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Stress-induced activation of heterochromatic transcription.

Tittel-Elmer M, Bucher E, Broger L, Mathieu O, Paszkowski J, Vaillant I - PLoS Genet. (2010)

Bottom Line: We have found that heterochromatin-associated silencing in Arabidopsis plants subjected to a particular temperature regime is released in a genome-wide manner.This occurs without alteration of repressive epigenetic modifications and does not involve common epigenetic mechanisms.Thus, our results reveal new regulatory aspects of transcriptional repression in constitutive heterochromatin and open up possibilities to identify the molecular mechanisms involved.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology, University of Geneva, Geneva, Switzerland.

ABSTRACT
Constitutive heterochromatin comprising the centromeric and telomeric parts of chromosomes includes DNA marked by high levels of methylation associated with histones modified by repressive marks. These epigenetic modifications silence transcription and ensure stable inheritance of this inert state. Although environmental cues can alter epigenetic marks and lead to modulation of the transcription of genes located in euchromatic parts of the chromosomes, there is no evidence that external stimuli can globally destabilize silencing of constitutive heterochromatin. We have found that heterochromatin-associated silencing in Arabidopsis plants subjected to a particular temperature regime is released in a genome-wide manner. This occurs without alteration of repressive epigenetic modifications and does not involve common epigenetic mechanisms. Such induced release of silencing is mostly transient, and rapid restoration of the silent state occurs without the involvement of factors known to be required for silencing initiation. Thus, our results reveal new regulatory aspects of transcriptional repression in constitutive heterochromatin and open up possibilities to identify the molecular mechanisms involved.

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Related in: MedlinePlus

Temperature shift induces transient transcriptional activation of endogenous silent loci.RNA was purified from plants of the Zurich (Zh) and Col-0 accessions after the indicated treatments. Detection of MULE-F19G14 transcripts was performed by Northern blot. Hybridization with an 18S rRNA-specific probe is shown as a loading control. Transcripts corresponding to 106B, 5S and 180-bp repeats were detected by reverse transcription-PCR (RT-PCR). Amplification of 18S rRNA was used to normalize the amounts of RNA template. Negative controls lacked reverse transcriptase (RT -).
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pgen-1001175-g003: Temperature shift induces transient transcriptional activation of endogenous silent loci.RNA was purified from plants of the Zurich (Zh) and Col-0 accessions after the indicated treatments. Detection of MULE-F19G14 transcripts was performed by Northern blot. Hybridization with an 18S rRNA-specific probe is shown as a loading control. Transcripts corresponding to 106B, 5S and 180-bp repeats were detected by reverse transcription-PCR (RT-PCR). Amplification of 18S rRNA was used to normalize the amounts of RNA template. Negative controls lacked reverse transcriptase (RT -).

Mentions: To investigate the effect of ITS on silencing of heterochromatic transcription at endogenous targets, we analyzed several silent loci that are activated in mutants impaired in TGS maintenance. First, we determined level of transcripts of a Mutator-like transposable element related locus (MULE-F19G14, AT2G15810) previously described as strongly transcriptionally activated in the TGS-deficient mutants mom1 and ddm1 [54]. We examined the levels of MULE-F19G14 transcripts in two Arabidopsis accessions Zürich and Columbia (Figure 3). The MULE-F19G14 remained silent in NTS and CTS in Zürich and in Columbia plants; however, it was strongly reactivated after ITS in both ecotypes. This suggests that the ITS-induced release of silencing is not restricted to transgenic loci and also not to a particular accession. MULE-F19G14 RNA was not detected by Northern blot in ITS+2d and ITS+7d plants, indicating that plants of both accessions were equally able to swiftly resilence this endogenous locus.


Stress-induced activation of heterochromatic transcription.

Tittel-Elmer M, Bucher E, Broger L, Mathieu O, Paszkowski J, Vaillant I - PLoS Genet. (2010)

Temperature shift induces transient transcriptional activation of endogenous silent loci.RNA was purified from plants of the Zurich (Zh) and Col-0 accessions after the indicated treatments. Detection of MULE-F19G14 transcripts was performed by Northern blot. Hybridization with an 18S rRNA-specific probe is shown as a loading control. Transcripts corresponding to 106B, 5S and 180-bp repeats were detected by reverse transcription-PCR (RT-PCR). Amplification of 18S rRNA was used to normalize the amounts of RNA template. Negative controls lacked reverse transcriptase (RT -).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2965753&req=5

pgen-1001175-g003: Temperature shift induces transient transcriptional activation of endogenous silent loci.RNA was purified from plants of the Zurich (Zh) and Col-0 accessions after the indicated treatments. Detection of MULE-F19G14 transcripts was performed by Northern blot. Hybridization with an 18S rRNA-specific probe is shown as a loading control. Transcripts corresponding to 106B, 5S and 180-bp repeats were detected by reverse transcription-PCR (RT-PCR). Amplification of 18S rRNA was used to normalize the amounts of RNA template. Negative controls lacked reverse transcriptase (RT -).
Mentions: To investigate the effect of ITS on silencing of heterochromatic transcription at endogenous targets, we analyzed several silent loci that are activated in mutants impaired in TGS maintenance. First, we determined level of transcripts of a Mutator-like transposable element related locus (MULE-F19G14, AT2G15810) previously described as strongly transcriptionally activated in the TGS-deficient mutants mom1 and ddm1 [54]. We examined the levels of MULE-F19G14 transcripts in two Arabidopsis accessions Zürich and Columbia (Figure 3). The MULE-F19G14 remained silent in NTS and CTS in Zürich and in Columbia plants; however, it was strongly reactivated after ITS in both ecotypes. This suggests that the ITS-induced release of silencing is not restricted to transgenic loci and also not to a particular accession. MULE-F19G14 RNA was not detected by Northern blot in ITS+2d and ITS+7d plants, indicating that plants of both accessions were equally able to swiftly resilence this endogenous locus.

Bottom Line: We have found that heterochromatin-associated silencing in Arabidopsis plants subjected to a particular temperature regime is released in a genome-wide manner.This occurs without alteration of repressive epigenetic modifications and does not involve common epigenetic mechanisms.Thus, our results reveal new regulatory aspects of transcriptional repression in constitutive heterochromatin and open up possibilities to identify the molecular mechanisms involved.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Biology, University of Geneva, Geneva, Switzerland.

ABSTRACT
Constitutive heterochromatin comprising the centromeric and telomeric parts of chromosomes includes DNA marked by high levels of methylation associated with histones modified by repressive marks. These epigenetic modifications silence transcription and ensure stable inheritance of this inert state. Although environmental cues can alter epigenetic marks and lead to modulation of the transcription of genes located in euchromatic parts of the chromosomes, there is no evidence that external stimuli can globally destabilize silencing of constitutive heterochromatin. We have found that heterochromatin-associated silencing in Arabidopsis plants subjected to a particular temperature regime is released in a genome-wide manner. This occurs without alteration of repressive epigenetic modifications and does not involve common epigenetic mechanisms. Such induced release of silencing is mostly transient, and rapid restoration of the silent state occurs without the involvement of factors known to be required for silencing initiation. Thus, our results reveal new regulatory aspects of transcriptional repression in constitutive heterochromatin and open up possibilities to identify the molecular mechanisms involved.

Show MeSH
Related in: MedlinePlus