Chapter 4 - Recent advances in precise plant genome editing technology

Abstract

Genome editing technologies include meganucleases, zing finger nucleases, transcription activation like effector like nucleases, and Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-Cas (CRISPR associated system). Out of these technologies, CRISPR/Cas is preferred due to its simplicity to execute genome editing experiments. CRISPR system comprises of Cas enzymes and guides RNA to traverse through the genome to identify a target site which matches the spacer sequence, followed by which formation of RNA/DNA hybridization and DNA cleavage at target site takes place. Cleavage by CRISPR/Cas system creates double-strand break, which is repaired either through non-homologous end joining (NHEJ) or homologous recombination (HDR). NHEJ is an error-prone DNA repair mechanism leading to random insertion and deletions, whereas HDR utilizes information provided on the donor template to precisely incorporate in the genome, hence a preferred method of genome editing. However, HDR a predominant DNA repair mechanism in meiotic cells is cell cycle-dependent; hence, HDR efficiency in somatic plants cells (cells used for genome editing reagent delivery) is low. In addition to HDR, base editors and prime editors are useful for performing precise genome editing but these methods are limited to incorporate a few nucleotide changes in the genome, hence have limited application for trait creation in plants. This chapter highlights progress made in the precise genome editing of plants and provides a future perspective on genome editing in plants. Moreover, technological advances highlighted here will be useful biofortification of rice and other crops.