Study On The Response Of ChlAPX-overexpressed Populus Tomenentosa To Stress

The production of reactive oxygen species (ROS) will be increased in plant cells whenthey suffer from environmental stress, such as drought stress and salt stress. ROS can cause cellinjury if they maintain in a high level. Ascorbate peroxidase (APX) plays an important role inremoving H2O2with AsA-GSH cycle and in protecting higher plant cells against the toxiceffects of H2O2. Chloroplasts are the main places producing ROS in plant cell. The chloroplastAPXs (chlAPX), including stromal APX(sAPX) and the thylakoid membranes APX (tAPX),were considered as the key enzymes in plant chloroplasts to remove H2O2. Researching on therelationship between chlAPX of Populus tomentosa and stress tolerance and breeding new plantvarieties with higher stress tolerance in the method of genetic engineering is very important.By using of pBI121-chlAPX recombinant plasmid, we integrated the target gene intowild-type741Populus tomentosa（the WT plants) with the method of leaf disc transformationwhich mediated by agrobacterium and obtained chlAPX-overexpressed Populus tomentosasuccessfully. In this study, the importance of chlAPX genes which enhance the bility ofresistance to oxidative stress, salt stress and drought stress in plants was analyzed. The mainresults were as follows:1. From the phenotypic, the chlAPX-overexpressed Populus tomentosa growed better thanthe WT plants. The extent of injury was lesser under the environment of the MV inducedoxidative. From physiological indicators, compared with WT plants, the content of protien,APX enzyme activity, GR enzyme activity and total chlorophyll content ofchlAPX-overexpressed Populus tomentosa was higher in transgenic Populus tomentosasignificantly. While MDA and H2O2contents of transgenic populus tomentosa were relativelylower. The test result showed that Pn and Fv/Fm of chlAPX-overexpressed Populus tomentosahad less fall range than WT plants.They had boost the resistant level of anti-oxidation.2. Under drought stress conditions, the chlAPX-overexpressed Populus tomentosa showeda higher water-tolerance than the WT plants. 3. From the phenotypic, under tissue culture with different concentrations of salt, rootgrowth and the number of roots were all greater in the transgenic lines than in the WT plants.The injury of chlAPX-overexpressed Populus tomentosa appearred relatively later. At the sametime, the extent of injury was lesser.4. Under salt stress conditions, the content of Na+and the ratio of Na+/K+were low. Thatwas to say,compared with WT plants, chlAPX-overexpressed Populus tomentosa can maintain alower the content of Na+and ratio of Na+/K+under stress conditions in the cell, maintain thestability of ion balance, alleviate nutrition stress and osmotic stress.Other physiological indexalso indicated that they had a higher salt-tolerance.In short, in a certain range of stress conditions, compared with wild-type Populustomentosa, chlAPX-overexpressed Populus tomentosa showed a higher stress resistance.