title: Control of exuT activity for galacturonate transport by the negative regulator ExuR in Erwinia chrysanthemi EC16.
abstract: The negative regulatory protein ExuR in Erwinia chrysanthemi regulates expression of the galacturonate uptake (exuT) and utilization (uxaA, uxaB, uxaC) genes. We cloned and determined the nucleotide sequence of the exuR gene from E. chrysanthemi EC16. Analysis of the deduced amino acid sequence indicates that this protein possesses a helix-turn-helix motif and belongs to the GntR family of transcriptional repressors. Northern blot analysis and studies with transcriptional fusions of exuT in wild-type and exuR mutant backgrounds indicate that exuT transcription is deregulated in the exuR strain in vivo and in planta. [14C]-galacturonic acid uptake was constitutively high under inducing and noninducing conditions in the exuR mutant. Maximal exuT transcription activity was observed within 8 h of bacterial inoculation into potato tubers, well before any visible symptoms of disease were detected. This suggests that ExuT transport activity in E. chrysanthemi is important in the early stages of disease development.
authors.affiliation: Department of Biological Sciences, Texas Tech University, Lubbock 79409, USA.
authors.forename: V
authors.initials: V
authors.lastname: Valmeekam
authors.forename: Y L
authors.initials: YL
authors.lastname: Loh
authors.forename: M J
authors.initials: MJ
authors.lastname: San Francisco
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001693:Biological Transport, Active; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins / Q000235:genetics; D016974:Dickeya chrysanthemi / Q000235:genetics* / Q000378:metabolism; D004187:Disaccharides / Q000378:metabolism; D029968:Escherichia coli Proteins; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D019077:Helix-Turn-Helix Motifs; D006603:Hexuronic Acids / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010368:Pectins / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D011198:Solanum tuberosum / Q000382:microbiology; D013400:Sugar Acids / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004187:Disaccharides; D029968:Escherichia coli Proteins; C438019:Exu R protein, Erwinia chrysanthemi; C111694:ExuT protein, bacteria; D005656:Fungal Proteins; C081598:GntR protein, E coli; D006603:Hexuronic Acids; D008565:Membrane Proteins; D012097:Repressor Proteins; D013400:Sugar Acids; D014157:Transcription Factors; C007819:galacturonic acid; D010368:Pectins; C090179:digalacturonic acid