engleski

Mre11 mutation causes genome instability, developmental defects and sterility in Arabidopsis thaliana, but the telomere length is unaffected

Mre11/Rad50/Xrs2 (MRX) complex has a central role in both homologous and non-homologous end-joining DNA repair pathways. This complex is important for DNA double strand breaks (DSB) repair and processing of DSBs during meiosis. Mutations in MRX complex in vertebrates are lethal. This, however, is not the case in plants, where viable mutants of the model plant Arabidopsis thaliana have been recently characterised. Interestingly, MRX complex is localised to human telomeres. Since Mre 11p has nuclease activities, there is a possibility that Mre 11p is involved in resection of the telomeric C-strand, and consequently in telomere replication or T-loop formation. In order to test the role of Mre 11p in telomere length maintenance, we characterised mutants with T-DNA insertion in MRE11 gene. Mutant plants exhibited developmental defects and were sterile. Cytogenetic analyses showed relatively high percentage of anaphase bridges in mitosis, indicative for chromosome/chromatid fusions. To investigate whether these defects were caused by telomere dysfunction, we analysed telomere structure using terminal restriction fragment analysis (TRF). Our results showed that telomere length of mre11 mutants remained unchanged and similar to the wild type. To further study genetic interactions between MRE11 and other genes involved in the telomere maintenance (TERT-telomerase reverse transcriptase, KU70 non-homologous end-joining factor), we generated mre11 ku70 and mre11 tert double mutants as well as mre11 tert ku triple mutant. These mutants are currently being examined for cytogenetic defects and telomere structure.

Mre11/Rad50/Xrs2; DNA repair; telomeres; Arabidopsis thaliana; meiosis

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