Study On The Function And Exploration On The Regulation Mechanism Of SlSTE1 Gene Under Salt Stress In Tomato

Soil salinization is a worldwide problem that threatening the growth quality and yield of crops.The accumulation of saline-alkali substances in irrigated agriculture results in a sharp decrease in crop yields.Therefore,it is very important to improve the soil quality and the tolerance of crops to salt stress.As the second largest fruit and vegetable crop in the world,tomato has very important economic and edible value.It is very important to understand the response mechanism and molecular mechanism of tomato to salt stress comprehensively and deeply,which is very important to improve the tolerance of tomato to salt stress.Although there is no studies on the function of Sl STE1 gene have been reported,previous studies have shown that the expression of Sl STE1 gene was significantly increased under the treatment of hormones such as salt and abscisic acid.In order to prove the relationship between Sl STE1 gene and salt stress tolerance of tomato,we treated wild type(WT)and transgenic tomato plants with silencing and overexpression of Sl STE1 gene by salt and ABA,respectively.Then we detected the physiological indexes of plant salt tolerance and analysed the expression patterns of ABA signal transduction-related genes in leaves treated with ABA.In addition,transcriptome sequencing of wild type and overexpression transgenic plants was carried out to study the molecular mechanism of Sl STE1 in salt tolerance of tomato.The results are as follows:1.To observe the phenotypic characteristics of WT,Sl STE1-silenced and overexpressed transgenic tomato seedlings were treated with different concentrations of Na Cl,and the root and stem lengths of tomato plants were calculated.We found that the growth of overexpression lines was better than that of WT,and the length of root was higher than that of WT under salt stress.2.The WT and overexpression transgenic tomato plants were treated with ABA,and the expression of receptor genes,positive and negative regulatory factor genes in ABA signal transduction pathway were detected.After ABA treatment,the expression of some genes decreased significantly.However,Sl PYL9 increased significantly,especially in over-expressed plants,indicating that Sl STE1 and ABA pathway might co-regulate tomato resistance to salt stress.3.In order to further prove that the function of salt tolerance of Sl STE1 gene is related to the ABA signaling pathway,yeast two-hybrid system was used to screen the ABA receptors and regulatory factors that might interact with Sl STE1 protein.The results showed that there was no interaction between the Sl STE1 protein and the proteins in the ABA pathway.4.The contents of chlorophyll,malondialdehyde(MDA)and the activities of superoxide dismutase(SOD),catalase(CAT)in WT and Sl STE1-silenced and overexpressed transgenic tomato plants under salt stress were determined.The results showed that the contents of chlorophyll,SOD and CAT activities in the over-expressed plants were higher than those in wild type,but the content of MDA was significantly lower than that of wild type.The results showed that the photosynthetic respiration and scavenging effect of reactive oxygen species and free radicals were stronger than that of wild type plants under salt stress,but lipid peroxidation was much weaker than wild type tomato.5.The transcriptome sequencing of wild type and over-expressed transgenic tomato showed that many abiotic stress-related genes were activated after overexpression of Sl STE1 gene,and they were involved in oxidative stress and osmotic stress.The results further confirmed that Sl STE1 gene plays a very important role in enhancing salt tolerance of tomato.All of the above results indicated that Sl STE1 gene could regulate the response mechanism of tomato to salt stress and enhance the salt tolerance of tomato.However,the expression of receptor and positive and negative regulatory factor genes of ABA pathway was up-regulated in Sl STE1 overexpression plants.However,there was no interaction between Sl STE1 and ABA signaling pathway proteins.We speculate that Sl STE1 may participate in the ABA signaling pathway through other stress signaling pathways or through binding ABA-related response elements to promote tomato salt stress tolerance.