Comparative Analysis Of Protein Expression Profile And The Changes In Photosynthetic And Nitrogen Metabolic Path Ways Of Wheat Leaves Under Nitrogen And Water Stress

In order to study the response of wheat to nitrogen stress,water stress and combined stress at the proteome level,wheat variety Yumai 49-198 was used as a material to perform a proteome analysis which can find the changes of protein expression level of wheat flag leaves under the three stress conditions.The changes of protein expression profiles under the three stresses were compared and analyzed,and the changes of photosynthesis and nitrogen metabolism pathway under three stresses were deeply analyzed.The main results are as follows:1.Nitrogen stress,water stress and combined stress could significantly reduce the yield of wheat,and the effect of nitrogen stress was greater than that of water stress,and the effect of combined stress was greater than that of any single stress.Under the three stresses,the Pn of flag leaves decreased significantly,and the effect of nitrogen stress was less than the effect of the other two stresses.The changes of Cond,Ci and Trmmol was basically the same with that of Pn.The contents of nitrate in leaves were also significantly reduced under three stresses.Among them,nitrogen stress had the greatest effect and water stress had the smallest effect.The effect of combined stress was between the other two stresses.2.Through i TRAQ proteomics analysis,160,274 and 274 differentially expressed proteins were identified under nitrogen,water and their combined stress.The number of identified proteins under water stress was the same with combined stress,but the the number of down regulation protein under combined stress was larger than that of water stress.Venn diagram analysis and the hierarchical cluster analysis showed that the protein expression profile of combined stress was more similar to that of nitrogen stress.The functional groups of differentially expressed proteins under three stress were similar,mainly including photosynthetic,carbohydrate,lipid metabolism,nucleic acid,stress,signal,protein,cell,development,transportation,etc.3.the pathway analysis showed that compared with the other two stresses,nitrogen stress had the smallest impact on photosynthesis,and the number of differentially expressed proteins involved in the photosynthetic pathway was the least,mainly showed that the protein which associated with light-harvesting complex and the oxygen-evolving complex was significantly down regulation,and the protein associated with Rubisco activity was also significantly down regulated.water stress had a greater effect on photosynthesis than nitrogen stress.The changes of some proteins indicating that water stress led to disordered electron transport,and resulted in the ratio of ATP/NADPH increased,thus affecting the supply of reducing power in dark-reaction.The significant down regulation of glyceraldehyde triphosphate dehydrogenase,triose phosphate isomerase ndicated that the entire dark reaction process was affected.The effect of combined stress of water and nitrogen on photosynthesis was greater than that of nitrogen stress and no less than water stress.Among these proteins,NADPH dehydrogenase was significantly down-regulated,indicating that cyclic electron transport was inhibited,which may lead to reduced ATP synthesis,affecting the supply of dark reaction energy;fructose diphosphate aldolase and sedoheptulose-1,7-diphosphatase was significantly down-regulated,indicating that the Calvin cycle was severely impaired.besides that,we also identified that the CURT1 which can modified the structuer of thylakoid was significantly down-regulated,suggesting that compared to single stress,the combined stress may lead to more severe damage to thylakoid structure.4.under nitrogen stress,the slight up regulation of GDH-related protein and GS showed that the intensity of photorespiration was enhanced.And increased expression of GDC,GS,and GOGAT under combined stress indicated the photorespiration intensity was higher than nitrogen stress,may be this is due to photorespiration plays an important role in supplementing nitrogen metabolism.The significant down regulation of GDH and GS under water stress indicates that photorespiration is severely inhibited,while the down regulation of GDH led to the accumulation of glycine and tryptophan,which may be more conducive to resist drought stress.5.Under nitrogen stress,the significant down-regulation of nitrate reductase may be related to the decrease of nitrate content in leaves.A slight up regulation of GS and GDH indicates that the reuse and redistribution of nitrogen are enhanced;the decrease of GS under water stress indicates the assimilation ability of ammonia nitrogen was weaken.,and the primary assimilation and reutilization of nitrogen are blocked.Under the combined stress,the up regulation of GS,Fd-GOGAT,and GDH indicates that nitrogen reuse and redistribution are enhanced,and this trend is stronger than single nitrogen stress.