Study Of The Relationship Between The AtGS1.1 Gene And Salt Tolerance During Seed Germination In Arabidopsis Thaliana

Salt stress is one of the major abiotic stress that limits crop growth,development and production,it is a growing problem for agricultural wordwide.Seed germination is a critical stage in the development of crops that grow in saline soils.An improved understanding of molecular mechanism to NaCl treatment on seed germination may has important significance for development of crops with increased tolerance to NaCl stress.We previously found that germinating seeds of an Arabidopsis urease mutant?aturease?have significantly increased salt stress tolerance,probably because blocking urea metabolism decreased the NH₄⁺ concentration.Glutamine synthetase?GS?as the key enzyme of the NH₄⁺ assimilation,to further investigate the relations between the nitrogen metabolism and salt tolerance during seed germination,in this study,we carried out the studies of A.thaliana glutamine synthetase?AtGS1.1?responses to salt stress during seed germination.The results show that: AtGS1.1 is constitutively expressed in all Arabidopsis plant organs,with the highest levels of expression in siliques;AtGS1.1 was up-regulated by NaCl and NH4 Cl supply during seed germination.Analysis of AtGS1.1 transformants and AtGS1.1 gene knockout mutant?atgs1.1?plant response to salt tolerance,we found that,AtGS1.1 transgenic plants significantly increased salt tolerance compared with wild-type?WT?and atgs1.1 plants during seed germination.In addition,overexpression of AtGS1.1 significantly increased tolerance to NH₄⁺ stress.Overexpression of AtGS1.1 in Arabidopsis increased GS activity in both cotyledon and root of transgenic plants under NaCl stress,NH₄⁺ levels of both cotyledon and root were significantly lower in AtGS1.1 transgenic plants during seed germination.Furthermore,adding two types inhibitor?L-methionine sulfoximine,MSX;Glufosinate ammonium?of GS activity to the NaCl medium,with increasing the concentration of inhibitors significantly inhibited seeds germination of WT plants.These results suggest that,AtGS1.1-induced salt tolerance during seed germination is caused by the increased GS activity,which in turn decreased NH₄⁺ accumulation in AtGS1.1 transgenic plants.Better characterization of the molecure responses to salt stress during seed germination will provide a sound basis foundation to improve agriculture productivity with increased tolerance to NaCl stress.