Enhancing tomato quality, high sugar content and GABA accumulation, with mutations in ESKs and GAD3 genes

Tomatoes are among the most widely cultivated crops worldwide, and their nutritional value has recently gained attention in the context of functional foods. In this study, we developed tomato varieties with elevated sugar content and high gamma-aminobutyric acid (GABA) levels using a genome editing technique to introduce mutations in SlESK and SlGAD3, aiming to enhance the nutritional value of tomatoes. Tomato plants possess three ESK homologs. We successfully generated tomatoes with mutations in all three SlESK genes and a separate line with a mutation in SlGAD3. Compared to the wild type (WT), which exhibited a sugar content of approximately 4.3% Brix, the mutants showed a significantly higher sugar content of approximately 7.9% Brix. GABA accumulation in the mutants was approximately five times higher than in WT. Additionally, the mutants contained 1.5 times more vitamin C than WT and demonstrated enhanced drought stress tolerance. Delayed plant growth and reduced yield were also observed in the genome-edited plants. Transcriptome analysis revealed that the expression of genes which are involved in vitamin C biosynthesis, the auxin signaling pathway, and ethylene biosynthesis were altered in the genome-edited plants. These results may contribute to cultivating high-quality tomatoes, which are expected to be in high demand.