Proteomic Analysis Of Flag Leaf Of Japonica-indica Subspecies Hybrid And Their Parents During Grain Filling

In order to explor the possible physiological and molecular mechanisms of leaf senescence of hybrid rice, four genotypes of rice, i.e., 93-11 (Oryza sativa L.ssp indica), Nippon bare (Oryza sativa L.ssp japonica) and F1 generation of their reciprocal cross were used as experimental materials. The photosynthetic characteristics, including photosynthetic rate, relative content of chlorophyll and photosynthetic photochemical activity (chlorophyll fluorescence), of flag leaf of four genotypes during different grain filling stage, i.e., 20, 30 and 40 days after grain filling, were measured. Both the differences of flag leaf protein expression profile of different grain filling stage for the same genotype and those of different genotype with the same grain fillinbg stage were analysized using a high resolution two-dimensional electrophoresis (2-DE), matrix assisted laser desorption/ionization time of flight tandem mass spectrometry (MALDI-TOF-TOF-MS) and bioinformatics technique. The results indicated that,1. The leaf photosynthetic rate of four genotypes rice declined as the grain filling progressed, but those of both F1 generations were higher than that of Nippon bare and lower than than that of 93-11 in three grain filling times (20 days, 30 days and 40 days). The relative chlorophyll content and absolute chlorophyll contents of four genotypes rice showed downward trend, and those of both F1generation were lower than those of their parents in three grain filling times. Similar trends were also observed for Fv/Fm,ΦPSⅡand qP.2. The differential expression profile of flag leaves for rice genotype 93-11 at the different grain filling stages showed that there were 1298 proteins to be identified, of them, 1051 proteins were matched for three grain filling stages and 247 proteins were not matched. Similarly, there were 1219, 1159, and 1099 proteins to be identified in Nippon bare, F1(93-11/Nippon bare) and F1( Nippon bare/93-11 ) , respectively. The total protein points of two parental rice varieties were more than those of both F1 generations. Using PQDuest7.0 software, It was found that 93-11 upregulated 6, downregulated 68, new appeared 52, disappeared 10. Nippon bare upregulated 7, downregulated 36, new appeared 34, disappeared 7. F1(Nippon bare/93-11) upregulated 18, downregulated 6, new appeared 59, disappeared 4. F1(93-11/Nippon bare) upregulated 9, downregulated 10, new appeared 44, disappeared 0.3. The protein expression profile was compared among four genotypes at the 40 days after grain filling. It was found that there were 887 proteins to be identified in four genotypes, 311 proteins were unmatched and 28 proteins were specific expressed. 4. 249 differential expressed proteins were selected for further MALDI-TOF-TOF-MS analysis and totally 135 proteins were identified. The identified proteins can be divided into 7 groups. The first group was related to leaf senescence, the second was defense proteins, the third was related signal transduction, and the other groups were related meatbolism, photosynthesis, structure and genetic proteins, respectively.