Alterations in protein expression associated with the development of mealiness in peaches

Abstract

SummaryTwo-dimensional electrophoresis (2-DE) combined with mass spectrometry was used to identify proteins related to the development of mealiness in peaches. Five proteins were identified that differed significantly in amount between peaches that had mealy flesh and those that remained juicy following 3 weeks of storage at 5°C and subsequent ripening for 3 – 4 d at 23°C. The accumulation of ACC oxidase (ACO), a key enzyme of ethylene biosynthesis, decreased in mealy peaches. Immunoblots probed with antibodies against ACO confirmed the 2-DE results, and showed that the relationship between ACO levels and mealiness also existed within individual fruit. Phosphoglycerate kinase, an enzyme in the glycolytic pathway, was reduced in amount in mealy fruit. In contrast, two heat shock proteins and hydroxymethylbutenyl-4-diphosphate synthase increased in amounts in mealy peaches. The results regarding ACO levels are of interest due to the confirmed association of mealiness and ethylene and, given the regulatory effect of ethylene on cell wall degrading enzymes, suggest that the reduction in ACO expression during cold storage and subsequent ripening may be pivotal in the development of mealiness.