Physiological And Proteomics Analysis Of Populus Simonii×P.nigra Leaves In Response To H₂O₂

Environmental factors often lead to oxidative stress,resulting in the accumulation of a large number of reactive oxygen species.H₂O₂ is one of the most important,as an ROS molecule,it can cause oxidative damage to DNA,proteins and lipids,leading to cell death.Populus simonii×P.nigra has a certain resistance,is an important cultivated species,it is also an important model of forest genetic engineering plant.Therefore,it is very important to explore the anti-oxidation mechanism,improve the antioxidant capacity and breed high quality varieties of Populus simonii×P.nigra.In this study,we have studied the response mechanism of H₂O₂ stress in the leaves of Populus simonii×P.nigra by physiological and proteomic methods.The results showed that H₂O₂ inhibite photosynthesis rate,break the integrity of the membrane structure and increase of malondialdehyde（MDA）content and relative electrolyte leakage（REL）.In addition,with the occurrence of oxidative stress,the osmotic protective substances（soluble sugar,proline and glycine betanine）in leaves of Populus simonii×P.nigra were accumulated,and the activities of antioxidant enzymes and antioxidants were changed.e.g.,the activity of peroxidase（POD）,ascorbate peroxidase（APX）,DHAR reductase and glutathione reductase（GR）were significantly increased.We obtained 81 differentially abundant protein spots by using two-dimensional electrophoresis（2-DE）approach.We found that the abundance of 12 spots were increased,61 spots were decreased and 8 spots showed multiple expression patterns under H₂O₂.These proteins were mainly involved in the formation of light harvesting complex,photosystem II,photosynthetic electron transfer chain,Calvin cycle,energy metabolism,metabolism,stress and defense,protein fate,cytoskeleton,signaling transduction and multifunctional or unknown.Taken together of our physiological and proteomics results reveal that P.simonii×P.nigra leaves may utilize various strategies to cope with H₂O₂ treatment.They include:（1）maintain osmotic balance through the accumulation of osmotic protective substances;（2）improve the activity of enzymes related to ROS clearance pathway,eliminate excess ROS efficiently,and prevent the occurrence of oxidative damage;（3）the absorption of light energy and electron transfer were decreased,and the Calvin cycle was inhibited,which led to the decrease of photosynthetic rate;（4）glycolytic pathway,TCA cycle,and partial basal metabolic pathways were inhibited;（5）increase abundance of the heat shock protein（HSP）and molecular chaperone（CPN）,ensure the stability of protein and membrane structure.These results provide an important theoretical basis for revealing the H₂O₂ stress-response mechanism in leaves of P.simonii×P.nigra.