The aim of this study was to explore the differences between melting flesh and stony hard peaches at the peptide level and precursor protein level during fruit ripening, so as to provide a theoretical basis for mining the key peptides of determining or regulating the ripening process.

The characteristics of peptides and precursor protein functions in CN13 (melting flesh, MF) and CN16 (stony hard, SH) peaches were analyzed by peptidome, the relative contents of precursor proteins and peptides during MF and SH peach fruit ripening were compared, and the precursor proteins of different peptide segments were analyzed by function enrichment.

In this study, the peptides of CN13 and CN16 (S3 and S4III) were extracted for mass spectrometry. A total of 473 precursor proteins were identified, including 2 580 specific peptide sequences. The molecular weight, isoelectric point and cleavage sites of the peptide were summarized. In addition, the high-abundance precursor proteins corresponding to endogenous peptides were explored by COG function annotations and pathway enrichment analysis, and the results showed that the precursor proteins were mainly involved in the processes of general function prediction, post-translational modification, protein turnover, energy production and conversion, carbohydrate transport and metabolism. The enrichment analysis showed that the differential peptide precursor proteins of CN13 were related to biological processes, such as oxidation reduction, oxygen and oxygen and electron transport chain, which were mainly involved in glycolysis/gluconeogenesis, pentose phosphate pathway and RNA transport; the differential peptide precursor proteins in CN16 were related to biological processes, such as response to metal ion, response to inorganic substance, and response to cadmium ion, which were mainly involved in microbial metabolism in diverse environments, spliceosome and RNA transport; the differential peptide precursor proteins at the same stage in CN13 and CN16 at S4III were related to gene expression, translation and cellular macromolecular biological processes, which were mainly involved in RNA degradation, RNA transport and splicing.

There were significant differences in peptides between CN13 and CN16 during fruit ripening. The precursor proteins of differential peptide were involved in starch/sucrose metabolism, glycolysis and ribosome synthesis, and it was suggested that these metabolic pathways were closely related to peach fruit ripening, which provided a theoretical reference for further exploring the key peptides of regulating peach fruit ripening and senescence.