Integrative N-glycomics and N-glycoproteomics landscape reveals up-regulation of complex-type N-glycosylation in the tolerance of peach fruit to chilling injury

Post-harvest chilling injury (CI) is a severe problem that causes great economic losses. The peach is an important fruit consumed worldwide but susceptible to CI under post-harvest storage, and thus serves as the typical model for CI research. Protein N-glycosylation plays a vital role under abiotic stress in plants. Here, a CI-associated up-regulation of N-glycosylation was observed in peach fruit stored at 5 ℃. An integrative N-glycomics and N-glycoproteomics analysis by reactive matrix-assisted laser desorption ionization time-of-flight mass spectrometry and ¹⁸O-labeled tagging with nano-liquid chromatography-electrospray ionization tandem mass spectrometry, respectively, was developed to provide first insights into N-glycosylation remodeling for fruit tolerance to CI. On one side, 27 N-glycans were identified by N-glycomics analysis and seven complex-type N-glycans were substantially up-regulated in CI group. On the other side, N-glycoproteomics analysis identified 1002 N-glycosites on 732 N-glycoproteins. Differential and gene set analyses revealed 88 common N-glycoproteins, based on which three KEGG pathways including metabolic pathways, amino sugar & nucleotide sugar metabolism, and protein processing in endoplasmic reticulum (ER) were highly enriched. Among N-glycoproteins in top three enriched KEGG pathways, 29 N-glycosites were anchored and nearly 80 % of them were up-regulated in CI group. The corresponding 22 hub N-glycoproteins were primarily involved in CI-related biological processes such as phytohormone signaling, redox homeostasis, biotic stress, ER quality control, cell wall metabolism, membrane lipid metabolism, and soluble sugar metabolism. Taken together, up-regulation of N-glycosylation, particularly complex-type N-glycosylation, as cellular responses to enhance chilling resistance may provide novel molecular insights and thus potential post-harvest solutions.