12 research outputs found
Integrative epigenomic mapping defines four main chromatin states in Arabidopsis
This first comprehensive view of the Arabidopsis epigenome reveals that it is organized into four main chromatin types based on the integrative mapping of a broad set of 11 histone marks and DNA methylation in seedlings
Detection of Transposable Element Insertions in Arabidopsis Using Sequence Capture
International audienceTransposable elements (TEs) are repetitive DNA sequences that have the ability to mobilize in the genome and create major effect mutations. Despite the importance of transposition as a source of genetic novelty, we still know little about the rate, landscape, and consequences of TE mobilization. This situation stems in large part from the repetitive nature of TEs, which complicates their analysis. Moreover, TE mobilization is typically rare and therefore new TE (i.e., non-reference) insertions tend to be missed in small-scale population studies. This chapter describes a TE-sequence capture approach designed to identify transposition events for most of the TE families that are potentially active in Arabidopsis thaliana. We show that our TE-sequence capture design provides an efficient means to detect with high sensitivity and specificity insertions that are present at a frequency as low as 1/1000 within a DNA sample
Cell Type-Specific Profiling of Chromatin Modifications and Associated Proteins
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A non-canonical role for Polycomb Repressive Complex 2 in the modulation of gene expression
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Colloque scientifique international sur le café = International conference on coffee science
Polycomb Repressive Complex 2 attenuates the very high expression of the Arabidopsis gene NRT2.1.
PRC2 is a major regulator of gene expression in eukaryotes. It catalyzes the repressive chromatin mark H3K27me3, which leads to very low expression of target genes. NRT2.1, which encodes a key root nitrate transporter in Arabidopsis, is targeted by H3K27me3, but the function of PRC2 on NRT2.1 remains unclear. Here, we demonstrate that PRC2 directly targets and down-regulates NRT2.1, but in a context of very high transcription, in nutritional conditions where this gene is one of the most highly expressed genes in the transcriptome. Indeed, the mutation of CLF, which encodes a PRC2 subunit, leads to a loss of H3K27me3 at NRT2.1 and results, exclusively under permissive conditions for NRT2.1, in a further increase in NRT2.1 expression, and specifically in tissues where NRT2.1 is normally expressed. Therefore, our data indicates that PRC2 tempers the hyperactivity of NRT2.1 in a context of very strong transcription. This reveals an original function of PRC2 in the control of the expression of a highly expressed gene in Arabidopsi
Fast coâevolution of antiâsilencing systems shapes the invasiveness of Mu âlike DNA transposons in eudicots
International audienceTransposable elements (TEs) constitute a major threat to genome stability and are therefore typically silenced by epigenetic mechanisms. In response, some TEs have evolved counteracting systems to suppress epigenetic silencing. In the model plant Arabidopsis thaliana, two such anti-silencing systems have been identified and found to be mediated by the VANC DNA-binding proteins encoded by VANDAL transposons. Here, we show that anti-silencing systems have rapidly diversified since their origin in eudicots by gaining and losing VANC-containing domains, such as DUF1985, DUF287, and Ulp1, as well as target sequence motifs. We further demonstrate that these motifs determine anti-silencing specificity by sequence, density, and helical periodicity. Moreover, such rapid diversification yielded at least 10 distinct VANC-induced anti-silencing systems in Arabidopsis. Strikingly, anti-silencing of non-autonomous VANDALs, which can act as reservoirs of 24-nt small RNAs, is critical to prevent the demise of cognate autonomous TEs and to ensure their propagation. Our findings illustrate how complex co-evolutionary dynamics between TEs and host suppression pathways have shaped the emergence of new epigenetic control mechanisms
Polycomb Repressive Complex 2 attenuates the very high expression of the Arabidopsis gene NRT2.1.
PRC2 is a major regulator of gene expression in eukaryotes. It catalyzes the repressive chromatin mark H3K27me3, which leads to very low expression of target genes. NRT2.1, which encodes a key root nitrate transporter in Arabidopsis, is targeted by H3K27me3, but the function of PRC2 on NRT2.1 remains unclear. Here, we demonstrate that PRC2 directly targets and down-regulates NRT2.1, but in a context of very high transcription, in nutritional conditions where this gene is one of the most highly expressed genes in the transcriptome. Indeed, the mutation of CLF, which encodes a PRC2 subunit, leads to a loss of H3K27me3 at NRT2.1 and results, exclusively under permissive conditions for NRT2.1, in a further increase in NRT2.1 expression, and specifically in tissues where NRT2.1 is normally expressed. Therefore, our data indicates that PRC2 tempers the hyperactivity of NRT2.1 in a context of very strong transcription. This reveals an original function of PRC2 in the control of the expression of a highly expressed gene in Arabidopsi
Direct conversion of root primordium into shoot meristem relies on timing of stem cell niche development
To understand how the identity of an organ can be switched, we studied the transformation of lateral root primordia (LRP) into shoot meristems in Arabidopsis root segments. In this system, the cytokinininduced conversion does not involve the formation of callus-like structures. Detailed analysis showed that the conversion sequence starts with a mitotic pause and is concomitant with the differential expression of regulators of root and shoot development. The conversion requires the presence of apical stem cells, and only LRP at stages VI or VII can be switched. It is engaged as soon as cell divisions resume because their position and orientation differ in the converting organ compared with the undisturbed emerging LRP. By alternating auxin and cytokinin treatments, we showed that the root and shoot organogenetic programs are remarkably plastic, as the status of the same plant stem cell niche can be reversed repeatedly within a set developmental window. Thus, the networks at play in the meristem of a root can morph in the span of a couple of cell division cycles into those of a shoot, and back, through transdifferentiation
Transposition favors the generation of large effect mutations that may facilitate rapid adaption
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