Functional Analysis Of Genes FtsH,hflK And HflC In Acidovorax Citrulli

Acidovorax citrulli causes bacterial fruit blotch?BFB?,a disease that poses a global threat to watermelon and melon production.AAA ATPase?ATPase associated with diverse cellular activities?plays an important role in various life processes of A.citrulli.FtsH protein?filamentation temperature-sensitive H?encoded by ftsH gene is an important member of AAA family,which involve in life process such as growth,pathogenicity,environmental stress reaction and protein mass balance control.In cell,FtsH can function together with the HflK/C dimers.In order to analyze the function of ftsH,hflK and hflC genes in A.citrulli,we carried out a bioinformatics analysis of these three genes.Based on the A.citrulli wild type strain Aac5,we constructed deletion mutant strain of ftsH,hflK,hflC by homologous recombination respectively.Their complementary strains were also constructed by three-parental hybrid.Through series of pathogenicity and phenotype determinations and testing the expression level of pathogenic genes,AAA ATPase genes and heat shock transcriptional factor?³² in three mutant strains,we found that:1.Through bioinformatics analysis,ftsH encodes FtsH protein,while hflK encodes HflK protein and hflC encodes HflC protein.In bacteria,FtsH can aggregate with the HflKC to function as protease complex.2.Compared with the wild type strain,the virulence,swimming motility,biofilm formation and growth ability were significantly decreased in?ftsH??hflK??hflC strains.The deletion of ftsH,hflK and hflC did not affect the HR on non-host Nicotiana tabacum.3.The absence of ftsH,hflK and hflC significantly weakened the tolerance of Aac5 under high temperature,salt stress and antibiotic stress.And the effect of the deletion of ftsH on environmental tolerance of A.citrulli was the most.The?ftsH showed most reduced environmental tolerance among the three mutant strains of A.citrulli.4.The expression of genes related to type?secretion system,toxic protein,flagellum,AAA ATPase,heat shock transcriptional factor?³² and 3 target genes?ftsH,hflK and hflC?in mutant strains were significantly changed.These results indicated that the function of ftsH,hflK and hflC in A.citrulli were closely related to the pathogenic phenotype?pathogenicity,and heat shock response?and also other AAA ATPase genes.In addition,the three target genes function closely with each other.