| In this study,two strains of cadmium tolerant endophytic bacterium were isolated and purified from rice seeds of Huang Hua Zhan in the early stage.These two endophytic strains have the physiological characteristics of iron carrier production,phosphorus solubility,nitrogen fixation and IAA production.Respectively Stentrophomonas sp.R5 and Pantoea sp.R3 strains.Inoculation of Stentrophomonas sp.R5 strain,R5 for short.The inoculation of Pantoea sp.R3 strain was abbreviated as R3.Analysis the changes of hormone content,gene expression of hormone,Cd transport and uptake,metabolites in hydroponic culture Arabidopsis thaliana by exogenous addition rice endophyte under Cd stress.The aim was to elucidate the role of endophytic bacterium inoculated with rice seeds on the defense stress of cadmium in Arabidopsis Thaliana plants.The main research results are as follows:1.Phenotypic analysis showed that exogenous addition R3,R5 endogenous bacterium could improve Arabidopsis thaliana wild-type resistance to cadmium stress,the OD value of 0.5,1.0 R5 endophytes to plant survival rate increased to 45%,95%respectively,the OD value of 0.5,1.0 R3 endophytes to plant survival rate upped to15%,30% respectively,and R5 endophytes have certain effect on promoting root growth.For the MYC2 mutant,both myc2 and myc2 /3/4 exhibited more sensitive phenotypes than col-0.Survival data showed that both myc2 and myc2/3/4 were significantly lower than CK.MYC2-OE phenotype was consistent with that col-0,both of which had a higher survival rate.2.The contents of JA and OPDA were increased in 1,2 days after the exogenous addition R5 endophytes,while the content of JA and OPDA were decreased in control group.The contents of JA and OPDA were much higher in the addition R5 endophytes group than in control group.After the endogenous bacterium colonization(6 days),JA contents of addition R5 endophytes group were higher than control group.In the early stages of cadmium stress,exogenous addition R5 endophytes could rapidly induce and promote the synthesis of JA and OPDA.The same effect could be achieved by colonizing endogenic bacteria.For JA-Ile,the contents in the treatment group were much lower than in the control group after the colonization of endophytic bacterium.For SA,the contents were increasing after R5 endophytic bacterium colonization.3.The expression level of JA synthesis gene AOS on day 5,6 and 7 after exogenous addition of endophytic R5 bacterium were lower than that of the control group.These results indicated that exogenous addition of R5 endophytes to colonization could inhibit the expression of Jasmonates synthesis gene AOS.The expression levels of genes related to Cd transport and uptake,HMA2,HMA3,NRAMP1 and NRAMP3,were all decreased to day 6,7 in the group treated with exogenous addition R5 endophytes under cadmium stress,compared with the control group only under cadmium stress.4.Analysis difference metabolites between addition R5 endophyte and without after cadmium treatment by using targeted metabolomics platform,totally we obtained 16 metabolic markers that regulated by R5 endophytic bacterium and response to cadmium stress.here were 11 metabolic markers content increases,including most of the fatty acid substances TCA cycle product of organic acids and part of sugars,amino acids.The contents of 5 metabolites were decreased,including some saccharides related to glycolysis.In general,R5 endophytic bacterium can improve the cadmium resistance of Arabidopsis thaliana,reduce the expression of genes related to Cd transport and uptake,and the enhancement of cadmium resistance is closely related to the accumulation of jasmonates.For metabolites,exogenous endophytic bacteria are involved in regulating metabolites in Arabidopsis thaliana,promoting the accumulation of fatty acids and organic acids.The results of this paper can provide new ideas and references for the study of the interaction between endophytic bacterium and Arabidopsis thaliana under cadmium stress on jasmonates and metabolites. |
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