A Preliminary Study Of Protein Phosphatase TOPP4 Involved In Salt Stress Response In Arabidopsis

Osmotic stress,ion toxic,and nutrient deficiency cause severe effects on physical activity and metabolic balance in the cells.For example,they could affect a series of life activity processes,such as lipid metabolism,protein synthesis and modification.In order to resist the adverse external environment,plants have evolved different physiological and biochemical mechanisms to ensure their growth and development.In this thesis,the results of physiological experiment showed that topp4-1,a point mutant of TOPP4,and topp4-3,a T-DNA insertion mutant of TOPP4,had defective response to salt and osmotic stress.However,the phenotype of topp4-1 and topp4-3 was similar to the phenotype of Col under the stress of peroxide,alkaline conditions,K~+and Li~+.The results of GUS staining and q RT-PCR indicated that the expression of TOPP4 was induced under salt stress,as well as the action of the salt stress response genes RD22 and RD29B.These results indicated that TOPP4 was involved in the process of salt stress response in Arabidopsis.Furthermore,the C-terminal domain of TOPP4 could complement yeast AXT3K which showed strong salt sensitive phenotype.Reactive oxygen species(ROS)and malonaldehyde(MDA)content accumulated in topp4-1 and topp4-3 under salt stress.Yeast two hybrid experiment and pull-down assay showed that TOPP4could interact with several regulatory factors of the SOS signal pathway,such as GT,GH6 and GH8.These results indicated that TOPP4 participated in the process of salt tolerance by regulating the SOS signal pathway.To identify the function of PP1 in plants under salt stress,the nine members of PP1 were transformed into salt sensitive yeast AXT3K respectively.TOPP1 and TOPP4 could complement yeast AXT3K salt sensitive phenotype strongly.In addition,TOPP5 could complement yeast AXT3K weakly.These results suggested that TOPP1,TOPP4 and TOPP5 may play an important role in salt stress response.Yeast two hybrid experiment results showed that TOPP1,TOPP4,TOPP6 and TOPP7 could interact with GT.In addition,GH8 could only interact with TOPP4.In summary,our study demonstrated that PP1 participated in the process of salt tolerance by regulating the SOS signal pathway in Arabidopsis.