Identification Of The Genes Involved In EPS Production Of Xanthomonas Campestris PV.Campestris 8004

Xanthomonas campestris pv. campestris (Xcc) is an important pathogen of cruciferous plants, it causes the black rot disease of cruciferous crops worldwide. One of the products of X. campestris is excellular polysacchride(EPS) named xanthan gum. EPS is currently regarded as a pathogenicity factor during interaction between Xcc and host plants. In addition, EPS is also a sort of important polysacchride in industry. The Xcc 8004 mutant library was constructed by the insertion of transposition Tn5gusA5 in the laboratory. The EPS production of 16462 Tn5gwsA5 inserted mutants Xcc 8004 strains were tested and 75 had a fall in EPS production. In this study, the NYGA containing 2% glucose is used to re-select these 75 mutants. The result of re-selecting is 51 strains of EPS production deficiency were obtained. They are distributed in 45 ORFs. Among them, 11 have been verified to be relevant to EPS, and 34 have not been reported to have relationship with EPS. Furthermore, 13 of these 34 ORFs encode conserved hypothetical protein. XC0877 is one of these 13 ORFs and it is used to make a further study in order to verify whether it is relevant to the EPS synthesizing. According to the information of Tn5gusA5 5inserted mutants library, there are 4 independent Tn5gwsA5 inserted mutants in XC0877 in which 2 of them are deficient in EPS production and the other 2 are normal in EPS production. Thereason why there are two phenotypes is thought initiatively as a fault of ORFs defining. In order to prove that XC0877 is related to EPS production, we construct the XC0877 non-polar site-specific insertion mutant. It is found that nearly half of these mutants are deficient in EPS production and the other half is normal in EPS production. Using the way of PCR to amplify wild type XC0877 (including promoter) and then clone it on pLAFR3 to undergo complemtation in trans, the result is that the EPS production of the mutant dose not recover. According to all the results above, whether XC0877 is relevant to EPS production is needed to do further research.