Label-free Quantitative Proteomics Analysis of Developing Winter Jujube Fruit

In this work, the proteomes of winter jujube at different ripening stages were studied, and the differentially expressed proteins (DEPs) and their functions were analyzed in order to provide a theoretical basis for understanding the mechanism of the maturation and development of winter jujube. Samples of Zhanhua winter jujube at 55 days (young fruit), 76 days (enlarging), 96 days (white mature) and 116 days (crisp ripe) after flowering were collected and analyzed by label-free quantitative proteomics. Compared with the previous stage, DEPs were obtained for each stage and analyzed using bioinformatics tools including Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. The results showed that a total of 2107 proteins were identified and 1986 proteins were quantified. Compared with the previous stage, 96, 185 and 138 proteins were differentially expressed in fruits at the enlarging, white mature and crisp ripe stages, respectively. GO annotation showed that the DEPs were mainly enriched in biological processes such as single biological cell process, single biological metabolic process, chemical response, and pressure response. KEGG metabolic pathway analysis showed that the DEPs were significantly enriched in photosynthesis, flavonoid biosynthesis, limonene and pinene degradation, phenylpropanol biosynthesis, glyoxylic acid and dicarboxylic acid metabolism, and ribosome biosynthesis. We concluded that there are significant differences in the proteome of winter jujube fruits at different developmental stages, and that the differentially expressed proteins are mainly involved in energy metabolism, genetic information processing and biosynthesis of other secondary metabolites.