Analysis The Stress Tolerance Of DmDREB And DlNAC Genes From Chrysanthemum In Transgenic Tobacco

Environmental stresses such as drought,high salt,high and low temperature affect plant growth and development extremely.DREB and NAC transcription factors both play the key roles in the response to abiotic stress.The DREB proteins,belonging to the transcription factors family AP2/EREBP,are able to bind specifically to the DRE/CRT sequence and activate the transcription of genes driven by the DRE/CRT sequence.The NAC proteins constitute one of the largest families of plant-specific transcription factors, and are involved in many physiological and biochemical process including plant growth and development,responsiveness to biotic and abiotic stress.DREB-like gene DmDREBb isolated from chrysanthemum was overexpressed in tobacco plants under the control of the constitutive promoter CaMV 35S.The transgenic tobacco plants were obtained by mediation of Agrobacterium tumefaciens.The 35S: DmDREBa and 35S:DmDREBb plants were analyzed for stress tolerance in the T₁ generation.Under cold stress,the fresh weight of 35S:DmDREBa and 35S:DmDREBb plants were significantly higher than wild tobacco.And the survival rates of 35S: DmDREBa and 35S:DmDREBb plants were 53%and 46%respectively,significantly higher than that of wild tobacco（which all died）.For the drought stress treatment,the survival rates of 35S:DmDREBa plants（60%） were clearly higher than wild tobacco （13%）.The activities of POD and content of proline were remarkable increased in overexpression of DmDREBa tabacoo.For salt stress treatment,the fresh weight of 35S: DmDREBb plants was significantly higher than wild tobacco,and the survival rates of 35S: DmDREBb plants（53%） was significantly higher than that of wild tobacco（20%）.And the 35S:DmDREBb plants had significantly higher activities of POD and content of proline. Our data suggest that overexpression of DmDREBa and DmDREBb enhanced cold stress tolerance in transgenic tobacco.Overexpression of DmDREBa resulted in significantly drought stress tolerance in transgenic tobacco.But overexpression of DmDREBb significantly increased salt stress tolerance in transgenic tobacco.Overexpression of DlNAC didn’t show significantly cold stress tolerance in transgenie tobacco,indicated that DlNAC from chrysanthemum is not involved in the response to cold stress.The transgenie tobacco plants overexpressing DlNAC showed increased tolerance to drought and salt.Under heat stress,the decrease in relative water content of 35S:N1NAC plants were slower than wild tobacco plants in T₀ generation.Then transgenic lines were analyzed for heat tolerance in the T₁ generation,and the survival rates of lines L-31;L-32 and L-33 were 88.24%,72.88%and 75.44%respectively,significantly higher than that of wild tobacco（which all died）.The results suggest that overexpression of DlNAC enhanced heat tolerance in transgenic tobacco.