Effects of Postharvest Gibberellic Acid Treatment on Chilling Tolerance in Cold-Stored Tomato (Solanum lycopersicum L.) Fruit

Bioactive gibberellic acid (GA(3)) has been reported to mediate chilling stress responses in tomato. In this study, tomato (Solanum lycopersicum L. cv. Zhefen No. 702) fruit harvested at the mature green stage were pre-treated with 0- and 0.5-mM GA(3) solution for 15 min and then stored at 4 +/- 1 A degrees C for 28 days to investigate the molecular mechanism underlying gibberellin (GA)-induced fruit tolerance to chilling stress. Results showed that GA(3) treatment effectively reduced chilling injury (CI) index in mature green tomato fruit during long-term cold storage. Compared with the control, fruit treated with GA(3) exhibited higher tissue GA(3) levels and lower expression of the gene encoding a crucial GA signaling component and growth repressor known as DELLA protein (GAI). The expression of key GA biosynthetic genes (GA20ox1 and GA3ox1) was down-regulated, whereas the expression of GA catabolic gene (GA2ox1) was up-regulated. C-repeat/dehydration-responsive element-binding factors (CBFs) are key regulators of cold response. Transcriptional levels of CBF1 gene in GA(3)-treated fruit were higher than those of the control fruit. The elevated CBF1 expression was correlated with GA2ox1 up-regulation. Furthermore, exogenous GA(3) treatment stimulated salicylic acid (SA) biosynthesis via isochorismate synthase (ICS) pathway. The study findings suggest new opportunities for investigation into the functional role of GA signaling network in fruit tolerance to chilling stress.