Quantitative proteomic investigations using stable isotope labeling by peptide dimethylation on fruit ripening, senescence and redox- antioxidant system

Proteomics has become a powerful post genomic tool to study biological samples. Quantitative proteomic approach employing stable isotope labeling as a triplex quantification method based on stable isotope dimethyl labeling at the peptide level was conducted. Around 900 and 925 and proteins were identified and quantified in apples and strawberries, respectively, using at least two peptides for each protein. The normalized ratio of protein abundance changes in relation to fruit maturity, fruit ripening and senescence revealed dynamic changes in protein profiles. Among the most significantly changed proteins were ones in metabolic pathways involving redox-antioxidant, energy, ethylene biosynthesis and perception, volatile biosynthesis, stress response, respiration and allergens. Through this labeling strategy, a group of proteins were found to be down regulated that are responsible for redox and antioxidant, energy and hormone interactions. Postharvest physiological quality indices such as respiration, ethylene production and chlorophyll fluorescence, firmness, soluble solids and titratable acidity were characterized during fruit ripening and senescence. Together, our results show that quantitative proteomic approaches can help unravel the highly complex system involving multi-physiological processes of fruit ripening and senescence and provide further insight into fruit ripening and senescence.