Proteomics Analysis Of ’Zaosu’ Pear (Pyrus Bretschneideri Rehd.) And Its Early-maturing Bud Sport

The proteomics is not only an important method for functional study of the gene, but alsoa key way to understand the essence of life activities. In recent years, it has been brought toour attention and applied widely. In this study, the fruit of ’Zaosu’ pear (Pyrus bretschneideriRehd.) and its early-maturing bud sport at DAF (day after flowering)25(S1), DAF40(S2),DAF55(S3), DAF70(S4), DAF85(S5) and DAF100(S6) were used as materials. Theseparation, identification and bioinformatics analysis of different proteins were done by thetechonology of proteomics. The purposes of this study were to find the key factors whichwere associated with pear’ maturing from the protein level, and to provide the importantinformation for molecular breeding of early-maturing pear. The main results were as follows:1. Fresh weight values, polar and equatorial lengths, total soluble solids content,titratable acidity and starch content of ‘Zaosu’ pear and its early-maturing bud sport weremeasured at different maturity stages. For the bud sport, fresh weight values, polar andequatorial lengths hardly increased between S5and S6stages, indicating that it had alreadymatured in S5stage. Conversely, during this period,‘Zaosu’ pear showed significant growthtrend and reached maturity in S6stage. In their respective mature stage of the two pears, thebud sport fruits (S5) presented higher fresh weight values, greater polar and equatorial lengthsthan ‘Zaosu’ pear. In addition, the maturation was accompanied by an increase of SSC levelsand a concomitant decrease of TA for both pears. However, the changes of SSC and TA weregreater for the early-maturing bud sport. Starch concentrations of the bud sport and ‘Zaosu’pear initially increased to reach maximum values at S2and S3stages respectively. During thefollowing growth stages (S3, S4, S5and S6), the ‘Zaosu’ pear had greater starch content thanbud sport. The data above described the changes during the growth of both pears, thusconfirming the good quality, large size, and most importantly, early maturation of the budsport.2. Through comparison of the extraction methods, IPG strip length, different equilibriumtime and different sample volume, the four impact factors of two-dimensional gelelectrophoresis system, we established and optimized a two-dimensional electrophoresissystem applicable for pear fruit proteomics analysis. That was to say using improved phenol precipitation method with17cm pH4-7IPG strips, sample volume0.8mg, equilibrium time15min, we could get a good repeatability, high resolution, clear background, almost novertical and horizontal stripes two-dimensional electrophoresis map.3. Protein sample of ‘Zaosu’ pear and its early-maturing bud sport were analysis bydimensional electrophoresis.75proteins were founded and68proteins were identifiedsuccessfully. Success rate of identify was90.67%. They mainly related to fruit enlargement,cell wall metabolism, oxidative stress, carbon metabolism and energy production.4. According to the analysis of differential proteins’ function and expression trend, wefound an increase of proteins related to cell-wall modification, oxidative stress and pentosephosphate metabolism and a decrease of proteins related to photosynthesis and glycolysisduring the development process of both pears, but all these proteins increased or decreasedfaster in the early-maturing bud sport.5. To identify proteins related to fruit maturation,68identified spots were clusteredaccording to their percentage of volume. Two significant clusters, cluster I (58spots) andcluster II (10spots) were formed. After analysis of protein changes in each cluster branch, thedata showed that the changes in spot abundance were not strictly related to the transition from‘immature’ to ‘mature’ itself but also to other aspects that could be linked to differences in thegenetic background between ‘Zaosu’ pear and its bud sport.6. Subcellular localization predictions were taken on the identified protein. The resultsshowed that16different proteins were located in cytoplasm,10different proteins werelocated in chloroplast,2different proteins were located in vacuolar membrane,2differentproteins were located in mitochondria,1different proteins were located in cell wall,1different proteins were located in endoplasmic reticulum,4different proteins were multisubcellular localization and the other different proteins could not found their subcellularlocalization by prediction.