| The increasing solar ultraviolet-B (UV-B:280-320nm) radiation on the earth's surface due to the depletion of the stratospheric ozone layer has been one of the most important environment problem catching people's attention. Numerous researches have indicated that with the increasing of the solar UV-B radiation, the configuration and genetic material of plant will be changed, the photosynthetic pigment will be destroyed and the intensity and ability of photosynthesis will be weakened, all of which will directly or indirectly affect people's life. Consequently, the influence of the UV-B radiation on crops and their protect mechanisms have become popular studies all over the world nowdays.In this study, we choose Dular (a sensitive type introduced from India) and Lemont (a resistant type from USA) as the materials to investigate UV-B resistance mechanism for rice (Oryza sativa L.). In the aid of the techniques of proteomics including two-dimensional gel electrophoresis(2-DE), mass spectrometry(MS) and the related bioinformatics, we compared the differences between the two rice varieties at their differentially expressed proteins after treated with UV-B.In the hydrponic experiment the rice seedlings of each entry were treated with UV-B for 1 day, 7 days and 14 days respectively, and the untreated rice seedlings were the control. Total leaf proteins were extracted from the rice seedlings including contol plants, and separated by two-dimensional gel electrophoresis (2-DE). It was found that there were 39 differentially expressed proteins in both the treated rice leaves and the control. Thirety out of the thirthy nine proteins, which are relatively higher in expression abundance, were analysed by MALDI-TOF/MS and database searching, of which 23 proteins were identified. They function in responses and resistance to enhanced UV-B radiation.The influence of enhanced UV-B radiation on rice was found in three aspects: (1) the enzymes involved in photosynthesis were degraded, leading to decreased photosynthesis. (2) the oxygenolysis of glucide was obstructed, in turn resulting in reduced supply of energy for cell. (3) the proteolysis was accelerated.The resistance of the rice to enhanced UV-B radiation was reflected in these aspects: (1) the synthesis of glucide was enhanced, which is helpful to increase the ability resistant to the stresses. The upregulation of the ribose-5-phosphate isomerase is favorable to DNA repair in rice after injured by UV-B. (2) the increased synthesis of unsaturated fatty acid led to reduced alteration of the membrane configuration and composition as a result of peroxidization. (3) the synthesis of the chloroplast proteins were promoted and the protein folding process was accelerated. (4) the activities of the related enzymes associated with the signal transduction was increased. (5) the defense of the cell including the scavengering of reactive oxygen species(ROS) and the accumulation of UV-B absorbing substance enhanced.According to the information of subcellular location for the identified proteins, most of these proteins locate in chloroplast, mitochondria amd cytoplasm. Specially, 47.8% of them are in chloroplast. And this provides us the valuable information to further study the molecular mechanism of UV-B resistance from the subcellular level.From the experiment, we found that all of identified proteins were changed in lemont while there were only 14 in dular. The expression patterns of differentially exptessed proteins are different in the two rice varieties. The Other 9 proteins that did not change in protein expression in dular, which were involved in glucide and fatty acid metabolism, signal transduction, protein synthesis and folding process.These findings suggested that there existed a regulative network of complex proteome in rice exposed to enhanced UV-B radiation and it paved the way for us to further study the molecular mechanism in rice resist to enhanced UV-B radiation. |
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