The Mechanism Investigaiton Of Arabidopsis Small GTP Binding Protein RABE1C In Plant Drought Response

Drought is one of the most serious abiotic stresses in restraining plant nomal growth and development,as well as crop yield.As a long-standing worldwide problem,drought also threats food security in our country.To screen and investigate the plant drought responsive genes,and to find out their regulatory mechanisms is an important way to improve plant drought tolerance and further development of water-use-efficiency agriculture.In this study,the model plant Arabidopsis thaliana was used,and a serial of candidate genes which were highly expressed in guard cess found by proteomics analysis were screened with drought treatment.Among them,a small GTP binding protein RABE1C encoding gene,At3g46060,was found to be involved in plant drought response.By using physiology,molecular biology,electrophysiology techniques,we have performed a thorough anaylyses to find out the molecular mechanism of RABE1C.RABE1C is a guard cell highly expressed GTP binding protein,and positive regulator in plant drought response.The transcripts of RABE1C could be induced by drought and ABA treatments,and the GUS staining assay confirmed that.RABE1C was highly expressed in guard cells.The RABE1C::GFP fusion protein assay showed that the RABE1C was subcellularly expressed in cell membrane and cytoplasm.The survival rate of the RABE1C loss-of-function mutants,rabelc-1 and rage1c-2,were significantly lower than wild type plants with drought treatment,and further water-loss experiment with detached leaves also showed that the mutant leaves lost water more quickly than those of wild type plants.ABA is the most important phytohormone in plant drought response.which plays essential roles in guard cell signaling and stomatal movements,the ABA regulated stomatal movements was employed as the model system to find out the molecular mechanism of RABE1C in plant drought response.The peel assay experiments showed that,the rabe1c mutants were hyposensitive to ABA in both ABA induced stomatal closure and ABA inhibited stomatal opening than Col-0.The guard cell patch clamp data revealed that,the slow anion currents of rabe1c-1 and-2 guard cells were hyposensitive to ABA activation than those of Col-0 as well.To confirm the physiological phenotypes of the rabe1c mutants were caused by the loss of RABE1C,we constructed two RABE1C over-expression transgenic lines(RABE1C-OE-1,RABE1C-OE-2)and two rabe1c/RABE1C functional complementation lines(RABE1C-C-1,RABE1C-C-2).The phenotypic analyses with these RABE1C over-expression and complementation line showed that,the RABE1C-OE-1 and RABE1C-OE-2 were hypersensitive to ABA in ABA regulated stomatal movement,and the ABA hyposensitivity of rabelc mutnats could be restored in RABE1C-C-1 and RABE1C-C-2 lines.Further drought and water-loss experiments also confirmed that the RABE1C over-expression lines enhanced plant drought tolerance of plant.All presented data demonstrated that,the RABE1C is the key positive regulator in ABA regulated stomatal movements,and thus to enhance the plant drought tolerance.It is of great significance to perfect the guard cell ABA signaling,and the potential application in development water-use-efficiency modern agriculture.