Analysis On Response Mechanism Of Different Ploidy Populus Ussuriensis Kom. To Drought And Salt Stress

Drought and salt stress are the main environmental factors that limit the growth and development of plants.These unfavorable environmental factors hinder the plant from fully exerting its genetic potential.In order to explore the stress resistance of different ploidy Populus ussuriensis Kom.,the plant materials were diploid(CK),triploid(T12)and tetraploid(F20).The PEG6000 was used to simulate the drought stress treatment,and the NaCl simulated the salt stress treatment.The physiological and biochemical changes of different ploidy lines under stress conditions were measured and the transcriptomes were sequenced and analyzed for each strain under salt stress.The main results of these studies are as follow:1.Under drought stress,the morphological observation and the drought injury index found that the polyploid poplar and the diploid were lower than the diploid,and the biomass distribution of the underground part was more;the relative conductance of polyploids was lower than that of diploids,polyploids had lower accumulation of MDA than diploids,polyploids had higher proline content than diploids,and triploid proline content highest.The activity of triploid SOD/POD/CAT was the highest in the whole stress treatment,followed by the tetraploid and the diploid activity was the lowest.The variation of chlorophyll content of the polyploidy lines was smaller than that of the diploid strain,and the photochemical energy conversion rate was.The decrease of net photosynthetic rate was slower than that of the diploid strain,and the net photosynthetic rate of triploid T12 had the smallest decline.Comprehensive analysis of the drought resistance of different ploidy P.ussuriensis Kom.T12>F20>CK.2.Under salt stress,the morphological observation and salt damage index survey showed that triploid(T12)performed better,tetraploid(F20)followed,and diploid(CK)performed the worst;The content of MDA in triploid T12 was the lowest;during the whole stress,the content of Pro in T12 leaves was the highest,and the activity of SOD/POD in triploid lines was higher than that in diploid(CK)and tetraploid(F20).Comprehensive analysis of triploid P.ussuriensis Kom.was more salt-tolerant than diploid and tetraploid.3.Through transcriptome sequencing,it was found that the differentially expressed genes between diploid,triploid and tetraploid before salt stress were mainly associated with glycometabolism.There were 104 Auxin genes and 35 UDP-glucosyltransferase genes significantly changed between diploid and triploid;There were 107 Auxin genes,56 cell cycle control and cell division related gene expression changes between diploid and tetraploid;There were 89 Auxin and 89 cytoskeletal genes were significantly changed between triploid and tetraploid.After the salt stress,the differentially expressed genes of the polyploid strains compared with diploids mainly changed in stress resistance mechanisms and signal transduction mechanisms.There were 36 WRKY genes,10 NAM genes,and 14 MYB genes were significantly changed between diploid and triploid;There were 41 MAPK cascade genes,20 WRKY genes,and 17 MYB genes showing significant changes between diploid and tetraploid;There were 44 MAPK cascade genes and 28 MYB genes were significantly changed between triploid and tetraploid.It is preliminarily considered that under salt stress,resistance Inverse mechanisms,signal transduction mechanisms and other related proteins increase the salt tolerance of polyploid plants.Although genes related to resistance mechanisms and signal transduction mechanisms have changed,the differentially expressed genes of diploids,triploids,and tetraploids before and after stress are different in both types and numbers,indicating that the salt tolerance mechanism between them may be different.