Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Expression data from Ler and TOP1a-2 inflorescences

ABSTRACT: DNA topoisomerases release supercoils in DNA introduced during replication or transcription. How DNA topoisomerases impact transcription in the context of eukaryotic chromatin is poorly understood. In this study, using a floral stem cell model in Arabidopsis, we uncovered a role of TOP1a in Polycomb Group (PcG) protein-mediated histone lysine 27 trimethylation at, and transcriptional repression of, the stem cell maintenance gene WUSCHEL (WUS). The strong genetic interactions between a TOP1a mutant and mutations in PcG genes and the overwhelming enrichment of PcG targets among genes affected in expression in the TOP1a mutant revealed a role of TOP1a in PcG-mediated regulation. Intriguingly, not only the repression of some PcG target genes but also the expression of others requires TOP1a. The mechanism that unifies the opposing effects of TOP1a on PcG target genes appears to lie in its role in decreasing nucleosome density. Genome-wide nucleosome mapping shows that TOP1a is required for the depletion of nucleosomes at regulatory regions of genes, which probably allows the binding of factors that either recruit PcG, as we show for AGAMOUS at the WUS locus, or counteract PcG-mediated regulation. This study uncovers a strong and previously unknown connection between TOP1a and PcG. 6 samples from wild-type and TOP1a-2 inflorescences, including three biological replicates per genotype.

ORGANISM(S): Arabidopsis thaliana

SUBMITTER: Lei Gao

PROVIDER: E-GEOD-42403 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

DNA topoisomerase I affects polycomb group protein-mediated epigenetic regulation and plant development by altering nucleosome distribution in Arabidopsis.

Liu Xigang X Gao Lei L Dinh Thanh Theresa TT Shi Ting T Li Dongming D Wang Ruozhong R Guo Lin L Xiao Langtao L Chen Xuemei X

The Plant cell 20140728 7

It has been perplexing that DNA topoisomerases, enzymes that release DNA supercoils, play specific roles in development. In this study, using a floral stem cell model in Arabidopsis thaliana, we uncovered a role for TOPOISOMERASE1α (TOP1α) in Polycomb Group (PcG) protein-mediated histone 3 lysine 27 trimethylation (H3K27me3) at, and transcriptional repression of, the stem cell maintenance gene WUSCHEL (WUS). We demonstrated that H3K27me3 deposition at other PcG targets also requires TOP1α. Intri ...[more]

PMID: 25070639

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Project description:Cell-cell communication is critical for stem cell maintenance. Shoot apical meristem (SAM) located at the shoot tip harbors stem cells within the central zone (CZ). Their progeny differentiate in the adjacent peripheral zone (PZ). WUSCHEL (WUS) is a homeodomain transcription factor produced in a few cells of the organizing center (OC), located beneath the CZ. It has been shown to specify stem cell fate and also activate CLAVATA3 (CLV3) expression in cells of the CZ. CLV3 is a secreted peptide that activates a membrane bound receptor kinase-CLAVATA1 to restrict WUS transcription to the OC. It has been hypothesized that WUS activates CLV3 expression and stem cell fate in adjacent cells of the CZ by activating a non-cell autonomous signal. Contrary to this hypothesis, here we show that the WUS protein after being synthesized in cells of the OC, migrates into the superficial cell layers of the CZ where it activates CLV3 transcription by binding to its promoter elements. WUS also migrates laterally into the PZ to repress the expression of differentiation promoting transcription factors by binding to their regulatory regions. Migration of a stem cell inducing transcription factor into adjacent cells to activate a negative regulator, whereby restricting its own accumulation is unique to plant stem cell niches. While stem cell promoting transcription factor directly repressing differentiation promoting transcription factors to prevent premature differentiation of stem cell progenitors is conserved among diverse stem cell niches. A dexamethasone inducible version of WUSCHEL was used to identify its direct tragets. To analyze WUS-regulated gene expression programs at a higher spatial resolution, we introduced a dexamethasone (Dex)-inducible form of WUS consisting of the WUS protein-coding region fused to sequences coding for the ligand-binding domain of the rat glucocorticoid receptor (GR), expressed under a ubiquitous promoter (35S::WUS-GR) into apetala1-1;cauliflower1-1 (ap1-1;cal1-1) double mutant background. 35S::WUS-GR; ap1-1;cal1-1 SAMs were either treated with 10μM Dex or mock solution for four hours and RNA samples were hybridized to Arabidopsis ATH1 gene Chip (Affymmetrix). To identify putative genes that are directly regulated by WUS, in independent experiments, SAMs were simultaneously treated with 10μM Dex and 10μM Cycloheximide (Cyc), protein synthesis inhibitor and Cyc alone for four hours. A comparison of Dex-treated samples with mock identified 641 genes as differentially expressed [DEGs] (≥/≤2 fold; p < 0.01) and comparison of Dex+Cyc with Cyc identified 457 genes as DEGs (≥/≤2 fold; p < 0.01).

Dataset Information

Expression data from Ler and TOP1a-2 inflorescences

Publications

DNA topoisomerase I affects polycomb group protein-mediated epigenetic regulation and plant development by altering nucleosome distribution in Arabidopsis.

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