Differential Proteomics Analysis On Rice (Oryza SativaL.) Response To Cadmium Stress

Rice is one of the most important global grain crops. The question of rice contaminated by heavy metal has drawn of the governments'high attention around the world. The arable land polluted by toxic heavy metals, which not only inhibits the growth and development of crops, leading to reduced yield and quality, but also poses a great threat to human health via food chain due to uptake by crops. The uptake, accumulation and resistance to some heavy metals vary greatly among different genotypes. To elucidate the absorption and accumulation mechanism of heavy metal in rice is important for breeding anti-heavy metal rice variety, reducing the heavy metal pollution, and harvesting non-pollution rice on the light and moderate polluted soils, which is a safeguarding for food security and sustainable production.Cadmium is listed in the first place of the 12 kinds global dangerous chemical substances by United Nations Environment Programme,it is also one of the heavy metals which contaminate the rice heavily in China. On the basis of former work, an cadmium resistance rice PI312777 and a cadmium sensitive rice IR24, treated by a gradient concentrations of cadmium 0μmol/L, 50μmol/L and 100μmol/L in hydroponic culture, were applied to study the differential expression of proteins in the roots and leaves responsing to the stress of cadmium. The main results were as follows.(1) The results showed that a total of 31 protein spots in rice leaf had significantly different expression the stress of cadmium, Apart from 4 redundant proteins, 24 proteins were identified successfullyby MALDI-TOF/MS analysis and database searching. These differently expressed proteins involved photosynthesis, plant resistance and other metabolism.(2) The results showed that a total of 18 protein spots in rice root had significantly different expression under Cd stress, among them, 12 proteins were identified successfully by MALDI-TOF/MS analysis and database searching. These differently expressed proteins involved singal transduction, plant resistance and other metabolism.(3) Under the stress of cadmium, similar response was found in the leaf and root of cadmium resistance rice PI312777, cadmium sensitive rice IR24. The performances were described in detail as follows: In the leaf, the expression of proteins related with photosynthesis rate, such as ribulose bisphosphate carboxylase large chain, was upregulated both in the two rice varieties. The expression of Drought-inducible protein, Dehydroascorbate reductase and Sorbitol-6-phosphate dehydrogenase were all higher than the control, but superoxide dismutase [Cu-Zn] was the inverse. The expression of Glyceracdehyde-3-phosphate dehydrogenase was not changed both in rice PI312777 and rice IR24 under 50μmol/L Cd²⁺ stress, but it was upregulated under the condition of 100μmol/L Cd²⁺ . In the root, the expression of stress-induced protein were upregulated both in PI312777 and IR24 under low Cd²⁺ concentration, but the expression of Methionine adenosyltransferase, Peroxidase and Glutamine synthetase cytosolic isozyme were down-regulated.(4) Under the stress of cadmium, different response was detected in the leaf and root of cadmium resistance rice PI312777, cadmium sensitive rice IR24. In the leaf, the expression of Phosphoenolpyruvate carboxylase was down-regulated in PI312777, but for IR24 was on the contrary. A new protein, called DNA repair-recombination protein was detected in PI312777, and absent in IR24. The expression of glutathione-diulfide reductase, Proteasome and Heat shock protein are higher than the control, but no difference was detected in IR24. The expression of Thioredoxin was upregulated, but it was opposite in rice IR24.The expression of Gutamate dehydrogenase in the root of PI312777 was not changed under lower Cd²⁺ treatment (50μmol/L), it down-regulated with the increasing of Cd²⁺ concentration, while for IR24, it down-regulated in all the treatment for Cd²⁺. The expression of S-adenosylmethionine synthetase in PI312777 was up-regulated under 50μmol/L Cd²⁺, while no change was found under 100μmol/L Cd²⁺ conditon, but up- regulation was detected under Cd²⁺ stress in IR24. The 60S acidic ribosomal protein, related with signal transduction, was up–regulated in PI312777 under Cd²⁺ stress, but it was opposite in IR24. In addition, the GTP-binding nuclear protein was up-regulated in PI312777 but IR24.