Study On The Function Of Gene Aave-3192、 Aave-2108 And Aave-4679、 Aave-2716 Of Acidovorax Citrulli

Based on Tn5’s insertion mutant library of Acidovorax. citrulli, which has been constructed in our Lab, we screened two mutants(labeled 166 and 167). Comparing with wild strain, they lacked of pathogenicity,enhanced on quorum sensing,declined in produce of exopolysaccharides and have no hypersensitive response(HR) on tobacco. This study got the insertion sites of Tn5 in mutant 166 and mutant 167 by subcloning, and the insert gene was Aave-3192 and Aave-2108 respectively. The two genes encode Hypothetical protein and Methyl-accepting chemotaxis sensory transducer,respectively. To identify the functions of two genes, the complementary strains 166hb and 167hb were constructed, and the pathogenicity and some other biological characteristics were tested. Our results showed that the biological characteristics of two strains were recovered on pathogenicity, motility, quorum sensing, exo-polysaccharides, the colonial morphology and biofilm inordinately. Overall, our studies indicated that the two genes are related to pathogenicity of A.citrulli on watermelon.As we have known that the A.citrulli has genetic diversity,which was divided into two groups, group Ⅰ and group Ⅱ.There are obvious differences between two groups on biological characteristics.In this study, we designed 16 pairs primers based on the genome of A.citrulli to amplify pili genes, and got 4 specific primers which could only amplify pili genes from group Ⅱ. These genes are Aave-4679、Aave-2716、 Aave-0532 and Aave-2725, respectively. And then, we studied the functions of genes Aave-4679(pilA) and Aave-2716(pilI) by site-directed mutagenesis.The results showed that the pathogenicity, biofilm formation, swimming and quorum sensing of knockout strain of gene pilA were lower than that of the wild strain. And the morphology was different from the wild strain’s, no apron existed.The hypersensitive response in accordance with the wild strain. And the strain of knockout gene pilI was reduced in swimming and became narrower in apron,but no significant changes with other biological characteristics. Overall, our study proved that gene pilA is related to pathogenicity, but gene pilI is not.