Comparative Analysis of Protein Patterns and Fruit Size in Three Asian Pears with Different Fruit Maturity Periods

This study aimed to investigate the relationships among fruit size and protein metabolism andprofiles during fruit development and ripening of three Asian pear (Pyrus pyrifolia Nakai) cultivarspredominantly grown in Korea. The final fruit dry weight was higher in the late-maturing cultivar‘Niitaka’ than in the early-maturing cultivars ‘Wonhwang’ and ‘Whangkeumbae’. After 87 daysafter full bloom (DAFB), the fruit amino acid content significantly decreased in ‘Niitaka’ and‘Wonhwang’ pears, while they remained stable at lower levels in the ‘Whangkeumbae’ pearsduring fruit development and ripening. At the beginning of our sampling period (57 DAFB) theprotein content was the highest in ‘Niitaka’, followed by ‘Wonhwang’ and ‘Whangkeumbae’. Thefruit protein content gradually decreased to 117 DAFB for ‘Niitaka’ or 102 DAFB for ‘Wonhang’and ‘Whangkeumbae’, and then maintained at the similar level to the last sampling date. Thesereductions in the protein content were consistent with the increases in the protease activity. A rapidincrease in the protease activity was observed in the ‘Niitaka’ and ‘Wonhwang’ pears during theearly stage of fruit development, whereas a gradual increase was observed in the ‘Whangkeumbae’pears during the entire period analyzed. The protein pattern varied across the various fruitdevelopmental stages, revealing up- and down-regulated proteins during fruit development as wellas highly expressed proteins at the middle phase of the period evaluated. Our results indicate thatprotein degradation by proteases in the early stage of fruit development, which in turn determinesthe fruit amino acid content, may affect the final size of Asian pears. KCI Citation Count: 1