Comparative metabolomics profiling reveals the molecular information of whole and fresh-cut melon fruit (cv. Xizhoumi-17) during storage

Abstract

This study aimed to elucidate the effect of cutting on the quality of melon fruit (cv. Xizhoumi-17) during storage as well as assess changes at metabolite level by an LC-MS-based comparative metabolomics profiling and multivariate analysis. A total of 93 differential metabolites were observed in whole and fresh-cut melon during storage. Among them, 10 differential metabolites were found exclusively in stored whole melon, and 17 nonrepetitive differential metabolites were found during storage of fresh-cut melon compared to stored whole melon. 4′-Methyl-(-)-epigallocatechin 3′-glucuronide (MEG) and pyranocyanin A of flavonoids accumulated in melon fruit during storage; in fresh-cut melon, increased flavonoid biosynthesis induced by the higher expression of CmPAL1-9, CmC4H1-4, and Cm4CH1/2/3 might explain accumulation of MEG and pyranocyanin A. Moreover, cell membrane composition in melon changed throughout storage, as indicated by the increased contents of phosphatidic acids (PAs), phospholipid inositols (PIs), phosphatidylglycerols (PGs), and monogalactosyldiacylglycerols (MGDGs) as well as the decreased contents of Lyso PG, Lyso PIs, Lyso PCs, Lyso PEs, and Lyso PAs. Cutting of melon promoted change in cell membrane composition, resulting from the increased expression of CmPLC1/2/3, CmPLD1/2/3, CmAGPAT, and CmGPAT1/2 in fresh-cut melon compared to whole melon. In addition, increased content of salicylic acid beta-D-glucoside (SAG) was observed in fresh-cut melon during storage compared to the whole melon, indicating that SAG helps the fresh-cut melon in resisting the cut-wounding stress. Therefore, metabolomics might provide a molecular basis for assessing the qualitative deterioration of whole and fresh-cut melon during storage.