| Loquat (Eriobotrya japonica Lindl.) is a subtropical fruit native to China. Generally, it can be sorted into red-and white-fleshed cultivars according to the color of the fruit. The white-fleshed cultivar is more exquisite and juicy, sweet sweetness compared with red-fleshed cultivars. However, the red-fleshed cultivar has more stress resistance, and longer time of storage period.In this experiment, we selected two cultivars of loquat fruit huangjinkuai (HJK, red-fleshed) and taichengbaimi (TCBM, white-fleshed) in the mature period as materials to study physiological indexes and proteomic differences of their pulp.1. In this experiment, we focus on the carotenoid, soluble sugar and titratable acid content in fruit. The result shows:soluble sugar content of HJK is about62mg/g, TCBM is about97mg/g; titratable acidity content of HJK is0.14mmol/100g, TCBM is0.04mmol/100g; carotenoid content of HJK is0.014mg/g, TCBM is0.002mg/g. This shows that the red flesh loquat carotenoid content is higher, the fruit color is more bright; And also shows that the ratio of sugar and acid is lower of the red flesh loquat, which means it is not good to eat.2. In this experiment, several enzymatic activity assays of polyphenol oxidase(PPO), superoxide dismutase(SOD), ascorbate peroxidase(APX) and cinnamyl alcohol dehydrogenase(CAD) were also carried out. The results shows that TCBM’s enzyme activity of PPO is almost twice as much to HJK; APX and SOD has little difference; CAD activity of TCBM is relatively higher than HJK. This result means that the pulp of TCBM is difficult to storage, and will produce more lignin in the storage process.3. The total proteins extracted from the two varieties of loquat pulp mature period were separated by two-dimensional electrophoresis(2-DE) to proteome analysis in this experiment. It is turn out that835protein spots of HJK and826protein spots of TCBM were detected. Quantitative analysis using ImageMaster software reveal that46protein spots were differentially expressed with1.5fold abundance change in2-DE gel. Among them40non-redundant protein were identified by MALDI-TOF-MS/MS. Through the analysis of bioinformatics we divided them into these types:1. stress response and defense(10);2. energy and metabolic pathways(10);3. Secondary metabolism(3);4. Proteometabolism(4);5. Signal transduction(7);6. Allergen(2);7. Unclassified(4). After the founction analysis of the protein which differentially expressed, we find that:1) In the mature stage, two varieties of loquat cultivars has no differentially expressed protein which related the synthesis of carotenoid.2) The storage time of the fruit is the result of a variety of protein interactions. The up-regulate expression of signal transduction proteins such as the14-3-3like protein strengthen the ability of the fruit to stress resistance; Stress response and defense protein and MDH can increase the reducing power and energy supply, improve the ability of scavenging free radicals, toxin, and prevent the protein denaturation, condensation, which result the maintain of the liquidity and integrity of the cell membrane, and the improve of the resistance. Thus, the storage of the fruits can last longer time.4. Western blot analysis to the HSP70protein, reveal that it’s abundance in this two loquat pulp is consistent with the results of two-dimensional electrophoresis; For major allergen protein allergen Mal d1gene cloning, the conservative sequence we got has98%similarity to the homologous gene in apple. The results show that our result is credible, and can laid a foundation for further study at the molecular level of loquat fruit quality,... |
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