Role of alternative telomere lengthening unmasked in telomerase knock-out mutant plants |
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Authors: | Eva R??ková Ji?í Friml Petra Procházková Schrumpfová Ji?í Fajkus |
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Institution: | (1) Department of Functional Genomics and Proteomics, Faculty of Science, Masaryk University, Building A2 – ILBIT, Kamenice 5, 625 00 Brno, Czech Republic;(2) Institute of Biophysics ASCR, v.v.i., Královopolská 135, 61265 Brno, Czech Republic;(3) VIB Department of Plant Systems Biology, Ghent University, Technologiepark 927, 9052 Gent, Belgium |
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Abstract: | Telomeres in many eukaryotes are maintained by telomerase in whose absence telomere shortening occurs. However, telomerase-deficient
Arabidopsis thaliana mutants (Attert
−/−) show extremely low rates of telomere shortening per plant generation (250–500 bp), which does not correspond to the expected
outcome of replicative telomere shortening resulting from ca. 1,000 meristem cell divisions per seed-to-seed generation. To
investigate the influence of the number of cell divisions per seed-to-seed generation, Attert
−/− mutant plants were propagated from seeds coming either from the lower-most or the upper-most siliques (L- and U-plants) and
the length of their telomeres were followed over several generations. The rate of telomere shortening was faster in U-plants,
than in L-plants, as would be expected from their higher number of cell divisions per generation. However, this trend was
observed only in telomeres whose initial length is relatively high and the differences decreased with progressive general
telomere shortening over generations. But in generation 4, the L-plants frequently show a net telomere elongation, while the
U-plants fail to do so. We propose that this is due to the activation of alternative telomere lengthening (ALT), a process
which is activated in early embryonic development in both U- and L-plants, but is overridden in U-plants due to their higher
number of cell divisions per generation. These data demonstrate what so far has only been speculated, that in the absence
of telomerase, the number of cell divisions within one generation influences the control of telomere lengths. These results
also reveal a fast and efficient activation of ALT mechanism(s) in response to the loss of telomerase activity and imply that
ALT is probably involved also in normal plant development. |
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Keywords: | Alternative telomere lengthening ALT Replicative telomere shortening Telomerase-deficient plants |
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