To explore the pathogenic mechanism of Pseudomonas syringae pv. actinidiae (Psa) from the perspective of plasmid,and to analyze the main genes and virulence factors they encode,we isolated high purity plasmid from the Psa strain JF8 (Yuexi,Anhui) by plasmid extraction kit,sequenced and analyzed it bioinformatically.The results showed that the plasmid was 50 724 bp with an average GC content of 56.29%,containing 83 protein-coding genes.Among the 83 genes,45 were predicted to encode hypothetical proteins and 38 were known functional genes.Bioinformatics analysis showed that the plasmid carried several genes associated with bacterial pathogenesis and disease resistance.The plasmid carries up to 8 mobile element proteins directly involved in gene recombination and metastasis.Five genes directly participate in the bacterial Ⅳ secretion system and one gene participates in the Ⅲ secretion system.The protein encoded by the gene ParA is an ATPase that plays an important role in the distribution of plasmids and maintaining plasmid stability.The gene LuxR,which encodes a transcriptional activator protein,is involved in the quorum sensing mechanism of bacteria and affects the expression and secretion of virulence factors.The UmuC gene is one of the components of the medium SOS response system,controlling the amount of polymerase Ⅴ in the cell.