Abstract: 【Objective】In order to reveal the molecular mechanism of sugar-apple flower development, the function of differential expression proteins among four flower developmental stages were studied by using an approach of plant proteomics. 【Method】Flower samples were collected at four flower developmental stages: floral bud stage, bud stage, the mature flowers with partially opened petals stage and mature flowers with opened petals stage. The expressed proteins of flowers in four stages were detected using two-dimensional gel electrophoresis (2-DE) technology. All expressed proteins and their functional annotation were analyzed by MALDI-TOF-MS mass spectrometry .【Result】The results of protein profiling showed that there was more than 800 protein spots in each gel electrophoresis and 50 of them showed differences in different stages of sugar apple flowers. 36 proteins were identified by spectrum analysis as well as MASCOT online retrieval. These proteins could be divided into 7 functional categories, including respiration and energy metabolism (11 proteins), protein synthesis and metabolism (8 proteins), transcription and translation (3 proteins), stress and defense (2 proteins), cell proliferation and differentiation (3 proteins), secondary metabolites (8 proteins) and unknown proteins (1 protein). Furthermore, the 36 identified proteins could be grouped into 20 GO classifications. Among 11 respiration and energy metabolism related proteins, three proteins (A07, C28, C42) were continuously decreased with flower development while the other four proteins (A36, A37, B13, B29) were significantly increased; among the proteins related synthesis and metabolism, two proteins (A13 and A22) expressed at low level for all four flower developmental stages, while other five proteins (B17, B20, A19, A21 and C21) expression increased significantly with the flower development. A stress and defense related protein (B32) showed highest expression in last flower developmental stage. The expression of two cell differentiation and proliferation related proteins (B27 and C57) expression was gradually increased. Five secondary metabolism related proteins expression (A06, A29, A34, C100 and C110) gradually decreased with flower development, while proteins C79 and D38 reached the maximum value in the bud stage, and then gradually decreased. 【Conclusion】Comparing the protein spectrum of the sugar-apple at four different flower developmental stages, 36 proteins were identified as differentially expressed proteins. The respiration and energy metabolism related proteins accounted as the largest proportion, such as two ATP synthase alpha subunits and pyruvate decarboxylation isozyme. Differential expression of these proteins suggested the flower development process requires a lot of energy. In addition, our study first reported two pentatricopeptide repeat-containing proteins, and the expression of them changed with the flower development process. However, the function of these proteins remains to be further study. The results suggest that energy metabolism, secondary metabolism, protein synthesis and other biological processes may be involved in the process of flowering regulation of sugar-apple.

Key words: sugar apple, flower development, differential expressed protein, protein function