Study Of The Resistance Mechanism Of Oyrza Sativa 9311 In Response To Bacillus Amyloliquefaciens FZB42 Induction

Bacillus is the most important plant growth promoting rhizobacteria,which could promote plant growth and reduce the plant diseases.Bacillus is widely applied in agriculture.Resistance of plants could be enhanced after the Bacillus induction.But the mechanism is unclear now.In former studying,difference expression genes after interaction between model Bacillus amyloliquefaciens FZB42 and Oryza sativa subsp.indica 9311 were analyzed using RNA-Seq technology.And response reactions of plant root and leaf to Bacillus were explored according to GO function annotation and KEGG pathway analysis.The analysis result showed that Bacillus could promote development and resistance of plant according to influence relative genes regulation and expression in the signal transduction and metabolism pathway.In this study,to clarify the complex mechanisms underlying plant-PGPR interactions,variations in the expression of crucial genes COI1,MEKK1,PR1 and WRKY that involved in signal transduction following plant-pathogen interaction at different interaction time points were examined.Significantly up-regulated expression of PR,LOX,and ERF genes involved in the salicylic acid,jasmonic acid,and ethylene signal transduction pathways,respectively,were detected,which suggested that defense reactions in rice were induced following interaction with FZB42.The changes of phytoalexin in rice induced by FZB42 were examined.The levels of momilactone A,phytocassane A,phytocassane D,phytocassane E all rose between 24 and 48 h,suggesting a PGPR-mediated mechanism of plant pathogen resistance.The quantity of the IAA in rice leave rose in 12 h after Bacillus induction.Further research indicated that FZB42 treatment may result in Ca2+ influx of plant guard cell and accumulation of ROS and NO.These signal modules may further participate in plant defense responses,reducing stomata closure and intracellular accumulation of H2O2.We inoculatd pathogen at rice leave after Baillus induction,testing the quantity of the pathogen in the rice leave 2 weeks later.The quantity of the XOO and XOC in rice was significantly decreased.Finally,Bacillus significantly improved plant resistance to the pathogen.Combining this result with former RNA-Seq analysis,we find:after FZB42 interaction,extracellular plant signals could be transformed into intracellular signals at the root cell membrane by FLS2 and EFR,which activating mitogen-activated protein kinase kinase kinase 1(MEKK1P),producing phosphorylation and amplifying the MAPKKK,MAPKK and MAPK cascade,and ultimately leading to the induction WRKY transcription factors.Furthermore,the expression of WRKY transcription factors could be inducted,affecting the transcription of many genes to conduct various biological functions,including the regulation of disease resistance genes expression and producting PR proteins,synthesising the phytoalexins,and so on.At the same time,the Bacillus induction may result in Ca2+ influx of plant guard cell and accumulation of ROS and NO.These signal modules may further participate in plant defense responses,such as inducing stomata closure,hypersensitive response and cell wall reinforcement,activation defense related genes involved in SA,JA and ET signal pathway,and ultimately improving plant resistance.This study was also conducted to select the Bcillus strains from the Antarctic soil,which had good biocontrol effect.The Bacillus strains EZ15-07 and EZ01-05 which isolated from Antarctic soil showed biocontrol effect against many pathogens.The lipopeptide compounds analysis suggested that strain EZ15-07 produced Surfactin and Bacillomycin D,whereas strain EZ01-05 produced Bacillomycin D and Fengycin.The results of field trail showed that the biocontrol effect of EZ15-07 and EZ01-05 reached to 59.3%and 55.3%,respectively.The Bacillus strains EZ15-07 and EZ01-05 had significant biocontrol effects against brown stalk rot on maize.Furthermore,we found the strains EZ15-07 and EZ01-05 could grow under 10?.The strain EZ15-07 could grown in LB liquid medium with pH of 5.0-9.0,while the strain EZ01-05 could grow with pH of 5.0-10.0.The survival rate of strains EZ15-07 was 29%after 30 mins in 0.5%H2O2 treatment,while survival rate of 17.7%after 90 mins;the survival rate of strains EZ01-05 was 19%after 30 mins in 0.5%H2O2 treatment,while survival rate of 8%after 90 mins.Both of them had good potential in application.