| Salt stress is very common in natural environment,which is one of the important factors restricting the development of agriculture worldwide.The damage of salt stress to plants usually manifests as osmotic stress,ion toxicity and secondary oxidative stress,leading to metabolic disorder and even plant death.Plant heat shock transcription factors can participate in various stress responses,play important roles in plant adapting to stressful environments.However,researches on plant heat shock transcription factors are mainly conducted in model plant species with low stress tolerance.There is few research on heat shock transcription factors in plants under extreme habitat.Haloxylon ammodendron is a typical desert xerophyte with excellent resistant to high temperature,cold,drought,salinity,alkaline and infertile.These performances originate from long-term natural selection and evolution which makes the species form a set of molecular mechanisms for adapting to extreme environments.Discovering genes involved in stress tolerance of H.ammodendron is of great significance to understand its stress tolerance mechanism and improve the tolerance of crops.In this study,the desert plant H.ammodendron was used as material to clone the full-length c DNAs of the heat shock transcription factor encoding genes HaHsfA1 and HaHsfA2;the subcellular locations of HaHsfA1 and HaHsfA2 were analyzed.The overexpression vectors of HaHsfA1 and HaHsfA2 were constructed and transformed into Arabidopsis thaliana,respectively.The effects of HaHsfA1 on sensitivity of Arabidopsis seedlings to exogenous ABA,osmotic stress and salt stress were analyzed;and the function of HaHsfA1 in Arabidopsis plants responding to salt stress was further studied.The main results were as follows:1.The HaHsfA1 and HaHsfA2 genes of the H.ammodendron heat shock transcription factors were cloned.The full-length c DNAs were 1719 bp and 1551 bp,respectively,and the full-length ORFs were 1599 bp and 1155 bp,encoding 532 and384 amino acids,respectively.The protein molecular weights of HaHsfA1 and HaHsfA2 were 59.4 k Da and 43.7 k Da,and their theoretical isoelectric points were 4.70and 5.42,respectively.They were all highly hydrophilic proteins and contained the conserved domains of DBD,HR-A/B,NLS,AHA and NES,which were unique features for heat shock transcription factors.They had the closest relationship with Beta vulgaris,Spinacia oleracea and Chenopodium quinoa,belonging to the family Chenopodiaceae.2.HaHsfA1 and HaHsfA2 proteins were located in the nucleus according to the prediction on the Genscript website.Subcellular localization vectors p BI121-HaHsfA1-GFP and p BI121-HaHsfA2-GFP were constructed and transformed into tobacco epidermal cells.The results confirmed that HaHsfA1 and HaHsfA2 were located in the nucleus.3.The 35S::HaHsfA1 and 35S::HaHsfA2 vectors were constructed and transformed into Arabidopsis thaliana,and homozygous lines overexpressing HaHsfA1and HaHsfA2 were obtained,respectively.4.Overexpression of HaHsfA1 significantly reduced the sensitivity of Arabidopsis seedlings to exogenous ABA,osmotic stress and salinity,especially the sensitivity to salinity.5.Under salt stress,overexpression of HaHsfA1 promoted the growth of Arabidopsis plants,increased the contents of chlorophyll,soluble sugar and proline in shoots,reduced osmotic potential and maintained a higher shoot water content,alleviated secondary oxidative stress,decreased relative plasma membrane permeability,increased root activity,resulted in stronger capacity for K~+absorption and Na~+ exclusion.Above results indicated that HaHsfA1 can improve the salt tolerance of plants,and implied that HaHsfA1 plays important roles for H.ammodendron to adapt to drought and salinity.This study laid a foundation for the elucidation of the stress tolerance mechanism and the discovery of stress tolerance relevant genes in H.ammodendron,and provided genetic resources for the genetic improvement of crop stress tolerance. |
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