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. CCoAOMT 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. • Pro was used as an indicator of fruits in chilling stress. • Exogenous Pro decreased the sugar acid ratio drop by 66 % after chilling storage. • The antioxidants (SOD, APX, Glu, and GABA) were positively correlated with Pro. • Significant changes occurred in phenylalanine metabolism and lignin biosynthesis. • CCoAOMT was a putative gene responsible for improving the chilling storability.