Physiological And Molecular Regulation Of OsU496A In Rice Seedlings Response To Salt Stress

Salt stress is one of the major abiotic stresses affecting rice production.As a salt sensitive crop,rice is very sensitive to salinity at seedling stage.Previous studies have shown that OsU496A is a membrane protein mainly localized in the radicle,and is involved in the regulation of root growth of rice.In this study,the physiological and molecular regulation of OsU496A in rice seedlings response to salt stress were investigated by using OsU496A interference knockdown and overexpression transgenic rice as materials.The main research results are as follows:1?The expression of OsU496A in roots of wild-type rice seedlings was significantly increased by NaCl treatment,and reached a maximum,which was nearly 7 times higher than that before treatment.2?Compared with the wild-type rice,the salt tolerance of OsU496A transgenic rice seedlings was significantly different.The Os U496A overexpression transgenic rice seedlings had lower relative water content,faster rate of water loss and lower survival rate.However,RNA interference of Os U496A reduced water loss and enhanced salinity tolerance.3?The proline content,soluble sugar content,antioxidant enzyme activity,malondialdehyde content and hydrogen peroxide content in roots and leaves of different transgenic rice seedlings all gradually increased,while K+ content in roots gradually decreased after NaCl treatment.Compared with the wild-type rice,the contents of proline,soluble sugar,K+ and the activities of antioxidant enzymes in roots and leaves of OsU496A interference knockdown transgenic rice seedlings were significantly increased,while the contents of malondialdehyde and hydrogen peroxide were significantly decreased.However,the contents of proline,soluble sugar,K+ and the activities of antioxidant enzymes in the roots and leaves of overexpressed transgenic rice seedlings were significantly decreased,while the contents of malondialdehyde and hydrogen peroxide were significantly increased.4?Transcriptome sequencing results showed that transcription of several salt tolerance-related genes,which involved in proline metabolism(such as MYB,P5CS2,PDH),antioxidant enzyme metabolism(such as AP2/ER,PRX,POD2),cell protection protein metabolism(such as pernieating proteins and aquapornn proteins)and salt stress response(such as SALT,NAC),were greater in OsU496A RNA interf-erence knockdown transgenic rice seedlings than in the WT under both normal and salt-stressed conditions.GO enrichment analysis showed that the differentially expressed genes were mainly related to the metabolism of hydrogen peroxide and reactive oxygen species in biological process.In cell component,differentially expressed genes were mainly related to membrane components.In molecular functional,differentially expressed genes are mainly related to the activity of oxidoreductase,tetrapyrrole binding and ion binding.Pathway significance enrichment analysis showed that the differentially expressed genes were mainly involved in the metabolic pathway,followed by the biosynthetic pathway of secondary metabolites.In conclusion,OsU496A negatively regulates the salt stress response of rice seedlings.Its proposed physiological and molecular mechanisms were as follows:under salt stress,the Os U496A inhibited the expression of MYB.MYB can recognize the sequence of P5CS2 promoter,thereby reduced the expression of P5CS2,and finally leading to a significant decrease in proline content.Proline can be used directly as an osmoprotective compound.It can also be used as a molecular chaperone and metal chelator to scavenge ROS,The decrease of proline content leads to the decrease of salt tolerance in rice.Secondly,the expression of AP2/ER and the content of potassium ions were inhibited by OsU496A,which resulted in the decrease of antioxidant enzyme activity,thereby accumulating ROS and reducing the salt tolerance of rice.In addition,OsU496A inhibited the expression of salt stress-induced genes,including late embryogenic abundant proteins,permeating proteins,aquaporin proteins,lipid transfer proteins and so on,thereby reducing the salt tolerance of rice.