >7200 genes are differentially expressed in the spaQ background compared to wild type in the dark. Comparison of the RNAseq data between cop1 and spaQ revealed a large overlapping set of genes regulated by the COP1-SPA complex. In addition, many of the genes coordinately regulated by the COP1-SPA complex are also regulated by HY5 directly and indirectly. Moreover, a large number of genes (~2790) are predominantly regulated by SPA proteins and not by COP1, suggesting that SPA proteins might regulate many biological processes independently of COP1. Conclusions: Taken together, our data reveal that SPA proteins repress photomorphogenesis by controlling expression of a large number of genes in concert with COP1, likely through regulating the abundance of downstream transcription factors in light signaling pathways. Moreover, SPA proteins may function both in a COP1-dependent and –independent manner in regulating many biological processes and developmental pathways in Arabidopsis.

2018-11-05 | GSE112662 | GEO

ChIP-chip analysis of GBF1 in the presence and absence of its heterodimerizing partners, HY5 and HYH

Project description:Transcription factors are key components of light signalling as they amplify the signal, which results in massive changes in genome-wide expression during photomorphogenesis. Three bZIP transcription factors (TFs), namely GBF1, HY5, and HYH, form heterodimers with each other and regulate photomorphogenesis in an interdependent manner. GBF1 acts as both a positive and negative regulator of photomorphogenesis, whereas HY5 and HYH mainly act as positive regulators of photomorphogenesis. In this study, the impact of heterodimerization of GBF1 with HY5 and HYH was analyzed for genome-wide binding of GBF1 through ChIP-chip in GBF1. We identified more than 2000 direct targets of GBF1 in the presence of HY5 and HYH. However, in the absence of HY5, very few binding sites were found, and in the absence of functional HYH protein, the number of GBF1 direct targets reduced to only half compared to when functional HYH was present.

2014-03-24 | GSE36965 | GEO

ChIP-chip analysis of GBF1 in the presence and absence of its heterodimerizing partners, HY5 and HYH

2014-03-24 | E-GEOD-36965 | biostudies-arrayexpress

Transcription profiling of Arabidopsis wild type, cop1-4, hy5-1 mutant seedlings exposed to polychromatic radiation

Project description:Seven-day-old white-light-grown wild-type, cop1-4 or hy5-1 mutant Arabidopsis seedlings were exposed for fifteen minutes to polychromatic radiation with decreasing short-wave cut-off in the UV range (WG305 = +UV-B, WG327 = -UV-B) and samples were taken 1 h after the onset of irradiation.

2006-08-16 | E-MEXP-557 | biostudies-arrayexpress

The JA-pathway MYC transcription factors regulate photomorphogenic responses by modulating the expression of HY5 and PIF targets

Project description:Jasmonates are key regulators of the balance between defence and growth in plants. However, the molecular mechanisms by which activation of defences reduces growth are not yet understood. Here, we analyze the role of MYC transcription factors (TFs) and JA in photomorphogenic growth. We found that multiple myc mutants share light-related phenotypes with mutants of the phytochrome B photoreceptor, regarding seed germination and hypocotyl growth. Over-expression of MYC2 in a phyB background partially suppressed its long hypocotyl phenotype. We show that the activity of MYC TFs is partially independent of COI1 and that JA inhibition of hypocotyl growth acts through alteration of auxin homeostasis and is partially independent of the classical JA signalling pathway. Transcriptomic analysis of multiple myc mutants confirmed that MYCs are required for full expression of R-light regulated genes, including the master regulator HY5. ChIP-Seq analyses revealed that MYC2 and MYC3 directly bind to the promoter of HY5 and that HY5 gene expression and protein levels are compromised in multiple myc mutants. Moreover, MYC2 and MYC3 share a high amount of direct targets with PIFs, and have an opposite effect on gene expression of these targets. Altogether, our results pinpoint MYCs as photomorphogenic TFs that regulate phytochrome responses by regulating PIFs targets and activating HY5 expression. This has important implication to understand the trade-off between growth and defence, since the same TFs that activate defence responses are photomorphogenic growth regulators.

2019-07-31 | GSE114590 | GEO

Expression data from gbf1, gbf1 hy5, and gbf1 hyh mutants

Project description:Three bZIP transcription factors (TFs), namely GBF1, HY5, and HYH, form heterodimers with each other and regulate photomorphogenesis in an interdependent manner. GBF1 acts as both a positive and negative regulator of photomorphogenesis, whereas HY5 and HYH mainly act as positive regulators of photomorphogenesis. To study the effect of HY5 and HYH on GBF1-mediated genome-wide expression, transcript profiling was performed in the gbf1 single mutant and gbf1hy5 and gbf1hyh double mutants. Our study revealed that GBF1 mainly acts antagonistic to HY5 and HYH for genome-wide expression.

2016-04-01 | GSE36964 | GEO

Analysis of transcription factor HY5 genomic binding sites in Arabidopsis

Project description:The transcription factor HY5 acts downstream of multiple families of the photoreceptors and promotes photomorphogenesis. Although it is well accepted that HY5 acts to regulate target gene expression, in vivo binding of HY5 to any of its target gene promoters has yet to be demonstrated. Here we used a chromatin immunoprecipitation procedure to verify suspected in vivo HY5 binding sites. We demonstrated that in vivo association of HY5 with promoter targets is not altered under distinct light qualities or during light-to-dark transition. Coupled with DNA chip hybridization using high density 60-nucleotide oligomer microarray that contains one probe for every 500 nucleotides over the entire Arabidopsis genome, we mapped genome wide in vivo HY5 binding sites. This analysis showed that HY5 binds preferentially to promoter regions in vivo and revealed over 3 thousand chromosomal sites as putative HY5 binding targets. HY5 binding targets tend to be enriched in the early light responsive genes and transcription factor genes. Our data thus supports a model in which HY5 is a high hierarchical regulator of the transcriptional cascades for photomorphogenesis. Keywords: ChIP-chip

2007-03-01 | GSE6510 | GEO

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