| In order to study the mechanisms of biological effects of space environment, in the present dissertation, the model plant rice was chosen as experimental material. After several seed spaceflights, proteomic expression profiles of different rice variety plants in 1st and 2nd generations were analysed. Space radiation inducement investigation through protein expression profile analysis based on on-ground simulated radiation experiments was also performed. In addition, mechanisms of tillering mutation induced by spaceflight were also explored by differential protein expression analysis of the tillering dwarf mutant.Using two-dimensional fluorescent differential electrophoresis (2-D DIGE) technology, 99 protein expression 2-D patterns were acquired from tillering rice plants of different varieties after two kinds of spaceflights in 1st and 2nd generations, after on-ground simulated radiation treatments and from the mutant variety. Standard gel image pattern including groups of proteins that co-expressed in all rice varieties and particularly expressed in every variety was established. The pattern was used as a normalized standard for comparing the large number of protein expression data in different status qualitively and quantitively. Tandem mass spectrometry identified 204 differentially expressed proteins that involved in biological processes including metabolic process, regulation of biological process, response to stimulus, cellular process and reproduction.For investigation of protein expression profiles of rice plants after spaceflights and the hereditary capacity in the offspring plants, clustering and principal component analysis were performed to summarize and compare the protein expression variations between the space samples and their corresponding ground controls in different spaceflights and in 1st and 2nd generations. Results indicated that protein expression profiles were changed after seed space environment exposures onboard the satellite or space craft, but there were variations in the degree of difference in different types of flights: the longer the flight duration lasted, which meant that rice seeds were affected by space radiation environment heavier, the greater differences existed in protein expression profiles. Distribution of biological processes of differentially expressed proteins indicated that physiological and biochemical changes of rice cells were induced by space environment. The biological processes impacted in 1st generation plants after flights were nucleic acid metabolic process,light reaction,proteolysis,defense response to fungus,response to stress with amino acid and derivative metabolism. Alterations of protein expression profiles in 1st generation would resume or recover in the corresponding 2nd generation plants, the degree of recovery was associated with the sensitivity of the rice variety to environment. Changes of proteins involving in biological processes such as cell wall organization, nucleic acid metabolic process, proteolysis, RNA-dependent DNA replication, amino acid and derivative metabolism, pentose-phosphate shunt, response to stress tended to recover in 2nd generation plants; while seed maturation, protein folding, glycolysis, lipid biosynthetic process, glycogen biosynthetic process and tricarboxylic acid cycle related proteins only differentially expressed in 2nd generation plants. Therefore,the biological effects of space environment could be reflected in protein expression level.Some of the space-environment-sensitive proteins were found, including nucleoside diphosphate kinase 1, Rieske (Fe-S) protein precursor, cysteine protease, isoflavone reductase-like protein, S-like RNase and molecular chaperones participating in protein folding. They could be used as potential biomarkers that would answer to the stimulus from space environment.Spaceflight represents a very complex environmental condition with highly ionizing radiations (HZE). To further investigate the incentives of ion effects in space environment, we performed on-ground simulated HZE particle radiations to rice seeds with the same dose (2mGy) as spaceflight but different liner energy transfer (LET) values (13.3keV/μm-12C, 30keV/μm-12C, 31keV/μm-20Ne, 62.2keV/μm-12C, 500keV/μm-56Fe) then compared the protein expression profiles between radiation and spaceflight plants. By data clustering, principal component analysis and correlation analysis, the results showed that protein expression profile of the LET-62.2keV/μm 12C radiation was most similar to spaceflight effect. The dose effect analysis of spaceflight by simulated radiations was also evaluated: radiations of LET-62.2KeV/μm 12C particles (most similar with spaceflight effect) with different cumulative doses (2mGy, 20mGy, 200mGy, 2000mGy) were further carried out. Comparisons of protein expression profiles between irradiated and spaceflight plants indicated that the 2mGy dose-value radiation shared most similar effect with the spaceflight, which confirmed the low-dose effect of space environment. A new space radiation environment effect incentive evaluation system was established based on the protein expression profile analysis.Comparative quantitative proteomic analysis between a high-tillering dwarf mutant R955 induced by spaceflight and its ground control was performed at three plant vegetative growth stages. It was found that biological processes including energy pathway, photosynthesis, protein metabolism, nitrogen assimilation, amino acid metabolism and response to stimulus were mainly involved in tillering mutation development. K-means clustering revealed that proteins regulated at different stages tended to be involved in different biological processes. Two-way analysis of variance (Two-way ANOVA) screened out that S-like RNases presented direct correlation with the high-tillering ability. The work might provide new insights for further understanding mechanisms of space induced tillering mutation in rice.
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