DNA double-strand breaks (DSBs) can be repaired by homologous recombination (HR) or by non-homologous end joining (NHEJ). The latter mechanism is the major route for DSB repair in the somatic cells... Show moreDNA double-strand breaks (DSBs) can be repaired by homologous recombination (HR) or by non-homologous end joining (NHEJ). The latter mechanism is the major route for DSB repair in the somatic cells of higher eukaryotes, including plants. If we could manipulate the balance of the DSB repair pathways towards HR on purpose, it would be possible to improve gene targeting (GT). I studied Arabidopsis mutants, which were deficient in genes involved in classical NHEJ (C-NHEJ) and back-up NHEJ (B-NHEJ). Like in mammals, B-NHEJ by proteins including AtParp facilitates micro-homology mediated end joining (MMEJ), which leads to deletions. Double mutants with mutations in both C-NHEJ and B-NHEJ still showed end joining, indicating that a third NHEJ pathway for DSBs repair must exist in plants. Though the frequency of T-DNA integration was decreased in most NHEJ mutants, unfortunately the frequency of gene targeting was not improved. Show less
