Physiological And Molecular Mechanisms Of Selenium Improving Salt Tolerance Of Arabidopsis Thaliana

Salt stress seriously threatens the growth and development of crops and restricts their yield and quality.Selenium(Se)is a beneficial element for plant growth and development,and plays an important role in improving plant response to various abiotic stresses.In this study,Arabidopsis thaliana wild type(WT)and salt-sensitive mutants(SOS1,SOS2,SOS3)were used as test materials.Under hydroponic conditions,Arabidopsis thaliana was treated with Na Cl to study the role and mechanism of exogenous selenium(Na2Se O3)in regulating Arabidopsis salt stress resistance.The main results are as follows:1.Under salt stress,the dry weight and fresh weight of wild type and mutant plants decreased to some extent compared with the control,and the contents of chlorophyll a and chlorophyll b in leaves decreased significantly,which inhibited the photosynthesis of plants.After exogenous selenium addition,the fresh weight of mutant plants was significantly increased compared with salt stress,and the dry weight of SOS1 and SOS3 was significantly increased compared with salt stress.Selenium application alleviated the growth inhibition of Arabidopsis thaliana under salt stress to a certain extent.Compared with salt stress,the contents of chlorophyll a and chlorophyll b increased under selenium application,but did not reach a significant level.Under salt stress,superoxide anion(O2·-)and hydrogen peroxide(H2O2)in wild type and mutant leaves increased significantly,and the content of malondialdehyde in mutant leaves increased significantly.After selenium treatment,the content of superoxide anion,hydrogen peroxide and malondialdehyde in mutant leaves decreased significantly.Salt stress increased the activities of superoxide dismutase(SOD),peroxidase(POD)and catalase(CAT)in Arabidopsis leaves,and selenium application further significantly increased the activities of these enzymes in the mutant.Salt stress significantly increased the contents of glutathione(GSH)and ascorbic acid(ASA)in Arabidopsis haliana leaves.After the addition of selenium,the GSH content further increased significantly,but the ASA content decreased significantly.Salt stress significantly increased the content of soluble sugar and soluble protein in the mutant.After selenium application,the content of soluble sugar in SOS1 and SOS2 leaves decreased significantly,and the content of soluble sugar in SOS3 decreased.The soluble protein content in leaves of wild type and mutant was further increased.Under normal conditions,there was no significant difference in the content of Na+ and K+ between the mutant and the wild type,but the content of K+ in the wild type and themutant decreased significantly after salt treatment,and the content of Na+ increased significantly.2.The changes of metabolites in the leaves of Arabidopsis wild type and salt sensitive mutant(SOS1)under salt stress were studied by non-targeted metabolomics.The results showed that a total of 201 differential metabolites were detected in wild-type Arabidopsis after salt stress treatment.The up-regulated differential metabolites were mainly lipids and organic acids.KEGG analysis showed that differential metabolites were mainly enriched in glycerophospholipid metabolism,arginine and proline metabolism,pyrimidine metabolism,ABC transporter and other metabolic pathways.A total of 265 differential metabolites were detected after adding selenium under salt stress.The up-regulated differential metabolites were mainly organic acids,lipids and organic oxygen-containing compounds.KEGG analysis showed that the differential metabolites were mainly enriched in ABC transporters,arginine and proline metabolism,purine metabolism,aminoacyl biosynthesis and other metabolic pathways.A total of 336 differential metabolites were detected in the SOS1 mutant after salt stress treatment.The up-regulated differential metabolites were mainly organic acids,lipids,organic oxygenates and organic heterocyclic compounds.KEGG analysis showed that the differential metabolites were mainly enriched in arginine and proline metabolism,betaine biosynthesis,phenylpropanoid metabolism,phenylpropanoid biosynthesis and other metabolic pathways.After adding selenium under salt stress,a total of 347 differential metabolites were detected.The up-regulated differential metabolites were mainly organic acids,lipids and organic heterocyclic compounds.KEGG analysis showed that the differential metabolites were mainly enriched in metabolic pathways such as biosynthesis of cofactors,glycerophospholipid metabolism,arginine and proline metabolism.3.The transcriptome method was used to study the changes of gene expression in the leaves of Arabidopsis wild type and salt sensitive mutant(SOS1)under salt stress,and the results showed that 611 differential genes were detected after wild type salt stress,and the differential genes were mainly enriched in plant hormone signal transduction,plant MAPK signaling pathway,plant pathogen interaction,diterpene biosynthesis and other metabolic pathways.After adding selenium under salt stress,631 differential genes were detected,and the differential genes were mainly enriched in plant MAPK signaling pathway,linolenic acid metabolism,glutathione metabolism,porphyrin and chlorophyll metabolism.After salt stress treatment,8316 differentially expressed genes were detected in the SOS1 mutant.The differentially expressed genes were enriched in metabolic pathways such as photosynthesis,ribosome biogenesis in eukaryotes,ribosome,photosynthesis-antenna protein;after the SOS1 mutant was treated with salt stress and selenium,1442 differential genes were detected.The differential genes were mainly enriched in metabolic pathways such as photosynthesis,photosynthesis-antenna protein,plant pathogen interaction,and plant hormone signal transduction.4.Through the combined analysis of transcriptome and metabolome,it was found that selenium application had a great influence on starch and sucrose metabolism and arginine and proline metabolism in wild type and mutant under salt stress.In the wild type,the downregulation of sucrose synthase gene in starch and sucrose metabolism pathway may be the reason for the change of sucrose,D-maltose and fructan content.In the arginine and proline metabolic pathways,the decrease of proline dehydrogenase expression may be the reason for the increase of proline abundance,and the increase of arginine abundance also indirectly increases the abundance of L-glutamic acid.In the mutant,the abundance of sucrose,Dmaltose and CDP-glucose decreased,which was regulated by multiple genes.In the arginine and proline metabolic pathways,the decreased expression of arginine decarboxylase may be the cause of arginine enrichment,which in turn increases the synthesis and transformation of coumaroyl putrescine and N-acetyl putrescine.Selenium may affect the differential genes and differential metabolites in these pathways to maintain the physiological homeostasis and growth and development of Arabidopsis under salt stress.