A gene involved in quinate metabolism is specific to one DNA homology group of Xanthomonas campestris.
A gene involved in quinate metabolism was cloned from Xanthomonas campestris pv. juglandis strain C5. The gene, qumA, located on a 4. 2-kb KpnI-EcoRV fragment in plasmid pQM38, conferred quinate metabolic activity to X. c. pv. celebensis. Tn3-spice insertional analyses further located the qumA gene on a region of about 3.0 kb within pQM38. Nucleotide sequencing of this 3.0-kb fragment reveals that the coding region of qumA is 2373 bp, the deduced amino acid sequence of which closely resembles a pyrrolo-quinoline quinone-dependent quinate dehydrogenase of Acinetobacter calcoaceticus. A 0.7 kb SalI-PstI fragment internal to qumA was used as a probe to hybridize against total genomic DNA from 43 pathovars of X. campestris. The fragment hybridized only to total genomic DNA from the four pathovars of DNA homology group 6, X. c. pv. celebensis, X. c. pv. corylina, X. c. pv. juglandis and X. c. pv. pruni, and from X. c. pv. carotae, which belongs to DNA homology group 5. This 0.7 kb fragment was also used as a probe to hybridize BamHI-digested total genomic DNAs from the four pathovars of DNA homology group 6 and X. c. pv. carotae. The restriction fragment length polymorphism pattern of DNA homology group 6 was different from that of X. c. pv. carotae. The probe hybridized to a 5.7-kb BamHI fragment in all four pathovars of group 6 and to a 6.1-kb BamHI fragment in three of four pathovars. It hybridized only to a 9. 9-kb BamHI fragment in X. c. pv. carotae. Quinate metabolism has previously been reported as a phenotypic property specific to X. campestris DNA homology group 6. Accordingly, a combination of the quinate metabolism phenotypic test and Southern hybridization using a qumA-derived probe will be very useful in the identification of pathovars in DNA homology group 6.
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Department of Biology, Fu Jen Catholic University, Taipei, Taiwan, Republic of China. bio1007@fujens.fju.edu.tw
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D000429:Alcohol Oxidoreductases / Q000235:genetics*; D000595:Amino Acid Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004251:DNA Transposable Elements; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D012150:Polymorphism, Restriction Fragment Length; D011801:Quinic Acid / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D016959:Xanthomonas campestris / Q000145:classification / Q000235:genetics*
D004251:DNA Transposable Elements; D011801:Quinic Acid; D000429:Alcohol Oxidoreductases; C022511:quinate dehydrogenase