Exogenous proline regulates the antioxidation system and fruit quality of cherry tomatoes under chilling storage: Integrated physiological, metabolomic, and transcriptomic study

Cherry tomatoes fruits suffer from chilling stress during storage. Proline (Pro) is a vital amino acid to alleviate the stress. However, the biochemical mechanisms remained unclear. A field experiment was conducted with spraying distilled water (T0) or Pro solution during the growth period (T1); mature fruits were sampled at the date of harvest (D0) and stored at 4 °C for 20 d after harvest (D1). Results showed that the alanine content was increased by 1.7 %-8.0 % while the arginine content was reduced by 12.7 %-61.5 % under D1T1 compared with D1T0. The sugar acid ratio in D0T1 vs D1T1 was reduced to 65.9 % lower than that in D0T0 vs D1T0, although Pro treatment decreased the sugar acid ratio. Multivariate analysis revealed that PC1 accounted for 93.1 % in principal component analysis. The enzymatic activity of superoxide dismutase, ascorbate peroxidase, the amino acid content of glutamate and γ-aminobutyric acid were positively related to Pro content. Integrated metabolomic and transcriptomic analysis revealed that differentially expressed metabolites and genes were enriched in phenylalanine metabolism and lignin biosynthesis pathways. <i>CCoAOMT</i> was a putative gene responsible for the changes. Applications of Pro regulated the level of relevant amino acids and antioxidants, preserving the flavor quality after chilling storage in cherry tomatoes.