Effects Of Cell Wall Invertase On The Resistance Of Tomato To Pst DC3000 And Underlying Regulatory Mechanisms

The study was conducted to learn the effect of sucrose metabolism on resistance to bacterial leaf spot disease（Pst DC3000）in tomato leaves and its possible physiological and biochemical mechanisms,in order to provide reference for the breeding of new resistive tomato varieties.In this study,transgenic tomatoes（RNAi）with up-regulated CWIN activity and wild-type tomatoes（WT）were used as experimental materials.These two kinds of leaves were immersed in the Pst DC3000suspension liquid or pure water.They were tested several kinds of indicators after 0h、24 h、36 h and 48 h hours.These indicators included Pst DC3000 resistance,bacterial density,soluble sugar,starch content,invertase activity,content of salicylic acid（SA）,jasmonic acid（JA）,cell death and H₂O₂content accumulation.（1）The up-regulation of CWIN can effectively reduce the H₂O₂content in tomato leaves in the middle and late period of inoculation,and its bactericidal effect is weakened.The up-regulation of CWIN can up-regulate PCD related genes to accelerating cell death.So these reason weakened the disease resistance of tomato leaves to Pst DC3000;（2）The up-regulation of CWIN can reduce the sugar signaling pathway（hexose/sucrose ratio in leaves）and delay the effect of resistance mechanism.The up-regulation of CWIN can reduce intracellular hexose content to weaken intracellular glucose metabolism pathway for self-metabolism to provide energy and synthesis of disease-resistant substances.The up-regulation of CWIN decreased the expression of STP gene and increased the expression of SWEET gene at the later stage of inoculation to increase extracellular fructose.Increasing the content of ectoplasmic hexose,especially fructose,resulted in the proliferation of the pathogen before infection into the plant cell,which ultimately weakened the resistance of tomato to Pst DC3000.The up-regulation of CWIN is a key factor and it may weaken the disease resistance of tomato leaves to Pst DC3000 by reducing the activities of VIN and the contents of intracellular hexose and sucrose;（3）The up-regulation of CWIN decreased SA content and increased JA content at the early stage of inoculation.The former matter played a positive role in the resistance of Pst DC3000;while the latter matter had an antagonistic effect with SA.The up-regulation of CWIN can reduce the resistance by delaying the induction expression of WRKY gene.The combined effect of these two matter weakened the resistance of tomato leaves to Pst DC3000.To sum up,CWIN can regulate H₂O₂through regulate CIN and VIN activities;Glucose signaling pathway and glucose metabolism pathway;JA and SA content;STP gene and SWEET gene expression;WRKY gene,SOD gene,JA/ET gene and PCD related genes were expressed to reduce the resistance to bacterial leaf spot.