Molecular Mechanism Of Arabidopsis Transcription Factor OXS2 Regulating Salt Stress Response

Mineral nutrients are essential for plant growth and development,however,excessive soluble salt in the soil is detrimental to most plants.Salt stress is one of the severest abiotic stresses,which affects plant growth and crop yield,and can have a serious impact on the whole life of plant development process.For a long time,how to improve the plant salt tolerance and thus to increase the crop yield and quality becomes the focus of plant physiologists.Therefore,to identify salt-tolerant genes by using genetic and genomic methods,and to investigate their molecular mechanisms in plant salinity response,will be helpful for supplying useful functional genes and theoretical guidance for further generation of salt-tolerant varieties.In previous study,a salt responsive gene,OXIDATIVE STRESS 2(OXS2),has been identified from Arabidopsis,which could be transiently induced by salt stress.OXS2 is a classical transcription factor with conserved sequences shared among the members of the family belonged.However,until now,there is no direct evidence showing that OXS2 is involved in plant salt response.In this study,we focused on the functional and molecular mechanism investigation of OXS2 of Arabidopsis in response to salt treatment.This thesis described the acquired salt tolerance gene,discussed the related molecular mechanism in plant,and provided candidate gene and guidelines for engineering a new salt tolerance crop cultivar.The following results were obtained:1)The GUS staining analysis showed that OXS2 was ubiquitously expressed in all tissues,especially highly expressed in roots;2)OXS2 is a positive regulator of plants response to salt stress:By using the loss-of function mutant oxs2-1.a T-DNA insertion mutant of OXS2 from ABRC,the physiological role of OXS2 was thoroughly screened.And the results turned out that,the oxs2-1 was hypersensitive to salt treatment than wild type plant,it showed slower germination rate,fewer cotyledon greening seedlings,and shorter root length.It indicated that the gene is involved in the regulation of salt stress response.3)The subcellular localization of OXS2 could be regulated by salt stress.To clarify the characteristics of OXS2 as a transcription factor,we used the particle bombardment transient transformation technique to detect the subcellular localization of OXS2.The result indicated that,under normal conditions,OXS2 distributed throughout the cytoplasm;however,when treated with salt,OXS2 signal could be observed in the nucleus;4)OXS2 function in plant salt stress invokes a set of genes downstream.To further explore the salt tolerance mechanism of OXS2,transcriptomic sequence technology(RNA-seq)was used to find out the genes with different transcription levels between wild-type plants and oxs2-1 under salt stress,and 137 genes were obtained.Considering that the loss of OXS2 may lead to the decreased transcription of putative downstream target genes,so,we selected 28 significantly down-regulated genes(DEGs)in oxs2-1 as further candidates.After further confirmed by RT-qPCR,13 DEGs were regarded as essential putative components.With KEGG and GO analyses,these 13 genes were regarded as modules of multiple signaling pathways.Our results indicated that OXS2 confers salt tolerance in Arabidopsis through multiple stress-dependent pathways including photosynthesis,oxidation-reduction process,carbon metabolism,ABA singaling process,and etc.This work systematically analyzed the physiological roles and molecular mechanisms of OXS2 in plant salt stress response.Our experiments provided ideas and approaches for exploring novel salt responsive genes and the salt tolerance mechanisms deeply.Our results suggested that,the OXS2 is positively involved in plant salt stress response,and maybe a useful candidate gene for further generation of salt-tolerant transgenic crop varieties,and thus to benefit the crop yield,as well as the management and improvement of saline and alkaline land.