Front. Plant Sci., 23 August 2017 | https://doi.org/10.3389/fpls.2017.01469
The genetic modifications through breeding of crop plants have long been used to improve the yield and quality. However, precise genome editing (GE) could be a very useful supplementary tool for improvement of crop plants by targeted genome modifications. Various GE techniques including ZFNs (zinc finger nucleases), TALENs (transcription activator-like effector nucleases), and most recently clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 (CRISPR-associated protein 9)-based approaches have been successfully employed for various crop plants including fruit trees. CRISPR/Cas9-based approaches hold great potential in GE due to their simplicity, competency, and versatility over other GE techniques. However, to the best of our knowledge no such genetic improvement has ever been developed in date palm—an important fruit crop in Oasis agriculture. The applications of CRISPR/Cas9 can be a challenging task in date palm GE due to its large and complex genome, high rate of heterozygosity and outcrossing, in vitro regeneration and screening of mutants, high frequency of single-nucleotide polymorphism in the genome and ultimately genetic instability. In this review, we addressed the potential application of CRISPR/Cas9-based approaches in date palm GE to improve the sustainable date palm production. The availability of the date palm whole genome sequence has made it feasible to use CRISPR/Cas9 GE approach for genetic improvement in this species. Moreover, the future prospects of GE application in date palm are also addressed in this review.
FIGURE 1. The CRISPR/Cas9-based resistance model in date palm depicting the recognition and disruption of the pathogen genetic material in three steps: acquisition, expression, and interference). During acquisition the invading DNA is integrated and duplicated into the CRISPR-locus at the leader side. The expression step involves the active transcription and expression of pre-CRISPR RNA (Pre-crRNA), which is further processed into mature crRNAs specifically with the help of different Cas proteins. During the third step of interference, any complementary target region of the foreign genetic material is recognized and cleaved as guided by crRNA and Cas9 protein.