Study On Mechanism Of Induced Systemic Resistance To Tobacco Mosaic Virus By Endophytic Bacteria Strain EBS05

Bacillus subtilis EBS05, endophytic bacteria strain isolated fromCinnamomum camphor, had strong ability of plant rhizosphere colonization andstrongly antagonist activity to many kinds of the plant pathogenic fungus and thetobacco mosaic virus. The metabolic active substances of EBS05had many excellentproperties as biological controls factor, such as tolerance of acid and alkali, salt, heat,etc. The chemical structure Leu7-surfactin, clearly proved to be the active substancesproduced by EBS05, had been regarded as the key factor of biological control and canbe used as an elicitor to induced systemic resistance antagonized to plant disease. Inorder to further research the bio-control potential of EBS05, this paper studied theplant promoting effect of EBS05, the Signal transduction pathway of inducedsystemic resistance to Tobacco Mosaic Virus by Leu7-surfactin and the changes ofactivity on PAL、 POD and SOD enzymes related to defense response, fordemonstrating the mechanism of Induced Systemic Resistance to Tobacco MosaicVirus by Leu7-surfactin A produced by endophytic bacteria Strain EBS05. Resultswere as follows:1. Surfactin A, the active compounds produced by endophytic bacteria EBS05,did promoting effect on tobacco growth without dosage effect. Surfactin A had strongpassivation effect to TMV in vitro and the inhibition rate of necrotic local lesions was91.80%by treated with Surfactin A on the concentration of800μg/mL2. The control effects between original strain EBS05and mutant strain EBS05Tfor tobacco mosaic virus were compared by means of space isolation inoculating.Results showed that the control efficiency of original strain EBS05was67.38%whilethe mutant strain EBS05Twas only19.08%. This indicated that the systemicresistance to TMV can be induced by endophytic bacteria EBS05, and Surfactin Awas the efficient elicitor of induced resistance.3. The expression differences of genes related to signal transduction in inducedresistance were detected by means of RT-PCR and Real-time PCR technology. Resultsshowed that Surfactin A can induce tobacco produce systemic resistance to tobaccomosaic virus by inducing the early and excessive expression of the key regulatory gene NPR1, which located in the downstream of SA signal transduction pathway, andthen lead to the expression of genes PR1a and PR1b related to defense response.Meanwhile, Surfactin A can induce the instantaneous high flux expression ofregulatory gene PDF1.2which depended on JA/ET signal transduction pathway. TheSurfactin A induced systemic resistance of tobacco plants on tobacco mosaic virusdepended on SA signal transduction pathway, which was cross-talk with JA/ET signaltransduction pathway.4. The activities of PAL、POD and SOD enzymes were determined. Resultsshowed that the activities of three enzymes increased significantly after treated withSurfactin A, and the change trends were according to that of the expressions ofNPR1、PR1a and PR1b genes related to SA signal transduction.