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.

Department of Functional Genomics and Proteomics Faculty of Science Masaryk University Building A2 ILBIT Kamenice 5 625 00 Brno Czech Republic

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Mol Gen Genet. 1998 Dec;260(5):470-4 PubMed

Nature. 2000 Dec 14;408(6814):796-815 PubMed

Cancer Biol Ther. 2003 Nov-Dec;2(6):679-84 PubMed

Science. 2001 Mar 2;291(5509):1797-800 PubMed

Plant Cell. 1998 Oct;10(10):1691-8 PubMed

Mol Cell. 2007 Jul 6;27(1):163-9 PubMed

Biochem Biophys Res Commun. 2001 Feb 2;280(4):961-3 PubMed

PLoS Biol. 2007 May;5(5):e102 PubMed

Proc Natl Acad Sci U S A. 1999 Dec 21;96(26):14813-8 PubMed

Mol Gen Genet. 1996 Sep 13;252(3):342-5 PubMed

Hum Mol Genet. 2005 Jul 1;14(13):1785-94 PubMed

EMBO J. 2004 Jun 2;23(11):2304-13 PubMed

Plant Cell. 2004 Jan;16(1):74-87 PubMed

Chromosome Res. 2005;13(5):469-79 PubMed

Chromosoma. 2003 Oct;112(3):116-23 PubMed

Mol Cell Biol. 2007 Mar;27(5):1706-15 PubMed

Nat Cell Biol. 2007 Dec;9(12):1436-41 PubMed

Nature. 1975 May 15;255(5505):197-200 PubMed

Bioessays. 2002 Jan;24(1):27-37 PubMed

Differentiation. 2002 Jan;69(4-5):188-97 PubMed

Am J Hum Genet. 2003 Apr;72(4):940-8 PubMed

Proc Natl Acad Sci U S A. 2004 Apr 20;101(16):6080-5 PubMed

Proc Natl Acad Sci U S A. 1996 Dec 10;93(25):14422-7 PubMed

Chromosome Res. 1996 Apr;4(3):207-13 PubMed

Am J Bot. 2006 Jun;93(6):814-23 PubMed

FEBS Lett. 1996 Aug 12;391(3):307-9 PubMed

Mol Gen Genet. 1995 Jun 10;247(5):633-8 PubMed

Plant J. 2003 Oct;36(2):271-9 PubMed

Nucleic Acids Res. 1991 Mar 25;19(6):1349 PubMed

Plant J. 2003 May;34(3):283-91 PubMed

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