Table 5 Alternative genome editing systems

Base editors

It is created by combining the single-stranded DNA deaminase enzyme with dormant SpCas9 (dSpCas9), which cannot create DSBs. Base editors precisely install targeted point mutations without the need for donor DNA templates, DSBs, or HDR. Adenine base editors (ABEs) and cytosine base editors (CBEs), which transform A•T to G•C pairings and C•G to T•A pairs, respectively, are the two main subcategories of base editors

A novel selectable marker for wheat and the development of herbicide tolerance traits; Development of herbicide-tolerant rice germplasm

Zhang et al. [192]; Kuang et al. [80]

CRISPR-associated transposases

It is an engineered Cas-transposon system that combines transposase with dCas9 for programmable DNA transposition. It efficiently inserts large genomic cargos into TA motifs in the genome. However, it has limitations, including off-target cargo integration and applicability only to bacterial cells

Type V-K CRISPR-associated transposases that are specifically designed to allow for precise cut-and-paste DNA insertion

Tou et al. [163]

Prime editors

It utilizes a specialized protein called Prime Editing Protein (PEP) and a prime editing guide RNA (pegRNA) with an extension containing the desired genetic edit. PEP introduces single-strand breaks in the DNA and copies the edit from the RNA extension into the genome, offering greater accuracy and versatility compared to traditional methods like CRISPR-Cas9

Correction of phenotypes and mutations in adult mice with hepatic and ocular disorders; Deletion and replacement of long genomic sequences

Jang et al. [70]; Jiang et al. [74]