The Plant Growth-Promoting Rhizobacterium Bacillus Subtilis HN09 And Its Metabolites Induced Plant Disease Resistance

Plant immune elicitors can activate the plant's own immune response and protect the plant from pathogenic microorganisms.Plants resist pathogenic microorganisms through defense responses such as tannin deposition and defense gene expression,and signaling of defense at the site of infestation to the whole plant through Salicylate(SA)and jasmonate/ethylene(JA/ET)resistance signal transduction pathways.In this study,two novel plant immune elicitors were discovered: Bacillus subtilis HN09 and acetybutanediol.We studied their activity through plant level,cell-level and molecular-level experiments,and initially explored the mechanism of action.At the plant level,we tested the induced resistance activity of HN09 in Arabidopsis(Arabidopsis thaliana),tomato(Lycopersicon esculentum)and rice(Oryza sativa).Root treatment of HN09 significantly increased tomato resistance to tomato fusarium wilt.HN09 also has excellent induced resistance activity in Arabidopsis and rice.In Arabidopsis,HN09 induce resistance against a broad pathogens includeing pseudomonas syringae pv.tomato DC3000,the inhibitory rate of HN09 treated Arabidopsis on DC3000 was 44.38%.In susceptible rice cultivar Lijiang and resistant rice cultivar HNBL9,the inhibitory rate of HN09-treated rice to Magnaporthe grisea was 50.7% and 73.3%.We also tested the induce resistance activity of acetybutanediol in the Arabidopsis thaliana system,and the inhibitory rate of B1,B2,B3 and B4-treated Arabidopsis on DC3000 was 2.63%,50.53%,66.58% and 67.54%.At the cellular level,we examined the callose deposition in B1,B2,B3,and B4 treated Arabidopsis that infected with the pathogen DC3000.Among them,the B2,B3 and B4 can advance and enhance callose deposition in Arabidopsis when DC3000 invades,but the B1 configuration is not.At the molecular level,the expression of plant defense genes after treatment with different elicitors was detected by RT-qPCR.In Arabidopsis,HN09 can induce SA and JA/ET pathway defense gene expression,B2,B3 and B4 can also induce SA pathway and JA/ET pathway defense gene expression without HN09 strong,and B1 can induce JA/ET pathway gene expression,but has no significant effect on the defense gene expression of the SA pathway.In rice,B1,B2,B3,and B4 induced the up-regulation of JA synthase gene AOS,LOX,and transcription factor NH1.The above results suggest that B1,B2,B3,and B4 may activate the plant immune response mainly through the JA/ET disease resistance pathway.According to the results of the RNA-seq analyses,B1,B2,B3,and B4 all induced a large number of differentially expressed genes related to disease resistance,and were mainly enriched in JA/ET disease resistance pathways.At 1,6,and 12 hours,B3 and B4 induced the differential expression of a large number of the same genes,while the differential genes induced by B1 and B2 were partially overlapping but more specific.This result suggests that the mechanisms of action of B3 and B4 in inducing disease resistance in Arabidopsis may be similar,while B1 and B2 stimulate the disease resistance of plants through different pathways.Through the phenotype experiments of three Arabidopsis mutant jar1,etr1 and npr1,we confirmed that the JA/ET disease resistance pathway is indeed involved in the resistance of B2,B3 and B4 induced Arabidopsis to the pathogen DC3000,and B1 is Wild-type Arabidopsis plants could not induce resistance to DC3000,so the effects of three mutants on B1-inducing activity could not be judged.