Regulation Of Chlorogenic Acid And Caffeic Acid Based On The Content Of Pingguoli Pear Peel On Reactive Oxygen Metabolism Of Alternaria Alternata

In this study,Alternaria alternata was used as the material.The effects of chlorogenic acid and caffeic acid based on the content of pear peel on the growth,active oxygen production systems,the antioxidant systems(AsA-GSH cycle and thioredoxin system system)related enzyme activities and their gene expressions,cell extracellular environment pH and redox potential of Alternaria alternata were studied by in vitro experiment.The results showed as follow:1.Chlorogenic acid and caffeic acid based on the content of pear peel had no significant inhibitory effect on the spore germination of A.alternata,but significantly inhibited germ tubes elongation,appressoriums formation and pathogenicity of A.alternate on Pingguoli pear.2.The content of H2O2,O2-.production rate and Nox activities of A.alternate were significantly increased by chlorogenic acid and caffeic acid based on the content of pear peel,and their stimulus effect had the phenolic species and concentration dependence.Chlorogenic acid treatment could significantly induce the production of reactive oxygen.H2O2 contents of A.alternate reached the peak at 6h after 1000 ppm,2000ppm and 4000 ppm chlorogenic acid treatments,which were 3.66,6.14,10.51 times higer respectively than that of the control.While H2O2 contents reached the maximum at 3h after 100 ppm,200 ppm and 400 ppm caffeic acid treatments,which only were 1.49,1.59 and 1.94 times higher than that of the control respectively.The Nox activity of A.alternata reached the maximum at 9h after chlorogenic acid and caffeic acid treatments,and were significantly higher than that of the control.3.Chlorogenic acid and caffeic acid based on the content of pear peel had some regulatory role on the enzymatic and nonenzymatic antioxidant system of A.alternate,but their regulatory effect varied with the types and concentration of phenolic substance.The activities of antioxidant enzymes GR,GPX,APX and MDHAR in the AsA-GSH cycle,gene expressions,the contents of antioxidant compounds GSH,AsA,DHA and GSH/GSSG ratio in A.alternate were significantly increased after treatment with two phenolic substances,while CAT,DHAR and GST activities were decreased.4000 ppm chlorogenic acid and 400 ppm caffeic acid significantly increased GR activity in A.alternata and reached a peak at 3h after treatment,which were increased by 49.8% and 36.6% compared with that of the control,respectively.SOD and GPX gene expression were significantly upregulated 3h after 1000 ppm chlorogenic acid treatment,which were 12.17% and 32.4% higher than that of the control.However,Trx content and TrxR activity were significantly decreased in thioredoxin system of A.alternata after treatment with two exogenous phenolic substances.4.Extracellular pH of A.alternata was acidic and significantly lower than that of the control after chlorogenic acid and caffeic acid based on the content of pear peel treatment.At the same time,the extracellular redox potential of the cells after chlorogenic acid treatment was higher than that of the control,and the extracellular redox potential of the cells after caffeic acid treatment was lower than that of the control.In summary,chlorogenic acid and caffeic acid based on the content of pear peel could affect the pathogen infection by altering redox balance and regulating the production and scavenging systems of reactive oxygen species of A.alternata.