Studies On Abiotic Stresses Of BcICE1-overexpression In Transgenic Tobacca

Plant growth and productivity are greatly limited by environmental stresses,such as drought,high salinity,and low temperature.Plants adapt to these stresses through physiological and biochemical changes,including the expression of stress-responsive functional and regulatory genes which are related and share common signaling pathways.Molecular and cellular responses to these stresses have been analyzed extensively at the biochemical level:various kinds of proteins and smaller molecules,including soluble sugar and proline,accumulate.In addition,stress-responsive marker genes are induced by stresses.ICE1-CBF regulating pathway is a major way of cold response gene activation,and play an important role in response to abiotic stress.ICEI(inducer of CBF expression 1),a MYC-type bHLH transcription factor,is an important activator of CBF3/DREB1A for regulating cold signaling and stress tolerance.In the present study,the over-expressing BcICE1 transgenic and wild type tobacco were used to study the responses of transgenic tobacco to abiotic stresses.The main results are as follows:1.The transgenic tobacco showed high expression of BcICE1 at both mRNA and protein levels by RT-PCR and Western blot.2.Under cold,salt and osmotic stress,transgenic tobacco germinated and grew normally while the wild type tobacco were severely inhibited.This result showed that over-expressing BcICE1 enhanced abiotic tolerance in transgenic tobacco.3.Under cold stress,BcICI1-overexpressing tobacco showed higher activities of antioxidant enzymes,such as SOD,POD,CAT and APX.Accumulation of H2O2 in transgenic tobacco was lower than that in wild type tobacco,suggesting that BcICE1-overexpressing tobacco was involved in removing ROS to enhance cold tolerance.Under cold stress,the relative electrical conductivity and MDA content in both wild type tobacco and transgenic tobacco increased,which resulted in the increase of membrane permeability and electrolyte leakage.However,the MDA and relative electrical conductivity in transgenic tobacco was lower than that in wild type tobacco,indicating the extent of the membrance lipid perioxidation in transgenic tobacco was smaller than that in wild type tobacco.4.Under cold,salt and osmotic stress,BcICE1-overexpressing tobacco showed higher chlorophyll content and accumulated more proline and soluble sugars compared with wild type tobacco.Under salt and osmotic stress,the antioxidant enzyme activities of APX and GPX were more accumulated in transgenic tobacco.5.Under cold stress,BcICE1-overexpressing tobacco improved the expression levels of CBFs and their target genes,including NtPOD,NtCAT,NtSOD,NtP5CS,NtERD10B and NtERD10C.