The Functional Characterization Of TtASR From Tetragonia Tetragonioides Under Salt And Drought Stress

Tetragonia tetragonioides(Aizoaceae)is an annual or biennial semi-vine herb which is a kind of halophytic vegetable with economic and ecological value being distributed in the coastal salt-rich areas of subtropical and temperate regions.As a salt-tolerant plant,Tetragonia tetragonioides can tolerate sea water salinity and grow normally in saline stagnant areas caused by seawater reverse irrigation.Futhermore,it can be used for improving and utilizing beach,salt wasteland and seawater irrigation farmland.So,Tetragonia tetragonioides is an economic crop with important ecological value.With Tetragonia tetragonioides as the research object,an ASR gene was isolated based on the construction of cDNA library from Tetragonia tetragonioides(Pall.)Kuntze and its sequences analysis,and it was designated as TtASR(GenBank accession no.: MH454101).In this work,the bioinformatics research and functional characterization of the gene was systematically performed and analyzed.The results were summarized as follows:1.Bioinformatics analysis of TtASR: The full-length of TtASR cDNA is 1112 bp,including a 723 bp open reading frame,encoding a protein with 243 amino acids.The isoelectric point of TtASR is 5.26,and the molecular weight is 25.29 KD.Tt ASR comprises an ABA/WDS domain,which is a common feature to all plant ASR members,and the N-terminal contains glycine-rich segment(Gly-rich motif),while the C-terminal contains a nuclear localization signal(NLS).2.Expression analysis of TtASR showed that TtASR is widely expressed in different tissues or organs of Tetragonia tetragonioides.Meanwhile,high salt,hypertonicity,ABA treatments can induce the expression of TtASR.3.TtASR heterologous expression assay in Escherichia coli showed that the induced accumulation of TtASR could improve the tolerance of E.coli strains to salt,hyperosmosis,and oxidative stresses.4.Functional analysis of TtASR in yeast: TtASR gene can can improve salt tolerance and antioxidant ability of yeast.5.Transcriptional activity analysis of TtASR: The transcriptional activity of TtASR was detected by the method of ?-galactosidase.It was found that the TtASR gene is different from some ASR family genes and does not have transcriptional activity,which is supposed to be related to its protein structure.6.Subcellular localization analysis of TtASR indicated that mainly distributed in cytoplasm and nucleus.7.The transgenic function verification in Arabidopsis of TtASR: the CDSs of TtASR was inserted into plant transgenic over-expression vector,and transformed into Arabidopsis through flora-dip method mediated by agrobacterium infection,and the homozygous transgenic plants were obtained.By the analysis of root length and plant groth under different stresses,the results indicated that the over-expression of TtASR in Arabidopsis could enhance plants' resistance to salt,drought stresses and oxidative stress.