Transcriptome and Metabolome Dynamics of Mango Fruit Response to Cold Storage

Cold storage is considered the most effective method for prolonging fresh produce storage. However, subtropical fruit is sensitive to cold. The response of ‘Keitt’ mango fruit to chilling stress was monitored by transcriptomic, volatiles metabolomics, physiological and microscopic analyses. Transcriptomic changes in mango fruit peel were evaluated during optimal (12°C) and suboptimal (5°C) cold storage. Two days exposure to chilling stress lead to upregulation of genes involved in the plant stress response, including those encoding to transmembrane receptors, calcium-mediated signal transduction, NADPH oxidase, MAP kinases and WRKYs, which can lead to cell death. Indeed, cell death was observed around the chilling injuries of discolored lenticels after 19 days of cold storage at 5°C. This cell death and cuticular opening in the lumen of discolored lenticels were correlated with increased general decay during shelf-life storage, possibly due to an earlier fungal penetration. We also observed increased phenolics accumulation around the discolored lenticels, which was correlated with the biosynthesis of phenylpropanoids that were probably transported from the resin ducts. Increased lipid peroxidation was observed during chilling injury by both biochemical and a new non-destructive luminescent technology. This lipid peroxidation was correlated to upregulation of fatty acid oxidation pathways and several volatiles, detected by GC-MS, that elevate during suboptimal cold storage and before the chilling symptom appears. This analysis provides an in-depth characterization of mango fruit response to chilling stress and could lead to the development of new tools, treatments and strategies to prolong cold storage of subtropical fruit.