Dear Editor,In the past few years,the use of sequence-specific nucleases for efficient targeted mutagenesis has provided plant biologists with a powerful new approach for understanding gene function and developing new traits.These nucleases create DNA double-strand breaks at chromosomal targeted sites that are primarily repaired by the non-homologous end joining (NHEJ) or homologous recombination (HR) pathways.NHEJ is often imprecise and can introduce mutations at target sites resulting in the loss of gene function.In contrast,HR uses a homologous DNA template for repair and can be employed to create site-specific sequence modifications or targeted insertions (Moynahan and Jasin,2010).