Study On The Function Of VgrG And PAAR Genes Of Acidovorax Citrulli And Identidication Of Pathogen On Peach Shoot Blight

Type VI secretory system(T6SS)affects the competition among bacteria.It is one of the reasons for virulence of plant pathogens.VgrG genes cluster is an important component of type VI secretory system and a key factor of T6SS mediated virulence.Although it has been deeply studied what virulence of vgrG genes in human and animal pathogenic bacteria,little is known about the function of T6SS in the pathogenic process of A.citrulli.Recent studies have proved that T6SS of A.citrulli mediated pathogen virulence.Compared with reported pathogen sequence of T6SS genes,this study analyzed 12 vgrG homologous genes and 7 PAAR homologous genes outside the T6SS gene cluster of Acidovorax citrulli.Then taken some determination of relative toxicity test such as melon seedlings,seed-seedling transmission and reproductive function of mutants.In addition,the interaction relationship between vgrG protein and other core components of T6SS was analyzed through Western blot analysis and other technical means.Then the core components of T6SS was drawn interaction network diagram of vgrg-PAAR and Hcp protein.The results showed that 3 vgrG homologous genes(Aave₀241,Aave₀481 and Aave₀497)and four PAAR homologous genes(Aave₀240,Aave₀483,Aave₀499 and Aave₃751)played an important role in T6SS-mediated virulence of pathogenic bacteria.It affects the virulence and antimicrobial activity of pathogenic bacteria.Real-time PCR and Western blot techniques were used to verify that the three vgrG homologous genes Aave₀241,Aave₀481 and Aave₀497 were necessary for the secretion of Hcp,the core component of T6SS.It is predicted that the Aave₀499 gene coding protein belongs to Class 7 type.However,whether Aave₀499 carries some effect factors needs further study.The results of bioinformatics analysis based on ?0497 and ?0499 show that Aave₀497 and Aave₀499 can cause dozens to hundreds of genes to be down-regulated in varying degrees.The functions of these genes can be classified into 12 categories,including signal transduction,material transport and metabolism,synthesis and metabolism of secondary metabolites,defense mechanism,etc.The function of vgrG homologous genes and PAAR homologous of A.citrulli genes in T6SS-mediated virulence are of great scientific significance to reveal the pathogenicity mechanism of A.citrulli.In addition,based on the previous study of peach canker disease in our laboratory,this study further studied the bacterial strains isolated from the disease samples which were collected from three orchards in Yangshan.The results showed that,not only Botryosphaeria dothidea which was reported before,but Phytophthora amygdali was also a common pathogen of Chinese Yangshan peach canker disease.This discovery lays a foundation for formulating effective management strategies.In addition to B.dothidea,emphasis should also be placed on P.amygdali for future disease management in Yangshan.