Evaluation of the effects of ripening-related genes on fruit metabolites and the associated regulatory mechanisms in tomato

Fruit ripening, which is a complex process involving dynamic changes to metabolites, is controlled by multiple factors, including transcription factors (TFs). Several TFs are reportedly essential regulators of tomato fruit ripening. To evaluate the effects of specific TFs on metabolite accumulation during fruit ripening, CRISPR/Cas9-mediated mutagenesis was combined with metabolome and transcriptome analyses to explore regulatory mechanisms. Specifically, we generated various genetically engineered tomato lines that differed regarding metabolite contents and fruit colors. The metabolite and transcript profiles indicated that the selected TFs have distinct functions that control fruit metabolite contents, especially carotenoids and sugars. Our findings may provide new insights into the regulatory mechanisms governing tomato fruit ripening. Moreover, a mutation to ELONGATED HYPOCOTYL5 (HY5) increased the tomato fruit fructose and glucose contents by approximately 20% (relative to the wild-type levels). Our in vitro assay showed that HY5 can bind directly to the G-box cis-element in the SWEET12c promoter to activate expression, thereby modulating sugar transport. Our findings have clarified the mechanism regulating fruit metabolic networks, while also providing the theoretical basis for breeding horticultural crops that produce fruit with diverse flavors and colors.g