Ongoings in the apple watercore: First evidence from proteomic and metabolomic analysis

The presence of watercored fruit with translucent mesocarp has attracted immense attention due to its unique morphology and taste, however, the metabolic reconstruction between watercored and non-watercored tissues remain elusive. Herein, the combined proteomic and metabolomic approach was carried out to characterize the protein abundance and metabolic profile in watercored apple. Results demonstrated that carbohydrate metabolism was prioritized enriched in watercored apple, including highly accumulated sucrose and sugar alcohols, and the increased level of transcription factor WHIRLY2 (WHY2), which is required in sugar reallocation. More than 50% overlap of differently abundant proteins involved in calcium ion binding, starch and sucrose metabolism implied the involvement of calcium signaling in watercore development. Moreover, significantly lower calcium content was detected in watercored apples. Sucrose synthase (SUSY) protein, which is involved both in calcium ion binding and sugar metabolism, was the potential basis of apple watercore development, which provided a likely candidate in regulation of apparent quality.