Regulation Of TOR Signaling On The Growth And Development Of Seedling And Sucrose Metabolism In Tomato

As an important model plant in modern research and an important vegetable crop,the yield and quality of tomato(Solanum lycopersicum)are the focus of people’s attention.The yield and quality of tomato are inextricably linked to sucrose metabolism.As a signaling molecule,TOR regulates many physiological processes in plants by responding to a variety of signals,thereby regulating the growth and development of plants.TOR signaling is an important factor in plant growth and metabolic regulation.However,the regulation of TOR signaling on tomato sucrose metabolism is still lacking systematic research.So first the role of TOR was determined in tomato seedling growth and development by external application of TOR inhibitor AZD8055 and activator MHY1485 in this study.Then,the regulatory effect of TOR signaling on tomato sucrose metabolism was explored by the external application of TOR inhibitor AZD8055 and activator MHY1485.Finally,a Sl TOR silencing line was constructed to further study the regulation of TOR signaling on sucrose metabolism in tomato.This study provided a theoretical basis for further clarifying the mechanism of sucrose metabolism in tomato.The main results were the following:(1)Tomato seeds were subjected to the TOR inhibitor AZD8055 and the activator MHY1485,seed germination rate,greening rate,hypocotyl length,fresh weight,root length,and leaf area were measured.The results showed that AZD8055 inhibited the germination,greening,fresh weight,root length and hypocotyl length of tomato seeds,and reduced the leaf area.But MHY1485 promoted the germination,greening,root growth of tomato seeds,leaf area enlargement.The results showed that TOR signaling affected seed germination and seedling growth and development of tomato.(2)AZD8055 and MHY1485 were applied to tomato seedlings at the stage of two-leaf with one heart.The photosynthetic pigment contents,photosynthesis-related parameters and fluorescence parameters were determined,the results showed that the TOR inhibitor AZD8055 suppressed photosynthetic pigment content in tomato leaves,but increased after treatment with activator MHY1485.Photosynthesis in tomato leaves was inhibited after treatment with TOR inhibitors and promoted by treatment with the activator MHY1485.There was no significant change in the fluorescence parameters of the leaves after AZD8055 and MHY1485 treatments.The results indicated that the influence on photosynthesis was mainly stomata factor.The starch content,soluble sugar contents,activities of enzymes related to sucrose metabolism,expression of enzyme genes related to sucrose metabolism,and expression of Sl TOR in tomato leaves were further determined.The results showed a decrease in sugar content and starch content,but an increase in fructose and glucose in tomato leaves after TOR inhibitor treatment.Also the enzymes with reduced activity in tomato leaves were sucrose phosphate synthase and neutral invertase,and those with elevated activity were sucrose synthase and acid invertase.The expressions of Sl SPS,Sl SS,Sl TIV1 and Sl TOR were decreased.TOR activators increased starch and sucrose content in tomato leaves,however,decreased glucose and fructose contents.Among the enzymes in tomato leaves that showed increased activities related to sucrose metabolism were sucrose phosphate synthase and neutral invertase activities,and the enzymes with decreased activities were sucrose synthase and acid invertase activities.The expressions of Sl SPS,Sl SS,Sl TIV1 and Sl TOR wwere increased.The results showed that TOR signaling played a role in sucrose metabolism in tomato.(3)The regulatory effect of TOR signaling on tomato sucrose metabolism was further verified by silencing Sl TOR.The tomato Sl TOR gene was silenced,and the Sl TOR silencing line was obtained.The photosynthetic pigment contents,photosynthesis-related parameters and fluorescence parameters of leaves were determined,the results showed that in the silenced plants the photosynthetic pigment content of tomato leaves was significantly reduced compared with that of the wild types,photosynthesis related parameters were also suppressed in leaves of the silenced lines,but the fluorescence parameters did not change significantly.Soluble sugar contents,starch content,enzyme activity and expression of the enzyme genes associated with sucrose metabolism were also determined,the results showed that the contents of starch and sucrose were decreased but the contents of fructose and glucose were increased in the tomato leaves of the silencing lines.The silenced lines had reduced sucrose phosphate synthase and neutral invertase activities and increased acid invertase and sucrose synthase activities in tomato leaves.The expressions of Sl SPS,Sl SS and Sl TIV1 were decreased,indicating that TOR signaling regulated sucrose metabolism in tomato by regulating the expressions of genes related to sucrose metabolism and enzyme activities.