Genome Editing by Grafting

TL;DR

This review explores how grafting can be used to edit plant genomes without introducing foreign DNA, offering a promising new method for crop improvement.

Contribution

The paper introduces grafting as a novel, transgene-free method for delivering CRISPR components to edit plant genomes.

Findings

Grafting allows delivery of CRISPR components via RNA without integrating foreign DNA into the genome.

This method can be used for plants that are difficult to edit using traditional in vitro techniques.

The technique shows potential for improving crop breeding but faces challenges like variable efficiency and graft incompatibility.

Abstract

Grafting is the process of joining parts of two plants, allowing the exchange of molecules such as small RNAs (including microRNAs and small interfering RNAs), messenger RNAs, and proteins between the rootstock and the scion. Genome editing by grafting exploits RNAs, such as tRNA-like sequences (TLS motifs), to deliver the components (RNA) of the clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) system from transgenic rootstock to wild-type scion. The complex Cas9 protein and sgRNA-TLS produced in the scion perform the desired modification without the integration of foreign DNA in the plant genome, resulting in heritable transgene-free genome editing. In this review, we examine the current state of the art of this innovation and how it helps address regulatory problems, improves crop recovery and selection, exceeds the usage of viral vectors, and may reduce potential off-target effects. We also discuss the promise of genome editing by grafting for plants recalcitrant to in vitro culture and for agamic-propagated species that must maintain heterozygosity for plant productivity, fruit quality, and adaptation. Furthermore, we explore the limitations of this technique, including variable efficiency, graft incompatibility among genotypes, and challenges in large-scale application, while highlighting its considerable potential for further improvement and future broader applications for crop breeding.

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