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PLoS Genet. 2010 Jun 10;6(6):e1000986. doi: 10.1371/journal.pgen.1000986.

siRNA-mediated methylation of Arabidopsis telomeres.

Author information

1
Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria.

Abstract

Chromosome termini form a specialized type of heterochromatin that is important for chromosome stability. The recent discovery of telomeric RNA transcripts in yeast and vertebrates raised the question of whether RNA-based mechanisms are involved in the formation of telomeric heterochromatin. In this study, we performed detailed analysis of chromatin structure and RNA transcription at chromosome termini in Arabidopsis. Arabidopsis telomeres display features of intermediate heterochromatin that does not extensively spread to subtelomeric regions which encode transcriptionally active genes. We also found telomeric repeat-containing transcripts arising from telomeres and centromeric loci, a portion of which are processed into small interfering RNAs. These telomeric siRNAs contribute to the maintenance of telomeric chromatin through promoting methylation of asymmetric cytosines in telomeric (CCCTAAA)(n) repeats. The formation of telomeric siRNAs and methylation of telomeres relies on the RNA-dependent DNA methylation pathway. The loss of telomeric DNA methylation in rdr2 mutants is accompanied by only a modest effect on histone heterochromatic marks, indicating that maintenance of telomeric heterochromatin in Arabidopsis is reinforced by several independent mechanisms. In conclusion, this study provides evidence for an siRNA-directed mechanism of chromatin maintenance at telomeres in Arabidopsis.

PMID:
20548962
PMCID:
PMC2883606
DOI:
10.1371/journal.pgen.1000986
[Indexed for MEDLINE]
Free PMC Article

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