Cloning And Function Analysis Of Transcription Factor AcDREB2 In Atriplex Canescens

Salinity and drought are the most destructive abiotic factors directly threatening agricultural productivity and ecological environment worldwide,which can cause a series of injuries such as membrane damage,cel ular metabolic disturbance and abnormal water distribution,thus result in seriously disruption on the normal growth and development of higher plants.In order to survive and reproduce in harsh environments,higher plants have evolved a series of physiological and biochemica l protective mechanisms to acclimatize to adversity.Under salt and drought stress,many stress tolerance-related genes in plant are significantly induced,and the expression of these genes can be regulated by the ABA-independent pathway in addition to the ABAdependent signaling pathway,in which the dehydration response element binding proteins(DREBs)play the important roles in this process.However,most of the studies on such transcription factors are concentrated in crops and model plants with limited resistance,there are few studies on desert halophytes with stronger adaptabilit y.Atriplex canescens is an excel ent fodder with excel ent adaptability,evolving unique mechanisms in response to adverse environment.Previous studies on A.canescens mainly focused on ecological restoration,seed germination,physiological adaptation and ion transport.The function of transcription factors in the process of stress resistance has not been reported in detail.Therefore,in this study,an AcDREB2 gene encoding DREB of A.canescens was cloned and its expression pattern in response to salt and osmotic stress was analyzed.Its transcriptional activity was also verified.Moreover,in order to further clarify the function of AcDREB2 in plant stress resistance,AcDREB2 was overexpressed in Arabidopsis thaliana.The findings are as follows:1.The cDNA of AcDREB2 gene includes 867 bp,in which the CDS sequence is 729 bp encoding a total of 242 amino acids,and its N-terminus contains a conserved domain of AP2/EREBP.The 14 th amino acid residue is a conserved valine.Amino acid alignment indicated that AcDREB2 shares high sequence similarity with homology proteins from other similar plants and desert plants.2.Under NaCl or osmotic stress treatments,the expressions of AcDREB2 in leaves of A.canescens were significantly higher than that in roots and stems,and the expression level increased rapidly after treatment for 3 h,indicating that the expression of AcDREB2 was rapidly induced by salt and osmotic stress.3.AcDREB2 is localized in the nucleus and showed transcriptional activatio n activity,which can successfully bind DRE cis-elements and activate the expression of downstream reporter genes.It is speculated that AcDREB2 plays the important regulation roles in plants response to stresses.4.Overexpression of AcDREB2 enhanced the salt and drought tolerance of transgenic A.thaliana.After 15 days of treatment with 200 mM NaCl,the wild-type plants showed dwarfed and wilting,while the AcDREB2 overexpression plants grew wel.It was found that overexpression plants were superior to wild-type by comparing and analyzing the indexes including biomass,chlorophyll content,photosynthe t ic parameters,relative water content,plasma membrane permeability and leaf water loss rate.Similarly,After being treated by periodic drought treatment for 14 days,the biomass,chlorophyll content,net photosynthetic rate,stomatal conductance,water use efficiency and relative water content of AcDREB2 overexpression plants were significantly higher than that of wild-type plants,and leaf water loss rate was also significantly lower compare to wild-type.In summary,AcDREB2 can positively respond to external salt and osmotic stress environments.The overexpression of AcDREB2 confer salt and drought tolerance intransgenic Arabidopsis,indicating that AcDREB2 plays key roles in abiotic resistance of A.canescens.