Mutantion Of Arabidopsis Armadillo/Beta-catenin Repeat Gene Causes Severe Defects In Abiotic Stresses Tolerance Ability At The Stage Of Seeds

Molecular chaperones are a group of proteins that influence the structure and function of many polypeptides.They assist the folding,the assembly,the translocation and the aggregation by controlling,binding and releasing the polytides.Under stress conditions, molecular chaperones stabilize the proteins' structure by hindering the aggregation of denatured proteins.Hsp70 proteins' structures are highly conserved,including two main functional areas:N-terminal ATPase domain and C-peptide-binding domain,N-terminal signal peptide could lead HSP70s to different organelles,the C-terminal 100 amino acids can form C-terminal subdomain,function with the HSP70s molecular chaperone.AtFes1-1 gene is a typical heat-inducible gene,which may be binds with plant Hsp70 and promotes the nucleotide exchange reaction of Hsp70.In this study,we studied the role of AtFes1-1 protein in the abiotic stress of Arabidopsis thaliana,with a main view of the mechanism of heat tolerance for plants.The results showed that the AtFes1-1 protein played an important role in the abiotic resistance of Arabidopsis thaliana.The results were shown as follows:1.Previous results indicated that AtFes 1-1 mutant showed severe defects in thermtolerance. In this study,we treated AtFes1-1 mutant seeds with heat-shock and salt stress,results showed that the AtFes1-1 mutant causes severe defects in both stresses.Compared to wild-type Arabidopsis thaliana seeds,the AtFes1-1 mutant showed significantly decrease in the rate of seed germination.Western blot analysis found that:AtFes1-1 protein content was increased in the process of seed development.The dry seeds have a weak signal of AtFes1-1 protein,as the seeds sprout,the signal gradually increased.In addition,the Hsp70 protein level of AtFes1-1 mutant is slightly lower than wild-type.2.The AtFes1-1 promoter sequence(673bp) was isolated from Arabidopsis thaliana genomic DNA.The sequence has several typical sequences,such as TATA box and CAAT box.A total of three HSEs and three AT-rich regions were found in the sequence. Additionally,there are some transcription binding motifs related to stress response,such as HSE,C-box and GAAAAA.AtFes1-1 construction of the promoter(673bp) and the gus gene fusion vector,was introduced into Arabidopsis thaliana.At normal temperature,most of the tissues didn't detecte GUS expression.After heat shock,strong GUS staining was detected in the roots, leaves,flowers,fruits and germinated seeds,under the control of AtFes1-1 promoter to the gus gene in transgenic Arabidopsis thaliana.The heat-induced GUS activity was different in the floral tissues at various developmental stages.Obvious GUS activities under NaCl and H₂O₂ stress conditions were also detected,but under low tempreture and drought conditions, the activity of the promoter was very weak.These results suggested that AtFes 1-1 promoter was heat-inducible strong promoter and was subject to other stresses.3.In order to study the mechanism of AtFes1-1 protein and HSP70,we carried out yeast two-hybrid experiments and nucleotide exchange experiments.It was found that yeast expressed AtFes1-1 protein and HSP70,but these yeast clones couldn't grow on the four defects SD medium;It was also found that AtFes1-1 didn't affect the nucleotide exchange rate, and didn't affect the Hsp70's steady-state ATPase activity.AtFes 1-1 has clear distinction with its homologs in chemical and biological characteristics.