Selection Of Salt Tolerant Wheat Germplasm And Analysis Of Salt Stress Response Transcriptome

Wheat is an important crop in the world.Screening salt tolerant wheat germplasm,investigating the physiological and growth response characteristics to salt stress,and exploring the key genes of salt tolerance are of great significance for understanding the physiological and molecular mechanisms of salt-tolerance and promoting salt tolerance breeding in wheat.In this experiment,121 wheat germplasm accessions were evaluated for salt tolerance,and salt-tolerant and salt-sensitive materials were selected for growth,physiological and transcriptome analyses.The main results were as follows:(1)One-hundred twenty-one wheat germplasm accessions were tested for salt-tolerance,and classified into five categories: high salt-tolerance,salt-tolerance,moderate salt-tolerance,salt-sensitivity and high salt-sensitivity.The average D values of 8 progeny populations from wheat distant crosses were higher than that of common wheat.Finally,a few of new salt-tolerant germplasm accessions(i.e.Y1805,P13,1713,082-1,1706,081)were identified.(2)The proline,soluble sugars and CAT contents of Y1805(salt-tolerant Triticum-Thinopyrum)were higher than those of CS(salt-sensitive wheat Chinese Spring).The root length and seedling height in Y1805 were inhibited less than those in CS.After the recovery from salt stress,the net photosynthetic rate and chlorophyll content of Y1805 were recovered more quickly than those of CS.Compared with CS,Y1805 showed higher salt tolerance in growth and physiological indexes.(3)By transcriptome analysis,a total of 112454 genes were detected,including92253 known genes and 20201 predicted new genes.Finally,44886 differentially expressed genes(DEGs)were obtained,30885 from Y1805 and 33694 from CS.The functions of three kinds of genes,i.e.the specific DEGs of Y1805 response to salt stress,the specific DEGs of Y1805 responses to salt stress and recovery,the common DEGs of Y1805 and CS under salt stress,were annotated by GO function.The specific GO items in Y1805 were obtained,such as the metabolisms of lutein(GO:0016122),carotenoid(GO: 0016116),respiratory electron transport chain(GO:0022904),ATP synthesis coupled electron transport(GO: 004277),peptide prolyl CIS trans isomerase activity(GO: 0003755)and CIS trans isomerase activity(GO:0016859).These metabolisms might be helpful to protect Y1805 against salt stress.Through KEGG functional annotation,it was found that y1805 DEG was enriched in RNA transport,plant pathogen interaction,phenylalanine biosynthesis,m RNA monitoring pathway,endoplasmic reticulum protein processing,MAPK signaling pathway-plant,plant hormone signaling pathway and other metabolic pathways.(4)Chromosomal thermogram analysis showed that the three types of DEGs and SNP / In Del loci in Y1805 and CS had different chromosome distribution,especially the number of SNP and In Del loci was very different.The number of DEGs in response to salt stress was the most on the chromosomes 2A,2B and 2D(or 2E),which was 348,368 and 355,respectively.The DEGs in Y1805 response to salt stress were distributed on many chromosomes(2B,3B,4B,5B and 6B,or their homoeologous group E chromosomes)of the B genome,which were mostly located at the ends of long arms.(5)796 wheat genes including CNL,RLP,NL domain types were obtained by plant disease resistance gene annotation.MYB,AP2-EREBP,b HLH,NAC,WRKY abiotic stress-related transcription factors were obtained by transcription factor annotation,among which Traes CS5B02G142100 and Traes CS1D02G078600 were reported as salt tolerance genes.The gene expression levels of the response to salt stress in Y1805 were higher than those in CS,indicating that a lot of salt-tolerant genes were expressed in large quantities in Y1805 under salt stress,which conferred it strong salt-tolerance.(6)A large number of variable splicing events,and SNP and In Del loci were found.352689 and 9237 SNP loci were found in Y1805 and CS,respectively,which showed a large difference between them.Their types of SNP and In Del loci were also different.(7)According to the analysis of KEGG annotation and the expression levels of the DEGs,combined with physiological and biochemical indexes,the response genes(Traes CS7D02G156800,BGI＿novel＿G007346,Traes CS2A02G207900,and Traes CS4B02G003600)to salt stress in Y1805 were found in the metabolic pathways such as glutathione(ko00480),starch and sucrose(KO 00500),MAPK signal pathway(ko04016),arginine and proline(ko00330),photosynthesis(ko00195),porphyrin and chlorophyll(ko00860),glyoxylate and dicarboxylic acid(ko00630)and the oxidoreductase pathway(ko04146).Ten key genes in response to salt stress were identified by qRT-PCR,and the expression levels of the genes Traes CS1A02G345600,Traes CS5A02G347300,Traes CSU02G080000,BGI＿novel＿G011173,BGI＿novel＿G013105,BGI＿novel＿G004826 and BGI＿novel＿G015026 were consistent with those by qRT-PCR analysis.In conclusion,some new salt-tolerant germplasm accessions were screened,the physiological and molecular mechanisms of salt tolerance in Y1805 were preliminarily understood,some key genes of the response to salt stress were explored in this work,which will lay an important foundation for the cloning,functional analysis of salt-tolerant genes,and genetics and breeding in wheat.