title: Transcriptional analysis of pmeA gene encoding a pectin methylesterase in Xanthomonas campestris pv. campestris.
abstract: Exopolysaccharides and several extracellular enzymes of Xanthomonas campestris pv. campestris (Xcc), the causative agent of black rot in crucifers, are virulence determinants. It is known that Clp (cAMP receptor protein-like protein) and RpfF (an enoyl-CoA hydratase homologue required for the synthesis of the diffusible signal factor, DSF) regulate production of these factors. In this study, plate assay revealed that Xcc possesses pectin methylesterase activity and that its expression is controlled by Clp and RpfF. Mutational analysis has demonstrated that pmeA encodes a pectin methylesterase. Using the 5' RACE method, the pmeA transcription initiation site was mapped. Transcriptional fusion assays showed that pmeA transcription is positively regulated by Clp and RpfF, subject to catabolite repression which is independent of Clp or RpfF, and repressed under conditions of high osmolarity or oxygen limitation. This study not only extends previous work on Clp and RpfF regulation by showing that they both influence the expression of pmeA in Xcc, but also, for the first time, characterizes pectin methylesterase gene expression in Xanthomonas.
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung 406, Taiwan, ROC. ymhsiao@ctust.edu.tw
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Hsiao
authors.forename: Yu-Fan
authors.initials: YF
authors.lastname: Liu
authors.forename: Yi-Ling
authors.initials: YL
authors.lastname: Huang
authors.forename: Pei-Yu
authors.initials: PY
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000378:metabolism*; D002265:Carboxylic Ester Hydrolases / Q000096:biosynthesis* / Q000235:genetics; D004746:Enoyl-CoA Hydratase / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism*; D024363:Transcription Initiation Site; D016959:Xanthomonas campestris / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C436751:Clp protein, Xanthomonas campestris; D014157:Transcription Factors; D002265:Carboxylic Ester Hydrolases; C022323:pectinesterase; D004746:Enoyl-CoA Hydratase