| Soil salinization is one of the main abiotic stresses in arid and semi-arid areas of Northwest China,which is an important factor restricting the efficient and high-quality production of tomato.Trehalose,as a signal molecule,plays an important role in plant response to abiotic stresses.In this study,"Micro-Tom"tomato was used as experimental material to analyze the changes of redox homeostasis,osmotic regulation,photosynthesis and ion balance of tomato plants under salt stress by foliar spraying trehalose.To reveal the physiological mechanism of trehalose resistance to salt stress in tomato plants.Furthermore,to explore the mechanism of trehalose involved in alleviating salt stress in tomato by combined transcriptome and metabolome analysis.The main findings were as follows:1.The growth and biomass of tomato plants were significantly inhibited under150m M Na Cl stress,and foliar spraying of 10m M trehalose significantly reduced the damage of tomato leaf tissue and the membrane system.Trehalose increased the activities of SOD,POD and CAT by activating the transcriptional expression of genes encoding antioxidant enzymes,and reduced the excessive accumulation of reactive oxygen species in tomato under salt stress.It also increased the accumulation of osmoregulatory substances(total phenol,total flavonoid,proline and betaine).At the same time,by regulating the trehalose metabolism pathway,the accumulation of glucose,sucrose and trehalose in tomato leaves was promoted,the content of gibberellin was decreased,the contents of zeatin,auxin,salicylic acid and jasmonate were increased,and the content of abscisic acid in leaves was decreased during salt stress stage and increased during the recovery stage after salt stress.2.Trehalose treatment promoted stomatal opening of tomato leaves under salt stress,reduced production of osmiophilic granules,maintained the integrity of chloroplast structure,promoted the activity of key enzymes of Calvin cycle and enhanced photosynthesis.At the same time,trehalose alleviated the inhibition of photosynthetic electron transfer from Q_A to Q_B by salt stress,reduced the heterogeneity of the PQ pool,increased the photochemical efficiency of PSII and the quantum efficiency of PSII to PSI,reduced the dissipation energy of light quantum flux per unit cross section and single active reaction center of leaves,and increased the trapping energy and electron transfer energy.Thus,the energy absorption efficiency of PSII was improved.3.Trehalose treatment could alleviate salt stress damage to tomato leaf structure,promote the accumulation of cellulose and lignin in plants,and change the absorption and distribution of Na and K elements in roots,stems and leaves and their subcellular fractions under salt stress.During the salt stress stage,Na~+was mainly discharged from the cells through the Na~+/H~+antiporter SOS1 and NHX1,which prevented Na~+from being transported upward.During the recovery phase,Na~+was transported out of the cell by plasma membrane H~+-ATPase and V-type H~+-ATPase in addition to the SOS1 with NHX1transporter pathway.In addition,trehalose treatment promoted the high expression of Sl HKT1.1 gene in leaves,increased K~+uptake,and maintained a normal Na~+/K~+ratio.4.Based on the transcriptome and metabolomics analysis,a total of 2487differentially expressed genes(DEGs)and 235 differential metabolites(DAMs)were identified in salt stress treatment versus control treatment,and 169 DEGs and 31 DAMs were identified in salt stress treatment versus trehalose mitigation treatment.The analysis showed that amino acid metabolism,hormone signal transduction,and sucrose/trehalose metabolism were the main reasons for trehalose induced resistance to salt stress in tomato.In the amino acid metabolism pathway,the number of up-regulated DEGs and DAMs in the trehalose alleviating salt stress treatment was more than that in the down-regulated DEGs and DAMs.The number of up-regulated DEGs enriched in salicylic acid,abscisic acid,cytokinin,brassinosteroids and jasmonate signal transduction pathways was higher than that of down-regulated DEGs,while the number of down-regulated DEGs enriched in gibberellin and auxin signal transduction pathways was higher than that of up-regulated DEGs.In the sucrose/trehalose metabolic pathway,32 DEGs and 5 DAMs were up-regulated in the trehalose mitigation treatment,among which solyc04g054930.3(Sl TPPJ)was significantly up-regulated under the condition of trehalose alleviating salt stress.5.Transgenic Arabidopsis and transiently overexpression tomato plants significantly increased the growth indicators,malondialdehyde content,antioxidant enzyme activities,and transcription levels of stress tolerance related genes,thereby inhibiting the excessive accumulation of reactive oxygen species.These results suggested that Sl TPPJ might improve plant salt tolerance by regulating the expression of stress tolerance related genes and maintaining redox homeostasis.In conclusion,trehalose improved in tomato plants by promoting trehalose metabolism to regulate osmotic substance accumulation,enhance antioxidant capacity,improve photosynthesis,and regulate ion homeostasis.Sl TPPJ played an active role in mediating trehalose regulation of plant resistance to salt stress,and was a key gene in trehalose induced response to salt stress in tomato. |
