Editing of the ethylene biosynthesis gene in carnation using CRISPR-Cas9 ribonucleoprotein complex

The study aimed to edit ethylene (ET) biosynthesis genes [1-aminocyclopropane-1-carboxylic acid (ACC) synthetase 1 (ACS1) and ACC oxidase 1 (ACO1)] in carnation using the CRISPR/Cas9 ribonucleoprotein (RNP) complex system. Initially, the conserved regions of the target genes (ACS1 and ACO1) were validated for the generation of different single guide RNAs (sgRNAs), followed by the use of an in vitro cleavage assay to confirm the ability of the sgRNAs to cleave the target genes specifically. The in vitro cleavage assay revealed that the sgRNAs were highly effective in cleaving their respective target regions. The complex of sgRNA: Cas9 was directly delivered into the carnation protoplast, and the target genes in the protoplast were deep-sequenced. The results revealed that the sgRNAs were applicable for editing the ET biosynthesis genes, as the mutation frequency ranged from 8.8 to 10.8% for ACO1 and 0.2-58.5% for ACS1. When sequencing the target genes in the callus derived from the protoplasts transformed with sgRNA: Cas9, different indel patterns (+ 1, - 1, and - 8 bp) in ACO1 and (- 1, + 1, and + 11) in ACS1 were identified. This study highlighted the potential application of CRISPR/Cas9 RNP complex system in facilitating precise gene editing for ET biosynthesis in carnation.