Storage temperature affects metabolism of sweet corn

Temperature is one of the critical factors affecting the postharvest storage quality of sweet corn, but effects of storage temperatures have not been elucidated at the molecular level. In this study, the effects of storage at 0 °C, 4 °C and 20 °C, on quality and associated effects on the transcriptome and metabolome were investigated. Compared with storage at 20 °C, cobs stored at 0 °C and 4 °C had up-regulated expression of genes associated with cell wall disassembly (PG, PE, BMY, β-Gal) and down-regulated expression of genes involved in lignin synthesis, the up-regulation of SPP, SPS and SUS involved in sucrose synthesis, and the down-regulation of IN, FK, HXK and PFK involved in sucrose catabolism. Most of the genes involved in ethylene biosynthesis and signaling were inhibited at 0 °C, except for ERFs, while abscisic acid synthesis and signal transduction were most active at this temperature. Near-freezing temperature also maintains the integrity of the cell membrane by inhibiting the expression of PLD, PLC and LOX, which encode membrane lipid-degrading enzymes. Metabolomics and combined analysis showed that the contents of lysophospholipid, glutathione and L-ascorbic acid in sweet corn increased at low temperatures. These results provide insight into the effects of low temperatures on sweet corn quality.