Effects Of TOR Inhibitor Rapamycin On Growth,Development And Low Temperature Response Of Tomato Seedlings

Tomato?Solanum lycopersicum?,which is the one of main facilities vegetable in China,originated South America,so it is a warm season crop.Low temperature stress is often encountered in the production of northern facilities,affecting the growth and development of tomato.The growth and development of tomato is regulated by many internal and external factors,thus the regulation of target of Rapamycin?TOR?is a hot research topic.The TOR signaling pathway plays a key role in the growth and development of eukaryotes and is highly conserved.It acts as a central regulator in a variety of biological processes.To explore the effect of tomato rapamycin target protein?SlTOR?on tomato growth and development,and the function of SlTOR signaling pathway in tomato response to low temperature stress,will provide a new idea and theoretical basis for the regulation mechanism of tomato growth and development.In this study,the Jing Guan No.5 tomato was used as the research material.The bioinformatics method was used to predict and analyze the tomato SlTOR,and the TOR inhibitor Rapamycin?Rap?and the low temperature were used to treat tomato seedlings in order to study the effect in growth and development of tomato.The main results were as follows:?1?The bioinformatics analysis of the tomato SlTOR showed that the tomato SlTOR protein was highly conserved compared with the ho mologues of other model organisms.Subcellular localization of the tomato SlTOR protein was predicted to exist in the nucleus and cytoplasm.?2?The differential expression of key genes in the SlTOR signaling pathway was detected by q RT-PCR.The results showed that they were expressed in different stages of tomato seedlings and in different tissues and organs,but the expression levels were very different.The relative expression levels of SlTOR,Sl LST8,SlE2Fa and SlSPS were the highest in cotyledons of tomato seedlings.The relative expression levels of SlSS was the highest in stem of tomato seedlings.In the mature tomato plants,the expression of SlTOR was the highest in the root,following was in fruitlet.The expression levels of Sl LST8 and SlSPS were the highest in leaves,but the expression of the SlE2Fa was in mature fruit,and the expression of the SlSS was the highest in the fruitlet,next was in mature fruits.?3?Pharmacological experiments showed that tomato was sensitive to rapamycin,which is the first generation inhibitor of TOR signaling pathway.Rapamycin could significantly inhibit the growth of tomato plants,and tomato was dose-dependent.Treatment with 10 ?mol·L^-1 rapamycin had significant effects on the growth and development of tomato seedlings.?4?After treatment with rapamycin,the net photosynthetic rate?Pn?and transpiration rate?Ts?of leaves decreased significantly.The net photosynthetic rate of leaves decreased significantly at 96 h after treatment,and the transpiration rate decreased significantly at 48 h and 96 h after treatment.The change of stomatal conductance?Gs?was a little.And the intercellular carbon dioxide concentration?Ci?showed a significant decrease at 48 h and 72 h after treatment,but increased again 15 d after rapamycin treatment.The ratio of F0/Fm,Fv/Fm and Fv/F0 did not change significantly within 120 h after treatment,and decreased significantly after 15 d of rapamycin treatment.The chlorophyll content showed a significant downward trend at 12 h and 24 h after treatment,significantly reduced after 15 d of rapamycin treatment.?5?Rapamycin-treated tomato leaves accumulated H₂O₂ and O₂·^-,but caused the defense response of tomato seedlings themselves.The SOD activity increased significantly after 72-120 h after rapamycin treatment.The PAL activity fluctuated greatly after treatment,and increased significantly at 6 h,24 h and 72 h after rapamycin treatment.The CAT activity increased at 6 h,24 h and 120 h.The POD activity showed a significant upward trend at 6 h and 12 h.The defense response of tomato plants after rapamycin treatment was faster.Moreover,tomato seedlings could respond to inhibition of rapamycin by increasing soluble sugar and soluble protein contents.?6?After treatment with rapamycin,the chlorophyll content increased significantly compared with the simple low temperature treatment.The malondialdehyde and soluble protein contents decreased significantly,and the soluble sugar content decreased.The activity of SOD enzyme was up-regulated,but the activities of PAL and CAT enzyme were down-regulated,as while as the activity of POD enzyme was no significant change.The expression level of SlTOR decreased,and the relative expression levels of Sl LST8,SlE2Fa and SlSPS were significantly down-regulated.The expression levels of Sl SNF1 and Sl SNF4 were down-regulated but no significant.This indicated that the tomato TOR signaling pathway might crosstalk with low temperature signaling pathway.