Study On Enzyme Activity And Metabonomic Changes Of Panax Ginseng To Fusarium Solani Infection

Objective: After ginseng was infected with Fusarium solani,the activities of cell wall degrading enzymes(CWDEs)in vitro and in vivo were extracted and measured,and the changes of related physiological and biochemical indicators in vivo were dynamically analyzed,and the overall changes of metabolites in this process were analyzed by UPLC-MS metabolomics technology.It is hoped that this study could provide a theoretical basis for elucidating the susceptibility mechanism of ginseng plants,further revealing the interaction mechanism of ginseng root rot and disease resistance breeding.Methods: 1.The activities of CWDEs produced by Fusarium solani in vivo and in vivo were determined by spectrophotometry,including PG,PMG,Cx,βG,PMTE and PGTE.2.The physiological and biochemical indexes of panax ginseng root infected with Fusarium solani were determined by spectrophotometric and microplate reader methods,including the activities of PAL,PPO,POD,SOD,CAT,and the contents of MDA and soluble sugar.3.The metabolites of ginseng root infected with Fusarium solani were determined by UPLC-MS metabolomics technology.The differential metabolites were screened by multivariate statistical analysis combined with PCA and OPLS-DA,and KEGG metabolic pathway enrichment analysis was performed.Results: 1.The activity of CWDEs produced by Fusarium solani in vitro showed that Cx and PMG activities reached the maximum at 5 d,PG and PMTE activities reached the maximum at 9 d,βG and PGTE activities reached the maximum at 3 d and 7 d,respectively.The results indicated that cellulase Cx and βG were activated first and then pectinase was activated.After panax ginseng was inoculated with Fusarium solani,the activities of PG,PMG and βG reached the maximum at 21 d,while the activities of Cx,PMTE and PGTE reached the maximum at 7 d,and were significantly higher than those of the control group.These results indicated that cellulase Cx first degraded matrix polysaccharides and cellobiose in cellulose into glucose,then pectinase PG and PMG degraded pectin in the cell wall of the host.2.After panax ginseng was inoculated with Fusarium solani,the physiological and biochemical indexes in vivo are closely related to its disease resistance.The activities of PAL,SOD and CAT in the inoculation group reached the maximum at 14 d,the activity of PPO reached the maximum at 7 d,and the activity of POD reached the maximum at 28 d,which were significantly higher than the control group.These results indicated that the activities of PAL,PPO,POD,SOD and CAT were all activated.The content of MDA in the inoculation group continued to increase and peaked at 21 d.The results showed that the damage to the cell membrane of ginseng was the greatest at 21 d after inoculation.The content of soluble sugar content in the inoculated group decreased rapidly,which might be a physiological and biochemical manifestation of infection.3.After panax ginseng was inoculated with Fusarium solani,the metabolite content changed with the time of infection.A total of 56 differential metabolites were screened from F7 vs S7 group(49 down-regulated and 7 up-regulated),a total of 77 differential metabolites were screened from F14 vs S14 group(59 down-regulated,18 up-regulated),a total of 28 differential metabolites were screened from F21 vs S21 group(14down-regulated and 14 up-regulated),and a total of 25 differential metabolites were screened from F28 vs S28 group(11 down-regulated and 14 up-regulated).The main difference metabolites were saponins,sugars and organic acids,among which the up-regulated metabolites were sugars and organic acids.It was speculated that these metabolites might be anti-disease substances.The down-regulated metabolites were mainly saponins,and the changes of these metabolites might affect the quality of ginseng.KEGG was used for enrichment analysis of differential metabolites,and five metabolic pathways were annotated.Conclusion: After panax ginseng was inoculated with Fusarium solani,the activity or content of CWDEs,physiological and biochemical indexes in panax ginseng reached the maximum on a certain day,which indicated that panax ginseng was activated to Fusarium Solani resistance.And the metabolite content in panax ginseng root also changed.Saponins,sugars and organic acids were the main differential metabolites of panax ginseng in response to Fusarium solani infection.The up-regulated metabolites of sugars and organic acids might be the main resistance substances to enhance the resistance of ginseng to Fusarium solani infection.This conclusion could lay a foundation for further study on the mechanism of ginseng root rot resistance.