Physiological And Molecular Regulation Mechanism Of Exogenous 24-epibrassinolide On Salt Tolerance Of Tall Fescue (Festuca Arundinacea)

Soil salinization is one of the major global environmental problems.The accumulation of salinity directly affects the biological processes such as plant growth and development and cell metabolism.Tall fescue(Festuca arundinacea)can grow in a wide range of soils.It is not only used for turf establishment,but also as forage or ecological restoration plants.Therefore,improving the salt tolerance of tall fescue is of great significance to the construction of environmentally sustainable development.Brassinosteroids is a plant hormone that plays an important role in plant growth and development.In recent years,exogenous 24-epibrassinolide(EBL)has been shown to alleviate various environmental stress injuries in plants.However,the role of EBL in improving salt tolerance of tall fescue is still unclear.In this experiment,the salt tolerance of ten tall fescue cultivars was evaluated,and the physiological and molecular mechanisms of exogenous EBL involved in regulating the salt stress response of tall fescue were discussed.1.In the test of salt tolerance evaluation in ten cultivars,‘Kentucky31’,’Persuasion’,’Endeavor Ⅱ’ and ’Rebounder’ had obvious blade bending due to water shortage,while ’Houndog5’,’Houndog6’ and ’Nightcrawler’ had smaller phenotypic changes.Combined with the results of chlorophyll content,malondialdehyde content,antioxidant enzyme activity and other indicators,we found that the most salt-tolerant cultivar was Houndog8,and the least salt-tolerant cultivar was Rebounder.2.In this experiment,’Houndog’(HD6)’ with medium salt tolerance and wide application in turf establishment was selected.Four groups were set up in the experiment:CK(control),EBL(1 μmol/L 24-epibrassinolide treatment),SALT(300 mmol/L NaCl solution treatment)and SE(300 mmol/L NaCl solution and 1μmol/L 24-epibrassinolide treatment).By detecting several physiological indexes,we found that the electrolyte leakage and malondialdehyde content of the SE group were lower than those of the SALT group,and the chlorophyll content and antioxidant enzyme activity were increased,indicating that 24-epibrassinolide could improve the salt tolerance of HD6.In the results of transcriptome sequencing,there were 10,265,13,830 and 10,537 differentially expressed genes(DEGs)in EBL,SALT and SE groups compared with the CK.In the comparison group of SE and SALT,DEGs mainly focused on plant hormone signal transduction,MAPK signaling pathway-plants,metabolic processes.These results will help us to further understand the molecular regulation mechanism of exogenous 24-epibrassinolide in improving salt tolerance of tall fescue.3.A significantly different gene FaGELP1 was selected from the SE/SALT comparison group.It was subjected to RACE amplification,cloning and transformation,transformed and sequencing comparison.In addition,the full-length sequence was analyzed for related bioinformatics analysis.It was found that the protein of this gene was a hydrophobic protein and had high homology with the gene of ryegrass and wimmera ryegrass.