Functional Analysis Of Genes BphP And BphO Related To Red-light Photosensory Protein In Acidovorax Citrulli

Bacterial fruit blotch(BFB)is a bacterial disease mainly occurring in cucurbit crops such as watermelon and melon,which seriously affects the healthy development of watermelon and melon industry.The pathogen of the disease is Acidovorax citrulli.Previous studies in the laboratory showed that the phenotype of key pathogenic factors such as motility and biofilm formation in the wild-type strain Aac5 of Acidovorax citrulli was significantly different under light and dark conditions.However,its molecular mechanism is still unclear.Studies have shown that the phytopathogenic bacterial red light receptor BphP senses the red light signal and regulates the pathogenic process.Is there a red light receptor BphP in Acidovorax citrulli? And is it involved in regulating the pathogenic differences in light and dark conditions?Bioinformatics analysis showed that BphP protein existed in Aac5,and the biological function of BphP was explored by gene knockout technique,phenotypic assay,qPCR and Western Blot.The results showed that Compared with the wild type,the formation ability of biofilm and motility were significantly improved under red light.The growth ability decreased under different light treatments,and the pathogenicity decreased under illumination after bphP gene deletion.The biofilm formation ability of the mutant ?bphO increased,motility and pathogenicity reduce.The absence of both genes does not affect HR of non-hosts.When exploring the relationship between BphP protein and T3 SS,qPCR and Western Blot showed that hrpG and hrpX were down-regulated at the transcriptional and protein levels after bphP deletion,which was not affected by light and darkness.Deletion of bphP and bphO genes affected flagellar-related gene fliC,extracellular hydrolytic enzymes eng,pili-related gene pilQ,chemotactic-related gene cheA,virulence protein gene trbC,and the key genes regulating T3 SS hrpG and hrpX.Moreover,bphP regulates the expression of these pathogenic genes and is also affected by light.In summary,the biological function of BphP regulates pathogenicity depends on light and dark conditions,and BphP senses red light signals and regulates the expression of virulence of biofilm,growth ability and other pathogenic factors,and participates in the regulation of the expression of T3 SS key factors hrpG and hrpX.