Carbon Dioxide Pretreatment and Cold Storage Synergistically Delay Tomato Ripening through Transcriptional Change in Ethylene-Related Genes and Respiration-Related Metabolism

The effects of CO(2) pretreatment before cold storage on tomato quality were investigated using physicochemical and transcriptome changes. Harvested tomatoes were treated with 30% or 60% CO(2) for 3 h before storage at 4 °C for 14 d (cold storage), followed by transfer to 20 °C for 8 d (ambient conditions). The CO(2)-treated fruits were firmer with a better appearance than untreated fruits, even after being transferred from 4 °C storage to 20 °C for 8 d. CO(2) pretreatment coupled with cold storage synergistically delayed tomato ripening by reducing respiration and lowering lycopene production. The tomatoes treated with 30% and 60% CO(2) had fewer pits than untreated fruits after cold storage, even after being transferred to ambient conditions. Moreover, the 60% CO(2) treatment significantly suppressed the decay rate. Transcriptome and metabolome functional enrichment analyses commonly showed the involvement of CO(2)-responsive genes or metabolites in sucrose and starch metabolism, as well as biosynthesis of secondary metabolites—in particular, glycolysis reduction. The most frequently detected domain was the ethylene-responsive factor. These results indicate that altered ethylene biosynthesis and ethylene signaling, via ethylene-responsive transcription factors and respiration-related pathways, appear to control CO(2)-induced fruit quality.