A Large-Scale Proteome Analysis of Proteins Expressed in the Peel of Malus Domestica 'Hong-Ro'

The proteome expressed in the peel of the Korean apple cv. 'Hongro' was analyzed using two-dimensional electrophoresis, and it was confirmed that 502 proteins were expressed. As a result of analyzing these proteins with MALDI-TOF/TOF, 408 proteins were identified. The identified proteins were sorted by biological function: the most abundant (87) were in the carbohydrate metabolism category [abundance value (AV) total 120.97, 18.2% of total 665.09 in AV]; followed by protein metabolism, 59 (AV total 72.08, 10.8%); protein folding, 37 (AV total 34.12, 5.1%); defense and stress response, 35 (AV total 56.95, 8.6%); protein degradation, 33 (AV total 28.87, 4.3%); antioxidant enzyme, 29 (AV total 41.58, 6.3%); secondary metabolite metabolism, 16 (AV total 16.4, 2.5%); lipid metabolism, 16 (AV total 8.89, 1.3%); transport, 15 (AV total 8.75, 1.3%); cytoskeleton constitution, 14 (AV total, 12.89, 1.9%); allergen, 12 (AV total 104.55, 15.7%); nucleotide metabolism, 11 (AV total 10.83, 1.6%); and ATP synthesis, 10 (AV total 18.46, 2.8%). Among the expressed protein spots, the 1st AV was spot 451 major allergen Mal d 1 (AV 54.42), 2nd was spot 419 unidentified protein (AV 28.40), 3rd was spot 455 MLP-like protein (AV 24.08), 4th was spot 480 glutathione S-transferase (AV 18.61), 5th was spot 166 glutamine cytosolic isozyme (AV 13.26), 6th was spot 421 L-ascorbate peroxidase (AV 12.67), 7th was spot 163 beta-cyanoalanine synthase (AV 10.81), 8th was spot 114 enolase-like (AV 10.48), 9th was spot 36 unidentified (AV 10.16), and 10th was spot 452 major allergen Mal d 1 ( AV 8.80). As described above, only a small number of allergen-related proteins were identified, but the total AV was found to be ranked second among all functional classifications, indicating that allergen-related proteins are expressed in large quantities in the peel. From the results of this experiment, it was possible to conceptualize the proteome expressed in the apple peel, and the results may be used as a coordinate for the study of the proteome related to the physiology and breeding fields of apples in the future.