| At present,acid rain has become one of the world's top ten environmental issues. Behind Europe,North America,China has become the third largest area of acid rain in the world.Acid rain,which affects plant growth and then decreases the production of agriculture and forestry,has become one of the important factors to retard socio-economic development.Hence,it is of great practical significance to study the mechanisms which acid rain affects plant growth.Currently,the relevant researches exploring the impact of acid rain on plants are mainly focusing on the physiological response rather than the protein molecular level.In this paper,the physiological targets,two-dimensional gel electrophoresis and MALDI-TOF-MS analysis are used to study the effects of simulated acid rain on physiologic and proteomic of Arabidopsis thaliana in order to better understand the impact of acid rain stress on plant in the protein molecular level.The preliminary results are showed as the follow:(1) Effect of simulated acid rain with pH value 5.6(control) and pH value 3.0 on the injury phenotype of Arabidopsis thaliana leaf at the different time stage(8 hours, 32 hours,68 hours and 116 hours),and on MDA content,the chlorophyll content,and the fresh weight of Arabidopsis thaliana at the 116 hours stage were studied.The results showed that the injury phenotype of Arabidopsis thaliana leaf was obvious, leaf injury spots was noticeable and leaf surface injury rate was 12.6%after 68 hours stress of simulated acid rain,While leaf surface injury rate was 43.8%,the average fresh weight was lower than the control 32.6%,and in the internal physiological level the total amount of chlorophyll was slightly higher than the control,MDA content was higher than the control 42.1%after 116 hours stress of simulated acid rain.(2) A comparative proteomic analysis of Arabidopsis thaliana that had been exposed to simulated acid rain with pH value 5.6(control) and pH value 3.0 for different time(8 hours,32 hours,68 hours and 116 hours) was conducted.Changes in the abundance of protein species within Arabidopsis thaliana leaf were examined using two-dimensional electrophoresis(2-DE).Fifty proteins showing at least a 2-fold change under simulated acid rain stress at least at one time stage with P＜0.05 were analyzed by MALDI-TOF-MS.(3) Fifty proteins which have been identified by bioinformatics include material and energy metabolism-related proteins(eg:lipoxygenase,methionine synthase, carbonic anhydrase and fructose 1,6-diphosphate enzymes);cell defense-related proteins(eg:thioredoxin,glutathione S-transferase and dehydroascorbate reductase); auxiliary functions and modification -related proteins(eg:molecular chaperone protein and heat shock protein);signal transduction-related proteins(eg:gibberellin response protein).(4) Subcellular localization analysis of the proteins showed that 31.2%of the proteins located in the chloroplast,29.1%of the proteins located in the cytoplasm, 11.2%of the proteins located in the nucleus,and 30%of the proteins located in the other organelles.The statistical results of subcellular localization of the proteins showed the majority of the proteins located in the intracellular,which mainly located in the chloroplast,cytoplasm,nucleus and mitochondria.(5) We found by the experiment that the amount change of the differentially expressed proteins at the different acid rain stress time stage(8 hours,32 hours,68 hours and 116 hours) reflected the different mechanism of Arabidopsis thaliana responsing to simulated acid rain stress in the different time gradients.Experimental results show that acid rain stress has a great impact on the metabolic activity of Arabidopsis thaliana and forced Arabidopsis thaliana to start a variety of metabolic pathways to resist acid rain stress.This study provides some new evidences to clarify the impact of acid rain stress on plants.
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