The Mechanism Of NAC Transcription Factor CsATAF1 In Response To Drought Stress In Cucumber

Cucumber is an important horticultural crop,the growth of cucumber has a great demand for water and is sensitive to water deficit,and drought stress significantly reduces yield even lead to complete failure of production.NAC transcription factors play important roles in response to drought stress,the molecular machnisms of NAC transcription factors are still unkown in cucumber.In this study,CsATAFl was characterized and isolated,and we studied the regulator machenisms of CsATAFl in response to drought stress.The main results as follow:1.CsATAF1 was isolated and characterized in cucumber,the CsATAF1 protein contained a high-conserved N-terminal domain,while the C-terminal domain of CsATAF1 had a low similarity with the NAC proteins in other species.A phylogenetic tree showed that CsATAF1 clustered in the same clade as ATAF1 in Arabidopsis.Subcellular location assay showed that CsATAFl localized in the nuclei.CsATAF1 was induced by different stress treatments and hormone treatements,after 9h of dehydration treatment,the relative expression of CsATAF1 increased more than 40-fold.The C-terminal region of CsATAF1 was the transcription activation domain,while the N-terminal region of CsATAF1 appeared to lack this activity.2.Overexpression(OE)of CsATAF1 promoted seed germination under PEG treatment,and enhanced drought tolerance under drought condition,the water loss rates and stomaotal apertures of OE plants were significantly lower than WT plants,while the photosynthetic efficiency was significantly higher than WT plants.OE plants might decrease water loss by regulating stomatal closure.Drought stress induced ROS accumulation,in OE plants,the anoxdiant enzymes activities increased to scavenge ROS,the H2O2and O2·-content were significantly lower than WT plants.Overexpressing CsATAF1 increased sensitivity to ABA and were more sensitive to promote stomata1 closure under drought condition.In contrast,CsATAF1-RNAi(Ri)plants decreased drought stress tolerance and sensitivity to ABA and accumulate more ROS.3.CsDREB2C,CsCu-ZnSOD,and CsABI5 were certified as the target genes of CsATAFl.In OE plants,the expressions of CsDREB2C,CsCu-ZnSOD,and CsAB15 were up-regulated and down-regulated in Ri plants.Yeast one hyrid and EMSA asssy showed that CsATAF1 could bind to the NACRS in the promoters of CsDREB2C,CsCu-ZnSOD,and CsAB15.Transient expression in tobacco leaves and cucumber protoplasts showed that CsATAFl directly up-regulated the expressions of CsDREB2C,CsCu-ZnSOD,and CsAB15.In summary,CsAAF1 functioned as a positive regulator in response to drought stress in an ABA-dependent pathway and decreased reactive oxygen species(ROS)accumulation in cucumber.