Mechanism Study Of Salinity Tolerance Of STMP Relied On MtSOS3 In Medicago Truncatula

Soil salinization refers to the accumulation of salt in soil due to human and natural factors,increasing the salt content in soil to affect the growth of plants.Alfalfa(Medicago sativa L.)is a kind of forage grass that is widely used.At present,alfalfa is facing the harm of salt-alkali stress in China,and its yield in high-salt areas is affected.In order to improve the yield and quality of alfalfa,it is of great significance to improve its resistance to salility stress.However,tetraploid makes alfalfa particularly unsuitable for genetic manipulation.Medicago truncatula is a model legume plant.It has the characteristics of small genome,diploid,short growth cycle,self-pollination,and high genetic transformation efficiency.Relevant theoretical research data in M.truncatula can be applied to alfalfa and other legumes to improve crop quality,yield and resistance.In the process of salt stress treatment of the mutants,a mutant line showed a tolerance phenotype to salt stress.It was also found that the mutant had more flowers and more pods than the wild type,so the mutant named stmp(salt tolerance and multiple pods).By the RNA-Seq analysis,it was found that the expression of some genes related to salt tolerance was up-regulated in stmp-1.Among the significantly up-regulated expressing genes in stmp-1,MtSOS3(Salt-Overly Sensitive in M.truncatula)was selected for further study.The results of subcellular localization showed that MtSOS3 was mainly localized in the nucleus and cell membrane.The results of expression pattern study showed that the relative expression level of MtSOS3 was the highest in roots.The results of ion content detection showed that MtSOS3 played an important role in the ion pathway.Then,mtsos3-1 and mtsos3-1;35S:MtSOS3#1 were treated with salt.The results showed that mtsos3-1 was sensitive to salt stress.mtsos3-1;35S:MtSOS3#1 recovered this phenotype to some extent,showing that MtSOS3 was a positive regulator of salt stress.The results of NBT staining showed that mtsos3-1 produced more superoxide anions,and the results of malondialdehyde content detection showed that mtsos3-1 suffered stronger oxidative stress.In order to further study the relationship between STMP and MtSOS3,stmp-1 mtsos3-1 was constructed.It was found that compared with the wild type,the survival rate of stmp-1 mtsos3-1 was lower under salt treatment.NBT and DAB staining results showed that stmp-1 mtsos3-1 produced more superoxide anion and hydrogen peroxide.Malondialdehyde content test results showed that stmp-1 mtsos3-1 suffered stronger oxidative stress.Hydrogen peroxide content test results showed that stmp-1 mtsos3-1 contained more hydrogen peroxide.The results of ion content showed that stmp-1 mtsos3-1 had a higher ratio of sodium to potassium.The above results proved that the function of STMP relied on MtSOS3.