title: Functional characterization and transcriptional analysis of galE gene encoding a UDP-galactose 4-epimerase in Xanthomonas campestris pv. campestris.
abstract: The Gram-negative plant pathogen Xanthomonas campestris pv. campestris (Xcc) is the causative agent of black rot in crucifers, a disease that causes tremendous agricultural loss. In this study, the Xcc galE gene was characterized. Sequence and mutational analysis demonstrated that the Xcc galE encodes a UDP-galactose 4-epimerase (EC 5.1.3.2), which catalyzes the interconversion of UDP-galactose and UDP-glucose. Alanine substitution of the putative catalytic residues (Ser124, Tyr147, and Lys151) of GalE caused loss of epimerase activity. Further study showed that the Xcc galE mutant had reduced biofilm formation ability. Furthermore, reporter assays revealed that galE transcription exhibits a distinct expression profile under different culture conditions, is subject to catabolite repression, and is positively regulated by Clp and RpfF. In addition, the galE transcription initiation site was mapped. This is the first time that UDP-galactose 4-epimerase has been characterized in the crucifer pathogen Xcc.
authors.affiliation: Division of Chest Medicine, Department of Internal Medicine, Changhua Christian Hospital, Changhua, Taiwan.
authors.forename: Chien-Te
authors.initials: CT
authors.lastname: Li
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan.
authors.forename: Chao-Tsai
authors.initials: CT
authors.lastname: Liao
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan.
authors.forename: Shin-Chiao
authors.initials: SC
authors.lastname: Du
authors.affiliation: Department of Dermatology, Chung Shan Medical University Hospital, Taichung, Taiwan; Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan.
authors.forename: Yu-Ping
authors.initials: YP
authors.lastname: Hsiao
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan.
authors.forename: Hsueh-Hsia
authors.initials: HH
authors.lastname: Lo
authors.affiliation: Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan. Electronic address: ymhsiao@ctust.edu.tw.
authors.forename: Yi-Min
authors.initials: YM
authors.lastname: Hsiao
mesh_terms: D019943:Amino Acid Substitution; D004252:DNA Mutational Analysis; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D014534:UDPglucose 4-Epimerase / Q000235:genetics* / Q000378:metabolism*; D016959:Xanthomonas campestris / Q000201:enzymology* / Q000235:genetics*
chemical_list: D014534:UDPglucose 4-Epimerase
keywords: Reporter assay; Transcriptional regulation; Xanthomonas