| The drought is common environment problem in our country and is also the important factor that affects the global crop production seriously.Glutamine synthase(GS)is the key enzyme of plant nitrogen assimilation and is involved in the synthesis of proline.In order to clarify the role of GS in plant drought resistance and its mechanism,this study selected three transgenic TaGS1/TaGS2 tobacco strains obtained in our lab as research materials,and took cultivar tobacco K326 as control,to take indoor potted drought experiment.The sample was took on 7d drought stress and 5d rewatering respectively,which was used to study the biomass,protective enzyme system,osmotic adjustment,membrane injury,photosynthesis,GS expression and so on.And then the drought resistance mechanism of the transgenic TaGS1/TaGS2 is discussed,which can provide the theoretical foundation for drought resistance breeding.The main results are as follows:(1)Compared with wild type,transgenic TaGS1/TaGS2 tobacco had stronger root system,better growth,higher biomass and relative water content in the process of drought stress and rewatering.And the self-recovery rate of the transgenic TaGS1/TaGS2 tobacco was significantly faster than wild type.(2)The expression of TaGS gene in transgenic TaGS1/TaGS2 tobacco decreased in drought stress,but it can promote the expression of Nt GS in tobacco.The expression of Nt GS2 in transgenic TaGS1/TaGS2 tobacco leaves was significantly higher than that in wild type,and the expression of Nt GS1;3 in transgenic TaGS1/TaGS2 tobacco root was also significantly higher than that in wild type.GS activity in transgenic TaGS1 /TaGS2 tobacco leaf and root were significantly higher than that in wild type under drought conditions,and the GS protein content and GS activity in the leaf and root of transgenic TaGS1 /TaGS2 tobacco were significantly higher than that of wild type under rewatering condition.It is indicated that the GS protein expression can improve the drought resistance of transgenic TaGS1 /TaGS2 tobacco.(3)Under drought stress,the three antioxidant enzymes activity(SOD,CAT and POD)and proline content of the transgenic TaGS1 /TaGS2 tobacco were significantly higher than that of wild type,while the MDA content of the transgenic TaGS1 /TaGS2 tobacco was significantly lower than that of wild type,which indicated that the transgenic TaGS1 /TaGS2 tobacco had the stronger abilities of osmotic regulation and oxidation resistance,preventing the peroxidation of the membrane.After rewater treatment,transgenic TaGS1 /TaGS2 tobacco had higher SOD enzyme activity and proline content as well as lower MDA content,which shows that the transgenic TaGS1 /TaGS2 tobacco has strong ability of self-repairing and drought resistance.(4)Compared with wild type,transgenic TaGS1/TaGS2 tobacco had higher chlorophyll content,net photosynthetic rate and stomatal conductance in the process of drought stress and water,which shows that transgenic TaGS1 /TaGS2 tobacco are still able to maintain a higher photosynthesis under drought conditions,reducing the effects of the drought stress on plant growth.In conclusion,compared with wild type,transgenic TaGS1/TaGS2 tobacco has stronger nitrogen assimilation ability with higher GS expression under the condition of drought stress and rewatering.Higher GS expression made for accumulating higher levels of soluble protein content,proline content and chlorophyll content,which improved the osmotic regulation ability and antioxidant capacity in the transgenic TaGS1/TaGS2 tobacco.Higher relative water content and membrane integrity kept stomata of transgenic plant open to absorb more carbon dioxide,improving the photosynthesis and carbon assimilation ability of transgenic tobacco.Furthermore,the higher ability of C and N assimilation in transgenic TaGS1/TaGS2 tobacco made it has better biological trait than wild type,such as stronger root system,higher biomass and plant height,which was the biological basis of transgenic plant to have stronger drought resistance.It is indicated that TaGS1/TaGS2 can improve the GS expression of transgenic TaGS1 /TaGS2 tobacco and improving its drought resistance. |
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