Limits...
Telomere stability and development of ctc1 mutants are rescued by inhibition of EJ recombination pathways in a telomerase-dependent manner.

Amiard S, Olivier M, Allain E, Choi K, Smith-Unna R, Henderson IR, White CI, Gallego ME - Nucleic Acids Res. (2014)

Bottom Line: In this work, we set out to specifically test this hypothesis in the plant, Arabidopsis.It is thus the chromosomal fusions, per se, which are the underlying cause of the severe developmental defects.This rescue is mediated by telomerase-dependent telomere extension, revealing a competition between telomerase and end-joining recombination proteins for access to deprotected telomeres.

View Article: PubMed Central - PubMed

Affiliation: Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France megalleg@univ-bpclermont.fr.

Show MeSH

Related in: MedlinePlus

Absence of TERT in ctc1 mutant plants leads to telomere shortening and increased cytogenetic damage. (A) Phenotypes of the mutants six weeks after germination. (B) Images of flower pistil mitotic anaphases showing chromosome bridges with subtelomeric signal in ctc1 tert analysed by FISH with the nine subtelomeric BAC fluorescent probes (magenta). DNA is stained with DAPI (blue). Bar = 2 μm. (C) Percentages of anaphases with chromosomal bridges and the percentages of anaphases with subtelomeric signal in bridges (from three different plants in each case) of ctc1 tert. (D) TRF analysis of bulk telomere length in DNA from flower buds of CTC1 TERT, CTC1 tert, ctc1 TERT and ctc1 tert mutants using telomeric (left) the chromosome 2 subtelomeric (right) probes.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4231758&req=5

Figure 6: Absence of TERT in ctc1 mutant plants leads to telomere shortening and increased cytogenetic damage. (A) Phenotypes of the mutants six weeks after germination. (B) Images of flower pistil mitotic anaphases showing chromosome bridges with subtelomeric signal in ctc1 tert analysed by FISH with the nine subtelomeric BAC fluorescent probes (magenta). DNA is stained with DAPI (blue). Bar = 2 μm. (C) Percentages of anaphases with chromosomal bridges and the percentages of anaphases with subtelomeric signal in bridges (from three different plants in each case) of ctc1 tert. (D) TRF analysis of bulk telomere length in DNA from flower buds of CTC1 TERT, CTC1 tert, ctc1 TERT and ctc1 tert mutants using telomeric (left) the chromosome 2 subtelomeric (right) probes.

Mentions: We show here that the telomerase enzyme has the ability to elongate and stabilize dysfunctional cst- telomeres, but only in the absence of EJ recombination pathways. This suggests a competition between the telomerase and the EJ pathways for access of telomere-free ends. Considering the unexpectedly mild phenotype of early generations of the single ctc1 mutant, we hypothesized that the telomerase is to some extent elongating telomeric ends in ctc1 plants, even in the presence of EJ pathways. If this assumption is true, we should be able to observe a decrease in telomere length in the ctc1 tert double mutant. The double mutant was thus generated by crossing tert and ctc1 heterozygotes. As shown in Figure 6A, ctc1 tert plants show a mild growth defect, but interestingly they are almost completely sterile. Only 46% (55/120) of second generation ctc1 tert seeds germinate and those that do result in plantlets unable to develop beyond the ‘two cotyledons’ stage. Cytogenetic analysis revealed that 44.2% of anaphases in buds of first generation ctc1 tert present at least one bridge and that 65.15% of bridges present a subtelomeric signal (Figure 6B and C). As expected, telomere length analyses reveal more dramatic telomere degradation in ctc1 tert double mutant than in either of the single mutants (Figure 6D). These results thus argue in favour of a role for telomerase in stabilizing telomeres of ctc1 mutant plants, even in the presence of EJ recombination pathway proteins.


Telomere stability and development of ctc1 mutants are rescued by inhibition of EJ recombination pathways in a telomerase-dependent manner.

Amiard S, Olivier M, Allain E, Choi K, Smith-Unna R, Henderson IR, White CI, Gallego ME - Nucleic Acids Res. (2014)

Absence of TERT in ctc1 mutant plants leads to telomere shortening and increased cytogenetic damage. (A) Phenotypes of the mutants six weeks after germination. (B) Images of flower pistil mitotic anaphases showing chromosome bridges with subtelomeric signal in ctc1 tert analysed by FISH with the nine subtelomeric BAC fluorescent probes (magenta). DNA is stained with DAPI (blue). Bar = 2 μm. (C) Percentages of anaphases with chromosomal bridges and the percentages of anaphases with subtelomeric signal in bridges (from three different plants in each case) of ctc1 tert. (D) TRF analysis of bulk telomere length in DNA from flower buds of CTC1 TERT, CTC1 tert, ctc1 TERT and ctc1 tert mutants using telomeric (left) the chromosome 2 subtelomeric (right) probes.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4231758&req=5

Figure 6: Absence of TERT in ctc1 mutant plants leads to telomere shortening and increased cytogenetic damage. (A) Phenotypes of the mutants six weeks after germination. (B) Images of flower pistil mitotic anaphases showing chromosome bridges with subtelomeric signal in ctc1 tert analysed by FISH with the nine subtelomeric BAC fluorescent probes (magenta). DNA is stained with DAPI (blue). Bar = 2 μm. (C) Percentages of anaphases with chromosomal bridges and the percentages of anaphases with subtelomeric signal in bridges (from three different plants in each case) of ctc1 tert. (D) TRF analysis of bulk telomere length in DNA from flower buds of CTC1 TERT, CTC1 tert, ctc1 TERT and ctc1 tert mutants using telomeric (left) the chromosome 2 subtelomeric (right) probes.
Mentions: We show here that the telomerase enzyme has the ability to elongate and stabilize dysfunctional cst- telomeres, but only in the absence of EJ recombination pathways. This suggests a competition between the telomerase and the EJ pathways for access of telomere-free ends. Considering the unexpectedly mild phenotype of early generations of the single ctc1 mutant, we hypothesized that the telomerase is to some extent elongating telomeric ends in ctc1 plants, even in the presence of EJ pathways. If this assumption is true, we should be able to observe a decrease in telomere length in the ctc1 tert double mutant. The double mutant was thus generated by crossing tert and ctc1 heterozygotes. As shown in Figure 6A, ctc1 tert plants show a mild growth defect, but interestingly they are almost completely sterile. Only 46% (55/120) of second generation ctc1 tert seeds germinate and those that do result in plantlets unable to develop beyond the ‘two cotyledons’ stage. Cytogenetic analysis revealed that 44.2% of anaphases in buds of first generation ctc1 tert present at least one bridge and that 65.15% of bridges present a subtelomeric signal (Figure 6B and C). As expected, telomere length analyses reveal more dramatic telomere degradation in ctc1 tert double mutant than in either of the single mutants (Figure 6D). These results thus argue in favour of a role for telomerase in stabilizing telomeres of ctc1 mutant plants, even in the presence of EJ recombination pathway proteins.

Bottom Line: In this work, we set out to specifically test this hypothesis in the plant, Arabidopsis.It is thus the chromosomal fusions, per se, which are the underlying cause of the severe developmental defects.This rescue is mediated by telomerase-dependent telomere extension, revealing a competition between telomerase and end-joining recombination proteins for access to deprotected telomeres.

View Article: PubMed Central - PubMed

Affiliation: Génétique, Reproduction et Développement, UMR CNRS 6293, Clermont Université, INSERM U1103, Aubière, France megalleg@univ-bpclermont.fr.

Show MeSH
Related in: MedlinePlus