Study On The Whole Transcriptome Of Suaeda Heteroptera In Response To High Salt Stress

Suaeda heteropteran,an annual salt tolerant herbaceous plant of Chenopodiaceae(Suaeda),grows in coastal wetlands,lakefront,deserts and other saline-alkali regions.It is considered as a typical saline soil indicator plant because of its strong salt tolerance.As a "pioneer plant," Suaeda heteroptera can be used as a model organism for the study of salt tolerance and stress resistance in plants.It can also be applied to the environmental protection of coastal wetlands,and to remediation of contaminated saline-alkali soils.Soil salinization has always been one of the main problems limiting agricultural production.Therefore,researchers hope to solve the limitation of soil salinization on plant productivity by analyzing mechanism of salt tolerance in plants and enhancing plant salt tolerance.However,the studies on salt tolerance of Suaeda heteroptera were mainly focused on physiology and biochemistry,and the molecular mechanism of salt tolerance was still in it's infancy.With the development of high-throughput sequencing technology,it is possible to study the salt-tolerant molecular mechanism of Suaeda heteroptera by modern biological methods,and it is also conducive to a more comprehensive understanding of the anti-regulatory mechanisms of Suaeda heteroptera.In this study,Illumina high-throughput sequencing technology was used to sequence transcriptomes of normal growing Suaeda heteroptera plants and plants treated with NaCl stress,and a large amount of transcript information was obtained.At the same time,combining with the changes of the content of chlorophyll and anthocyanin,the level of transcriptome and plant physiological and biochemical reactions in response to salt stress were analyzed,and the genes and metabolic pathways related to tolerance to salinity stress in Suaeda heteroptera were initially explored.It is hoped to provide a theoretical basis for a deeper understanding of the molecular mechanism of salt tolerance of Suaeda heteroptera.The main results are as follows:1.A series of NaCl concentration gradients were set up to screen,and finally the salt stress treatment concentration of Suaeda heteroptera plants was determined.2.Compared with Suaeda heteroptera grown under normal conditions,the content of chlorophyll and anthocyanin of Suaeda heteroptera after salt stress treatment had a significant decrease,in which the content of chlorophyll reduced by 19.84% and the content of anthocyanin decreased by 9.91%.3.A total of 12.94 Gb data were obtained from Suaeda heteroptera transcriptome sequencing.There were 147176 transcripts with an average length of 695 bp.After splicing,84,545 unigenes were obtained with an average length of 590 bp.4.Unigenes were sequenced for gene function annotation in the seven databases Nr,Nt,Pfam,KOG,Swiss-prot,KEGG and GO,53.43% of the unigenes were successfully annotated in at least one of the above seven databases,and 5.89% of the unigenes were all successfully annotated in the seven databases.5.The GO enrichment analysis of the differentially expressed genes in the transcriptome data of Suaeda heteroptera showed that there were multiple genes up-regulated or downregulated in carbohydrate metabolic process under the biological process classification.There are several genes in hydrolase activity,hydrolyzing O-glycosyl compounds and hydrolase activity,acting on glycosyl bonds under the molecular function classification,which are upregulated or down-regulated.In addition,several genes are up-regulated under photosynthetic electron transport in the photosynthetic system II;several genes are down-regulated in the transfer glycosyl and hydrolase activities.6.The KEGG enrichment analysis of the differentially expressed genes in the Suaeda heteropter transcriptome data showed that the process of significant enrichment was: Photosynthesis,Starch and sucrose metabolism,Phenylpropanoid biosynthesis,Alanine,aspartate and glutamate metabolism,Sesquiterpenoid and triterpenoid biosynthesis,Amino sugar and nucleotide sugar metabolism,Cysteine and methionine metabolism,Plant hormone signal transduction,Linoleic acid metabolism,Cyanoamino acid metabolism,Nitrogen metabolism,alpha-Linolenic acid metabolism.Differentially expressed genes in the KEGG pathway annotated to photosynthetic metabolism include the up-regulated photosystem II P 680 response center D1 protein and photosystem II chlorophyll apolipoprotein CP 43 and down-regulated plastocyanin.EIN3-binding F-box protein and xyloglucan(xyloglucosyl transferase TCH4),both of which are annotated to the phytohormone signaling pathway of the down-regulated genes on the KEGG pathway.Down-regulation of gene glutamate synthase(NADPH/NADH)is annotated to the pathway of Nitrogen metabolism.The KEGG pathway genes that are annotated to starch and sucrose metabolism contain up-regulated ?-glucosidase,?-amylase and down-regulated genes trehalose 6-phosphate phosphatase.The genes of the KEGG pathway metabolized by the phenylpropanoid biosynthesis annotation include up-regulated ?-glucosidase and down-regulated peroxidase.The down-regulated genes that are annotated to the alanine,aspartate and glutamate metabolism KEGG pathway include the asparagine synthase(glutamine-hydrolysing)and glutamate synthase(NADPH/NADH)coding genes.