Jonathan Townson

The development of programmable nucleases in the past two decades has enabled scientists to generate specific mutations to the genomes of many different organisms and tissues. Programmable nucleases including meganucleases, zinc finger nucleases (ZFNs), transcription activator like effector nucleases (TALENs) and RNA-guided engineered nucleases (RGENs), create double-stranded breaks in specific DNA sequences. Mutations can be introduced at these breaks during repair by non-homologous end joining (NHEJ) or homologous recombination (HR), this is gene editing. Application of gene editing in plants has been highly successful using programmable nucleases, with one of the main inhibitors of progress being the efficiency with which they can be transformed into plants. The more recently described RGENs were developed from clustered regularly interspaced palindromic repeat (CRISPR) sequences and CRISPR-associated (Cas) protein systems in bacteria. They provide a simple, adaptable and facile mechanism for gene editing, especially multiplex genome editing. Off-target effects are a cause for concern but the fast pace of research is quickly improving specificity and further developing CRISPR/Cas technology for other functions such as regulating gene transcription. The use of gene editing in crop plants could provide a solution towards establishing sustainable agriculture to support the worlds growing population and adapt to climate changes. Here the application of programmable nucleases in plants is reviewed and the potential future uses of CRISPR/Cas systems in plants discussed. The importance of establishing suitable regulatory procedures to deal with potentially transgene-free gene editing crops is also highlighted.