The Study On The Effect Of Overexpressing SlSAMS1 On Alleviating Cadmium And Drought Stress In Tomato Seedling

Abiotic stresses such as heavy metals and drought seriously affect the growth and developmentaswellasthesafeyandefficientproductionofvegetables.S-adenosyl-L-methioninesynthetase?SAMS?catalyzestheformationof S-adenosyl-L-methionine?SAM?from methionine and ATP.SAM is the precursor of ethylene,polyamines and glutathione,which play an important role in resisting adverse conditions in plant.In the study,inbred lines‘895'and overexpressing SlSAMS1 tomato plants was used as experimental materials,and the effects of SlSAMS1 regulating cadmium and drought stress were studied,and the possible physiological pathway was further explored.The main results are as follows:1.50?M CdCl₂ was used to simulate cadmium stress by hydroponics.It was found that SlSAMS1 alleviated the inhibition of Cd stress on seed germination and plant growth,and Transgenic tomato seedlings maintained higher chlorophyll content,net photosynthetic rate,Fv/Fm and?PSII.Cd stress promoted the accumulation of reactive oxygen species?ROS?.Overexpression of SlSAMS1 significantly increased ascorbic acid-glutathione?AsA-GSH?cycle efficiency and guaiacol peroxidase?POD?and catalase?CAT?activities under cadmium stress,promoted the expression of glutathione synthases?GSH1,GSH2?,phytochelatin synthase?PCS?,enhanced the Cd detoxification ability of plants,and reduced the accumulation of ROS and membrane lipid peroxidation level induced by Cd stress.Overexpression of SlSAMS1 reduced the Cd accumulation in tomato roots,thereby reduced the damage of cadmium to tomato roots.SlSAMS1 up-regulated the expression levels of polyamine synthesis-related enzymes?SAMdc,SPDS,SPMS?and polyamine oxidase-related enzyme?PAO?genes in roots,increased the activity of cell wall-bound PAO and POD under Cd stress,and accelerated the lignification of roots at the early stage of Cd stress.In addition,SlSAMS1 regulated the expression of some metal transporters in roots and leaves.2.Overexpression of SlSAMS1 alleviated the inhibition of drought stress on tomato seed germination?PEG treatment?.Natural drought and rewatering conditions to the plant growth,carbon and nitrogen metabolisms and primary metabolites accumulation of tomato were analyzed.The results showed that plant fresh weight,soluble sugar content,sucrose content,soluble protein content and total nitrogen content in leaves of overexpressing SlSAMS1tomato plants were higher than those of WT under drought stress and rewatering conditions.Drought stress hindered the GS/GOGAT?glutamine synthase/glutamate synthase?cycle and enhanced the activity of GDH enzyme,SlSAMS1 alleviated the inhibition of ammonium assimilation under drought stress.Before and after drought,the content of primary metabolites in leaves of wild type and transgenic tomato changed greatly.SlSAMS1 gene enhanced fructose-6-phosphate,glucose-6-phosphate,and?-ketoglutarate citric acid,fumaric acid and malic acid in tomato leaves,which may play an important role in regulating the drought resistance of tomato seedlings.