The CRISPR system has become a widely used technique to perform targeted
mutagenesis in a variety of species. However, few studies have modified
metabolic pathways in plants using the CRISPR system. China Agricultural
University researchers, led by Rui Li introduced the pYLCRISPR-Cas9 system,
with has one or more single-site guide RNAs to target the ?-aminobutyric
acid (GABA) shunt in tomatoes, which has five key genes.

The team first tested the efficiency of the pYLCRISPR-Cas9 system in
tomatoes by editing the tomato phytoene desaturase gene (slyPDS). It
resulted in an albino phenotype, suggesting the pYLCRISPR-Cas9 system's
effectiveness in tomato.

For metabolic engineering in tomatoes using multiplex CRISPR-Cas9 system,
the team developed six guide RNAs that targeted the five key genes. The
resulting CRISPR mutants had significantly higher GABA contents in the
leaves and fruits than in the wild types. Furthermore, GABA overaccumulation
significantly affected plant vegetative and reproductive growth.

These results provide new knowledge on the application of multiplex
CRISPR-Cas9 genome editing to plant metabolic engineering and reveal the
functional role of GABA in tomato growth.

[onlinelibrary.wiley.com]