Gene editing in tomatoes

Tomato is an effective model plant species because it possesses the qualities necessary for genetic and functional studies, but is also a food crop making what is learned more translatable for crop improvement when compared with other non-food crop models. The availability of genome sequences for many genotypes and amenability to transformation methodologies (Agrobacterium-mediated, direct DNA uptake via protoplasts, biolistics) make tomato the perfect platform to study the application of gene-editing technologies. This review includes information related to tomato transformation methodology, one of the necessary requirements for gene editing, along with the status of site-directed mutagenesis by TALENs (transcription activator-like effector nucleases) and CRISPR/Cas (clustered regularly interspaced short palindromic repeats and CRISPR-associated Proteins). In addition to the reports on proof-of-concept experiments to demonstrate the feasibility of gene editing in tomato, there are many reports that show the power of these technologies for modification of traits, such as fruit characteristics (ripening, size, and parthenocarpy), pathogen susceptibility, architecture (plant and inflorescence), and metabolic engineering. Also highlighted in this review are reports on the application of a recent CRISPR technology called base editing that allows the modification of one base pair in a gene sequence and a strategy that takes advantage of a geminivirus replicon for delivery of DNA repair template.