Telomeres, nucleoprotein structures at the ends of linear eukaryotic chromosomes, are important for the maintenance of genomic stability. Telomeres were considered as typical heterochromatic regions, but in light of recent results, this view should be reconsidered. Asymmetrically located cytosines in plant telomeric DNA repeats may be substrates for a DNA methyltransferase enzyme and indeed, it was shown that these repeats are methylated. Here, we analyse the methylation of telomeric cytosines and the length of telomeres in Arabidopsis thaliana methylation mutants (met 1-3 and ddm 1-8), and in their wild-type siblings that were germinated in the presence of hypomethylation drugs. Our results show that cytosine methylation in telomeric repeats depends on the activity of MET1 and DDM1 enzymes. Significantly shortened telomeres occur in later generations of methylation mutants as well as in plants germinated in the presence of hypomethylation drugs, and this phenotype is stably transmitted to the next plant generation. A possible role of compromised in vivo telomerase action in the observed telomere shortening is hypothesized based on telomere analysis of hypomethylated telomerase knockout plants. Results are discussed in connection with previous data in this field obtained using different model systems.
- MeSH
- Arabidopsis enzymologie genetika metabolismus MeSH
- cytosin metabolismus MeSH
- homeostáza telomer MeSH
- metylace DNA * MeSH
- repetitivní sekvence nukleových kyselin MeSH
- rostliny genetika metabolismus MeSH
- telomerasa metabolismus MeSH
- telomery chemie metabolismus MeSH
- zkracování telomer * MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Telomere homeostasis is regulated at multiple levels, including the local chromatin structure of telomeres and subtelomeres. Recent reports demonstrated that a decrease in repressive chromatin marks, such as levels of cytosine methylation in subtelomeric regions, results in telomere elongation in mouse cells. Here we show that a considerable fraction of cytosines is methylated not only in subtelomeric, but also in telomeric DNA of tobacco BY-2 cells. Drug-induced hypomethylation (demonstrated at subtelomeric, telomeric, and global DNA levels) results in activation of telomerase. However, in contrast to mouse cells, the decrease in 5-methylcytosine levels and upregulation of telomerase do not result in any changes of telomere lengths. These results demonstrate the involvement of epigenetic mechanisms in the multilevel process of regulation of telomerase activity in plant cells and, at the same time, they indicate that changes in telomerase activity can be overridden by other factors governing telomere length stability.
- MeSH
- adenin analogy a deriváty farmakologie MeSH
- aktivace enzymů účinky léků MeSH
- cytidin analogy a deriváty farmakologie MeSH
- DNA rostlinná chemie účinky léků MeSH
- epigeneze genetická MeSH
- genetická transkripce účinky léků MeSH
- kultivované buňky MeSH
- metylace DNA účinky léků MeSH
- nukleozomy účinky léků fyziologie MeSH
- rostlinné proteiny genetika metabolismus MeSH
- tabák cytologie účinky léků genetika metabolismus MeSH
- telomerasa metabolismus MeSH
- telomery chemie účinky léků metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
