Study On The Mechanism Of Phenazine-1-carboxylic Acid Inhibiting The Synthesis Of Exopolysaccharide In Pseudodiscus Polysaccharide Of Te

Tea grey blight is a diseases of tea leaves,which occurs in all tea areas in the world.tea grey blight is a seriously disease of tea leaves,which seriously affects the quality and yield of tea.At present,chemical control is mainly used for tea grey blight.Chemical agents used to control tea grey blight have risks of environmental pollution and resistance.Therefore,it is of great significance to study the action mechanism of green pesticides on tea grey blight for the prevention and control of this disease.Previous studies have shown that Phenazine-1-carboxylic acid(PCA),the active ingredient of the biopesticide the Shenzamycin,has inhibitory activity against the pathogen and PCA treatment could induce significant differences in genes related to extracellular polysaccharide biosynthesis,thus reducing the extracellular polysaccharide content on mycelium surface.However,the mechanism of PCA inhibition of extracellular polysaccharide synthesis in pathogenic bacteria is not clear.Therefore,based on the transcriptome data of PCA-treated Ps.camelliae-sinensis,this study has mined for four differentially expressed genes that related to the synthesis of mannose(the main component of extracellular polysaccharide),and prokaryotic expression,molecular docking,and microscale thermophoresis(MST)techniques were used to investigate whether PCA directly targeted mannose synthesis proteins and affected extracellular polysaccharide synthesis.The main findings were as follows:(1)The Ps.camelliae-sinensis of the inhibitory medium concentration was 11.23μg/m L.(2)The mycelium of Ps.camelliae-sinensis in semi-synthetic medium were treated with different concentrations of PCA.The dry weight of the mycelium in the control without PCA group and the treatment with PCA group(concentrations for 10,20 and30μg/m L)were 0.357 g,0.284 g,0.207 g and 0.172 g,respectively;the mass of crude exopolysaccharide was 2.329 mg,1.641 mg,1.528 mg and 1.393 mg;the relative increased mass of exopolysaccharide was 0.939 mg,0.252 mg,0.138 mg and 0.003 mg,respectively.(3)Differentially expressed genes related to the synthesis of mannose(the main component of exopolysaccharide)were obtained by prokaryotic expression technique,and the affinity between PCA and target protein was studied by MST.The results showed that PCA could bind to all four proteins.The dissociation constants between mannan polymerase II complex anp1 subunit,mannan polymerase complexes mnn9 subunit,alpha-mannosyltransferase as well as glycolipid 2-alpha-mannosyltransferase and PCA were 48.533μM,0.327 μM,63.185 μM and 4.971 μM,respectively.(4)After homologous modeling of four proteins related to mannose synthesis,molecular docking was carried out.The results showed that PCA can stably bind to protein Mannan polymerase II complex anp1 subunit,mannan polymerase complexes mnn9 subunit,glycolipid 2-alpha-mannosyltransferase and alpha-mannosyltransferase,and interact with protein specific amino acids and PCA mainly formed stable hydrogen bonds with specific amino acids of proteins,and formed hydrophobic interaction with amino acids in their respective A chains,which were the main driving forces for PCA to bind to them.