Applying CRISPR/Cas for genome engineering in plants: the best is yet to come

Less than 5 years ago the CRISPR/Cas nuclease was first introduced into eukaryotes, shortly becoming the most efficient and widely used tool for genome engineering. For plants, efforts were centred on obtaining heritable changes in most transformable crop species by inducing mutations into open reading frames of interest, via non-homologous end joining. Now it is important to take the next steps and further develop the technology to reach its full potential. For breeding, besides using DNA-free editing and avoiding off target effects, it will be desirable to apply the system for the mutation of regulatory elements and for more complex genome rearrangements. Targeting enzymatic activities, like transcriptional regulators or DNA modifying enzymes, will be important for plant biology in the future.