Functional Study Of OsCYP714D1 And PtGSTF1 In Improving Poplar Growth And Salt Resistance

Soil salinization is a global problem that limits plant growth and crop yield.Saline alkali soil contains high concentration of sodium ions,which will rapidly reduce the availability of water and prevent plants from absorbing water and nutrients from the soil.When plants are subjected to salt stress,the physiological stability of the body is seriously disturbed.These ionic poisons can harm the normal cellular metabolism,trigger membrane lipid peroxidation,diminish the photosynthetic rate as well as the conversion capacity of antioxidant enzymes,and lower the scavenging capability against reactive oxygen species.In severe cases,they may even lead to plant death.In order to adapt to the saline alkali growth environment,plants have formed a series of physiological regulation mechanisms through long evolution,mainly including osmotic regulation,ROS scavenging system and ion regulation.Cytochrome P450(CYPs)plays an important role in plant growth regulation and response to abiotic stress.However,their function in woody plants needs to be further supplemented.In this work,we cloned the CYPs member gene OsCYP714D1 from rice and ectopic expressed it in poplar,proving that OsCYP714D1 expression improves the growth and salt tolerance of transgenic poplar.Under salt stress,plant height and tissue K~+content of transgenic plants were significantly higher than those of wild type,while plant growth inhibition rate and Na~+content were significantly lower than those of wild type.Transcriptome analysis showed that the heterologous expression of OsCYP714D1upregulated GA biosynthesis,signal and stress response genes in transgenic plants under normal and high salt stress conditions.Further gene ontology(GO)analysis showed that transgenic plants were rich in genes involved in plant hormones and ion metabolism activities.These results indicate that OsCYP714D1 plays a role in the growth and salt tolerance of poplar by regulating the biosynthesis and signal transduction of gibberellin and the balance of ion homeostasis.Glutathione S-transferases(GSTs)play an important role in detoxification and secondary metabolism of plant cells.However,their functions in the growth of woody plants and in response to abiotic stresses are largely unknown.In this work,we isolated a Phi like glutathione S-transferase encoding gene PtGSTF1 from Populus trichocarpa,and studied its biological functions in plant growth,secondary development and salt tolerance regulation in transgenic poplar.PtGSTF1 was localized in the cytoplasm and widely expressed in various tissues and organs,mainly in leaves,and can be induced by salt stress.The transgenic poplars overexpressing PtGSTF1 showed improvement in growth,secondary development and salt tolerance,which was consistent with the increase in the number and size of xylem cells under normal conditions and the optimized Na~+and K~+homeostasis and enhanced active oxygen scavenging during salt stress.Further transcriptome analysis showed that the expression of genes related to hydrolase,cell wall modification,ion homeostasis and ROS clearance significantly changed in transgenic plants.In addition,several abscisic acid response elements(ABA)were found in the promoter region of PtGSTF1,and q RT-PCR showed that PtGSTF1 was induced by ABA.These results indicate that PtGSTF1 can improve biomass production and salt tolerance by regulating the hydrolase activity,cell wall modification,ion homeostasis and ROS clearance of transgenic poplar,and may be induced and regulated by ABA.In this study,OsCYP714D1 gene from and PtGSTF1 from poplar were both studied in transgenic poplar.Our results show that OsCYP714D1 and PtGSTF1 can play a role in the growth and salt stress of poplars.The related phenotypes were explained by molecular validation,transcriptome analysis and physiological indicators detection.