| Pantothenate is the essential precursor for phosphopantotheine, the acyl carrier found in CoA and acyl carrier protein. The major route of β-alanine production for pantothenate in Escherichia coli is through the α-decarboxylation of L-aspartate, which is catalysed by the enzyme L-aspartate-α-decarboxylase. The panD mutant of E. coli is β-alanine auxotrophy. ApanD gene (ORF2380) is identified in Xanthomonas campestris pv. campestris strain 8004 (Xcc 8004) by genome annotation. The predicted product of ORF XC2380 shows 70.6% amino acid similarity with the PanD of E. coli. We had got a Tn5gusA5 insertional mutant of XC2380, 121C07, in the Xcc 8004 mutant library constructed in our lab. In this study, the biological function of panD in Xcc is determined by phenotypic analysis and complementation of the panD mutant. The panD mutant 121C07 can grow on minimal medium indicate that panD mutant is not a β-alanine auxotrophy. This indicates that the pantothenate synthesis pathway may be different in Xcc 8004 and E. coli. The virulence of panD mutant 121C07was determined by inoculated the mutant cell onto the host plant Chinese radish (Raphanus sativus L. var. radiculus Pers) by leaf clipping method with cell concentration of OD600= 0.001. Results showed that, 10 days post-inoculation, a lesion length with a mean of 12.29mm was observed on leaves inoculated with the Xcc 8004, while mean lesion length of 4.56mm was observed with panD mutant 121C07). The effects of panD mutation on the production of EPS and extracellular enzymes were also determined. Results showed that the EPS production of Xcc 8004 is 11.3g/L culture while the mean EPS production of the mutant is only 5.4g/L culture, and the complemented stain is 11.4g/L culture. The activities of extracellular amylase, extracellular proteinase, and extracellular cellulase are reduced in panD mutant. These results suggested that XC2380 might play role in EPS production and extracellular enzymes activity in Xcc.
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