Abstract
Tomato fruit are especially susceptible to chilling injury (CI) when continuously exposed to temperatures below 12 °C. In this study, integrative comparative analyses of transcriptomics and metabolomics data were performed to uncover the regulatory network in CI tomato fruit. Metabolite profiling analysis found that 7 amino acids, 27 organic acids, 16 of sugars and 22 other compounds had a significantly different content while transcriptomics data showed 1735 differentially expressed genes (DEGs) were down-regulated and 1369 were up-regulated in cold-stored fruit. We found that the contents of citrate, cis-aconitate and succinate were increased, which were consistent with the expression of ATP-citrate synthase (ACS) and isocitrate dehydrogenase (IDH) genes in cold-treated tomato fruit. Cold stress promotes the expression of ACS and IDH which may increase the synthesis of citrate, cis-aconitate and succinate. Alanine and leucine had increased contents, which may result from alanine aminotransferase (ALT) and branched-chain amino acid aminotransferase (BcAT)’s high expression levels, respectively. Overall the transcriptomics and metabolomics data in our study explain the molecular mechanisms of the chilling injury and expands our understanding of the complex regulatory mechanisms of a metabolic network in response to chilling injury in tomato fruit.
Highlights
Low-temperature storage is one of the most effective methods to maintain the nutrients and reduce postharvest decay of fruits and vegetables
Tomato fruit stored at 4 °C (Fig. 1A) delayed the maturation process and 50% of the tomato fruit exhibited skin pitting when storage was continued at 25 °C for 3 days, mimicking the 28 days 4 °C shelf selling storage condition
The higher expression of ALT and branched-chain amino acid aminotransferase (BcAT) genes induced by cold stress may improve the synthesis of alanine and leucine in fruit, respectively
Summary
Low-temperature storage is one of the most effective methods to maintain the nutrients and reduce postharvest decay of fruits and vegetables. An expression analysis of tomato fruit with CI visual symptom after a long period of cold storage (4 weeks at 3 °C) indicated the alterations of genes involved in cell wall modifications, carotenoid biosynthesis, ethylene biosynthesis and signaling[8]. Proteomic analysis of cold storage tomato fruit indicated that the CI tolerance mechanisms were related to the accumulation of heat shock proteins (HSPs), molecular chaperones (GR-RBP), late embryogenesis abundant (LEA) proteins, and antioxidant enzymes (TPxI)[11]. Volatile analysis of tomato fruit found that cold storage reduced the production of alcohol, aldehyde, ester, ketone, terpene and acid volatile compounds, and heat shock treatment prior to chilling exposure alleviated the suppression of the key volatile compounds[13]. Integrative comparative analysis of transcriptomics and metabolomics data from cold treatment tomato fruit was conducted to gain a broader systems perspective and to identify distinct molecular regulatory response during cold storage
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