RAD50 function is essential for telomere maintenance in Arabidopsis

We have identified and characterized an Arabidopsis thaliana and rad50 muta nt plant containing a T-DNA insertion in the AtRAD50 gene and showing both meiotic and DNA repair defects. We report here that rad50/rad50 mutant cell s show a progressive shortening of telomeric DNA relative to heterozygous r ad50/RAD50 controls and that the mutant cell population rapidly enters a cr isis, with the majority of the cells dying. Surviving rad50 mutant cells ha ve longer telomeres than wild-type cells, indicating the existence in plant s of an alternative RAD50-independent mechanism for telomere maintenance. T hese results report the role of a protein essential for double-strand break repair in telomere maintenance in higher eukaryotes.