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Chromatin features of plant telomeric sequences at terminal vs. internal positions.

Majerová E, Mandáková T, Vu GT, Fajkus J, Lysak MA, Fojtová M - Front Plant Sci (2014)

Bottom Line: Chromatin of genuine telomeres displayed heterochromatic as well as euchromatic marks, while ITRs were just heterochromatic.Telomeric transcripts TERRA (G-rich) and ARRET (C-rich) were identified in both plants and their levels varied among tissues with a maximum in blossoms.Plants with substantially different proportions of internally and terminally located telomeric repeats are instrumental in clarifying the chromatin status of telomeric repeats at distinct chromosome locations.

View Article: PubMed Central - PubMed

Affiliation: Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology and Faculty of Science, Masaryk University Brno, Czech Republic.

ABSTRACT
Epigenetic mechanisms are involved in regulation of crucial cellular processes in eukaryotic organisms. Data on the epigenetic features of plant telomeres and their epigenetic regulation were published mostly for Arabidopsis thaliana, in which the presence of interstitial telomeric repeats (ITRs) may interfere with genuine telomeres in most analyses. Here, we studied the epigenetic landscape and transcription of telomeres and ITRs in Nicotiana tabacum with long telomeres and no detectable ITRs, and in Ballantinia antipoda with large blocks of pericentromeric ITRs and relatively short telomeres. Chromatin of genuine telomeres displayed heterochromatic as well as euchromatic marks, while ITRs were just heterochromatic. Methylated cytosines were present at telomeres and ITRs, but showed a bias with more methylation toward distal telomere positions and different blocks of B. antipoda ITRs methylated to different levels. Telomeric transcripts TERRA (G-rich) and ARRET (C-rich) were identified in both plants and their levels varied among tissues with a maximum in blossoms. Plants with substantially different proportions of internally and terminally located telomeric repeats are instrumental in clarifying the chromatin status of telomeric repeats at distinct chromosome locations.

No MeSH data available.


Related in: MedlinePlus

Fluorescence in situ localization of the telomeric repeats in B. antipoda and N. tabacum. In B. antipoda, the telomere repeats (red) hybridize preferentially to centromeres, whereas minor signals at chromosome termini are less prominent on mitotic (A) and pachytene (B) chromosomes. The exclusive terminal location of the telomere repeats was detected on mitotic chromosomes of N. tabacum(C).
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Figure 1: Fluorescence in situ localization of the telomeric repeats in B. antipoda and N. tabacum. In B. antipoda, the telomere repeats (red) hybridize preferentially to centromeres, whereas minor signals at chromosome termini are less prominent on mitotic (A) and pachytene (B) chromosomes. The exclusive terminal location of the telomere repeats was detected on mitotic chromosomes of N. tabacum(C).

Mentions: To specify the localization of ITRs in B. antipoda, we performed FISH on extended meiotic pachytene chromosomes. FISH analysis corroborated the previous report (Mandaková et al., 2010) and showed that ITRs localized to highly condensed centromeric heterochromatin of all chromosomes (Figures 1A,B). Bal31 digestion of high molecular weight DNA confirmed the presence of large Bal31-resistant blocks comprising Arabidopsis-like TTTAGGG telomeric repeats in the B. antipoda genome (Figure 2A). Approximately 750 bp units of these ITRs were separated by NlaIV, HaeIII, and HinfI recognition sites (Figure 2B), but a considerable fraction of ITR units was not digested, forming DNA clusters of ca. 20 kb (Figure 2B). Previous cytogenetic and phylogenetic analyses showed that the B. antipoda genome has descended from eight ancestral chromosomes (n = 8) through an allopolyploid whole-genome duplication event. Due to the extensive reduction of chromosome number (presumably from n = 16 to n = 6), the six B. antipoda chromosomes represent complex mosaics of duplicated ancestral genomic blocks, reshuffled by numerous chromosome rearrangements. Based on knowledge of the exact karyotype structure of B. antipoda (Mandaková et al., 2010), we can exclude large ITR tracts as being relics of chromosome rearrangements bringing telomeres into centromere regions.


Chromatin features of plant telomeric sequences at terminal vs. internal positions.

Majerová E, Mandáková T, Vu GT, Fajkus J, Lysak MA, Fojtová M - Front Plant Sci (2014)

Fluorescence in situ localization of the telomeric repeats in B. antipoda and N. tabacum. In B. antipoda, the telomere repeats (red) hybridize preferentially to centromeres, whereas minor signals at chromosome termini are less prominent on mitotic (A) and pachytene (B) chromosomes. The exclusive terminal location of the telomere repeats was detected on mitotic chromosomes of N. tabacum(C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4219495&req=5

Figure 1: Fluorescence in situ localization of the telomeric repeats in B. antipoda and N. tabacum. In B. antipoda, the telomere repeats (red) hybridize preferentially to centromeres, whereas minor signals at chromosome termini are less prominent on mitotic (A) and pachytene (B) chromosomes. The exclusive terminal location of the telomere repeats was detected on mitotic chromosomes of N. tabacum(C).
Mentions: To specify the localization of ITRs in B. antipoda, we performed FISH on extended meiotic pachytene chromosomes. FISH analysis corroborated the previous report (Mandaková et al., 2010) and showed that ITRs localized to highly condensed centromeric heterochromatin of all chromosomes (Figures 1A,B). Bal31 digestion of high molecular weight DNA confirmed the presence of large Bal31-resistant blocks comprising Arabidopsis-like TTTAGGG telomeric repeats in the B. antipoda genome (Figure 2A). Approximately 750 bp units of these ITRs were separated by NlaIV, HaeIII, and HinfI recognition sites (Figure 2B), but a considerable fraction of ITR units was not digested, forming DNA clusters of ca. 20 kb (Figure 2B). Previous cytogenetic and phylogenetic analyses showed that the B. antipoda genome has descended from eight ancestral chromosomes (n = 8) through an allopolyploid whole-genome duplication event. Due to the extensive reduction of chromosome number (presumably from n = 16 to n = 6), the six B. antipoda chromosomes represent complex mosaics of duplicated ancestral genomic blocks, reshuffled by numerous chromosome rearrangements. Based on knowledge of the exact karyotype structure of B. antipoda (Mandaková et al., 2010), we can exclude large ITR tracts as being relics of chromosome rearrangements bringing telomeres into centromere regions.

Bottom Line: Chromatin of genuine telomeres displayed heterochromatic as well as euchromatic marks, while ITRs were just heterochromatic.Telomeric transcripts TERRA (G-rich) and ARRET (C-rich) were identified in both plants and their levels varied among tissues with a maximum in blossoms.Plants with substantially different proportions of internally and terminally located telomeric repeats are instrumental in clarifying the chromatin status of telomeric repeats at distinct chromosome locations.

View Article: PubMed Central - PubMed

Affiliation: Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology and Faculty of Science, Masaryk University Brno, Czech Republic.

ABSTRACT
Epigenetic mechanisms are involved in regulation of crucial cellular processes in eukaryotic organisms. Data on the epigenetic features of plant telomeres and their epigenetic regulation were published mostly for Arabidopsis thaliana, in which the presence of interstitial telomeric repeats (ITRs) may interfere with genuine telomeres in most analyses. Here, we studied the epigenetic landscape and transcription of telomeres and ITRs in Nicotiana tabacum with long telomeres and no detectable ITRs, and in Ballantinia antipoda with large blocks of pericentromeric ITRs and relatively short telomeres. Chromatin of genuine telomeres displayed heterochromatic as well as euchromatic marks, while ITRs were just heterochromatic. Methylated cytosines were present at telomeres and ITRs, but showed a bias with more methylation toward distal telomere positions and different blocks of B. antipoda ITRs methylated to different levels. Telomeric transcripts TERRA (G-rich) and ARRET (C-rich) were identified in both plants and their levels varied among tissues with a maximum in blossoms. Plants with substantially different proportions of internally and terminally located telomeric repeats are instrumental in clarifying the chromatin status of telomeric repeats at distinct chromosome locations.

No MeSH data available.


Related in: MedlinePlus