MAIN CONCLUSION: In tobacco, three sequence variants of the TERT gene have been described. We revealed unbalanced levels of TERT variant transcripts in vegetative tobacco tissues and enhanced TERT transcription and telomerase activity in reproductive tissues. Telomerase is a ribonucleoprotein complex responsible for the maintenance of telomeres, structures delimiting ends of linear eukaryotic chromosomes. In the Nicotiana tabacum (tobacco) allotetraploid plant, three sequence variants (paralogs) of the gene coding for the telomerase reverse transcriptase subunit (TERT) have been described, two of them derived from the maternal N. sylvestris genome (TERT_Cs, TERT_D) and one originated from the N. tomentosiformis paternal genome (TERT_Ct). In this work, we analyzed the transcription of TERT variants in correlation with telomerase activity in tobacco tissues. High and approximately comparable levels of TERT_Ct and TERT_Cs transcripts were detected in seedlings, roots, flower buds and leaves, while the transcript of the TERT_D variant was markedly underrepresented. Similarly, in N. sylvestris tissues, TERT_Cs transcript significantly predominated. A specific pattern of TERT transcripts was found in samples of tobacco pollen with the TERT_Cs variant clearly dominating particularly at the early stage of pollen development. Detailed analysis of TERT_C variants representation in functionally distinct fractions of pollen transcriptome revealed their prevalence in large ribonucleoprotein particles encompassing translationally silent mRNA; only a minority of TERT_Ct and TERT_Cs transcripts were localized in actively translated polysomes. Histones of the TERT_C chromatin were decorated predominantly with the euchromatin-specific epigenetic modification in both telomerase-positive and telomerase-negative tobacco tissues. We conclude that the existence and transcription pattern of tobacco TERT paralogs represents an interesting phenomenon and our results indicate its functional significance. Nicotiana species have again proved to be appropriate and useful model plants in telomere biology studies.
- MeSH
- buněčné jádro genetika MeSH
- chromatinová imunoprecipitace MeSH
- euchromatin metabolismus MeSH
- genetická transkripce MeSH
- genetická variace * MeSH
- histony metabolismus MeSH
- messenger RNA genetika metabolismus MeSH
- orgánová specificita genetika MeSH
- polyribozomy metabolismus MeSH
- posttranslační úpravy proteinů MeSH
- pylová láčka růst a vývoj MeSH
- regulace genové exprese u rostlin * MeSH
- tabák genetika MeSH
- telomerasa genetika metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
Telomerase, an enzyme responsible for the maintenance of linear chromosome ends, is precisely regulated during plant development. In animals, involvement of the epigenetic state of the telomerase reverse transcriptase (TERT) gene in the complex regulation of telomerase activity has been reported. To reveal whether epigenetic mechanisms participate in the regulation of plant telomerase, the relationship between telomerase activity in tissues of Arabidopsis thaliana and DNA methylation and histone modifications in the A. thaliana TERT (AtTERT) upstream region was studied. As expected, a gradual decrease of telomerase activity during leaf maturation was observed. A different pattern with a more progressive loss of telomerase activity and AtTERT transcription during leaf development was revealed in MET1 gene-knockout mutants. Analysis of DNA methylation in the AtTERT upstream region showed low levels of methylated cytosines without notable differences between telomerase-positive and telomerase-negative wild-type tissues. Surprisingly, a high level of CG methylation was found in the AtTERT coding region, although this type of methylation is a characteristic attribute of constitutively expressed genes. Analysis of chromatin modifications in the AtTERT upstream region and in exon 5 showed increased loading of the H3K27me3 mark in the telomerase-negative mature leaf compared to telomerase-positive seedlings, whereas H3K4me3, H3K9Ac, and H3K9me2 were approximately at the same level. Consistently, the chromatin structure of the AtTERT gene was maintained. These results are discussed in the context of the general involvement of epigenetic mechanisms in the regulation of gene expression and with respect to similar studies performed in animal models.
- MeSH
- Arabidopsis enzymologie genetika růst a vývoj metabolismus MeSH
- epigeneze genetická MeSH
- euchromatin metabolismus MeSH
- exony MeSH
- histony metabolismus MeSH
- metylace MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- telomerasa genetika metabolismus MeSH
- umlčování genů MeSH
- upregulace MeSH
- vývojová regulace genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Nucleosome movement is, at least in part, facilitated by ISWI ATPase Smarca5 (Snf2h). Smarca5 gene inactivation in mouse demonstrated its requirement at blastocyst stage; however its role at later stages is not completely understood. We herein determined nuclear distribution of Smarca5 and histone marks associated with actively transcribed and repressed chromatin structure in embryonic and adult murine tissues and in tumor cells. Confocal microscopy images demonstrate that Smarca5 is localized mainly in euchromatin and to lesser extent also in heterochromatin and nucleoli. Smarca5 heterozygous mice for a null allele display decreased levels of histone H3 modifications and defects in heterochromatin foci supporting role of Smarca5 as a key regulator of global chromatin structure.
- MeSH
- adenosintrifosfatasy genetika metabolismus MeSH
- blastocysta metabolismus MeSH
- buněčné jadérko metabolismus MeSH
- chromozomální proteiny, nehistonové genetika metabolismus MeSH
- euchromatin metabolismus MeSH
- heterochromatin metabolismus MeSH
- konfokální mikroskopie MeSH
- myši inbrední C57BL MeSH
- myši MeSH
- nádorové buněčné linie MeSH
- umlčování genů MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
