Overview of CRISPR-Cas9 technologies and its application in crop improvement

Abstract

Genome editing offers a range of solutions for more efficient development of crops that are productive, adapted to stresses, climate-resilient, and less dependent on agro-inputs. Clustered regularly interspaced short palindromic repeats (CRISPR)–CRISPR-associated protein (Cas9) technology is the current dominant tool used for genome editing. Originally, a Cas9 nuclease was employed to induce a double-strand break in its target site, causing the deletion of a few base pairs, inversion and gene integration to deliver desired changes in organisms. Aside from the primary nuclease activity (knock-in/out), a Base editor system, Gene priming and Cargo chauffeuring activities have been reported to deliver functionalities to specific regions in the DNA such as regulating transcription and fluorescence DNA for visualizing and understanding biological systems. Limitations of the scope of Cas9 activity were also eliminated by the recent development of more Cas9 orthologues (Cpf1-RR and Cpf1-RVR). Cas9 together with the advent of novel base editing tools that enable precise genome modifications and DNA-free genome editing via ribonucleoproteins demonstrate significant promise in the development of future crop improvement strategies. However, large-scale adoption of CRISPR/CAS will require optimizing strategies while accounting for costs, ease of implementation, and potential impacts on production gains. This review focuses on CRISPR application in plants, advances in CRISPR technology, regulations that may disadvantage scientists, resources for the smooth application of CRISPR and the preparedness of Africa to benefit from CRISPR technology.