The Research On Physiological Mechanism Of Thellungiella Salsuginea In Response To The Imbalance Of Sodium And Potassium Ions

The most fundamental reason that soil salinization affects plant growth and development is that it breaks the ion balance of plants.The imbalance of Na~+/K~+in plants'cells leads to the destruction of cell membrane,osmotic stress and ion toxicity.This research,studying salt-stressed(100 m M Na Cl and 100 m M KCl)Thellungiella salsuginea(of relatively high salt-resistance),wild type Arabidopsis thaliana and its mutants(Nah G:transgenic plant with a lower SA content;c2h2:C2H2 knocked out mutant;C2H2-OX:C2H2 overexpressed mutant;Nah G×C2H2-OX:C2H2-OX and Nah G double transgenic material),is to explore the physiological mechanism of Thellungiella salsuginea in response to Na~+/K~+imbalance,through transcriptome sequencing as well as other techniques.The main findingsarelisted below:(1)Thellungiella salsuginea is more sensitive to K~+stress due to its potassium absorption and sodium removal mechanismUnder the stress of 100 m M sodium ions,the decline of biomass and water content and increase of ion-leakage and MDA in Thellungiella salsuginea are apparently lower compared to in Arabidopsis thaliana.However,underthe 100 m M K~+stress,the change in Thellungiella salsuginea was more obvious than Arabidopsis thaliana.Under Na~+stress,the phenomenon of membrane lipid peroxidation was not that serious in Thellungiella salsuginea.While,Thellungiella salsuginea lost the selective permeability of cell membrane under K~+stress,the membrane lipid peroxidation was more serious than Arabidopsis thaliana,with cell membrane severely damaged.In addition,after being treated with 100 m M Na Cl,Thellungiella salsuginea accumulated more K~+and restrained the sharp upward trend of Na~+,leaving Na~+content in Arabidopsis thaliana at only 62%.Thus,the Na~+/K~+imbalance caused by Na~+stress was reduced.In contrast,after being treated with 100 m M KCl,the K~+content of Thellungiella salsuginea increased by 1.7 times than that of Arabidopsis thaliana and Na~+content decreased significantly.The accumulation of K~+made it suffer more severe K~+stress than Arabidopsis thaliana.In addition,100 m M Na~+and 100 m M K~+produced oxidative stress to Thellungiella salsuginea and Arabidopsis thaliana.Compared with Na~+stress,Thellungiella salsuginea accumulated more reactive oxygen species under K~+stress,the content of reactive oxygen species significantly higher than that of Arabidopsis thaliana.Moreover,the content of ascorbic acid(As A),glutathione(GSH)and antioxidant enzyme activity of Thellungiella salsuginea under K~+stress was lower than that of Arabidopsis thaliana.The results showed that Thellungiella salsuginea was more sensitive to K~+stress and had no tolerance to K~+stress.Therefore,the tolerance of Thellungiella salsuginea to salt stress is specific to Na~+stress.Thellungiella salsuginea enhances plant's tolerance to salt stress by promoting K~+absorption and Na~+expelling.(2)Lacking of endogenous SA and the overexpression of C2H2 transcription factor are conducive to improving the salinity tolerance of plantsThis research conducted the Transcriptome analysis of Thellungiella salsuginea and Arabidopsis thaliana under salt stress,and the transcription factor C2H2 which was involved in salt stress resistance mechanism of Thellungiella salsuginea was screened.100 m M Na~+treatments were administrated to Col,Nah G,c2h2,C2H2-OX and Nah G×C2H2-OX transgenicplants,respectively.After being stressed for 3 days,some physiological and biochemical indicators were detected.The results showed that the plant's fresh weight,water content and chlorophyll content were suppressed by the salt stressed at different levels.Na~+content increased significantly,while K~+content decreased.Ion-leakage,MDA content and ROS content increased.In the determination of chlorophyll fluorescence parameters,it found salt stress decreased Fv/Fm??PSII and q P,but induced an increase in NPQ.The activeness of antioxidant enzymes(SOD,CAT,POD,APX,GPX,GR)and Antioxidant(As A,GSH)content increased.Among all the plants,c2h2 mutant plants were hardest affected by salt stress.Compared to the wild type plants,Nah G and C2H2-OX were less affected by salt stress,and had better salt tolerance.This indicated that the absence of endogenous SA and the over-expressed C2H2 transcription factor-both could improve the salt tolerance of Arabidopsis thaliana.In addition,the two factors have synergistic effects,which can enable Nah G×C2H2-OX plants have the strongest capacity of resistance to salt stress.(3)Transcriptome sequencing analysis of C2H2-OX under salt stressWith the aim of conducting transcriptome sequencing and bioinformatics analysis,100 m M Na~+stress was employed to deal with wild-type Arabidopsis thaliana,c2h2and C2H2-OX mutants.After the stress,the results showed that there were 302 genes with highly specific expression in C2H2-OX.Enrichment analysis of GO(Gene Ontology)and KEGG(Kyoto Encyclopedia of Genes and Genomes)pathways of differentially expressed genes showed that those genes are mainly associated with biological metabolic processes,including growth and reproduction,cell response to external stimuli,hormone stress response,REDOX,proline decomposition,glutathione metabolism,ion transmembrane transport,photosynthetic regulation and the like.This research screened the specific and salt-stress-related differential genes in C2H2-OX,and found 42 genes[Fold change(FC)>8]with great specific differences,including peroxidase genes,factors related to metal ion absorption and transport,and transcription factors related to salt stress.It was speculated that these genes closely related to C2H2 transcription factor might be target genes of C2H2 transcription factor binding.C2H2 transcription factor can induce the expression of these genes,thus enhancing plants'“absorption of K~+and excretion of Na~+”mechanism and boosting their ability to resist salt stress.