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  • The EMBO Journal (2004) 23, 2304 - 2313
  • doi:10.1038/sj.emboj.7600236

Published online: 13 May 2004

Molecular analysis of telomere fusions in Arabidopsis: multiple pathways for chromosome end-joining

Michelle Heacock1,a, Elizabeth Spangler1,2,a, Karel Riha3, Jasna Puizina3 and Dorothy E Shippen1

  1. Department of Biochemistry and Biophysics, Texas A&M University, TAMU, College Station, TX, USA
  2. Department of Veterinary Pathobiology, Texas A&M University, College Station, TX, USA
  3. Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences Rennweg 14, Vienna, Austria

Correspondence to:

Dorothy E Shippen, Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA. Tel.: +1 979 862 2342; Fax: +1 979 845 9274; E-mail: dshippen@tamu.edu

aThese authors contributed equally to this work

Received 30 January 2004; Accepted 21 April 2004

End-to-end fusion of critically shortened telomeres in higher eucaryotes is presumed to be mediated by nonhomologous end-joining (NHEJ). Here we describe two PCR-based methods to monitor telomere length and examine the fate of dysfunctional telomeres in Arabidopsis lacking the catalytic subunit of telomerase (TERT) and the DNA repair proteins Ku70 and Mre11. Primer extension telomere repeat amplification relies on the presence of an intact G-overhang, and thus measures functional telomere length. The minimum functional telomere length detected was 300–400 bp. PCR amplification and sequence analysis of chromosome fusion junctions revealed exonucleolytic digestion of dysfunctional ends prior to fusion. In ku70 tert mutants, there was a greater incidence of microhomology at the fusion junction than in tert mutants. In triple ku70 tert mre11 mutants, chromosome fusions were still detected, but microhomology at the junction was no longer favored. These data indicate that both Ku70 and Mre11 contribute to fusion of critically shortened telomeres in higher eucaryotes. Furthermore, Arabidopsis processes critically shortened telomeres as double-strand breaks, using a variety of end-joining pathways.

  • Keywords:

    • Ku70,
    • Mre11,
    • NHEJ,
    • telomerase,
    • telomeres