Telomere length deregulation and enhanced sensitivity to genotoxic stress in Arabidopsis mutants deficient in Ku70.
The Ku70/80 heterodimer is a critical component of the non-homologous end-joining (NHEJ) pathway and of the telomere cap in yeast and mammals. We report the molecular characterization of the KU70 and KU80 genes in Arabidopsis and describe the consequences of a Ku70 deficiency. Arabidopsis KU70/80 genes are ubiquitously expressed and their products form stable heterodimers in vitro. Plants harboring a T-DNA insertion in KU70 exhibit no growth or developmental defects under standard growth conditions. However, mutant seedlings are hypersensitive to gamma-irradiation-induced double-strand breaks. Unexpectedly, we found that mutants are hypersensitive to methyl methanosulfonate during seed germination, but lose this sensitivity in seedlings, implying that the requirement for NHEJ varies during plant development. Lack of Ku70 results in a dramatic deregulation of telomere length control, with mutant telomeres expanding to more than twice the size of wild type by the second generation. Furthermore, in contrast to the situation in mammals, chromosome fusions are not associated with a Ku deficiency in Arabidopsis. These findings imply that Ku may play a different role in capping plant and animal telomeres.
Riha
Karel
K
Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA.
Watson
J Matthew
JM
Parkey
Jeffrey
J
Shippen
Dorothy E
DE
D000483:Alleles; D000595:Amino Acid Sequence; D034961:Antigens, Nuclear; D017360:Arabidopsis / Q000235:genetics*; D004265:DNA Helicases; D018076:DNA, Complementary / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019281:Dimerization; D005816:Genetic Complementation Test; D000072200:Ku Autoantigen; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009153:Mutagens / Q000494:pharmacology; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018075:RNA, Complementary / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D016615:Telomere / Q000648:ultrastructure
D034961:Antigens, Nuclear; D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D009153:Mutagens; D009687:Nuclear Proteins; D018075:RNA, Complementary; D029701:Saccharomyces cerevisiae Proteins; C081647:high affinity DNA-binding factor, S cerevisiae; D008741:Methyl Methanesulfonate; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen