The Function Identification Of Alps Biosynthesis Related Gene Of Xanthomonas Campestris PV. Campestris

A virulence retarded mutant 008G04 was selected by plant assay from the mutant library of Xanthomonas campestris pv. campestris (Xcc) 8004 constructed by transposon Tn5gusA5 random mutagenesis method. The Tn5gusA5 was inserted in the wxcB-like gene, which presumptively involved in lipopolysaccharide (LPS) biosynthesis, localized by TAIL-PCR and sequencing. To identify the function of wxcB in Xcc 8004, a nonpolar mutant of wxcB gene, named 3512nk, was generated by homologous suicide vector integration. The 3512nk mutant decreased the virulence on Chinese radish, similar to Tn5gusA5 mutant 008G04, but displayed no any difference in growth rate in NYGB compared with wild type strain. The SDS-PAGE analysis showed that there were alterations in the electrophoretic patterns of water-soluble LPS forms, which suggested that defects in biosynthesis of the O-antigen. In addition, the extracellular polysaccharide (EPS) production of 3512nk also decreased significantly (to 45.3% of the amount in 8004). The altered phenotypes were partially restored by introducing the pLAFR3 containing entire wxcB gene into the mutant strain. The synthesis of LPS was completely restored, however only 64.6% of the virulence was recovered. Interestingly the EPS production of the complemented strain was four times higher than that of wild type Xcc 8004. It indicated that the wxcB plays an important role both in biosynthesis of LPS and EPS of Xcc and is involved in virulence to Chinese radish plant.