Changes in protein <i>N</i>-glycosylation during the fruit development and ripening in melting-type peach

Abstract

The posttranslational modification of proteins with complex carbohydrate moieties (glycosylation) regulates the process of fruit ripening. Exoglycosidases are enzymes that can trim this protein glycosylation and are therefore considered to be important targets in the control of fruit ripening and softening. Melting-type peaches are popular seasonal fruits in many Asian regions, but the extremely short shelf-life of the peach fruits significantly hampers their economic value. To investigate the effect of the protein glycosylation and exoglycosidase activities on the development and ripening of the peach fruit, the fruit flesh of the melting peach cultivar 'Xia hui 6' at five different maturity stages were analyzed. The N-glycan profile of each sample was characterized and quantified by HILIC-UPLC and MALDI-TOF mass spectrometry, revealing two characteristic N-glycan structures (MMXF and GnGnMXF) which were strongly affected by the state of maturity. Furthermore, it was shown that one of the endogenous exoglycosidase activities analyzed (<i>β</i>-N-acetylhexosaminidase, <i>β</i>-Hex) correlated with the MMXF and GnGnMXF N-glycan structures (<i>p</i> &lt; 0.05) in an obverse manner. These findings lay the foundation for further elucidation of the physiological functions of protein glycosylation in peach fruit development and ripening.